Stochastic characteristics of interlaminar shear strengths of laminated composites

Experimental observations clearly show that delamination failure of laminated composites exhibits two distinct characteristics; (1) the corresponding failure strengths display considerable variability, and (2) the morphologies of the fracture surfaces and thus the interlaminar strengths are strongly dependent on the magnitude of the fiber orientation difference (abbreviated as f.o.d) between the two adjacent layers of the interface. These characteristics need to be thoroughly investigated in order to have accurate information on the delamination strength. The stochastic analysis technique, in which the interlaminar strength is represented as a stochastic process with respect to the f.o.d. angle, can be an efficient method for this investigation. In the present work, a stochastic model for the interlaminar shear strengths is developed based on a number of discrete experimental sample data sets. The associated experimental scheme is also described, which is performed to measure the randomness in the interlaminar shear strengths using the double notch shear specimens with multidirectional lay-up.