Low Velocity Impact Study of Laminate Composites with Mode I Crack Using Dynamic Optical Caustics

The dynamic evolutions of stress singularities at mode I crack tip in laminate composites are studied by combining optical caustic with high-speed schardin camera. Theoretical caustics and initial curve for two different fiber laminate composites are simulated. Some characteristics of stress singularity at crack tip are analyzed. On the other hand, the generation and the subsequent evolution of dynamic failure around the crack tip are visualized by the optical shadow spots. The characteristic sizes of local stress concentration are extracted and the stress intensity factors at crack tip are determined. The local response and failure evolution mechanism of laminated composite after impact are analyzed by means of a series of optical caustic image and the deformation of composites.