Artículos de revistas: "Composite materials. Stress waves"

1

Clements, B. E., J. N. Johnson y R. S. Hixson. "Stress waves in composite materials". Physical Review E 54, n.º 6 (1 de diciembre de 1996): 6876–88. http://dx.doi.org/10.1103/physreve.54.6876.

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Abd-alla, Abo-el-nour N., MIA Othman y NF Hasbullah. "Shear horizontal waves in composite materials: Behavior under rotation and initial stress". Mathematics and Mechanics of Solids 24, n.º 1 (6 de octubre de 2017): 85–97. http://dx.doi.org/10.1177/1081286517730682.

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The main scope of this paper is to present in a simple and concise way a mathematical model of composite materials able to describe the propagation of shear horizontal waves in the case where composite is rotating and subjected to an initial stress. This work is aimed at the relevant possibility to apply the obtained results for the establishment of high-achievement applications of piezoelectric and semiconductor composites and surface acoustic waves devices. We conclude by analyzing numerical computations in which the influence of the rotation, initial stress and electromagnetic boundary conditions are graphically observed.

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3

Xu, Dandan y Yu Guo. "Local Resonant Attenuation of Stress Waves in Particulate Composites". Materials 14, n.º 11 (1 de junio de 2021): 2991. http://dx.doi.org/10.3390/ma14112991.

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The attenuation of stress waves due to the local resonance is numerically studied using the finite element method (FEM) in this work. The natural frequency of a representative composite unit embedded with coated particles is analyzed and the major factors that influence the natural frequency are examined. Local resonance is inspired when the frequency of the incident stress wave is close to the natural frequency of the particles in the composite. Significant reduction in the amplitude of the stress is obtained when the local resonance occurs, because a large amount of the incident energy is converted to the kinetic energy of the particles, which is rapidly dissipated through the strong oscillations of those particles. It is also observed that the attenuation for the incident stress waves with a range of frequencies can be achieved by using the particles with various local natural frequencies in a composite.

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4

Kim, Jin O. y Haim H. Bau. "A Study of the Fiber-Matrix Interface in Composite Materials". Journal of Applied Mechanics 59, n.º 2S (1 de junio de 1992): S163—S165. http://dx.doi.org/10.1115/1.2899482.

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A novel experimental technique for studying the characteristics of the interface between the fibers and the matrix in both undamaged and damaged fiber-reinforced composite materials is described. The experimental technique involves the transmission of stress waves in one or more fibers of the composite. The characteristics of the stress waves, such as speed, dispersion, and attenuation, are measured. These measured variables can be correlated with the characteristics of the bonding between the fiber and the matrix.

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5

Chimenti, D. E. "Guided Waves in Plates and Their Use in Materials Characterization". Applied Mechanics Reviews 50, n.º 5 (1 de mayo de 1997): 247–84. http://dx.doi.org/10.1115/1.3101707.

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In this review article, the ultrasonic characterization of materials using guided plate waves and their usage to elucidate mechanical properties of plate-like structures is reviewed. The purpose here is to summarize and explain the large body of theoretical and experimental work in this developing field. It is also to gain a perspective on recent salient contributions and to analyze the current state of knowledge and practice in guided wave ultrasonics. Models of waves in plates are examined, as are the means to generate and detect them. Their application to several problems of current interest in materials characterization is treated in detail. In particular, composite materials and their inspection and characterization have been a major impetus in the development of guided wave methods. Techniques to inspect composites sensitively and reliably for defects and to probe their micromechanical behavior are a major focus of this article. Also considered are the characterization of adhesive bonds, the measurement of stress and texture, and the detection of defects using guided waves. This review article contains 362 references.

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6

Ejaz, K. y M. Shams. "Love waves in compressible elastic materials with a homogeneous initial stress". Mathematics and Mechanics of Solids 24, n.º 8 (18 de junio de 2018): 2576–90. http://dx.doi.org/10.1177/1081286518771726.

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In this paper, the motion of Love waves is considered in hyperelastic materials with an initially stressed reference configuration. Here, the Love wave is directed by a compressible layer on a compressible half-space and both are considered to be initially stressed. For the basic formulation of the problem, we make use of the nonlinear theory of elasticity and invariants of the stress tensor and deformation tensor. The equations governing a finite deformation superimposed by infinitesimal motions are used to the study the composite effect of finite deformation and initial stress on wave speed. Graphical illustrations are presented for theoretical results for a prototype model of material and also compared with the results already obtained for incompressible materials.

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7

Walker, James Davidson y Efthymios Stefanos Folias. "Effect of stress waves on laminated composite plates". International Journal of Solids and Structures 29, n.º 2 (1992): 145–70. http://dx.doi.org/10.1016/0020-7683(92)90104-2.

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8

Glukhov, A. Yu. "Axisymmetric waves in laminated composite incompressible materials with initial stresses under the slipping of layers". Reports of the National Academy of Sciences of Ukraine, n.º 10 (16 de noviembre de 2016): 42–46. http://dx.doi.org/10.15407/dopovidi2016.10.042.

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9

Zou, Zhouyiao, Yanpeng Hao, Yao Zheng, Weiming He, Fangyuan Tian, Lin Yang y Licheng Li. "Subsurface Stress Measurement in GIS Epoxy Composite by Using LCR Waves". Energies 13, n.º 14 (20 de julio de 2020): 3725. http://dx.doi.org/10.3390/en13143725.

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Internal stress in basin insulators of gas-insulated metal-enclosed switchgear (GIS) can lead to cracks, which affects the safe operation of these apparatuses. In this research, we proposed a subsurface internal stress measurement method for GIS epoxy composites. This method is based on an ultrasonic longitudinal critically refracted (LCR) wave technique. In this study, some epoxy composite specimens were synthesized with similar materials and manufacturing processes to those of 252 kV GIS basin insulators. An ultrasonic stress measurement system that utilized the LCR wave technique was set-up to investigate the relationship between stress and LCR wave propagation time, as well as to measure the compressive stress of the epoxy specimen within 0–50 MPa. The results show that LCR wave propagation time linearly decreased when stress increased in the subsurface zone and the acoustoelastic coefficient was −4.95. We found the relative errors of stress measurements to be less than 13%.

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10

Zou, Zhouyiao, Yanpeng Hao, Fangyuan Tian, Yao Zheng, Weiming He, Lin Yang y Licheng Li. "An Ultrasonic Longitudinal Through-Transmission Method to Measure the Compressive Internal Stress in Epoxy Composite Specimens of Gas-Insulated Metal-Enclosed Switchgear". Energies 13, n.º 5 (7 de marzo de 2020): 1248. http://dx.doi.org/10.3390/en13051248.

