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1
Phillips, John L. "Structural analysis and optimum design of geodesically stiffened composite panels". Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040802/.
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Anders, William S. "Structural acoustic analysis of shape memory alloy hybrid composite panels". Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-11012008-063243/.
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Pierce, Matthew Ryan. "Microvascular Heat Transfer Analysis in Carbon Fiber Composite Materials". University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1280944914.
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Kang, Paul J. (Paul Ji Hwan) 1974. "A technical and economic analysis of structural composite use in automotive body-in-white applications". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/34697.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering; and, (S.M.)--Massachusetts Institute of Technology, Technology and Policy Program, 1998.Science Library copy in pages.
Includes bibliographical references (leaves 163-170).
by Paul J. Kang.
S.M.
5
Hou, An. "Strength of composite lattice structures". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/12475.
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Singh, Mukti Nath. "Efficient reliability estimation approach for analysis and optimization of composite structures". Master's thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-11072002-103328.
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Stone, Daniel Paul. "The influence of ply orientation on the open-hole tension strength of composite laminates". Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Spring2008/d_stone_042208.pdf.
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Anghelescu, Mihnea S. "Thermal and Mechanical Analysis of Carbon Foam". View abstract, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3353337.
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Rantis, Theofanis D. "Probability-based stability analysis of a laminated composite plate under combined in-plane loads". Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07292009-090358/.
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Culler, Adam John. "Coupled Fluid-Thermal-Structural Modeling and Analysis of Hypersonic Flight Vehicle Structures". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1280930589.
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Kahle, Matthew Gilbert. "Partially restrained composite connections : design and analysis of a prototype structure". Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20830.
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Salehian, Armaghan. "Identifying the location of a sudden damage in composite laminates using wavelet approach". Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0711103-155908.
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Odi, A. R. A. "Bonded Repair of Composite Structures; A Finite Element Approach". Thesis, Department of Materials and Medical Sciences, 2009. http://hdl.handle.net/1826/3893.
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This thesis addresses the issues surrounding the application of the finite element
method to analyse composite structure repairs with an emphasis on aircraft
applications. A comprehensive literature survey has been carried out for this purpose
and the results are presented.
A preliminary study and a comparative study of different modelling approaches have
been completed. These studies aim to explore and identify the problems in modelling
repairso n simplec ompositep anelsw ith speciala ttention given to adhesivem odelling.
Three modelling approaches have been considered: Siener's model which is an
extension of the traditional plane strain 2D model used for adhesively bonded joints,
Bait's model which is a promising new approach and a full 3D model. These studies
have shown that these methods are complementary providing a different insight into
bonded repairs. They have also highlighted the need for a new modelling approach
which will provide an overall view of bonded repairs.
Improved modelling approachesh ave been developedf or externallyb onded patch and
flush repairs. These models enable the study of adhesive failure as well as composite
adherendf ailures.T hesea pproachesh aveb eena ppliedt o real repairs and the predicted
results compared to experimental data. Four case studies have been conducted:
external bonded patch repairs to composite plates, a scarf joint for bonded repairs, a
flat panel repaired with a scarfed patch and a repaired curved panel.
These case studies have shown that bonded repairs to composite structures can be
analyseds uccessfullyu sing PC-basedc ommercialf inite elementc odes.
14
Odi, A. Randolph A. "Bonded repair of composite structures : a finite element approach". Thesis, Cranfield University, 1998. http://dspace.lib.cranfield.ac.uk/handle/1826/3893.
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This thesis addresses the issues surrounding the application of the finite element method to analyse composite structure repairs with an emphasis on aircraft applications. A comprehensive literature survey has been carried out for this purpose and the results are presented. A preliminary study and a comparative study of different modelling approaches have been completed. These studies aim to explore and identify the problems in modelling repairso n simplec ompositep anelsw ith speciala ttention given to adhesivem odelling. Three modelling approaches have been considered: Siener's model which is an extension of the traditional plane strain 2D model used for adhesively bonded joints, Bait's model which is a promising new approach and a full 3D model. These studies have shown that these methods are complementary providing a different insight into bonded repairs. They have also highlighted the need for a new modelling approach which will provide an overall view of bonded repairs. Improved modelling approachesh ave been developedf or externallyb onded patch and flush repairs. These models enable the study of adhesive failure as well as composite adherendf ailures.T hesea pproachesh aveb eena ppliedt o real repairs and the predicted results compared to experimental data. Four case studies have been conducted: external bonded patch repairs to composite plates, a scarf joint for bonded repairs, a flat panel repaired with a scarfed patch and a repaired curved panel. These case studies have shown that bonded repairs to composite structures can be analyseds uccessfullyu sing PC-basedc ommercialf inite elementc odes.
