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Journal articles on the topic 'Aramid honeycomb'

Author: Grafiati

Published: 4 June 2021

Last updated: 5 February 2022

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1

Khakhin, L. A., A. V. Kulik, I. A. Arutyunov, S. N. Potapova, E. V. Korolev, and D. V. Svetikov. "Synthesis and Application of Aramids." Oil and Gas Technologies 129, no. 4 (2020): 3–9. http://dx.doi.org/10.32935/1815-2600-2020-129-4-3-9.

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Presented overview covers existing methods for aromatic heterocyclic polyamides (aramids) production. Aramids application areas are also covered. Aramids are used to produce light, high-strength, heat-resistant, and fire-resistant multifunctional materials. Examples are honeycomb plastics, polymer paper and high-modulus fibers. The latter capable of maintaining high mechanical properties under load at elevated temperatures. In 2018, the global market for aramids was 97,000 tonnes per year. According to the forecast, it will reach 110 thousand tons per year by 2020. Development of production of aramid fibers is important for the global industry.

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2

Yeo, Eudora Sia Ying, John Wang, Leo Mirabella, and Andrew N. Rider. "Effect of Humidity and Thermal Cycling on Carbon-Epoxy Skin/Aramid Honeycomb Structure." Materials Science Forum 654-656 (June 2010): 2600–2603. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2600.

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Many modern military aircraft are constructed from composite and bonded structure, such as thin carbon-epoxy laminate bonded to Kevlar® and Nomex® honeycomb. Operation of these platforms in Australian and global conditions will subject the structure to potentially high levels of humidity, extremes in temperature, and for maritime operations, exposure to salt spray conditions. The thin composite laminate is likely to rapidly absorb moisture in a humid environment and enable permeation of moisture into the adhesive and core. In addition to the chemical influence of moisture on the composite structure, the moisture trapped in the honeycomb structure may freeze and expand with changes in altitude during operations or simply due to daily temperature fluctuations at the resident airbase. The combination of moisture ingress in the honeycomb structure and thermal cycling may lead to deteriorated strength of the honeycomb panels over time that would not be observed for long term humid exposure alone. Long term salt water absorption may also have an adverse effect on composites structures. This study investigates the effects of humid environments and thermal cycling on the mechanical properties of composite and honeycomb structures.

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3

Kumar, Ramesh, Lijo James, and Nalla Perumal. "NCCR - Aramid Sandwich Insulator for Cryogenic Applications." International Journal of Computational Physics Series 1, no. 1 (March 5, 2018): 197–203. http://dx.doi.org/10.29167/a1i1p197-203.

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Structural integrity of cryogenic propulsion system in which fuel and oxidizer tanks are connected using truss tubes was well established. The critical issue in the design is the temperature constraint so that temperature is limited to within K for LH2 tank as against K for the LOX. In the present work, based on transient heat transfer analysis for 600s, polyimide foam filled aramid honeycomb core sandwich insulator is designed for common bulkhead instead of truss tubes each for cryogenic and semi cryogenic systems. Non conducting cryo compatible resin (NCCR) is used to bond the skin and core. Comparison of the back wall temperature for different heat flux and different thermal specifications obtained from test and prediction shows a good agreement. The study shows that a small increase in core height of foam filled sandwich insulator considerably controls the temperature increase of LH2. Test data on flat - wise tensile strength at 77K of NCCR resin used in the honeycomb sandwich insulator shows the values in the acceptable range.

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4

Shan, Junfang, Songlin Xu, Lijiang Zhou, Daorong Wang, Yonggui Liu, Ming Zhang, and Pengfei Wang. "Dynamic fracture of aramid paper honeycomb subjected to impact loading." Composite Structures 223 (September 2019): 110962. http://dx.doi.org/10.1016/j.compstruct.2019.110962.

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5

Wu, Yi-Jui, James C. Seferis, and Vincent Lorentz. "Evaluations of an aramid fiber in nonwoven processes for honeycomb applications." Journal of Applied Polymer Science 86, no. 5 (August 21, 2002): 1149–56. http://dx.doi.org/10.1002/app.11069.

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6

Li, X. Y., X. P. Hu, and X. Wu. "Shear Fracture Model of Ultrasonic Cutting for an Aramid Paper Honeycomb." Strength of Materials 51, no. 4 (July 2019): 541–47. http://dx.doi.org/10.1007/s11223-019-00099-0.