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Situations of internal stress in basin insulators inside gas-insulated metal-enclosed switchgear (GIS) can lead to cracks, which can influence the safety and stability of apparatus. However, there is currently no research on internal stress measurements for composites of GIS basin insulators, and only measurements for surface stress. In this paper, an internal stress measurement method for GIS epoxy composite is proposed using an ultrasonic longitudinal through-transmission technique based on the acoustoelastic effect. An internal stress measurement system is developed to investigate the relationship between the uniaxial compressive internal stress and the velocity of the ultrasonic wave vertical to the stress in epoxy composite within a range of 0–70 MPa, and to calculate the acoustoelastic coefficient of epoxy composite. The effects of system delay are eliminated in measuring the propagation time. Some epoxy composite cuboid specimens with similar materials and using a manufacturing process similar to those of 252 kV GIS basin insulators are synthesized, and the uniformity of the internal stress in cuboid specimens is verified by finite element simulation. The results reveal a linear increase of the ultrasonic longitudinal wave velocity with increasing stress. It has been shown that the average acoustoelastic coefficient of GIS epoxy composites, using the longitudinal waves vertical to the stress, is 4.556 × 10−5/MPa. Additionally, the absolute errors of the internal stress measurements are less than 12.397 MPa. This research shows that the ultrasonic method based on the acoustoelastic effect for measuring the internal stress in GIS epoxy composites is feasible.

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11

Adams, Daniel O’Hare y Michael W. Hyer. "Analysis of Layer Waviness in Flat Compression-Loaded Thermoplastic Composite Laminates". Journal of Engineering Materials and Technology 118, n.º 1 (1 de enero de 1996): 63–70. http://dx.doi.org/10.1115/1.2805935.

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A finite element analysis was used to investigate layer waviness effects in flat compression-loaded composite laminates. Stress distributions in the vicinity of the layer waves as well as the locations and modes of failure were investigated. Two layer wave geometries were considered, each modeled within an otherwise wave-free thermoplastic composite laminate. These two wave geometries, classified as moderate and severe, corresponded to layer waves fabricated in actual laminates and tested under uniaxial compression loading. Material nonlinearities obtained from intralaminar shear and 0 and 90 deg tension and compression testing were incorporated into the analysis. The nonlinearity observed in the intralaminar shear stress-strain behavior was assumed to be valid for interlaminar shear stress-strain behavior, and the nonlinearity observed in the 90 deg tension and compression stress-strain behavior was assumed to be valid for interlaminar normal stress-strain behavior. Failure was predicted using a maximum stress failure theory. An interlaminar tension failure was predicted for the severe layer wave geometry, producing a large compression strength reduction in comparison to the wave-free laminate. Fiber compression failure was predicted for the moderate layer wave, producing only a slight compression strength reduction. Although significant material nonlinearity was present in the interlaminar compression and shear response of the material, the inclusion of material nonlinearity produced only slight decreases in predicted compression strengths relative to predictions based on linear material behavior.

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12

Green, E. Rhian. "Propagation of impact-induced stress waves in composite plates". Journal of Nondestructive Evaluation 13, n.º 2 (junio de 1994): 45–54. http://dx.doi.org/10.1007/bf00730955.

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13

Zou, Youchun, Chao Xiong, Junhui Yin, Huiyong Deng, Kaibo Cui y Sa Zhang. "Experimental and Modeling Studies of Stress Wave Propagation and Energy Dissipation Mechanism in Layered Composite Structures". Shock and Vibration 2021 (28 de julio de 2021): 1–13. http://dx.doi.org/10.1155/2021/9912709.

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Four composite structures (SiC/UHMWPE/TC4, SiC/TC4/UHMWPE, SiC/UHMWPE/MR/TC4, and SiC/TC4/MR/UHMWPE) were prepared using silicon carbide (SiC) ceramics, ultrahigh molecular weight polyethylene (UHMWPE), titanium alloy (TC4), and metal rubber (MR). The transmitted waves, failure forms, stress wave propagations, and energy dissipations of the composite structures were studied through Split Hopkinson Pressure Bar (SHPB) tests and numerical simulations. The results show that MR in composite structures can delay, attenuate, and smooth the stress wave, thereby reducing SiC damage. UHMWPE on the back of SiC provides cushioning for SiC, while TC4 on the back of SiC aggravates the damage of SiC. The composite structures with MR mainly dissipate the impact energy by reflecting energy, and the energy dissipation performance is better than that of composite structures without MR. A comprehensive comparison of transmitted waves, damage forms, stress wave propagations, and energy dissipations of the four composite structures shows that SiC/UHMWPE/MR/TC4 structure has the best impact resistance. Increasing the thickness of MR in the composite structures can improve the impact resistance, but there are also stress concentration and interface tensile stress.

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14

Romashchenko, V. A., Z. G. Alpaidze y I. S. Dyachenko. "Stress waves in the coupling zones of composite shells of revolution". Strength of Materials 21, n.º 10 (octubre de 1989): 1360–64. http://dx.doi.org/10.1007/bf01529266.

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15

Shi, Wei y Li Xia Ma. "Scattering of SH Wave on Periodic Cracks in an Infinite Plane of Piezoelectric/Piezomagnic Composite Materials". Applied Mechanics and Materials 166-169 (mayo de 2012): 3364–68. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.3364.

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In this paper, the scattering problems of SH waves on periodic cracks in an infinite of piezoelectric/piezomagnic composite materials bonded to an infinite of homogeneous piezoelectric materials is investigated, the Fourier transform techniques are used to reduce the problem to the solution of Hilbert singular integral equation, the latter is solved by Lobotto-Chebyshev and Gauss integral equation, at last, numerical results showed the effect of the frequency of wave, sizes and so on upon the normalized stress intensity factor.

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16

Guz’, A. N. y N. A. Shulga. "Dynamics of Laminated and Fibrous Composites". Applied Mechanics Reviews 45, n.º 2 (1 de febrero de 1992): 35–60. http://dx.doi.org/10.1115/1.3119748.