15
Chandrashekhara, K. "Geometric and material nonlinear analysis of laminated composite plates and shells". Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/54739.
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An inelastic material model for laminated composite plates and shells is formulated and incorporated into a finite element model that accounts for both geometric nonlinearity and transverse shear stresses. The elasto-plastic material behavior is incorporated using the flow theory of plasticity. In particular, the modified version of Hill's initial yield criterion is used in which anisotropic parameters of plasticity are introduced with isotropic strain hardening. The shear deformation is accounted for using an extension of the Sanders shell theory and the geometric nonlinearity is considered in the sense of the von Karman strains. A doubly curved isoparametric rectangular element is used to model the shell equations. The layered element approach is adopted for the treatment of plastic behavior through the thickness. A wide range of numerical examples is presented for both static and dynamic analysis to demonstrate the validity and efficiency of the present approach. The results for combined nonlinearity are also presented. The results for isotropic results are in good agreement with those available in the literature. The variety of results presented here based on realistic material properties of more commonly used advanced laminated composite plates and shells should serve as references for future investigations.Ph. D.
16
REY, JOSE F. Q. "Obtenção e caracterização do Basub(2)Insub(2)Osub(5) puro e contendo Gd e Er como aditivos". reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11505.
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Made available in DSpace on 2014-10-09T12:52:38Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:02:24Z (GMT). No. of bitstreams: 0
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:01/14033-0
17
Geyer, Susanna Elizabeth. "Advanced low order orthotropic finite element formulations". Diss., Pretoria : [s.n.], 2001. http://upetd.up.ac.za/thesis/available/etd-03062006-114313/.
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Guan, Juan. "Investigations on natural silks using dynamic mechanical thermal analysis (DMTA)". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:c16d816c-84e3-4186-8d6d-45071b9a7067.
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This thesis examines the dynamic mechanical properties of natural silk fibres, mainly from silkworm species Bombyx mori (B. mori) and spider species Nephila edulis, using dynamic mechanical thermal analysis, DMTA. The aim is not only to provide novel data on mechanical properties of silk, but also to relate these properties to the structure and morphology of silk. A systematic approach is adopted to evaluate the effect of the three principal factors of stress, temperature and hydration on the properties and structure of silk. The methods developed in this work are then used to examine commercially important aspects of the ‘quality’ of silk. I show that the dynamic storage modulus of silks increases with loading stress in the deformation through yield to failure, whereas the conventional engineering tensile modulus decreases significantly post-yield. Analyses of the effects of temperature and thermal history show a number of important effects: (1) the loss peak at -60 °C is found to be associated the protein-water glass transition; (2) the increase in the dynamic storage modulus of native silks between temperature +25 and 100 °C is due simply to water loss; (3) a number of discrete loss peaks from +150 to +220°C are observed and attributed to the glass transition of different states of disordered structure with different intermolecular hydrogen bonding. Excess environmental humidity results in a lower effective glass transition temperature (Tg) for disordered silk fractions. Also, humidity-dynamic mechanical analysis on Nephila edulis spider dragline silks has shown that the glass transition induces a partial supercontraction, called Tg contraction. This new finding leads to the conclusion of two independent mechanisms for supercontraction in spider dragline silks. Study of three commercial B. mori cocoon silk grades and a variety of processed silks or artificial silks shows that lower grade and poorly processed silks display lower Tg values, and often have a greater loss tangent at Tg due to increased disorder. This suggests that processing contributes significantly to the differences in the structural order among natural or unnatural silks. More importantly, dynamic mechanical thermal analysis is proposed to be a potential tool for quality evaluation and control in silk production and processing. In summary, I demonstrate that DMTA is a valuable analytical tool for understanding the structure and properties of silk, and use a systematic approach to understand quantitatively the important mechanical properties of silk in terms of a generic structural framework in silk proteins.
19
Wang, Yeqing. "Modeling of lightning-induced thermal ablation damage in anisotropic composite materials and its application to wind turbine blades". Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2164.
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A primary motivation for this research comes from the need to improve the ability of polymer-matrix composites to withstand lightning strikes. In particular, we are concerned with lightning strike damage in composite wind turbine blades. The direct effects of lightning strike on polymer-matrix composites often include rapid temperature rise, melting or burning at the lightning attachment points, and mechanical damage due to lightning-induced magnetic force and acoustic shock wave. The lightning strike damage accumulation problem is essentially multiphysic. The lightning plasma channel discharges an electric current up to 200 kA, inducing a severe heat flux at the surface of the composite structure, as well as generating Joule heating through the composite structure. The resulting electro-thermo-mechanical response of the composite structure may include matrix degradation and decomposition, delamination, and fiber breakage and sublimation, thus leading to catastrophic failure.