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7

Liu, Longquan, Han Feng, Huaqing Tang, and Zhongwei Guan. "Impact resistance of Nomex honeycomb sandwich structures with thin fibre reinforced polymer facesheets." Journal of Sandwich Structures & Materials 20, no. 5 (August 12, 2016): 531–52. http://dx.doi.org/10.1177/1099636216664076.

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In order to investigate the impact resistance of the Nomex honeycomb sandwich structures skinned with thin fibre reinforced woven fabric composites, both drop-weight experimental work and meso-mechanical finite element modelling were conducted and the corresponding output was compared. Drop-weight impact tests with different impact parameters, including impact energy, impactor mass and facesheets, were carried out on Nomex honeycomb-cored sandwich structures. It was found that the impact resistance and the penetration depth of the Nomex honeycomb sandwich structures were significantly influenced by the impact energy. However, for impact energies that cause full perforation, the impact resistance is characterized with almost the same initial stiffness and peak force. The impactor mass has little influence on the impact response and the perforation force is primarily dependent on the thickness of the facesheet, which generally varies linearly with it. In the numerical simulation, a comprehensive finite element model was developed which considers all the constituent materials of the Nomex honeycomb, i.e. aramid paper, phenolic resin, and the micro-structure of the honeycomb wall. The model was validated against the corresponding experimental results and then further applied to study the effects of various impact angles on the response of the honeycomb. It was found that both the impact resistance and the perforation depth are significantly influenced by the impact angle. The former increases with the obliquity, while the latter decreases with it. The orientation of the Nomex core has little effect on the impact response, while the angle between the impact direction and the fibre direction of the facesheets has a great influence on the impact response.

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8

Griefahn, D., J. Wollnack, and W. Hintze. "Principal component analysis for fast and automated thermographic inspection of internal structures in sandwich parts." Journal of Sensors and Sensor Systems 3, no. 1 (May 14, 2014): 105–11. http://dx.doi.org/10.5194/jsss-3-105-2014.

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Abstract. Rising demand and increasing cost pressure for lightweight materials – such as sandwich structures – drives the manufacturing industry to improve automation in production and quality inspection. Quality inspection of honeycomb sandwich components with infrared (IR) thermography can be automated using image classification algorithms. This paper shows how principal component analysis (PCA) via singular value decomposition (SVD) is applied to compress data in an IR-video sequence in order to save processing time in the subsequent step of image classification. According to PCA theory, an orthogonal transformation can project data into a lower dimensional subspace with linearly uncorrelated principal components preserving all original information. The effect of data reduction is confirmed with experimental data from IR-video sequences of simple square-pulsed thermal loadings on aramid honeycomb-sandwich components with CFRP/GFRP (carbon-/glass-fiber-reinforced plastic) facings and GFRP inserts. Hence, processing time for image classification can be saved by reducing the dimension of information used by the classification algorithm without losing accuracy.

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9

Grünewald, Jonas, Tilman Orth, Patricia Parlevliet, and Volker Altstädt. "Modified foam cores for full thermoplastic composite sandwich structures." Journal of Sandwich Structures & Materials 21, no. 3 (June 22, 2017): 1150–66. http://dx.doi.org/10.1177/1099636217708741.

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Full thermoplastic composite sandwich structures with a foam core offer the possibility to be manufactured by fusion bonding in significant shorter cycle times than thermoset-based sandwiches. However, the application of foam cores results in lower mechanical properties such as compression and shear strength compared to honeycomb cores, therefore foam-based sandwiches cannot compete with sandwich structures based on Aramid/phenolic honeycomb cores, the current state of the art. In order to improve the mechanical performance of foam core-based sandwiches while maintaining their advantages, concepts to reinforce the foams were developed in this study. By introducing rods either orthogonally or diagonally to the skin plane, which are fusion bonded to the skins during processing, the compression and shear properties can be improved by up to 1000% and 72%, respectively. Even when correcting for the weight increase, an improved specific compression strength could be achieved. And therefore, the pinning looks especially promising when only applied locally in highly loaded areas for example.

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10

MINOSHIMA, Kohji, Kazuto TANAKA, Daisuke GOSHIMA, and Kenjiro KOMAI. "Impact and Compression after Impact Fracture Behavior of CFRP/Aramid Honeycomb Core Sandwich Panel." Proceedings of the JSME annual meeting 2000.1 (2000): 569–70. http://dx.doi.org/10.1299/jsmemecjo.2000.1.0_569.

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11

Zhao, Yayun, Yuxin Sun, Ruiyu Li, Qiran Sun, and Jiangtuo Feng. "Response of aramid honeycomb sandwich panels subjected to intense impulse loading by Mylar flyer." International Journal of Impact Engineering 104 (June 2017): 75–84. http://dx.doi.org/10.1016/j.ijimpeng.2017.02.008.

