Papers by Keyword: Composite Sandwich

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Authors: Zong Hong Xie, Fei Peng, Peng Zhang, Wei Zhao
Abstract: This paper introduces the research work on the development of a Smart Skin Antenna Structure (SSAS) for Global Navigation Satellite System (GNSS) by embedding a navigation antenna with working frequency from 1.2GHz to 1.6GHz into a composite sandwich structure. The structure possesses the load-bearing, shape maintaining and navigation capabilities at the same time. Numerical models have been generated to design and evaluate the EM property of this multifunctional structure. Specimens have been manufactured and tested. The test data show relatively good correlation to the numerical results.
316
Authors: Aldyandra Hami Seno, Eko Koswara, Hendri Syamsudin, Djarot Widagdo
Abstract: This research was done to evaluate the bending behavior (load-deflection curve and failuremode) of sandwich structures using Tali Bamboo strips as sandwich skin material. Bending tests wereconducted on sandwich specimens with end grain balsa (3-point bending) and polypropylene (PP)honeycomb cores (4-point bending) to evaluate their bending behavior. From the test results,analytical and numerical models were developed to simulate the observed bending behavior. Themodels are able to simulate the pre-failure bending behavior and failure modes (core shear failure) ofthe specimens. It is also shown that for thin (length/thickness > 20) sandwiches the models are moreaccurate since shear effects are less prominent. With the obtained models a predictive comparison isdone between the PP and balsa cored specimens since the testing configuration for each type wasdifferent. The analysis results show that balsa cored specimens are able to withstand higher transversebending loads due to the higher shear strength of the balsa core. These prediction results are to beproven by specimen testing which is the subject of future research.
94
Authors: Hoon Cheol Park, Jung Park, Nam Seo Goo, Kwang Joon Yoon, Jae Hwa Lee
Abstract: Low-velocity impact on composite sandwich panels has been investigated. The contact force is computed from a proposed modified Hertzian contact law. In the proposed contact law, the exponent is adjusted and the through-the-thickness elastic constant of honeycomb core is reduced properly to approximately predict the measured contact force-time history during the impact. The equivalent transverse elastic constant is calculated from the rule of mixture. Nonlinear equation to calculate the contact force is solved by the Newton-Raphson method and time integration is done by the Newmark-beta method. A finite element program for the low-velocity impact analysis is coded by implementing these techniques and an 18-node assumed strain solid element. Behaviors of composite sandwich panels subjected to low-velocity impact are analyzed for various cases with different geometry and lay-ups. It has been found that the present code with the proposed contact law can predict measured contact forces and contact times for most cases within reasonable error bounds, especially for thick sandwich plates.
283
Authors: Xiao Wen Li, Ping Li, Zhuang Lin, Hao Yu
Abstract: Composite to metal joints are gradually found in the marine industry for the attachment of lightweight components to metallic structures. The puropose of this study is to invistigate the composite sandwich to steel joint for naval ships. The main emphasis of the study was placed on the mechanical properties of a hybrid joint between a sandwich glass fibre reinforced plastic superstructure and a steel hull. Based on the experiments of a base joint, a new numerical simulation method was used to analyze the performance of the base joint and the optimized joint. The optimized joint was presented due to reducing weight and avoiding eccentric load. The numerical predictions of the base hybrid joint showed a very good correlation with the experiment results, which validated the reliability of the new numerical simulation method. The strength of the optimized hybrid joint was evaluated through static simulation. This phenomenon is similar to the base joint. But there is no additional stress concentration induced by load eccentricity and internal bending. The optimized joint has 11% lower weight than the base joint, and the stress of the optimized joint is only about 4% ~ 67% of the base one. The results of the present work imply that the change of geometry and material is an effective method to improve the performance of the composite sandwich to steel joint.
210
Authors: Andrea Alaimo, Alberto Milazzo, Davide Tumino
Abstract: In this paper a structural Finite Element analysis of a 50 ft pleasure vessel is presented. The study is performed under different loads conditions: modal analyses have been done in order to find the natural frequencies of the vessel, structural analyses to verify the strength of the vessel to design loads. The design loads for the vessel considered are computed according to RINA rules for the construction and classification of pleasure vessels [1]. Two different composites are used for the lamination: one is a monolithic sequence of short fibre and balanced glass lamina, used for the bottom of the vessel and for structural reinforcements, the other is a sandwich made of glass fibre composite skins and a PVC core, used for the main deck and sides of the vessel. All the analyses are performed by using Patran/Nastran™ finite element commercial software in order to identify critical areas where possible reinforcement or redesign needs to be considered.