The existing studies related to the lightning strike damage in composites ignored the lightning channel radius expansion during the initial lightning discharge and lacked adequate treatment of material phase transitions. These assumptions significantly simplify the mathematical treatment of the problem and affect the predictive capabilities of the models. Another common feature of these limited studies is that they all focused on carbon-fiber-reinforced polymer-matrix (CFRP) composites, which are electrically conductive.
In the present thesis, the thermal responses and thermal ablations in a non-conductive glass-fiber-reinforced polymer-matrix (GFRP) composite wind turbine blade and in a conductive CFRP composite wind turbine blade are studied, respectively. In the case of non-conductive GFRP composite wind turbine blade, prior to the thermal response and thermal ablation analysis, a finite element analysis is performed to calculate the electric field due to lightning stepped leader to estimate the dielectric breakdown of the non-conductive composite wind turbine blade. The estimation of dielectric breakdown is used to determine whether Joule heating needs to be included in the problem formulation. To predict the thermal response and thermal ablation in the composite structure due to lightning strike, a physics-based model describing surface interaction between the lightning channel and the composite structure has been developed. The model consists of: (i) spatial and temporal evolution of the lightning channel as a function of the electric current waveform; (ii) temporary and spatially non-uniform heat flux and current density (in the case of electrically conductive CFRP composite or if dielectric breakdown occurs in the case of non-conductive GFRP composite) generated at the composite structure; and (iii) nonlinear transient heat transfer problem formulation for layered anisotropic composites that includes the moving boundary of the expanding lightning channel and the phase transition moving boundary associated with instantaneous material removal due to sublimation. The model has been employed to investigate the thermal responses and thermal ablations in a GFRP composite laminated panel used in a Sandia 100-meter all-glass baseline wind turbine blade (SNL 100-00) and a typical CFRP composite laminated panel subjected to lightning strike. The temperature-dependent directional material properties for both the GFRP and CFRP composites have been determined in this thesis using a micromechanics approach based on the experimental data for fibers and resin. An integrated Matlab-ABAQUS numerical procedure features the aforementioned aspects (i), (ii), and (iii) of the developed model. The obtained results include the evolution of temperature fields in the composite laminated panel and the progressive shape change of the composite laminated panel due to thermal ablation. The predictions of thermal ablation in the CFRP composite laminated panel are validated by reported experimental results.
20
Kim, Joun S. "A Comparison Study of Composite Laminated Plates With Holes Under Tension". DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1895.
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A Comparison Study of Composite Laminated Plates with Holes under Tension
A study was conducted to quantify the accuracy of numerical approximations to deem sufficiency in validating structural composite design, thus minimizing, or even eliminating the need for experimental test. Error values for stress and strain were compared between Finite Element Analysis (FEA) and analytical (Classical Laminated Plate Theory), and FEA and experimental tensile test for two composite plate designs under tension: a cross-ply composite plate design of [(0/90)4]s, and a quasi-isotropic layup design of [02/+45/-45/902]s, each with a single, centered hole of 1/8” diameter, and 1/4" diameter (four sets total). The intent of adding variability to the ply sequences and hole configurations was to gauge the sensitivity and confidence of the FEA results and to study whether introducing enough variability would, indeed, produce greater discrepancies between numerical and experimental results, thus necessitating a physical test. A shell element numerical approximation method through ABAQUS was used for the FEA.
Mitsubishi Rayon Carbon Fiber and Composites (formerly Newport Composites) unidirectional pre-preg NCT301-2G150/108 was utilized for manufacturing—which was conducted and tested to conform to ASTM D3039/D3039M standards.
A global seed size of 0.020, or a node count on the order of magnitude of 30,000 nodes per substrate, was utilized for its sub-3% error with efficiency in run-time.
The average error rate for FEA strain from analytical strain at a point load of 1000lbf was 2%, while the FEA-to-experimental strains averaged an error of 4%; FEA-to-analytical and FEA-to-tensile test stress values at 1000lbf point load both averaged an error value of 6%. Suffice to say, many of these strain values were accurate up to ten-thousandths and hundred-thousandths of an in/in, and the larger stress/strain errors between FEA and test may have been attributed to the natural variables introduced from conducting a tensile test: strain gauge application methods, tolerance stacks from load cells and strain gauge readings.
