Experimental and theoretical studies on inter-fiber failure of unidirectional polymer-matrix composites under different strain rates

Polymer-matrix composites (PMCs) are widely used in many fields. However, the accurate characterization of their failure behavior is still a challenge. At present, the inter-fiber failure of unidirectional PMCs under compression is not well predicted, and the corresponding strain rate dependent failure theory remains less explored. This paper aims to study and characterize the inter-fiber failure behavior of unidirectional PMCs under different strain rates. Unidirectional glass/epoxy specimens with various off-axis angles were tested at three strain rates (quasi-static, 383 and 646 s⁻¹), and the measured strain rate dependent strength is modelled by an empirical formula. To evaluate the test results, a new failure theory that incorporates strain rate effects is proposed. The theory is developed based on three different failure modes, with each represented by a new and simple formula. Comparison shows that the predicted failure envelopes and fracture angles are in excellent agreement with the experimental results.