692
Authors: Yao Hsu
Abstract: The Composite sandwich plate is made of two laminated face-sheets and one core material. Since such a kind of structure has many advantages, they have been widely used in structural manufacturing industry. However, when sandwich plates are impacted by transverse loadings, damages that are usually invisible would occur inside the sandwich plate and those damages would potentially reduce the structural safety. Therefore, it is necessary to elucidate the failure mechanism and how they affect the failure behaviors of sandwich structures for safety purpose. To this end, the present study is to investigate the impact failure behaviors of sandwich plates subjected to a rigid spherical impactor. Numerical simulation approach is carried out by finite element method. To predict the initial failure, several failure criteria to face-sheets and core material are proposed. In addition, to further simulate the progressive failure behaviors, a stiffness modification method is proposed and incorporated into the finite element software. The analytical results show that the local failure including fiber breakages, delamination, core cracking and plasticity is the main failure mechanism of cases studied. Furthermore, parametric study is also conducted and discussed in the paper.
178
Authors: Jun Li, Ba Ta Xi
Abstract: This note presents the main process of optimization design of foam core/carbon fiber composite sandwich which primarily designed for UAV wing beams. During the actual application, the original design provided excessive structural strength and it has certain capacity to be optimized. So the weight of structure can be reduced under the premise of meet the strength requirement. In order to characterize fully the complex mechanical behavior of such a highly heterogeneous material and find the ultimate strength of this structure, MSC.Patran/Nastran has be applied on analysis of this composite sandwich structure. Base on the result of the numerical simulations, the best combination of composite laminated and the material layer thickness have be determined, and the beams structure of the lightweight has be designed ultimately.
2256
Authors: Amarpreet S. Bir, Hsin Piao Chen, Hsun Hu Chen
Abstract: In the present study, both critical buckling load maximization and face-sheet laminate thickness minimization problems for the composite sandwich panel, subjected to bi-axial compressive loading under various imposed constraints have been investigated using genetic algorithms. In the previously published work, the optimization of simple composite laminate panels with only even number of laminae has been considered [1, 3]. The present work allows the optimization of a composite sandwich panel with both even and odd number of laminae in the face-sheet laminates. Also, the effects of the bending-twisting coupling terms (D16 and D26) in bending stiffness matrix which were neglected in the previous studies [1, 2, 3], are considered in the present work for exact solutions. In addition effect of both balanced and unbalanced face-sheet laminates on the optimum solutions have also been investigated, whereas only balanced laminates were considered in the previous studies [1, 2, 3].
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Authors: Pramaditya Ardiyanto, Putu Suwarta, Sutikno, Indra Sidharta, Wahyu Wijanarko
Abstract: This study explored the feasibility of flexural performance of composite sandwich material composed of various low density polyurethane foam core thickness sandwiched between GFRP skins. The mechanical behaviour of this material was assessed by carrying out a flexural testing. Each spesimen had a nominal dimensions of 110 mm x 30 mm x (c + 4 mm). These spesimens with various core thickness (c) of 2 mm. 5 mm. and 8 mm were then tested in three point bending according to ASTM C 393-00. This study revealed that. by incorporating the thickest core ( 8 mm ) . the bending strength decreases by 42.3 % compared to 5 mm core and it further decreases by 72.6 % compared to 2 mm core. The material stiffness showed positive trend for the thickest core (8 mm). it increases by 53.1 % and 78.1 % compared to 5 mm core and 2 mm core respectively. Low shear modulus of polyurethane foam core contributed to the low bending strength of composite sandwich material with 8 mm core. This was further confirmed by failure analysis under optical microscope which revealed that core shear failure was the dominant failure mechanism for 8 mm core. Meanwhile the dominant failure mechanism for 2 mm core and 5 mm core was microbuckling which confirm the high modulus of GFRP skin. The material stiffness was affected by the high modulus of GFRP skin and the core thickness.
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