Despite the variables, it was determined that numerical analysis could, indeed, replace experimental testing. It was observed through this thesis that a denser, more intricate mesh design could provide a greater level of accuracy for numerical solutions, which proves the notion that if lower error rates were necessitated, continued research with a more powerful processor should be able to provide the granularity and accuracy in output that would further minimize error rates between FEA and experimental. Additionally, design margins and factors of safety would generally cover the error rates expected from numerical analysis.
Future work may involve utilizing different types of pre-preg and further varied hole dimensions to better understand how the FEA correlates with analytical and tensile test results. Other load types, such as bending, may also provide insight into how these materials behave under loading, thus furthering the conversation of whether numerical approximations may one day replace testing all together.
21
Davis, Dan M. "Finite Element Modeling of Ballistic Impact on a Glass Fiber Composite Armor". DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/815.
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Finite Element Modeling of Ballistic Impact on a Glass Fiber Composite Armor
Dan Davis
Experiments measuring the ballistic performance of a commercially available fiberglass armor plate were used to guide the development of constitutive laws for a finite element model of the impact. The test samples are commercially available armor panels, made from E-glass fiber reinforced polyester rated to NIJ level III. Quasi-static tensile tests were used to establish material properties of the test panels. These properties were then used to create models in the explicit finite element code LSDYNA.
Ballistic impact testing of the panels was conducted using a compressed gas gun firing spherical steel projectiles oriented normal to the test panel surface. The V50 ballistic limit of these panels was found to be approximately 560 m/s. Tuning parameters in the finite element models were adjusted to match the experimentally measured penetration depths and ballistic limits. Models were created in LSDYNA by adjusting the available material library types 3 and 59 for the target, and material type 15 for the projectile. Type 3 models are isotropic, and resulted in shear punch-out type failures of the plate that poorly replicated the test results. Type 59 takes orthotropic properties into consideration, and can analyze delamination when used with solid elements. Results with model type 59 were significantly better than those using type 3, however, this model was found to vastly underestimate the impact resistance of the plate. With significant adjustments to the material properties in the type 59 model, the LSDYNA simulations were found to better replicate the experimentally observed response of the panels. However, these deformations are questionable since they required quite unrealistic adjustments to the material properties.
22
Rajagopal, Anurag. "Advancements in rotor blade cross-sectional analysis using the variational-asymptotic method". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51877.
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Rotor (helicopter/wind turbine) blades are typically slender structures that can be modeled as beams. Beam modeling, however, involves a substantial mathematical formulation that ultimately helps save computational costs. A beam theory for rotor blades must account for (i) initial twist and/or curvature, (ii) inclusion of composite materials, (iii) large displacements and rotations; and be capable of offering significant computational savings compared to a non-linear 3D FEA (Finite Element Analysis). The mathematical foundation of the current effort is the Variational Asymptotic Method (VAM), which is used to rigorously reduce the 3D problem into a 1D or beam problem, i.e., perform a cross-sectional analysis, without any ad hoc assumptions regarding the deformation. Since its inception, the VAM based cross-sectional analysis problem has been in a constant state of flux to expand its horizons and increase its potency; and this is precisely the target at which the objectives of this work are aimed. The problems addressed are the stress-strain-displacement recovery for spanwise non-uniform beams, analytical verification studies for the initial curvature effect, higher fidelity stress-strain-displacement recovery, oblique cross-sectional analysis, modeling of thin-walled beams considering the interaction of small parameters and the analysis of plates of variable thickness. The following are the chief conclusions that can be drawn from this work:
1. In accurately determining the stress, strain and displacement of a spanwise non-uniform beam, an analysis which accounts for the tilting of the normal and the subsequent modification of the stress-traction boundary conditions is required.
2. Asymptotic expansion of the metric tensor of the undeformed state and its powers are needed to capture the stiffnesses of curved beams in tune with elasticity theory. Further improvements in the stiffness matrix can be achieved by a partial transformation to the Generalized Timoshenko theory.
3. For the planar deformation of curved laminated strip-beams, closed-form analytical expressions can be generated for the stiffness matrix and recovery; further certain beam stiffnesses can be extracted not only by a direct 3D to 1D dimensional reduction, but a sequential dimensional reduction, the intermediate being a plate theory.
4. Evaluation of the second-order warping allows for a higher fidelity extraction of stress, strain and displacement with negligible additional computational costs.
5. The definition of a cross section has been expanded to include surfaces which need not be perpendicular to the reference line.
