Experimental Study Of Impact Behavior Of Laminated Composite

The widely application of fiber-reinforced composites in the field of the aerospace and automotive industries is due to the fact that these materials have a very high stiffness to weight ration, high strength to weight ratio, and impact resistance. But there are many unsolved mechanical problems about composites that must be researched on the instant. Especially, the study of dynamic deformation and impact behavior of composites subjected to concentrated load is an important subject.In this paper high speed photography and optical caustic method is introduced to study impact behavior of laminated Composite. The research includes two aspects: dynamic stress concentration of region of loading and crack tip of Mode I. First, the parametric equations of the caustic and its initial curve surrounding the stress concentration zone are derived by the theoretical closed-form elastic solutions and the principle of reflective caustics. Theoretical caustics and initial curves for laminate orthotropic composites are simulated and analysed. Second, experimental study of two kinds of materials by means of multi-spark high-speed camera is performed to investigate the dynamic evolution of local stress singularities in laminated composites subjected to impact-concentrated loading. Using relation between the local concentrated load or the stress intensity factor and the geometric characteristic size of caustic curve, the local concentrated load and the stress intensity factor is obtained. Finally, the impact behavior of two kinds of materials is compared. These results account with theoretical analysis and can help to evaluate strength and predicte service life for composite structures.