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12

Vakilinejad, Mohammad, Adel Olabi, Olivier Gibaru, and Bruno Botton. "Geometrical error improvement of Aramid honeycomb workpieces in robot-based triangular knife ultrasonic cutting process." International Journal of Advanced Manufacturing Technology 110, no. 1-2 (August 13, 2020): 523–41. http://dx.doi.org/10.1007/s00170-020-05855-0.

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13

Yang, Weichao, Xufeng Zhang, Kuijian Yang, Bing Pan, Binjun Fei, Xiaosu Yi, and Yuli Chen. "Shear property characterization of aramid paper and its application to the prediction of honeycomb behaviors." Composite Structures 254 (December 2020): 112800. http://dx.doi.org/10.1016/j.compstruct.2020.112800.

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14

KOMAI, Kenjiro, Sohei SHIROSHITA, and Gilles KILIDJIAN. "INFLUENCE OF WATER ON MECHANICAL PROPERTIES AND FRACTURE MECHANISM OF CFRP/ARAMID HONEYCOMB CORE SANDWICH BEAM." Journal of the Society of Materials Science, Japan 44, no. 507Appendix (1995): 226–31. http://dx.doi.org/10.2472/jsms.44.507appendix_226.

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15

KOMAI, Kenjiro, Sohei SHIROSHITA, and Gilles KILIDJIAN. "Influence of Water on Mechanical Properties and Fracture Mechanism of FRP/Aramid Honeycomb Core Sandwich Material." Journal of the Society of Materials Science, Japan 44, no. 505 (1995): 1273–78. http://dx.doi.org/10.2472/jsms.44.1273.

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16

Schwan, Marina, Matthias Rößler, Barbara Milow, and Lorenz Ratke. "From Fragile to Resilient Insulation: Synthesis and Characterization of Aramid-Honeycomb Reinforced Silica Aerogel Composite Materials." Gels 2, no. 1 (December 22, 2015): 1. http://dx.doi.org/10.3390/gels2010001.

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17

Zhao, Yayun, Qiran Sun, Jiangtuo Feng, Ruiyu Li, and Yuxin Sun. "Internal-structure-model based simulation research of aramid honeycomb sandwich panel subjected to intense impulse loading." Engineering Fracture Mechanics 204 (December 2018): 1–14. http://dx.doi.org/10.1016/j.engfracmech.2018.09.038.

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18

Butukuri, R. R., V. P. Bheemreddy, K. Chandrashekhara, T. R. Berkel, and K. Rupel. "Evaluation of skin-core adhesion bond of out-of-autoclave honeycomb sandwich structures." Journal of Reinforced Plastics and Composites 31, no. 5 (March 2012): 331–39. http://dx.doi.org/10.1177/0731684412437267.

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Composite sandwich structures offer several advantages over conventional structural materials such as lightweight, high bending and torsional stiffness, superior thermal insulation and excellent acoustic damping. One failure mechanism in a composite sandwich structure is the debonding of the composite facesheets from the core structure. A well-formed adhesive fillet at the interface of the honeycomb core cell walls and the laminate is a significant factor in preventing bond failure. In the present work, honeycomb composite sandwich panels are manufactured using a low-cost vacuum-bag-pressure-only out-of-autoclave manufacturing process. CYCOM®5320 out-of autoclave prepreg is used for the facesheet laminates and FM® 300-2U film adhesive is used for the facesheet-to-core bond. The manufactured composite sandwich panels are of aerospace quality with a facesheet laminate void content of around 1%. In this study, adhesive fillet formation and adhesive mechanical strength are evaluated as a function of several different sandwich construction design variables. Both aluminum and aramid Nomex® honeycomb core materials are considered to study the effect of core cell size and core material. The effect of film adhesive thickness is studied. A process for reticulation of the adhesive is applied and studied. A quantitative investigation of the adhesive fillet geometry is carried out for all the panels. Manufactured panels are evaluated for flatwise tensile strength in accordance with test method ASTM C297. Optimized combinations of core material, core density, cell size and adhesive thickness are identified. Results show that the reticulation process improves fillet formation and increases flatwise tensile properties.

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19

Ahcene, Ait Said, Bey Kamel, and Mzad Hocine. "Mechanical Fatigue Test of Aluminium Composite Panel (ACP) with Aramid Nida-Core Under Cyclic Bending." Strojnícky časopis - Journal of Mechanical Engineering 70, no. 2 (November 1, 2020): 1–10. http://dx.doi.org/10.2478/scjme-2020-0015.