6. Analysis of thin-walled rotor blade segments using asymptotic methods should consider a small parameter associated with the wall thickness; further the analysis procedure can be initiated from a laminated shell theory instead of 3D.
7. Structural analysis of plates of variable thickness involves an 8×8 plate stiffness matrix and 3D recovery which explicitly depend on the parameters describing the thickness, in contrast to the simplistic and erroneous approach of replacing the thickness by its variation.
23
Liu, Albert Darien. "THE EFFECT OF SENSOR MASS, SENSOR LOCATION, AND DELAMINATION LOCATION OF DIFFERENT COMPOSITE STRUCTURES UNDER DYNAMIC LOADING". DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/917.
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This study investigated the effect of sensor mass, sensor location, and delamination location of different composite structures under dynamic loading. The study pertains to research of the use of accelerometers and dynamic response as a cost-effective and reliable method of structural health monitoring in composite structures. The composite structures in this research included carbon fiber plates, carbon fiber-foam sandwich panels, and carbon-fiber honeycomb sandwich panels. The composite structures were manufactured with the use of a Tetrahedron MTP-8 heat press. All work was conducted in the Cal Poly Aerospace Structures/Composites Laboratory. Initial delaminations were placed at several locations along the specimen, including the bending mode node line locations. The free vibration of the composite structure was forced through a harmonic horizontal vibration test using an Unholtz-Dickie shake system. A sinusoidal sweep input was considered for the test. The dynamic response of the composite test specimens were measured using piezoelectric accelerometers. Measurements were taken along horizontal and vertical locations on the surfaces of the composite structures. Square inch grids were marked on the surfaces to create a meshed grid system. Accelerometer measurements were taken at the center of the grids. The VIP Sensors 1011A piezoelectric accelerometer was used to measure vibration response. The measurements were then compared to response measurements taken from a PCB Piezotronics 353B04 single access accelerometer to determine the effects of sensor mass. Deviations in bending mode natural frequency and differences in mode shape amplitude became the criteria for evaluating the effect of sensor mass, sensor location, and delamination location. Changes in damping of the time response were also studied. The experimental results were compared to numerical models created using a finite element method. The experimental results and numerical values were shown to be in good agreement. The sensor mass greatly affected the accuracy and precision of vibration response measurements in the composites structures. The smaller weight and area of the VIP accelerometer helped to minimize the decrease in accuracy and precision due to sensor mass. The effect of sensor location was found to be coupled with the effect of sensor mass and the bending mode shape. The sensor location did not affect the vibration response measurements when the sensor mass was minimized. Off-center horizontal sensor placement showed the possibility of measuring vibration torsion modes. The effect of delamination changed the bending mode shape of the composite structure, which corresponded to a change in natural frequency. The greatest effect of the delamination was seen at the bending mode node lines, where the bending mode shape was most significantly affected. The effect of delamination was also dependent on the location of the delamination and the composite structure type. The results of this study provided considerations for future research of an active structural health monitoring system of composite structures using dynamic response measurements. The considerations included sensor mass reduction, sensor placement at constraints and bond areas and the presence of damping material.
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Lo, Patrick Kar-Leung. "Comparison of theory and experiment for flexural-torsional buckling of laminated composite columns". Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/50051.
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Vlasov’s one-dimensional structural theory for thin-walled open section bars was originally developed and used for metallic elements. The theory was recently extended to laminated bars fabricated from advanced composite materials. The purpose of this research is to provide a study and assessment of the extended theory. The focus is on flexural and torsional-flexural buckling of thin-walled, open section, laminated composite columns. Buckling loads are computed from the theory using a linear bifurcation analysis, and are compared to available experimental data. Also, a geometrically nonlinear beam column analysis by the finite element method is developed from the theory. Results from the nonlinear compression response analysis are compared to limited available test data. The merits of the theory and its implementation are discussed.Master of Science
incomplete_metadata
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Tilton, Gregory J. "Finite Element Modeling of Thermal Expansion in Polymer/ZrW2O8 Composites". University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1321465255.
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Swindeman, Michael James. "A Regularized Extended Finite Element Method for Modeling the Coupled Cracking and Delamination of Composite Materials". University of Dayton / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1324605778.
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Pérez, Galmés Magdalena. "Analysis and development of experimental characterization methodologies of mode II fracture toughness on CFRP bonded joints". Doctoral thesis, Universitat de Girona, 2018. http://hdl.handle.net/10803/664508.