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In the present review investigation results are presented on the elastic wave propagation in laminated and fibrous unidirectional composite materials modeled by the piecewise-homogeneous medium (the structural model). In contrast to continual theories, the model of such a type does not essentially impose additional restrictions (other than those postulated by solid deformable body mechanics) on frequencies and gradients of the spatial alteration of the wave processes investigated. However, it should be stressed that, within the framework of this approach, it is necessary to solve complicated boundary-value or initial-boundary-value problems, which considerably complicate investigations in this area. Currently, regularly laminated materials are most thoroughly investigated. A detailed, comprehensive analysis is given of bulk, surface, and normal waves. The rule of selection, choice of modes, is formulated for piecewise-inhomogeneous spectra, the structure of the pass bands zones for bulk, shear and longitudinal–transverse waves is described with its dependence of the relative thickness and mechanical properties of layers, and vibration modes on transmission zone boundaries are determined. The theory of Love- and Rayleigh-type surface waves is presented. These waves may propagate in regularly laminated composites at frequencies corresponding to the stop band zones of bulk waves. A highly significant influence of the correspondence of the set of frequency and other composition properties to the pass band or stop band zones for bulk waves in the reflecting materials is noted on the reflection character of shear and longitudinal–transverse plane waves. The existence of frequency intervals and several incidence angles in the cases of the complete internal wave reflection is shown. Penetration of surface disturbances deep into the regularly laminated materials was investigated on plane cylindrical and spherical interface surfaces of properties. The character of the displacements and the stress attenuation is essentially different for pass band and stop band zones of bulk longitudinal and transverse waves in the medium with plane boundaries. Results are also presented for thermoelastic, magnetoelastic and electroelastic (acoustoelectric) waves. The application of the superposition principle and the summation theorems for cylindrical functions for unidirectional fibrous materials with regular packing allows us to construct formal solutions both for doubly periodic media and for the separately situated row of elastic inclusions with periodic location. Solutions of such a type may be extended to smooth inclusions of noncircular cylindrical form. In all cases boundary value problems are reduced to infinite systems of algebraic equations with complex coefficients containing cylindrical functions. For the row of periodically located fibers, the informal character of solutions is shown, and infinite systems of equations are investigated. Specific quantitative results are also obtained. The diffraction of shear and longitudinal-transverse waves on solid and hollow fibers was analyzed. In the discrete frequency spectrum, the existence of resonance effects of the Wood-anomaly type is shown. For shear waves on separately located inclusion, the influence of the noncircular fiber form on the stress distribution was investigated. The prospects for development of wave theory are pointed out within the framework of the structural composite model.

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17

Pih, H., Q. Bi, Y. Y. Chen y P. Ye. "Dynamic stress-concentration effects on stress waves in composite models with different fiber-end geometries". Experimental Mechanics 25, n.º 3 (septiembre de 1985): 214–25. http://dx.doi.org/10.1007/bf02325090.

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18

RAHEEM, ABDUL y K. M. SUBBAYA. "A Review on Hybrid Composites used for Marine Propellers". Material Science Research India 18, n.º 1 (30 de abril de 2021): 01–06. http://dx.doi.org/10.13005/msri/180101.

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Parts and constructions performance in the marine environments are subjected to high stress a priori to the measures of wind and waves. This review involve about the hybrid composite fabrication from artificial fibers of polymer composite. Hybrid composite furnish combination of property such as tensile modulus, compressive and impact strength which cannot realized in composite materials. The materials used for marine propellers of a varying number of blades with the fixed and controllable pitch having different diameters and skew angles and type of propellers were reviewed. Structural simulation, erosion wear tests, cavitations, bend twist coupling analyses, CFD case studies, fluid simulation method reviewed in this paper. Glass fiber composites proved to be economical and its adaptable in economical point of view. Carbon fiber composite propellers have more advantages than others with little compromise. In current scenario hybrid composite have been established as highly efficient, structural materials, high performances and their use is rapidly increasing. The current paper outline the utilizing of hybrid composite material for marine propellers as their versatility in enhancing good results.

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19

Fang, Xue-Qian, Chao Hu y Wen-Hu Huang. "Scattering of elastic waves and dynamic stress in two-particle reinforced composite system". Mechanics of Materials 39, n.º 6 (junio de 2007): 538–47. http://dx.doi.org/10.1016/j.mechmat.2006.08.007.

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20

Wang, Li-Lih. "Stress Wave Propagation for Nonlinear Viscoelastic Polymeric Materials at High Strain Rates". Journal of Mechanics 19, n.º 1 (marzo de 2003): 177–83. http://dx.doi.org/10.1017/s1727719100004184.

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ABSTRACTWithout knowing the dynamic constitutive relation of materials under high strain rates, no wave propagation can be correctly analyzed. A Series of experimental and theoretical investigation at high strain rates revealed that the nonlinear viscoelastic behavior of polymers and the related composites are well described by the Zhu-Wang-Tang (ZWT) nonlinear viscoelastic constitutive equation. The impulsive reponse of ZWT materials consists of a rate independent nonlinear elastic response and a high frequency linear viscoelastic response. The dispersion and attenuation of nonlinear viscoelastic waves mainly depend on the effective nonlinearity and the high frequency relaxation time θ2. An “effective influence distance” or “effective influence time” is defined to characterize the wave propagation range where θ2 dominates the impact relaxation process.

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21

Chaudhary, Soniya, Sanjeev A. Sahu y Abhinav Singhal. "On secular equation of SH waves propagating in pre-stressed and rotating piezo-composite structure with imperfect interface". Journal of Intelligent Material Systems and Structures 29, n.º 10 (5 de marzo de 2018): 2223–35. http://dx.doi.org/10.1177/1045389x18758192.

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An analytical approach is adopted to investigate the SH waves in a composite structure consisting of initially stressed rotating piezoelectric layer and initially stressed substrate with rotation. The interface between the layer and the substrate is assumed to be imperfect. Two distinct types of imperfect interfaces (dielectrically weakly and highly conducting) are considered. Secular equations have been obtained for both electrically open and short cases with weakly and highly performing interface. Particular cases have been derived and matched with existing result. The characteristics of SH wave through the considered framework and their state of relying on different physical and geometrical parameters have been scrutinized based on their numerical results. The parallel simulated outcomes of disparate physical quantities, namely, phase velocity, group velocity, dispersive curves, initial stress, rotation and electromechanical coupling factor, and stress distribution of SH wave in the considered structure are investigated. The considered model may be useful in theoretical foundation and practical application for the development of piezoelectric sensors, structural health monitoring, and surface acoustic wave devices.

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22

Lee, Min Rae y Joon Hyun Lee. "Evaluation of Defect in Compostie Using Acousto-Ultrasonic Technique". Key Engineering Materials 326-328 (diciembre de 2006): 1267–70. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1267.

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This paper is focused on the capability of the Acousto-Ultrasonic (AU) technique and the non-contact technique to provide diagnostic information useful to detect defect in composite. An acousto-ultrasonics (AU) is to simulate stress wave that resemble acoustic emission waves but without disrupting the material. One launched inside the material sample, the wave are modified by stochastic processes like those that affect spontaneous acoustic emissions from internal sources during stressing, deformation, etc. Moreover, acousto-uloasonic waves are launched periodically at predetermined times and with predetermined reparation rates. A fiber reinforced composite materials should be inspected in fabrication process in order to enhance quality by prevent defects such as delamination and void. In conventional ultrasonic technique for the evaluation of FRP, the transducer should be contacted on FRP. Therefore, in this study, advanced conventional contacting method (AU) and non-contact technique using air-coupled transducer can make contact and noncontacting ultrasonic technique available in evaluation of FRP. This paper demonstrates first results using an acousto-ultrasonic technique.