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AbstractThe selection of a composite material for any application will involve selection of reinforcing fibre and matrix, and their fractional volume in the resulting material. A properly selected combination will give a composite material high strength and stiffness, low weight, excellent fatigue and corrosion resistance. The present experimental work is a contribution to the study of the mechanical fatigue behaviour under 3-point bending stress, of aramid/aluminium composite panel with honeycomb core. The tests were performed on four specimens for three cyclic loadings (90%, 80% and 70%), and imposed deformation with a load ratio of 0.2 and a frequency of 5 Hz. The results show that the optimal load ensuring better service resistance of the experimented sandwich panel is 0.7 of the material elastic limit (720 N). Observation using optical microscope of fracture faces in static and cyclic flexion showed the different damage modes of skins and core.

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20

Zaharia, Sebastian Marian, Mihai Alin Pop, Augustin Semenescu, Bogdan Florea, and Oana Roxana Chivu. "Mechanical Properties and Fatigue Performances on Sandwich Structures with CFRP Skin and Nomex Honeycomb Core." Materiale Plastice 54, no. 1 (March 30, 2017): 67–72. http://dx.doi.org/10.37358/mp.17.1.4788.

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Composite sandwich structures with Nomex honeycomb core are commonly used in industrial applications. This paper was focused on the study of the mechanical properties of sandwich structures with CFRP (carbon fibre reinforced polymer) skin and a phenolic resin-impregnated aramid paper core, known as Nomex. The paper analyzes behaviour and determines the mechanical properties of the CFRP-Nomex specimens to different types of tests, such as: three - point bending, compression, impact. The exceptional fatigue resistance of the composite structures is responsible for their success in a variety of industrial applications. For this reason, in this paper were implemented accelerated testing techniques for CFRP-Nomex sandwich structures, resulting in a significant reduction of the test time (of 13.9 times). The main indicator that was determined using the accelerated testing methodology was the mean life that has value of 268554 cycles.

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21

KUWABARA, Akitsu, Megumi OZASA, Toshiyuki SHIMOKAWA, Naoyuki WATANABE, and Kazuhiko NOMOTO. "Basic Mechanical Properties of TEEK Polyimide-Foam and TEEK-Filled Aramid Honeycomb Core-Materials for Sandwich Structures." Journal of the Society of Materials Science, Japan 54, no. 1 (2005): 97–103. http://dx.doi.org/10.2472/jsms.54.97.

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22

Sun, Gaohui, Wenpeng Wang, Leichao Wang, Zuodong Yang, Lianhe Liu, Jun Wang, Ning Ma, Hao Wei, and Shihui Han. "Effects of aramid honeycomb core on the flame retardance and mechanical property for isocyanate-based polyimide foams." Journal of Applied Polymer Science 134, no. 28 (March 11, 2017): 45041. http://dx.doi.org/10.1002/app.45041.

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23

Tsujii, Yasutaka, Kiyoshi Tanaka, and Yoshiteru Nishida. "Analysis of Mechanical Properties of Aramid Honeycomb Core. Investigation on the Compression Strength and the Shear Modulus." Transactions of the Japan Society of Mechanical Engineers Series A 61, no. 587 (1995): 1608–14. http://dx.doi.org/10.1299/kikaia.61.1608.

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24

Medina, SA, JM Meza, and Luiz F. Kawashita. "Damage sequence of honeycomb sandwich panels under bending loading: Experimental and numerical investigation." Journal of Reinforced Plastics and Composites 39, no. 5-6 (October 8, 2019): 175–92. http://dx.doi.org/10.1177/0731684419880970.

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This work presents a numerical modelling study on the bending response and failure mechanisms of aramid skin/aluminium honeycomb core sandwich panels under quasi-static bending loads. These composite sandwich panels are widely used in aerospace and automotive industries, in spite of the limitations for their use in complex structures, such as the extensive experimental testing needed at the component and full-size structural levels, which are expensive and time-consuming. The aim of this study was to capture the initiation of different failure mechanisms and their multiple interactions, which are known to strongly influence the observed microscopic behaviour of the material. Furthermore, a series of detailed Finite Element models were built and analysed in an attempt to replicate the complex damage mechanisms observed experimentally. The results show good correlation between numerical models and experimental results, both in terms of the global load–displacement behaviour and the observed damage mechanisms, including skin in-plane shear and compression damage, intralaminar fracture, delamination within the skin and core crushing. No debonding between the core and the skins was evidenced. It is proposed that this modelling approach can become a feasible alternative to component-level experimental testing when designing complex sandwich structures.