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Adhesives have been shown to be an excellent solution for joining fibre reinforced polymer (FRP) components thanks to their capacity to redistribute loads, reduces stress concentrations and contribute to overall weight saving in the structure. The most relevant mechanical property in adhesive bonded joints design is the shear (mode II) fracture toughness of the adhesive.
The application of the existing mode II delamination standards to adhesive joints entails some major limitations that result in severe under/over estimations of the adhesive properties and, in many cases, can even prevent results from being obtained from tests.
The main objective of the present thesis is to develop robust tools for the determination of shear (mode II) facture toughness in adhesive joints. This includes studying data reduction methods as well as the test geometriesEls adhesius han demostrat ser una magnífica solució per unir components de polímers reforçats amb fibres (FRP) gràcies a la seva capacitat per redistribuir càrregues, reduir les concentracions de tensions i contribuir a l’estalvi general de pes en l’estructura. La propietat mecànica més rellevant en el disseny d’unions adhesives és la tenacitat a la fractura a tallant (mode II) de l’adhesiu. L’aplicació dels actuals assajos estandaritzats a les unions adhesives pot derivar en estimacions errònies, per sota o per sobre, de les propietats adhesives i, en molts casos, evitar que l’assaig es pugui realitzar satisfactòriament. L’objectiu principal d’aquesta tesi és el desenvolupament d’eines robustes per a la determinació de la tenacitat a la fractura a tallant (mode II) d’unions adhesives. S’estudia l’aplicabilitat dels mètodes d’assaig de deslaminació en mode II existents a les unions adhesives estructurals. Això inclou l’estudi dels mètodes de reducció de dades i de les geometries d’assaig
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Kuprienko, Alexey. "Development of Physics-Based Model of Mash Seam Welding". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574255491050953.
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Guraydin, Alec D. "Analysis of Bimetallic Adhesion and Interfacial Toughness of Kinetic Metallization Coatings". DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/979.
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Due to their ability to confer enhanced surface properties without compromising the properties of the substrate, coatings have become ubiquitous in heavy industrial applications for corrosion, wear, and thermal protection, among others. Kinetic Metallization (KM), a solid-state impact consolidation and coating process, is well-suited for depositing industrial coatings due to its versatility, low substrate heat input, and low cost. The ability of KM coatings to adhere to the substrate is determined by the quality of the interface. The purpose of this study is to develop a model to predict the interfacial quality of KM coatings using known coating and substrate properties. Of the various contributions to adhesion of KM coatings, research suggests that the thermodynamic Work of Adhesion (WAD) is the most fundamental. It is useful to define interfacial quality in terms of the critical strain energy release rate (GC) at which coating delamination occurs. Studies show that GC for a given interface is related to WAD. This study attempts to develop a theoretical model for calculating WAD and understand the relationship between GC and WAD. For a bimetallic interface between two transition metals, WAD can be theoretically calculated using known electronic and physical properties of each metal: the molar volume, V, the surface energy, γ, and the enthalpy of alloy formation, ΔHinterface; ΔHinterface is a function of the molar volume, V, the work function, φ, and the electron density at the boundary of the Wigner-Seitz cell, nWS.WAD for Ni-Cu and Ni-Ti interfaces were 3.51 J/m2 and 4.55 J/m2, respectively. A modified Four-point bend testing technique was used to experimentally measure GC for Ni-Cu and Ni-Ti specimens produced by KM. These tests yielded mean GC values of 50.92 J/m2 and 132.68 J/m2 for Ni-Cu and Ni-Ti specimens, respectively. Plastic deformation and surface roughness are likely the main reasons for the large discrepancy between GC and WAD. At the 95% confidence level, the mean GC of the Ni-Ti interface is significantly higher than that of the Ni-Cu interface. Further testing is recommended to better understand the relationship between WAD and GC.
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Sakarya, Arzu. "Multidisciplinary Design Of An Unmanned Aerial Vehicle Wing". Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613606/index.pdf.
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In this thesis, the structural design, structural analysis and producibility analysis of an unmanned aerial vehicle wing were performed. Three different wing models, made of different materials, were designed. The wings were aluminum wing model and composite wing modelsmade of prepreg and wet lay-up. All wings have the same aerodynamic geometry and structural configuration under the same flight conditions. The structural designs of three wings were done by using Unigraphics NX. The finite element modeling of the wings were built by using MSC Patran package program. After the application of the loads on models, structural analyses were performed by MSC Nastran. Finally, the producibility analysis of prepreg wing model was conducted by using FiberSIM package program. The prepreg wing model was selected as optimum design with studies conducted in the study considering weight, producibility, cruise and gust stress and displacement conditions.
