Interactive failure criteria for glass fibre reinforced polypropylene: validation on an industrial part

Interactive criteria describe the failure of a material as a function of the stress or strain tensor components, which are combined into a functional that denotes material failure when a threshold level is reached. Although no indication is given of the failure mode, these criteria are definitely interesting since they can be easily implemented in a Finite Element code, which is the established numerical technique for crash simulation. In this paper, we explore the applicability of these criteria to short glass fibre reinforced polypropylene, which is widespread in structural applications. For this class of materials, a compression-sensitive, strain-rate and orientation-dependent implementation is proposed, which is needed due to the characteristics of the polymeric matrix. In particular, the criteria of Tsai–Hill and Tsai–Wu are here investigated and validated in an application to an industrial part, as a bumper stiffener beam, for which a dedicated set of impact tests has been carried out. Notwithstanding the limitations of the approximate material laws here used, which is suitable for an early stage design, the prediction of the part failure proved to be more accurate than what can be achieved with simpler criteria based on maximum admissible strain.