Papers by Keyword: Sandwich Structure

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Authors: S.N. Abdul Razak, A.R. Othman
Abstract: Past and on-going research works on adhesive bonding in composite and sandwich were reviewed. Discussion was emphasized on critical failure mechanisms (e.g. mechanism of peel fracture) to enhance the performance of the bonding. This paper also focused on the application of good adhesive bonding in the application of sandwich structures. Debonding between skin and core is one of the failure mechanisms that should be given more attention in fabrication of sandwich structures. Incorporating fillet in composite bonding is one of the alternative ways to reduce the stress concentration at the edges of overlap length and to produce high peel strength for bonding. Basic understanding of the designs, theories and manufacturing of adhesive bonding were also presented. Several important parameters in the design such as the strain energy release rate (SERR) and formation of fillet also discussed. The analysis of SERR using virtual crack closure technique (VCCT) has also been highlighted to achieve high strength of adhesive bonding, providing the key element for optimization of the delamination resistance in maximizing energy absorption during fracture. Significant challenges or limitations in improving and optimizing the design were also highlighted.
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Authors: Phacharaporn Bunyawanichakul, Patinya Kumsantia, Bruno Castanié
Abstract: Sandwich structures are widely used in the aerospace field, also for primary parts. However, due to the low strength of core properties, the failure behavior under high stress concentration such as joining position is hard to evaluate. This study is, at present, a key task to enable future exploitation of the joint for structural sandwich consisted of Carbon Fiber Reinforced Polymer (CFRP) face and a Honeycomb core made of phenolic impregnated NomexTM paper. Previous experimental investigations provided the failure mechanism of sandwich plates with hard points in the form of inserts, and special attention is focused on the problem of sandwich panels with inserts of the fully potted types. Numerical simulations are achieved in this work with good correlation based on experimental test.
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Authors: Hamdan Ajmal Khan, Faizan Habib Vance, Asif Israr, Tanzeel Ur Rehman
Abstract: In this paper weight optimization of sandwich structure consisting of a honeycomb core sandwiched between two layers is presented through the use of Sequential Quadratic Programming & Genetic Algorithm by constraining of certain parameters such as buckling stress, cost and geometry. The variables to be optimized are core height, face sheet thickness and cell thickness for an effective design and better performance of the entire structural system. Sequential Quadratic Programming in Matlaband Genetic Algorithm technique with high robustness is performed and comparison between the two results is made for early convergence of the variables to be optimized. In this way, the structure could easily be monitored for any volatility, and avoid probable failure by employing proper remedial action.
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Authors: Qing Hua Qin, Tie Jun Wang
Abstract: A unified yield criterion is proposed in this paper, which is valid for the metallic sandwich sections with various core strength and geometrical dimensions and can reduce to the classical yield criteria for solid monolithic section and sandwich section with weak core, respectively. Then, the unified yield criterion is used to derive the analytical solution for the large deflection of fully clamped metallic sandwich beam subject to a transversely concentrated load, in which the interaction of bending and stretching is considered. Comparisons of the present solutions with experimental results are carried out and good agreements are found. It is seen that the axial stretching induced by large deflection has a significant effect on the deflection of sandwich structure in the post-yield regime, and the load carrying capacity of metallic foam core sandwich beam may be underestimated as the core strength is neglected in analysis.
559
Authors: Xin Zhu Wang, Lin Zhi Wu, Shi Xun Wang
Abstract: In present work, the critical buckling load of metallic foam composite sandwich panels is calculated by experimental, finite element methods (FEM) and theoretical analysis. The experimentally investigated is based on an edgewise compression test program to examine buckling failure and compressive properties. The metallic foam sandwich panels under edgewise compression tend to collapse in overall buckling mode. The most important factor that determines the overall buckling load of a sandwich panel under edgewise compression is the shear properties the metallic foam core. The sandwich beam theory and the FE model are developed for prediction of the buckling load of metallic foam sandwich structure. In despite of some differences existed among experimental data, FE and theoretical results, considering the existence of initial defects in sandwich structures which can’t be calculated in FE model and theory anlysis, the differences are in the reasonable range. The FE program developed in this paper can effectively be used to simulation of edgewise compression response for metallic foam composite sandwich structures. Theoretical and FE model results are in agreement with experimental result.
1241
Authors: Zheng Fa Li, Zheng Dao Wang
Abstract: Shape memory polymers (SMPs) can have a large frozen strain but providing much lower recovery stresses. To overcome such disadvantage, sandwich structures consisted of a SMP core and two thin metallic skins was considered. Due to much compliance of the SMP core, SMP sandwich beam is buckled at a lower packaging strain. Buckling is the fundamental character of SMP sandwich beam under bending. The critical buckling parameters about two types of SMP sandwich beams were theoretically derived.
939
Authors: A. V. Chzhan, G.S. Patrin, S. Ya. Kiparisov, V. A. Seredkin
Abstract: Exchange bias and coercivity of the hysteresis loop of a low-coercive layer in magnetic three-layered structure prepared by chemical deposition are studied. It is established that the coercive force in the films obtained nonmonotonically changed with the low-coercive layer thickness. The specificity of magnetization reversal of exchange-biased layers is analyzed.
463
Authors: Md Akil Hazizan, C.Y. Tan
Abstract: In this study, the impact responses of sandwich structure with both FML and aluminum skins were compared. The force-time histories from the low-velocity drop weight impact tester were recorded under various impact energies. Energy absorbed from the two types of sandwich structures under various impact energies were also calculated by measuring its initial velocity before impact from a series of recorded high speed camera pictures and force-time histories. Based on results obtained, pure aluminum skins with PP honeycomb core that being impacted by lower impact energies shows higher absorbed energies as compared to FML skins. However with higher impact energies the FML skins shows improvement over the aluminum with higher energy absorption capacity. Damages created were also being characterized under optical microscope for further investigation.
524
Authors: Dong Seob Kim, Jin Yul Kim, Woon Bong Hwang
Abstract: We study a composite-antenna-structure (CAS) having high electrical and mechanical performances that we have designed and fabricated. The CAS, consisting of a glass/epoxy face sheet and a honeycomb core, acts as a basic mechanical structure, in which a spiral antenna type is embedded. To increase the intensity, a carbon fiber plate is used as a bottom sheet. This structure of the 0.5 ~ 2 GHz band has a gain of 5 ~ 9 dBi with circular polarization characteristics and reflection loss below -10 dB within the desired frequency band.
143
Authors: Seung Il Kim
Abstract: Time Domain Reflectometry has been applied to detect damage on sandwich structure. Face plated need to be copper plated to embed sensor on surface. Core also needs to be conductive to send signal back. Total 6 lines of sensor were tested with varying impact energy and impact location. TDR were able to locate damage with high accuracy. Damage degrees were detectable for critical hit, but not clear enough to predict impact energy. However TDR was sensitive enough to detect damage that wasn’t visible by visual inspection.
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