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Zhang, Chao. "Multi-Scale Characterization and Failure Modeling of Carbon/Epoxy Triaxially Braided Composite". University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1384174136.
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Nezamian, Abolghasem 1968. "Bond strength of concrete plugs embedded in tubular steel piles". Monash University, Dept. of Civil Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/5601.
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BARATELA, FERNANDO J. C. "Estudo das propriedades biocompatíveis de arcabouços poliméricos derivados de óleos vegetais para aplicação na engenharia de tecidos". reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26377.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Avachat, Siddharth. "Experimental and numerical analyses of dynamic deformation and failure in marine structures subjected to underwater impulsive loads". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44904.
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The need to protect marine structures from the high-intensity impulsive loads created by underwater explosions has stimulated renewed interest in the mechanical response of sandwich structures. The objective of this combined numerical and experimental study is to analyze the dynamic response of composite sandwich structures and develop material-structure-property relations and design criteria for improving the blast-resistance of marine structures. Configurations analyzed include polymer foam core structures with planar geometries. A novel experimental facility to generate high-intensity underwater impulsive loads and carry out in-situ measurements of dynamic deformations in marine structures is developed. Experiments are supported by fully dynamic finite-element simulations which account for the effects of fluid-structure interaction, and the constitutive and damage response of E-glass/polyester composites and PVC foams.
Results indicate that the core-density has a significant influence on dynamic deformations and failure modes. Polymeric foams experience considerable rate-effects and exhibit extensive shear cracking and collapse under high-magnitude multi-axial underwater impulsive loads. In structures with identical masses, low-density foam cores consistently outperform high-density foam cores, undergoing lesser deflections and transmitting smaller impulses. Calculations reveal a significant difference between the response of air-backed and water-backed structures. Water-backed structures undergo much greater damage and consequently need to absorb a much larger amount of energy than air-backed structures. The impulses transmitted through water-backed structures have significant implications for structural design. The thickness of the facesheets is varied under the conditions of constant material properties and core dimensions. The results reveal an optimal thickness of the facesheets which maximizes energy absorption in the core and minimizes the overall deflection of the structure.
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Covi, Patrick. "Multi-hazard analysis of steel structures subjected to fire following earthquake". Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/313383.
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Fires following earthquake (FFE) have historically produced enormous post-earthquake damage and losses in terms of lives, buildings and economic costs, like the San Francisco earthquake (1906), the Kobe earthquake (1995), the Turkey earthquake (2011), the Tohoku earthquake (2011) and the Christchurch earthquakes (2011). The structural fire performance can worsen significantly because the fire acts on a structure damaged by the seismic event. On these premises, the purpose of this work is the investigation of the experimental and numerical response of structural and non-structural components of steel structures subjected to fire following earthquake (FFE) to increase the knowledge and provide a robust framework for hybrid fire testing and hybrid fire following earthquake testing. A partitioned algorithm to test a real case study with substructuring techniques was developed. The framework is developed in MATLAB and it is also based on the implementation of nonlinear finite elements to model the effects of earthquake forces and post-earthquake effects such as fire and thermal loads on structures. These elements should be able to capture geometrical and mechanical non-linearities to deal with large displacements. Two numerical validation procedures of the partitioned algorithm simulating two virtual hybrid fire testing and one virtual hybrid seismic testing were carried out. Two sets of experimental tests in two different laboratories were performed to provide valuable data for the calibration and comparison of numerical finite element case studies reproducing the conditions used in the tests. Another goal of this thesis is to develop a fire following earthquake numerical framework based on a modified version of the OpenSees software and several scripts developed in MATLAB to perform probabilistic analyses of structures subjected to FFE. A new material class, namely SteelFFEThermal, was implemented to simulate the steel behaviour subjected to FFE events.
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Narasimhan, S. "Three Dimensional Viscoplastic And Geomertrically Non-Linear Finite Element Analysis Of Adhesively Bonded Joints". Thesis, 1998. http://etd.iisc.ernet.in/handle/2005/2166.
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Liu, Kai. "Concurrent topology optimization of structures and materials". Thesis, 2013. http://hdl.handle.net/1805/3755.