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23

dos Santos, Auteliano Antunes, Leandro Bannwart Ambiel, Rafael Henrique Garcia y Tainá Gomes Rodovalho. "Stress analysis in carbon/epoxy composites using Lcr waves". Journal of Composite Materials 48, n.º 27 (27 de noviembre de 2013): 3425–34. http://dx.doi.org/10.1177/0021998313509866.

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24

Cui, Yu Qing, Zhong Wei Yin y Hu Lin Li. "Influence of tension in T300/epoxy prepreg winding process on the performance of the bearing composites". Journal of Reinforced Plastics and Composites 36, n.º 15 (13 de abril de 2017): 1099–115. http://dx.doi.org/10.1177/0731684417702750.

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In recent years, composite bearings are increasingly employed in marine and heavy load situations due to the specific properties of composites. However, for the tape winding composite bearings, the tension in process has not been studied in depth. In this study, a device was manufactured to apply tension to the process and the prepreg tape was T300/epoxy. Specimens with different tension values were selected for the experiment and the autoclave technology was applied to the curing process. Then, the appearance image and roundness of the bearing composites were acquired. Meanwhile, physical and mechanical properties of the specimen as well as the residual stress were measured. The experimental results show that the influence of tension in winding process on bearing composites is significant and the optimum tension can be defined. Subsequently, the article analyzes the function of the tension and it is concluded that the wrinkles and waves on the surface of the T300/epoxy bearing composites can be eliminated using proper method and the optimum tension should be determined through testing and experiment.

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25

Pavlopoulou, Sofia, Costas Soutis y Wieslaw Jerzy Staszewski. "Structural Health Monitoring of Composite Scarf Repairs with Guided Waves". Key Engineering Materials 518 (julio de 2012): 328–37. http://dx.doi.org/10.4028/www.scientific.net/kem.518.328.

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The interest in composite repair technologies has been recently increased following the wide applications of composite materials in aerospace industry. Bonded patch repair technologies provide an alternative to mechanically fastened repairs with significantly higher performance. Scarf repairs offer great advantages compared to external patch repairs since they provide higher stiffness by matching ply to ply the original structure and by reducing stress discontinuities in the repaired region. Ultrasonic guided waves have been extensively used for the health monitoring of complex structures due to their remarkable ability of defect recognition. The authors have previously investigated the extraction of the instantaneous characteristics of Lamb waves for the monitoring of an aluminium repaired structure, highlighting the potential use of such waves in the inspection of repaired structures [1]. In the current study, the behaviour of a scarf repair was monitored with guided ultrasonic waves excited by low profile, surface bonded piezoceramic transducers under longitudinal tensile loading. Appropriate damage indices were extracted and the results were correlated with images taken through a 3-Dimensional Digital Image Correlation (3-D DIC) technique. The correlation of the extracted features with the early stage damage is performed and conclusions about the recovered strength through the scarf repair are deduced. Finally the study compares results obtained from the on-line analysis and from off-line techniques such as ultrasonic C-scanning and X-ray radiography.

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Hayashi, T., R. Ugo y Y. Morimoto. "Experimental observation of stress waves propagating in laminated composites". Experimental Mechanics 26, n.º 2 (junio de 1986): 169–74. http://dx.doi.org/10.1007/bf02320011.

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27

Yu, Jiangong, Chuanzeng Zhang y Xiaoming Zhang. "Circumferential waves in pre-stressed functionally graded cylindrical curved plates". Science and Engineering of Composite Materials 21, n.º 1 (1 de enero de 2014): 87–97. http://dx.doi.org/10.1515/secm-2013-0042.

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AbstractInitial stress (pre-stress) in functionally graded material (FGM) structures is often inevitable because of the limitation of available manufacturing technology. On the basis of the “mechanics of incremental deformations”, the circumferential wave characteristics in FGM cylindrical curved plates under uniform initial stresses in the radial and axial directions are investigated. The Legendre polynomial series method is used to solve the coupled wave equations with variable coefficients. Through numerical examples, the convergence of the polynomial method is discussed. The influences of the initial stresses on the circumferential Lamb-like and the circumferential SH waves are investigated, respectively. Numerical results show that they are quite distinct. Moreover, the influences of the initial stress in the axial direction are very different from those in the radial direction, both on the dispersion curves and on the displacement and stress distributions.

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28

Kumar, Rajneesh y Geeta Partap. "Wave Propagation in Microstretch Thermoelastic Plate Bordered with Layers of Inviscid Liquid". Multidiscipline Modeling in Materials and Structures 5, n.º 2 (1 de febrero de 2009): 171–84. http://dx.doi.org/10.1163/157361109787959912.

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The propagation of free vibrations in microstretch thermoelastic homogeneous isotropic, thermally conducting plate bordered with layers of inviscid liquid on both sides subjected to stress free thermally insulated and isothermal conditions is investigated in the context of Lord and Shulman (L‐S) and Green and Lindsay (G‐L) theories of thermoelasticity. The secular equations for symmetric and skewsymmetric wave mode propagation are derived. The regions of secular equations are obtained and short wavelength waves of the secular equations are also discussed. At short wavelength limits, the secular equations reduce to Rayleigh surface wave frequency equations. Finally, the numerical solution is carried out for magnesium crystal composite material plate bordered with water. The dispersion curves for symmetric and skew‐symmetric wave modes are computed numerically and presented graphically.

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29

Sun, Baozhong y Bohong Gu. "Frequency Analysis of Stress Waves in Testing 3-D Angle-interlock Woven Composite at High Strain Rates". Journal of Composite Materials 41, n.º 24 (diciembre de 2007): 2915–38. http://dx.doi.org/10.1177/0021998307082181.

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30

He, Zhijie, Meng Wang, Kang Zhao, Hong Su, Zekan He y Haijun Xuan. "Research on Explosive Separation of Carbon Fiber Composite Weave Plate". Shock and Vibration 2021 (19 de julio de 2021): 1–11. http://dx.doi.org/10.1155/2021/6633595.

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By using the C-shaped metal lead shell and copper shell to wrap the detonating cord, the restraint of the explosion energy is improved, and the simple charge structure is used to achieve the purpose of effectively separating the carbon fiber composite woven plate in a limited and small space. The commercial software AUTODYN was used for numerical simulation, The monitoring points of stress, velocity, and specific internal energy were set up, combined with Tsai-Wu tensor strength criterion, the plate failure and the process of shell metal reflecting and absorbing energy when the plate was separated under the shell constraint were observed, respectively. Through further analysis of the experimental phenomena and calculated data, it is concluded that the main reason for the fracture failure of the plate is the opposing compression of the shock waves on both sides of the plate, and the layer cracks are caused by the tension of the stress wave in the later stage. The charge structure of the detonating cord wrapped by the metal shell can effectively use its inertia to restrain the explosion energy and improve the separation ability during the process of explosively separating the carbon fiber composite woven plate.

