The influence of material shear nonlinearity on predictive failure envelopes of multidirectional laminates

Abstract

In present study, laminates with the type of [+/-theta degrees](S) and [0 degrees(2)/+/-theta degrees](S) are investigated in order to clearly show the effect of material shear nonlinearity, and then theoretical predictions are compared with experimental data. In the whole process of generating failure envelopes, secant shear modulus instead of initial shear modulus is used for accurate shear stress-strain relation. The modulus values are recalculated every time when the combining load is changed. Final failure envelopes are then compared between numerical models. It is found that the variation in the size of safe regions from nonlinear analysis is closely related to the way of combing load and fiber directions. So in the process of improving failure theories or in the applications of failure theories, the effect of material nonlinearity can be considered appropriately.