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Indiana University-Purdue University Indianapolis (IUPUI)Topology optimization allows designers to obtain lightweight structures considering the binary distribution of a solid material. The introduction of cellular material models in topology optimization allows designers to achieve significant weight reductions in structural applications. However, the traditional topology optimization method is challenged by the use of cellular materials. Furthermore, increased material savings and performance can be achieved if the material and the structure topologies are concurrently designed. Hence, multi-scale topology optimization methodologies are introduced to fulfill this goal. The objective of this investigation is to discuss and compare the design methodologies to obtaining optimal macro-scale structures and the corresponding optimal meso-scale material designs in continuum design domains. These approaches make use of homogenization theory to establish communication bridges between both material and structural scales. The periodicity constraint makes such cellular materials manufacturable while relaxing the periodicity constraint to achieve major improvements of structural performance. Penalization methods are used to obtain binary solutions in both scales. The proposed methodologies are demonstrated in the design of stiff structure and compliant mechanism synthesis. The multiscale results are compared with the traditional structural-level designs in the context of Pareto solutions, demonstrating benefits of ultra-lightweight configurations. Errors involved in the mult-scale topology optimization procedure are also discussed. Errors are mainly classified as mesh refinement errors and homogenization errors. Comparisons between the multi-level designs and uni-level designs of solid structures, structures using periodic cellular materials and non-periodic cellular materials are provided. Error quantifications also indicate the superiority of using non-periodic cellular materials rather than periodic cellular materials.
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Rama, Mohan P. "Development Of Robust Higher Order Transverse Deformable Elements For Composite Laminates". Thesis, 1997. http://etd.iisc.ernet.in/handle/2005/1774.
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Khadke, Kunal R. "Material design using surrogate optimization algorithm". Thesis, 2015. http://hdl.handle.net/1805/6694.
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Indiana University-Purdue University Indianapolis (IUPUI)Nanocomposite ceramics have been widely studied in order to tailor desired properties at high temperatures. Methodologies for development of material design are still under effect. While finite element modeling (FEM) provides significant insight on material behavior, few design researchers have addressed the design paradox that accompanies this rapid design space expansion. A surrogate optimization model management framework has been proposed to make this design process tractable. In the surrogate optimization material design tool, the analysis cost is reduced by performing simulations on the surrogate model instead of high fidelity finite element model. The methodology is incorporated to and the optimal number of silicon carbide (SiC) particles, in a silicon-nitride(Si3N4) composite with maximum fracture energy [2]. Along with a deterministic optimization algorithm, model uncertainties have also been considered with the use of robust design optimization (RDO) method ensuring a design of minimum sensitivity to changes in the parameters. These methodologies applied to nanocomposites design have a significant impact on cost and design cycle time reduced.
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Khandelwal, Ratnesh. "Studies On The Evaluation Of Thermal Stress Intensity Factors For Bi-Material Interface Cracks". Thesis, 2008. http://hdl.handle.net/2005/797.
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Components of turbines, combustion chambers, multi-layered electronic packaging structures and nuclear reactors are subjected to transient thermal loads during their service life. In the presence of a discontinuity like crack or dislocation, the thermal load creates high temperature gradient, which in turn causes the stress intensification at the crack tips. If proper attention is not paid in the design and maintenance of components on this high stress in the vicinity of crack tips, it may lead to instability in the system and decrease in the service life. The concepts of thermal fracture mechanics and its major parameter called transient thermal stress intensity factors can greatly help in the assessment of stability and residual life prediction of such structures.
The evaluation of thermal stress intensity factors becomes computationally difficult when the body constitutes of two different materials or is non-homogenous or made of composites. Fracture at bi-material interface is different from its homogenous counterpart because of mixed mode stress condition that prevails at the crack tip even when the geometry is symmetric and loading unidirectional. Because of this, the mode 1 and mode 2 stress intensity factors can not be decoupled to represent tension and shear stress fields as can be done in the case of homogeneous materials. Mathematically, the stress intensity factors at bi-material interfaces are complex due to oscillatory singularity that exists at the crack tip.
Although plenty of literature is available for bi-material systems subjected to mechanical loads, very little information is available on problems related to thermal loads. Besides, problems related to transient thermal loads need special attention, since no thermal weight functions are available and the existing methods are computationally expensive. Therefore, the present investigation has been undertaken to develop computational and analytical approaches for obtaining the Mode 1 and Mode 2 stress intensity factors for bi-material interface crack problems using conservation of energy principle in conjunction with the weight function approach for various kinds of thermal loads. In the beginning of the studies, a method to extract the Mode 1 and Mode 2 stress intensity factors for bi-material interface crack subjected to mechanical load is proposed using the concept of Jk integrals. This is extended to thermal loads using J2 line integral and J2 domain integral. Furthermore, weight functions are analytically derived for thermal bi-material stress intensity factors and a computational scheme is developed. These methods are validated for several benchmark problems with known solutions.