| Summary: | 碩士 === 國立交通大學 === 機械工程系所 === 102 === The research aims to investigate the failure behaviors of the composite sandwich structures with debond defect subjected to compression loading. Both experimental observations and numerical simulation were conducted to understand the effect of face-sheet thickness as well as the debond length on the strength of the composites sandwich structures. Experimental results revealed that the sandwich structures with either thick face-sheet or short debond length exhibit higher buckling load and failure strength. Moreover, as the debond length is short, the failure is dominated by global buckling, however, when the debond length is long, the failure mechanism becomes the local buckling in conjunction with the crack extension from the debond edge. In order to characterize the failure mechanism, the nonlinear finite element (FEM) simulation was implemented on the sandwich samples with imperfection. In addition, the failure load was predicted based on either the maximum principal strain criterion or the damage zone method. It was found that when the failure is dominated by the global buckling, it occurs at intermediate portion of the foam core and the strength can be obtained from the maximum principal strain criterion. On the other hand, when the failure mode is local buckling, the failure initiates from the debond tip and the strength can be predicted using the damage zone method.
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