Experimental Study of Deformation and Failure Mechanisms in Unidirectional Fiber-reinforced Polymers

Nonlinear mechanical response of fiber-reinforced polymer matrix composites is a result of two major interactive phenomena: a) brittle microcracking, b) deformation of the matrix. Earlier studies on the deformation of composites with thermosetting matrix show some form of plastic localization along certain planes. In this study, tension and compression tests were carried out on unidirectional carbon/epoxy specimens to measure the irreversible deformations occurring along the action planes. Results suggest that in the case of UD laminates, accumulation of plastic shear strains on a critical plane controls the response. Using the experimental measurements, yielding behavior of the matrix under different loading conditions was modeled. This physically-based modeling strategy is able to reproduce the complex effects of multi-axial loading.