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25

KOMAI, Kenjiro, Kohji MINOSHIMA, Kazuto TANAKA, and Daisuke GOSHIMA. "406 Influence of Water Absorption on Impact and Compression Fracture Behavior of CFRP/Aramid Honeycomb Core Sandwich Panel." Proceedings of Conference of Kansai Branch 2000.75 (2000): _4–15_—_4–16_. http://dx.doi.org/10.1299/jsmekansai.2000.75._4-15_.

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26

Kim, Minkook, Jaeheon Choe, and Dai Gil Lee. "Development of the fire-retardant sandwich structure using an aramid/glass hybrid composite and a phenolic foam-filled honeycomb." Composite Structures 158 (December 2016): 227–34. http://dx.doi.org/10.1016/j.compstruct.2016.09.029.

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27

TANAKA, Kazuto, Kohji MINOSHIMA, Daisuke GOSHIMA, and Kenjiro KOMAI. "Influence of Water Absorption on Impact Fracture Behavior and Residual Strength after Impact of CFRP/Aramid Honeycomb Core Sandwich Panels." Transactions of the Japan Society of Mechanical Engineers Series A 70, no. 690 (2004): 250–57. http://dx.doi.org/10.1299/kikaia.70.250.

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28

Bakar, Mohamed, Wojciech Kucharczyk, Sylwester Stawarz, and Wojciech Żurowski. "Effect of nanopowders (TiO2 and MMT) and aramid honeycomb core on ablative, thermal and dynamic mechanical properties of epoxy composites." Composite Structures 259 (March 2021): 113450. http://dx.doi.org/10.1016/j.compstruct.2020.113450.

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29

Wang, Wang, Liu, Zhang, Wan, and Zhang. "Mechanical Respond and Failure Mode of Large Size Honeycomb Sandwiched Composites under In-Plane Shear Load." Molecules 24, no. 23 (November 21, 2019): 4248. http://dx.doi.org/10.3390/molecules24234248.

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The present work focuses on the in-plane shear respond and failure mode of large size honeycomb sandwich composites which consist of plain weave carbon fabric laminate skins and aramid paper core. A special size specimen based on a typical element of aircraft fuselage was designed and manufactured. A modified in-plane shear test method and the corresponding fixture was developed. Three large size specimens were tested. The distributed strain gauges were used to monitor the mechanical response and ultimate bearing capacity. The results show that a linear respond of displacement and strain appears with the increase of the load. The average shear failure load reaches 205.68 kN with the shear failure occurring on the face sheet, and the maximum shear strain monitored on the composite plate is up to 16,115 με. A combination of theoretical analysis and finite element method (FEM) was conducted to predict the shear field distribution and the overall buckling load. The out-of-plane displacement field distribution and in-plane shear strain field distribution under the pure shear loading were revealed. The theoretical analysis method was deduced to obtain the variation rule of the shear buckling load. A good agreement was achieved among the experiment, theoretical analysis, and FEM results. It can be concluded that the theoretical analysis method is relatively conservative, and the FEM is more accurate in case of deformation and strain. The results predicted by h element and p element methods are very close. The results of the study could provide data support for the comprehensive promotion of the design and application of honeycomb sandwich composites.

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30

Kuwabara, Akitsu, Megumi Ozasa, Toshiyuki Shimokawa, Naoyuki Watanabe, and Kazuhiko Nomoto. "Basic mechanical properties of balloon-type TEEK-L polyimide-foam and TEEK-L filled aramid-honeycomb core materials for sandwich structures." Advanced Composite Materials 14, no. 4 (January 2005): 343–63. http://dx.doi.org/10.1163/156855105774470384.

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31

Kratz, James, and Pascal Hubert. "Vacuum-bag-only co-bonding prepreg skins to aramid honeycomb core. Part II. In-situ core pressure response using embedded sensors." Composites Part A: Applied Science and Manufacturing 72 (May 2015): 219–27. http://dx.doi.org/10.1016/j.compositesa.2014.11.030.

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32

Coskun, Onur, and Halit S. Türkmen. "Bending Fatigue Behaviour of Laminated Sandwich Beams." Advanced Materials Research 445 (January 2012): 548–53. http://dx.doi.org/10.4028/www.scientific.net/amr.445.548.