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31

Rhee, Sang Ho, Jeong Ki Lee y Jung Ju Lee. "The Group Velocity Change in the Unidirectional Composite Materials". Key Engineering Materials 353-358 (septiembre de 2007): 1584–86. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.1584.

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The group velocity of the S0 mode of a Lamb wave under the first cut-off frequency is measured during the tensile loading for the unidirectional composite materials. The group velocity of the S0 mode has the characteristic of increasing with the strain. The propagation velocity of a wave is generally proportional to the square root of the ratio of the modulus to the density. The elastic modulus is considered as a constant as the stress linearly increases with the strain. The increase of the group velocity with the strain is caused by a decrease in the density. It is proposed that the measurement of the group velocity of the S0 mode is useful for making an evaluation of the tensile strain and of any degradation in the unidirectional composite materials.

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32

Zou, Youchun, Chao Xiong, Junhui Yin, Kaibo Cui, Huiyong Deng, Xiujie Zhu y Shijun Song. "Research on Dynamic Cumulative Damage Effect of Metal Rubber and Stress Wave Propagation Characteristics of Layered Composite Structure". Science of Advanced Materials 13, n.º 5 (1 de mayo de 2021): 981–90. http://dx.doi.org/10.1166/sam.2021.3997.

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The development of protective materials and structures is of great significance for improving the impact resistance, penetration resistance and spalling resistance of military equipment. At present, the layered composite structure has been widely used due to its good protective performance. In this paper, a special elastic porous material-metal rubber (MR) with excellent cushioning and damping properties was used to prepare high-performance layered composite structures. To begin with, the dynamic mechanical response and the dynamic cumulative damage effect of MR were studied through Split-Hopkinson Pressure Bar (SHPB) tests. Then, the failure form and stress wave propagation characteristics of the layered composite structures were investigated through SHPB tests and finite element method. The results show that repeated impacts can enhance the compactness of MR, thereby increasing the ultimate bearing capacity and energy absorption capacity, which is beneficial for MR to resist repeated impacts. The MR in composite structures can reduce ceramic damage, attenuate stress wave and smooth stress distribution. The titanium alloy on the back of the ceramic will aggravate the damage of the ceramic, and ultra-high molecular weight polyethylene on the back of the ceramic provides cushioning for the ceramic. Therefore, the impact resistance of the composite structure can be improved by adding MR and the reasonable arrangement of materials, and the SiC/UHMWPE/MR/TC4 composite structure has relatively reasonable stress distribution and better protection performance.

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33

Cao, Xiaoshan, Zhen Qu, Junping Shi y Yan Ru. "Lamb Waves in a Functionally Graded Composite Plate with Nonintegral Power Function Volume Fractions". Advances in Materials Science and Engineering 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/137913.

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An analytical modelling is carried out to determine the Lamb wave’s propagation behavior in a thermal stress relaxation type functionally graded material (FGM) plate, which is a composite of two kinds of materials. The mechanical parameters depend on the volume fractions, which are nonintegral power functions, and the gradient coefficient is the power value. Based on the theory of elastodynamics, differential equations with variable coefficients are established. We employ variable substitution for theoretical derivations to solve the ordinary differential equations with variable coefficients using the Taylor series. The numerical results reveal that the dispersion properties in some regions are changed by the graded property, the phase velocity varies in a nonlinear manner with the gradient coefficient, nondispersion frequency exists in the first mode, and the set of cutoff frequencies is a union of two series of approximate arithmetic progressions. These results provide theoretical guidance not only for the experimental measurement of material properties but also for their nondestructive testing.

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34

Matikas, Theodore E. "Characterization of Interphase Environmental Degradation at Elevated Temperature of Fibre-Reinforced Titanium Matrix Composites". Advanced Composites Letters 16, n.º 6 (noviembre de 2007): 096369350701600. http://dx.doi.org/10.1177/096369350701600603.

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Fibre reinforced metallic composite materials are being considered for a number of applications because of their attractive mechanical properties as compared to monolithic metallic alloys. An engineered interphase, including the bond strength between the composite's constituents, contributes to a large extent to the improvement of strength and stiffness properties of this class of materials. However, in high temperature applications, where combination of cyclic loading with environmental effects is expected, consideration should be given to interphase degradation, especially in the vicinity of stress risers, such as notches and holes. The applicability of damage tolerance analysis in structural components made of titanium matrix composite materials designed to operate under high temperature environments would depend on the availability of adequate characterization methods for the evaluation of interfacial degradation. The objective of this paper is to provide a basic understanding of interfacial degradation mechanisms due to oxidation in environmentally exposed titanium-based composites subjected to cyclic stresses. A non-destructive method has been developed enabling high-resolution monitoring of interfacial damage initiation and accumulation as well as surface/subsurface cracking behaviour during interrupted fatigue tests. This nondestructive technique is based on surface acoustic wave propagation in the composites and can detect minute changes in elastic properties of the interfacial region due to elevated temperatures as well as oxygen effects.

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CHOI, JUNG-HUN, MIN-SUNG KANG, JAE-MEAN KOO, CHANG-SUNG SEOK y HYUNG-ICK KIM. "FATIGUE CRACK PROPAGATION BEHAVIOR ACCORDING TOFIBER ARRAYING DIRECTION FOR LOAD DIRECTION INWOVEN CFRP COMPOSITE". International Journal of Modern Physics B 24, n.º 15n16 (30 de junio de 2010): 2615–20. http://dx.doi.org/10.1142/s0217979210065350.

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The fatigue crack propagation of CFRP (carbon fiber reinforced composite material) laminates is of current interest, particularly with regard to their durability under fatigue loading. Recently, carbon fiber reinforced composite materials (Woven fabric) are widely used in various fields of engineering because of its advanced properties. Then, many researchers have studied woven fabric CFRP materials but fatigue crack propagation behaviors for composites have not been still standardized . It shows the different crack propagation behavior according to load and fiber direction. Therefore, there is a need to consider fatigue crack propagation behavior in conformity with fiber arraying direction to load direction at designing structure using woven CFRP materials. In this study, therefore, the fatigue crack propagation for plain woven CFRP composite materials was investigated under two different fiber array direction (fiber arraying direction to load : 0°, 45°). Fatigue crack propagation tests of the woven CFRP composite were conducted under sinusoidal wave-form with stress ratios of 0.3 at a frequency of 10Hz, respectively. As a result of test, fatigue crack propagation rates (da/dN) were plotted against the stress-intensity factor amplitude (ΔK) and other factor. Also we compared ΔK with other factor that considering in-plain anisotropy. All of tests of fatigue crack propagation were carried out under mode I opening loading by using compact tension specimens.

