Carbon fiber reinforced epoxy resin composite honeycomb sandwich structure is prone to various unpredict-able impact damage and damage in engineering applications,and is very sensitive to impact loads,especially after low-speed impact,although there is no obvious damage on the surface,the internal structure may be seriously dam-aged,and the failure mechanism and failure mode of the composite sandwich structure are very complex.In this study,the damage mode of the composite honeycomb sandwich structure surface was investigated based on low ener-gy impact,and the influence of low energy impact on the crack growth mode,damage area,crack length and number of epoxy resin film on the structure surface was analyzed.The bending properties and damage limits of carbon fiber reinforced composite laminates after low-energy impact were studied by three-point bending test.The results show that impact energy affects the damage expansion mode of epoxy resin film on the surface.The cracks are centered on the impact point and spread irregularly around,and the damage area formed increases with the impact energy.The crack propagation length is positively correlated with the impact energy,and the damage modes of laminates are domi-nated by delamination and fiber bending.Moreover,low energy impact tests have proved that there is a specific rela-tionship between the crack propagation mode and damage area of the surface epoxy resin film and the impact damage degree inside the sandwich structure laminates,so it can provide a possibility for forming a new non-destructive test-ing method to quickly characterize the impact damage inside the structure.
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