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In this study, the bending fatigue behaviour of laminated sandwich beams, which are made of carbon/epoxy face sheets and aramid honeycomb core, has been investigated experimentally. The wet hand lay-up technique is used and curing is processed on the heated vacuum table at an elevated temperature to manufacture the sandwich beams. The experimental set-up for bending fatigue test provides a cantilever in one end and a cyclic load at the free end with constant displacement amplitude at room temperature. The load applied to the beam is measured using a load cell during the bending test. Different displacement amplitudes are performed. Mechanical properties, bending stiffness and free vibration frequency of the sandwich beam are investigated. The bending test of the beams and vibration identification test using a vibration analyzer, a hammer and an accelerometer are performed to measure the bending stiffness and determination of free vibration frequency of the clamped sandwich beams before starting and after completion of the fatigue tests. The bending stiffness and free vibration frequencies before and after the fatigue tests are compared to understand the effect of repeated loadings on the mechanical performance of the laminated sandwich beams.

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33

Wang, Kai Lun, Zhi Dong Guan, Jun Guo, and Zeng Shan Li. "Impact Damage Resistance of Thin-Core Sandwich Structures Subjected to Low-Velocity Impact." Applied Mechanics and Materials 684 (October 2014): 176–81. http://dx.doi.org/10.4028/www.scientific.net/amm.684.176.

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This paper aims at evaluating the damage resistance of thin core sandwich structures, composed of aramid paper honeycomb core and carbon/ epoxy laminates face-sheets subjected to low velocity impact. The impact tests are performed using the instrumented impact-testing machine and resulting impact damages are inspected by Ultrasonic C-scan. In order to study the failure process of the core, which is important in the damage of the structures, flatwise compression test was carried out. Four parameters have been analyzed as follows: maximum load, total energy absorbed during impact, impact dent depth, and impact damage area. Nearly all impact force histories of panels have “twin peaks”, but the second peak of the 3mm-core structure is much larger than the first, which is quite different from others, when impact energy reached 5J, which were caused by the thickness of the core. Impact damages of thin-core sandwich structures are mainly delamination in the face-sheet and core crushing at low energy, and fiber breakage at relatively high energy. The damage processes of different groups of structures are essentially different and the impact resistance of the sandwich structure is greatly influenced by the face-sheet and core thickness.

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34

Kratz, James, and Pascal Hubert. "Vacuum bag only co-bonding prepreg skins to aramid honeycomb core. Part I. Model and material properties for core pressure during processing." Composites Part A: Applied Science and Manufacturing 72 (May 2015): 228–38. http://dx.doi.org/10.1016/j.compositesa.2014.11.026.

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35

Kurosawa, Yoshinari, and Jianmei HE. "High-performance Evaluation of Composite Panel Structures using Lightweight Aramid Honeycombs." Proceedings of The Computational Mechanics Conference 2019.32 (2019): 123. http://dx.doi.org/10.1299/jsmecmd.2019.32.123.

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36

Schwan, Marina, Barbara Milow, and Lorenz Ratke. "Novel superflexible resorcinol–formaldehyde aerogels and combining of them with aramid honeycombs." MRS Communications 4, no. 4 (November 11, 2014): 177–81. http://dx.doi.org/10.1557/mrc.2014.31.

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37

M., Saleh. "HONEYCOMB WEATHERING OF SANDSTONE OUTCROPS AT AL-HIJRv(MADA'IN SALIH), SAUDI ARABIA." Egyptian Journal of Archaeological and Restoration Studies 3, no. 2 (December 1, 2013): 85–93. http://dx.doi.org/10.21608/ejars.2013.7278.

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38

Abbadi, A., Z. Azari, S. Belouettar, J. Gilgert, and P. Freres. "Modelling the fatigue behaviour of composites honeycomb materials (aluminium/aramide fibre core) using four-point bending tests." International Journal of Fatigue 32, no. 11 (November 2010): 1739–47. http://dx.doi.org/10.1016/j.ijfatigue.2010.01.005.

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39

Richert, Philip, Athanasios Dafnis, and Kai-Uwe Schröder. "Experimental investigation of the failure modes of in-plane loaded inserts in CFRP sandwich panels." MATEC Web of Conferences 188 (2018): 04025. http://dx.doi.org/10.1051/matecconf/201818804025.