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36

Nayfeh, A. H. y T. W. Taylor. "Dynamic Distribution of Displacement and Stress Considerations in the Ultrasonic Immersion Nondestructive Evaluation of Multilayered Plates". Journal of Engineering Materials and Technology 112, n.º 3 (1 de julio de 1990): 260–65. http://dx.doi.org/10.1115/1.2903320.

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A unified theoretical treatment is presented for the calculation of displacements and stresses within multilayered media subjected to incident ultrasonic waves. The wave is supposed to be incident from water, at an arbitrary angle, upon a plate consisting of an arbitrary number of different isotropic material layers. In the first part of the analysis displacements and stresses are determined as functions of position within the plate while all layer interfaces are assumed to be rigidly bonded. A smooth interface is subsequently introduced to simulate debonding of two material layers. The composite plate is assumed to be bounded at the bottom by either a free surface, a fluid half-space or an elastic solid half-space. A byproduct of the analysis is the derivation of the reflection and transmission coefficients for the systems. Extensive numerical results are given in order to delineate the influence of the plate material orderings, layer thicknesses and interfacial conditions on the displacements and stresses within the plate. The model developed here will be of value in material characterization and in the nondestructive evaluation of advanced material applications.

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37

OU, Z. Y. y D. W. LEE. "EFFECTS OF INTERFACE ENERGY ON MULTIPLE SCATTERING OF PLANE COMPRESSIONAL WAVES BY TWO CYLINDRICAL FIBERS". International Journal of Applied Mechanics 04, n.º 04 (diciembre de 2012): 1250040. http://dx.doi.org/10.1142/s1758825112500408.

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The multiple scattering of plane compressional waves by two cylindrical fibers with interface effects is investigated. Based on surface elasticity theory, the wave fields in a nanoscale solid medium can be obtained by applying the eigenfunction expansion method and the Graf's addition theorem. Our results indicate that surface energy significantly affects the diffraction of elastic waves, as the radii of the fibers approach nanometers. The dynamic stress concentration factors at the interfaces between the fibers and the matrix under incident plane compressional waves at different frequencies are examined to determine the effects of surface energy, properties of inhomogeneous materials, and the interaction between fibers in multiple scattering phenomena. These results are helpful in understanding the dynamic mechanical properties of nanocomposites, and the proposed method for investigating the multiple scattering of plane compressional waves can be extended to the case of fiber-reinforced composites.

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38

Qian, Z., F. Jin, K. Kishimoto y Z. Wang. "Effect of initial stress on the propagation behavior of SH-waves in multilayered piezoelectric composite structures". Sensors and Actuators A: Physical 112, n.º 2-3 (mayo de 2004): 368–75. http://dx.doi.org/10.1016/j.sna.2004.02.004.

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39

Jasiński, Radosław. "Identification of Stress States in Compressed Masonry Walls Using a Non-Destructive Technique (NDT)". Materials 13, n.º 12 (25 de junio de 2020): 2852. http://dx.doi.org/10.3390/ma13122852.

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The structure safety can be assessed, but only indirectly, by identifying material properties, geometry of structures, and values of loads. The complete and comprehensive assessment can be done only after determining internal forces acting inside structures. Ultrasonic extensometry using an acoustoelastic effect (AE) is among the most common non-destructive techniques (NDT) of determining true stresses in structures. Theoretical bases of the method were described in the mid 20th century. They were founded on the correlation between ultrasonic waves and the value and direction of stresses. This method is commonly used to determine stresses mainly in homogeneous materials without any inherent internal defects. This method is rarely applied to porous or composite materials, such as concrete or rock due to a high dispersion of results. Autoclaved aerated concrete (AAC), characterized by high homogeneity and porosity, is the popular material in the construction sector, used to produce masonry units. The discussed tests involved the acoustoelastic effect to determine stresses in the masonry wall made of AAC. This paper presents a widely theoretical background for the AE method, and then describes the author’s own research on AAC divided into two stages. At first, the empirical relationships between compressive stress and velocity of longitudinal ultrasonic wave, including humidity, were determined. In stage II, nine masonry walls were tested in axial compression. Mean compressive stresses in the masonry wall determined with the proposed method were found to produce a satisfactory confidence level up to ca. 50% of failure stresses. Results were significantly understated for stresses of the order of 75% of failure stresses.

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40

LAVERTY, RICHARD R. y GEORGE A. GAZONAS. "AN IMPROVEMENT TO THE FOURIER SERIES METHOD FOR INVERSION OF LAPLACE TRANSFORMS APPLIED TO ELASTIC AND VISCOELASTIC WAVES". International Journal of Computational Methods 03, n.º 01 (marzo de 2006): 57–69. http://dx.doi.org/10.1142/s0219876206000849.

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A parametric study of composite strips leads to systems of partial differential equations, coupled through interface conditions, that are naturally solved in Laplace transform space. Because of the complexity of the solutions in transform space and the potential variations due to geometry and materials, a systematic approach to inversion is necessarily numerical. The Dubner-Abate-Crump (DAC) algorithm is the standard in such problems and is implemented. The presence of discontinuous wavefronts in the problems considered leads to Gibbs phenomenon; which, in turn, overestimates the values of maximum stress. These errors are mitigated by use of Lanczos' σ-factors, which combine naturally with the DAC algorithm.

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41

Willberry, James Owen y Mayorkinos Papaelias. "Structural Health Monitoring Using Fibre Optic Acoustic Emission Sensors". Sensors 20, n.º 21 (8 de noviembre de 2020): 6369. http://dx.doi.org/10.3390/s20216369.

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Acoustic emission (AE) is widely used for condition monitoring of critical components and structures. Conventional AE techniques employ wideband or resonant piezoelectric sensors to detect elastic stress waves propagating through various types of structural materials, including composites during damage evolution. Recent developments in fibre optic acoustic emission sensors (FOAES) have enabled new ways of detecting and monitoring damage evolution using AE. An optical fibre consists of a core with a high refractive index and a surrounding cladding. The buffer layer and outer jacket both act as protective polymer layers. Glass optical fibres can be used for manufacturing AE sensors of sufficiently small size to enable their embedding into fibre-reinforced polymer composite materials. The embedding process protects the FOAES against environmental stresses prolonging operational lifetime. The immunity of FOAES to electromagnetic interference makes this type of sensor attractive for condition monitoring purposes across a wide range of challenging operational environments. This paper provides an exhaustive review of recent developments on FOAES including their fundamental operational principles and key industrial applications.

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42

Rocha, MG, DCRS de Oliveira, MAC Sinhoreti, JF Roulet y AB Correr. "The Combination of CQ-amine and TPO Increases the Polymerization Shrinkage Stress and Does Not Improve the Depth of Cure of Bulk-fill Composites". Operative Dentistry 44, n.º 5 (1 de septiembre de 2019): 499–509. http://dx.doi.org/10.2341/18-234-l.

