Real-time Detection and Explicit Finite Element Simulation of Delamination in Composite Laminates under Impact Loading

A new experimental technique is developed to determine the onset and evolution of delamination in fiber-reinforced composites under impact loading. The configuration uses a split-Hopkinson bar for low-velocity impact loading and two Polytec laser vibrometer systems for real-time monitoring of the initiation and progression of delamination. The experiment allows the histories of load, displacement, and velocity of impacted specimens to be recorded and analyzed. The recorded profiles are used to characterize the damage initiation and evolution in the laminate. Numerical simulations are conducted using a cohesive finite element method. The method employs a cohesive zone model to simulate inply cracking and interlaminar delamination and a transversely isotropic, elastic model to characterize the bulk behavior of each ply. The simulations provide timeresolved characterization of damage during the impact loading. The damage modes predicted by the numerical simulations agree well with experimental observations.