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The aim of this paper is the experimental determination and investigation of the different failure modes of various insert types under inplane load in sandwich materials with CFRP face sheets and a perforated aluminum honeycomb core. In addition, also insert under an out-of-plane load are tested. In total three different kind of inserts are investigated: blind inserts, trough-the-thickness inserts and special inserts which are developed within the iBOSS research project. The inserts are tested until failure and monitored with the digital image correlation system Aramis. This test monitoring is intended to determine the first failure mode. It is shown that this works well for out-of-plane loaded insert connections and the special inserts under in-plane load. However, this does not work so well with in-plane loaded standard inserts. In further investigations, a failure of the adhesive shortly before failure of the top layers can be shown.

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40

NAEEM, Nida, Mudassar ABBAS, and Mumtaz Hasan MALIK. "GRAPHENE/GRAPHENE OXIDE BASED COATINGS FOR ADVANCED TEXTILE APPLICATIONS." TEXTEH Proceedings 2019 (November 5, 2019): 148–52. http://dx.doi.org/10.35530/tt.2019.31.

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Today, graphene oxide has been significantly used in many technological sectors, medical sectors as well in textiles due to its abundant applications and dominant characteristics. Graphene oxide is basically a mono layered material synthesized by the oxidation of graphite by the addition of multiple functional groups containing oxygen such as alcohols, carboxylic acids and epoxides and presenting a 2-diamentional honeycomb structure. On the textile surfaces the grapheme oxide can be applied through Pad dry-cure, Dip dry-cure and Spray coating methods. However, the most appropriate method is dipping of the fabric into the graphene suspension and the process is followed by drying and curing techniques. Initially, the fabric swatches have been cut out in a suitable size according to the padder or adjustments on the machine can also be done. 100% pure cotton, polyester, cotton polyester blend, silk, aramids and acrylics have been used as a substrate for the application of graphene to imparts different functional properties. The oxygen content is reduced resulting the increase in the interlayer spacing’s well as functionalization. The oxygen containing groups have been removed with the repossession of the conjugated structure. The reduced graphene oxide has the higher strength as well as high electrical and thermal conductivity which effect the final performance of a materials.

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Šajn, Viktor. "Semi-Analytical Multidimensional Algorithm for Aircraft Design Optimisation: Student Design Build Fly (DBF) Competition." Strojniški vestnik – Journal of Mechanical Engineering 65, no. 11-12 (November 18, 2019): 728–40. http://dx.doi.org/10.5545/10.5545/sv-jme.2019.6459.

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The winner of American Institute of Aeronautics and Astronautics (AIAA)/Textron Aviation/Raytheon Missile Systems Design/Build/Fly (DBF) Competition 2019 was Edvard Rusjan team from Faculty of Mechanical Engineering, University of Ljubljana, Slovenia. Edvard Rusjan team use a strict scientific approach to beat opposing teams from most prestigious US Universities. Team developed a semi-analytic multidimensional algorithm for aircraft design optimization with an aim to maximize competition score in accordance with the competition rules. Two intermediate prototype models were produced and tested for single ground and three flying missions to fine tune algorithm empirical coefficients. Aircraft model aerodynamics was predicted with RANS numerical simulations and dynamic stability with Inviscid Panel method. By measurement in Low Turbulence Wind Tunnel the low drag of selected aircraft external load configuration was verified. Wing and fuselage of competition aircraft model named by Ljubljana students "Pretty Boy" were made of carbon-glass sandwich composite and Aramide honeycomb as sandwich filler. At final fly-off at TIMPA field in Tucson, in final flight mission team pilot Timotej Hofbauer with "Pretty Boy" scored 18 laps in 10 minutes time slot which was absolute record of competition. Runner-up Georgia Institute of Technology team was 22% slower and finished with 14 scored laps.

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Šajn, Viktor. "Semi-Analytical Multidimensional Algorithm for Aircraft Design Optimisation: Student Design Build Fly (DBF) Competition." Strojniški vestnik – Journal of Mechanical Engineering 65, no. 11-12 (November 18, 2019): 728–40. http://dx.doi.org/10.5545/sv-jme.2019.6459.

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Abstract:

The winner of American Institute of Aeronautics and Astronautics (AIAA)/Textron Aviation/Raytheon Missile Systems Design/Build/Fly (DBF) Competition 2019 was Edvard Rusjan team from Faculty of Mechanical Engineering, University of Ljubljana, Slovenia. Edvard Rusjan team use a strict scientific approach to beat opposing teams from most prestigious US Universities. Team developed a semi-analytic multidimensional algorithm for aircraft design optimization with an aim to maximize competition score in accordance with the competition rules. Two intermediate prototype models were produced and tested for single ground and three flying missions to fine tune algorithm empirical coefficients. Aircraft model aerodynamics was predicted with RANS numerical simulations and dynamic stability with Inviscid Panel method. By measurement in Low Turbulence Wind Tunnel the low drag of selected aircraft external load configuration was verified. Wing and fuselage of competition aircraft model named by Ljubljana students "Pretty Boy" were made of carbon-glass sandwich composite and Aramide honeycomb as sandwich filler. At final fly-off at TIMPA field in Tucson, in final flight mission team pilot Timotej Hofbauer with "Pretty Boy" scored 18 laps in 10 minutes time slot which was absolute record of competition. Runner-up Georgia Institute of Technology team was 22% slower and finished with 14 scored laps.