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SUMMARY Objectives: To evaluate the effect of combining camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) on the depth of cure and polymerization shrinkage stress of bulk-fill composites. Methods and Materials: Experimental bulk-fill composites were produced containing equal molar concentrations of either CQ-amine or CQ-amine/TPO. The degree of in-depth conversion through each millimeter of a 4-mm-thick bulk-fill increment was evaluated by Fourier transform near-infrared microspectroscopy using a central longitudinal cross section of the increment of each bulk-fill composite (n=3). Light-transmittance of the multi-wave light-emitting diode (LED) emittance used for photoactivation (Bluephase G2, Ivoclar Vivadent) was recorded through every millimeter of each bulk-fill composite using spectrophotometry. The volumetric shrinkage and polymerization shrinkage stress were assessed using a mercury dilatometer and the Bioman, respectively. The flexural modulus was also assessed by a three-point bend test as a complementary test. Data were analyzed according to the different experimental designs (α=0.05 and β=0.2). Results: Up to 1 mm in depth, adding TPO to CQ-based bulk-fill composites increased the degree of conversion, but beyond 1 mm no differences were found. The light-transmittance of either wavelengths emitted from the multi-wave LED (blue or violet) through the bulk-fill composites were only different up to 1 mm in depth, regardless of the photoinitiator system. Adding TPO to CQ-based bulk-fill composites did not affect volumetric shrinkage but did increase the flexural modulus and polymerization shrinkage stress. Conclusion: Adding TPO to CQ-based bulk-fill composites did not increase the depth of cure. However, it did increase the degree of conversion on the top of the restoration, increasing the polymerization shrinkage stress.

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43

Majzoobi, G. H., D. C. Barton y M. Ramezani. "Stress wave effects in the Flying Wedge high strain rate tensile testing device". Journal of Strain Analysis for Engineering Design 42, n.º 7 (1 de octubre de 2007): 507–16. http://dx.doi.org/10.1243/03093247jsa289.

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Stress wave effects in the high-rate tensile testing apparatus known as the ‘Flying Wedge’ have been investigated using both experimental and numerical approaches. The experiments were conducted on R2000 glass/epoxy composites and iron specimens at strain rates up to 103/s. Numerical simulations were carried out using the LS-DYNA hydro code. Both the numerical and the experimental results showed that the results for small and low-strength specimens were significantly affected by the stress waves that propagate through the parts of the testing machine following the impact. The time period of the resulting load oscillations was found to be similar to that calculated from one-dimensional stress wave theory for different load paths in the apparatus. Therefore, it is concluded that stress wave effects play a dominant role in the Flying Wedge for small and low-strength specimens and consequently this machine is not a suitable choice for dynamic testing of such specimens.

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44

Li, Hong Liang y Hong Li. "Interaction of Multiple Circular Inclusions and a Linear Crack by SH-Wave". Key Engineering Materials 452-453 (noviembre de 2010): 677–80. http://dx.doi.org/10.4028/www.scientific.net/kem.452-453.677.

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Multiple circular inclusions exists widely in natural media, engineering materials and modern municipal construction, and defects are usually found around the inclusions. When composite material with multiple circular inclusions and a crack is impacted by dynamic load, the scattering field will be produced. The problem of scattering of SH waves by multiple circular inclusions and a linear crack is one of the important and interesting questions in mechanical engineering and civil engineering for the latest decade. It is hard to obtain analytic solutions except for several simple conditions. In this paper, the method of Green’s function is used to investigate the problem of dynamic stress concentration of multiple circular inclusions and a linear crack for incident SH wave. The train of thoughts for this problem is that: Firstly, a Green’s function is constructed for the problem, which is a fundamental solution of displacement field for an elastic space possessing multiple circular inclusions while bearing out-of-plane harmonic line source force at any point: Secondly, in terms of the solution of SH-wave’s scattering by an elastic space with multiple circular inclusions, anti-plane stresses which are the same in quantity but opposite in direction to those mentioned before, are loaded at the region where the crack is in existent actually; Finally, the expressions of the displacement and stress are given when multiple circular inclusions and a linear crack exist at the same time. Then, by using the expression, an example is provided to show the effect of multiple circular inclusions and crack on the dynamic stress concentration.

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45

Li, Yi, Zhen Kai Wan y Jia Lu Li. "Research on Acoustic Emission Signal of Three Dimensional Braided Composite Material". Applied Mechanics and Materials 48-49 (febrero de 2011): 1395–400. http://dx.doi.org/10.4028/www.scientific.net/amm.48-49.1395.

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This paper discusses the application and experimental method of acoustic emission for the three-dimensional (3D) braided composite material under flexural testing. It describes the feature of acoustic emission when applied to three-dimensional braided composite material under flexural testing. In order to know the materials damage position precisely, it is very important to collect the signal of acoustic emission source. The results of flexural experiment show that it is precise on the research of acoustic emission source location by the method of wave form analysis .During the collecting signal of acoustic emission , it is compared between parameter analysis and wave form analysis. According to the attenution degree of signal, it is selected signal of acoustic emission source exactly. It is the method to extract the precise acoustic emission signal by the different algorithm of wavelet analysis. We know that humans have been using materials by testing activities support, these tests have developed several centuries. From the traditional rough test to support materials and materials used in all aspects of science and technology, modern, scientific program, at present, there are mutual dependencies between the progress of scientific knowledge and the development of test methods. The 3D braided composite material is a kind of complex structure. Because of the many components and weaving material preparation process characteristic, material mechanics behavior is very complicated. It is characteristics of the 3D braided composite material, that the application on composites is widely more and more. The 3d braided composites have been used widely in aerospace, aviation, transportation, chemical, sports, medical care and other fields, so it is extremely vital significance for research on mechanics performance analysis of 3D braided composite material. Current studies of damage fracture behavior of composite materials are used in homogeneous materials research methods, namely the mechanical test and microscopic observation, but the research cannot distinguish and identify different damage fracture source, due to the combination of mechanical test parameters of the complex fracture micro-mechanism not sensitive. Microscopic observation is in fact observation later, local fracture surface morphology research, so can not observe the interaction of numerous fracture source and micro behavior, and can not study in the character of fracture source of composite materials, therefore the source faults already can not adapt to the traditional methods of composite material damage fracture process. From external or internal force effect material and structure produced deformation or fracture with elastic wave form, the strain energy release phenomenon called acoustic emission or stress wave [1]. Acoustic emission testing method is a kind of material internal defects or potential defects in the dynamic changes in movement, the damage detection method is real-time monitoring and can reflect the characteristics of acoustic emission sources in the load of the dynamic response. The AE information can directly reflect defects and changes [2, 3].

