Dynamic Failure Mechanism Of Sandwich Structures

The composite sandwich structure is also known as composite sandwich plate. Composite sandwich structure commonly consists of five parts: top face sheet, bottom face sheet, two adhesive layers between face sheets and core, core. The face sheets and core are glued together by adhesive layer. The top and bottom face sheets are usually made by thin plate, for instance carbon fiber laminates, usually required large panel stiffness. The core material is usually lightweight materials. The composite sandwich structure has many advantages, such as high specific stiffness and strength, excellent thermal stability, good molding performance and easy to be design, so the composite sandwich structure has been widely used in different fields.In this paper, we analyzed the existing research of composite sandwich structure firstly and put forward some problems of the existing research. Common damage forms of composite sandwich structures and their research models were proposed. The Hashin failure criterion and progressive damage evolution model were used to analyze inner damage of panel layer. Cohesive contact technology was used to research delamination of face sheets. The debonding between face sheets and care were modeled by binding domain model. The damage of nomex honeycomb core was modeled by perfectly elastic-plastic model.Drop-weight impact tests and residual compressive strength tests were conducted on composite sandwich structure with different composite laminates face sheets and different honeycomb cores. Nondestructive inspection was carried on the sandwich structures damaged by impact. The damage behavior was discussed by analyzing the results of the impact tests and nondestructive inspection. The effects of face sheets and honeycomb core to sandwich structure were studied. The influence of the impact damage on the residual compressive strength was studied by comparing residual strengths of different specimens. Face sheets make no difference to the damage resistance of sandwich structure in impact test. Density of honeycomb core evidently affects the peak value of impact force. Impact damage will obviously reduce the residual strength of sandwich structure.A discrete finite element model was built and employed in ABAQUS/Explicit to simulate the impacting process. The discrete model was validated by experiments. We studied the effect of the cell size, cell wall thickness of honeycomb and core thickness, and the impact energy on the damage resistance of sandwich structures. It was found that the cell wall thickness and core thickness had considerable influence, but cell size made little difference. The simulations with different impact energies have a similar elastic stage and a fluctuated phase, while large impact energy would lead to a second sharply rising period.