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Chen, Lin, and Fengyun Mu. "Spatiotemporal characteristics and driving forces of terrorist attacks in Belt and Road regions." PLOS ONE 16, no. 3 (March 11, 2021): e0248063. http://dx.doi.org/10.1371/journal.pone.0248063.

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To achieve the strategic goals of the Belt and Road Initiative (BRI), it is necessary to deepen our understanding of terrorist attacks in BRI countries. First, we selected data for terrorist attacks in BRI regions from 1998 to 2017 from the Global Terrorism Database and analyzed their time distribution using trend analysis and wavelet analysis. Then, we used honeycomb hexagons to present the spatial distribution characteristics. Finally, based on the Fragile States Index, we used GeoDetector to analyze the driving forces of the terrorist attacks. The following conclusions were obtained: (1) During 1998–2017, the number of events was the highest on Mondays and the lowest on Fridays. In addition, the incidence of events was high between Monday and Thursday but was the lowest on Fridays and Saturdays. The number of events was the largest in January, May, July, and November and was the lowest in June and September; the incidence of terrorist attacks from April to May and July to August was high. (2) Terrorist attacks showed a 10-year cycle during the study period. Terrorist attacks in the last 10 years of the study period were broader in scope and higher in number compared with the previous 10 years. In addition, China, Russia, Saudi Arabia, and northeastern Europe saw many new terrorist attacks during the latter 10 years. (3) The number of terrorist attacks by bombing/explosion was the largest, followed by armed attack; assassination, kidnapping, and infrastructure attacks were the least frequent. The core areas of the terrorist attacks were Iraq, Israel, Afghanistan, Pakistan, and India. (4) The driving force analysis revealed that the indicators “security apparatus,” “human flight and brain drain,” and “external intervention” contributed the most to BRI terrorist attacks.

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Sumith, S., and R. Ramesh Kumar. "Thermo-structural analysis of cryogenic tanks with common bulkhead configuration." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, June 11, 2021, 095441002110247. http://dx.doi.org/10.1177/09544100211024789.

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In launch vehicles, cryogenic propulsion stages store liquid oxygen (LOX) at 76 K and liquid hydrogen (LH2) at 20 K, generally in two separate insulated tanks connected through tubular truss components. Consequently, load transfer from the LH2 tank to the LOX tank is very much localized, resulting in a nonoptimal design. This article presents an alternative single tankage design using a common bulkhead (CBH) to enhance the payload capability, which enables maintaining LH2 temperature within a specified temperature when exposed to a temperature gradient. A sandwich insulator using aramid honeycomb embedded with polyimide foam keeps the LH2 temperature within 20 ± 1 K is proposed, based on transient heat transfer analysis for 1000 s. The foam-filled honeycomb core is treated as equivalent foam in the analysis as the thermal conductivity of the core and the foam is quite close. The efficacy of the insulator is established by an experiment to measure the back wall temperature when liquid nitrogen is loaded on the top skin of the panel, and the insulator maintains a temperature gradient of 123 K for 1000 s. A good agreement is obtained between the transient finite element analysis results with experimental data. An externally insulated LOX tank configuration with an optimum length of the skirt–cylinder where the temperature reaches 80 K is arrived at based on slosh, buckling, and thermal analyses. No thermal gradient is found across the thickness of the skirt, while the thermal gradient is observed along the length of the skirt as anticipated. An integrated thermo-structural analysis of the cryo-system is carried out considering temperature-dependent material properties. A positive margin for the skirt is obtained. A payload gain of 366 kg is estimated based on the present study for the new design option with a CBH and skirt as compared to the traditional tubular truss arrangements.

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Ashikhmina, Ekaterina, and Pavel Prosuntsov. "Numerical simulation and experimental validation of effective thermal conductivity coefficient of hexagonal aramid honeycomb used in wing skin of tourist class reusable spaceplane." Materials Today: Proceedings, November 2020. http://dx.doi.org/10.1016/j.matpr.2020.10.033.

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