Equivalent Theory And Application Of Structural Failure Of Composite Laminates With Delamination

Composite material is a popular engineering material nowadays.According to the theory of plate and shell and mechanics of composite materials,the contact performance at the interface of delamination was determined by examining the local deformation mechanism of sublaminates above and below the delamination.With the available contact property,governing equations for buckling of the composite panel with single delamination were established and were solved using the boundary conditions and continuity conditions at the delamination fronts.Exact solutions of the buckling loads and buckling modes were obtained.By analyzing the contact property in the exact solutions,it was found that:(1)the two parts above and below the delamination experienced the same overall deflection;(2)the composite laminate undergoes the delamination propagation of mode II due to in-plane sliding.Based on this observation,a perfect equivalent model without delamination was proposed to replace the delaminated portion of the laminate.The equivalent model had the same geometry size and was stacked in the same order as the delaminated one.The exact solution of the global bending mode also showed that the stiffness of the equivalent model should be considered as the sum of the two parts above and below the delamination.Parametric studies show that the solutions from the equivalent model and the exact model are in good agreement which demonstrates the accuracy of the equivalent model.Furthermore,experimental test for buckling of composite laminates with single delamination were undertaken by preparing test specimens with delamination using hot pressing machine.Finite element analysis was simulated using ABAQUS software.The comparison between the two results proved the validity of the finite element model.Using the established equivalent model and finite element model,buckling of composite laminates with multiple delaminations was inspected.The effects of delamination conditions(such as the number of delaminations and the depth,location and length of each delamination)on the buckling behavior of composite laminates were evaluated by parameter study.The effectiveness of the equivalent model was verified against the finite element results.