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46

Zhang, Wen Qun, Xin Yue Wu y Wen Cao. "Analysis of Piezoelectric Acoustic Sensor Based on Negative Impedance with FEM in Composite Materials". Advanced Materials Research 321 (agosto de 2011): 109–12. http://dx.doi.org/10.4028/www.scientific.net/amr.321.109.

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Piezoelectric acoustic sensor with negative impedance matching circuit is put forward to enhance its sensitivity at low frequencies. The multi-physics problem coupled with sound wave equations, structure stress-strain equations, piezoelectric constitutive equations and electric ordinary equations is analyzed with FEM in detail. Frequency response characteristics are simulated when shunted with negative-capacitance, resistance in series. Sensitivity is obtained from 1kHz to 5kHz. When used proper electrical elements, the sensitivity of the piezoelectric sensor can even exceed that of no matching circuit over 2 factors in broad band.

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47

Antypas, I. R., Amer Karnoub y A. G. Dyachenkо. "Influence of wave effect on fiber stress limit under tensile tests of composite material". Vestnik of Don State Technical University 19, n.º 4 (3 de enero de 2020): 310–16. http://dx.doi.org/10.23947/1992-5980-2019-19-4-310-316.

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Introduction. The response of composite materials to the impact of a certain kind of load is difficult to predict, therefore, research in this area has often been neglected. The work objective was to study the influence of the wave effect on the tensile strength of polymer composites of a fibrous structure.Materials and Methods. In the tests, samples of multilayer materials of various thicknesses with continuous, long and short fibers that form a fabric, as well as a layered structure, were used. The number of layers corresponds to the resistance to the applied loads. Fibers of glass, carbon, kevlar, or their combinations were used. Isotropic materials – epoxide, polyester and vinyl ether – were used as binders.Research Results. The tensile test results of homogeneous samples and samples of fibrous structure are obtained. In this case, the values of fiber angle varied. The stability of their intercomparison test results is established. The dependence of the maximum tensile stresses σmax, MPa, (on the vertical axis) on the fiber angle θmax is obtained. These stresses for a fibreless material amounted to 250 MPa. Normal and tangential stresses acting perpendicular to the fibers, as well as shear stresses of the layered material, are calculated. As follows from the analysis of the dependences for the significant tensile stresses and from the study on refraction in the section of the sample damage, it was established that the shear stress τ???????????????? was the cause of the fracture. Using an equation providing the compensation for the angle of inclination θ = 45, it was determined that the shear stress of the polyester is τху = 35 MPa. This was the stress that caused subsequently the destruction of the samples.Discussion and Conclusions. The tensile stresses of the composite material decrease with increasing the fiber angle in certain areas. The destruction of all fiber samples occurred when the shear stress reached a value approximately equal to the shear stress at which the destruction of samples made only from a binder material happened. When the specimen broke, the fracture mode had the form similar to the shear failure; besides, at the moment of fracture, the object having a rectangular shape, being deformed at an angle, took the form of a parallelogram.

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48

Kushvaha, Vinod, S. Anand Kumar, Priyanka Madhushri y Aanchna Sharma. "Artificial neural network technique to predict dynamic fracture of particulate composite". Journal of Composite Materials 54, n.º 22 (8 de marzo de 2020): 3099–108. http://dx.doi.org/10.1177/0021998320911418.

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In this paper, the artificial neural network technique using a multi-layer perceptron feed forward scheme was used to model and predict the mode-I fracture behaviour of particulate polymer composites when subjected to impact loading. A neural network consisting of three-layers was employed to develop the network. Artificial neural network was constructed using six input parameters such as shear wave speed ( CS), density ( D), elastic modulus ( Ed), longitudinal wave speed ( CL), volume fraction ( Vf) and time ( t). The influence of input parameters on the output stress intensity factor and crack-initiation fracture toughness were found to be in the order of t > CS > D > Ed > CL > Vf. The degree of accuracy of prediction was 92.7% for stress intensity factor. In this regard, artificial neural network can be used in the modelling and prediction of fracture behaviour of particulate polymer composites under impact loading.

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49

Shevtsova, Maria, Evgenia Kirillova, Eugeny Rozhkov, Valery Chebanenko, Sergey Shevtsov, Jiing Kae Wu y Shun Hsyung Chang. "Piezoelectric Based Lamb Waves Generation and Propagation in Orthotropic CFRP Plates: II. Influence of Interfacial Stress Distribution". Materials Science Forum 962 (julio de 2019): 227–35. http://dx.doi.org/10.4028/www.scientific.net/msf.962.227.

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This paper investigates the Lamb wave generation by the surface bonded circular piezoelectric (PZT) actuator and wave propagation within the orthotropic Carbon Fiber Reinforced Plastic (CFRP) plate considering the anisotropy of the elastic and damping properties of the materials; existence of the adhesive layer; and dependence of the interfacial stress distribution on the surface between host plate and actuator, on the anisotropy of the plate material, and on the excited frequency, wavelength and plate thickness. This part of our investigation includes FE based study of the shear stress distribution on the interface between circular PZT actuator and surface of orthotropic CFRP plate, and its dependence on the excited wavelength and plate thickness. The anisotropic elastic and damping properties of the plate material, which are used in the implemented finite element (FE) model, have been preliminary determined in the first part of our investigation. We compare the behavior of the wave generation, propagation and attenuation that are studied using this model with the similar dependencies obtained at the simulation of the non-dissipating plate excited by the periodical radially oriented force, which is distributed along the circumference bounding the actuator, i.e. 3D pin-force excitation case. The proposed results can be used at the design of SHM for the composite structures with the structural anisotropy and damping, and at making a reasonable choice of the frequency, type, dimensions and optimum placement of the actuators and sensors.

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50

Tsai, Y. M. "Symmetrical Propagation of a Central Crack in Orthotropic Material". Journal of Applied Mechanics 62, n.º 4 (1 de diciembre de 1995): 1047–52. http://dx.doi.org/10.1115/1.2896041.

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A central crack which propagates symmetrically in an orthotropic composite plate is investigated using the techniques of Fourier and Laplace transforms. The crack is located along one of the principal axes of the material. Complete contour integrations are carried out in the evaluation of the Laplace inversion integrals. For the crack tips running at a constant speed, exact expressions for the dynamic crack shape and the dynamic stress distribution with singularities in the crack plane are obtained in terms of anisotropic material constants and crack speed. The dynamic expressions are evaluated numerically by using graphite/epoxy and glass/ epoxy composites and an isotropic material as sample materials. The dynamic solution reduces to the static solution at zero crack speed. During crack propagation, the deviation between dynamic and static solutions is governed by dynamic correction factors which are nondimensional functions of the ratios among anisotropic material constants and the ratio of crack speed to shear-wave speed. Values of these dynamic factors are obtained for the sample composites at a large range of crack speed. The dynamic stress intensity factor vanishes at the corresponding Rayleigh wave speed.

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