Analysis of local stress redistribution effects in short glass fibre-reinforced thermoplastics during fatigue using mesomechanical simulations

Abstract

Injection moulded short fibre-reinforced thermoplastics (SFRT) consist of a layer structure of different fibre orientations. As a result, the material’s stiffness and strength properties are highly anisotropic across the part and through the thickness. This study investigates the stress redistribution between layers with transverse and parallel fibre orientation caused by fatigue loading. For the analysis, fatigue data obtained from homogeneous highly oriented specimens are used to avoid layer interactions. The degradation of the dynamic stiffness of the meso plane acquired during the tests is implemented in a finite element (FE) model. Homogenisation methods for the fibre-matrix system are applied to describe the orthotropic layer stiffness. The study reveals stress redistributions from layers with transversely oriented fibres to layers with parallel fibres in relation to the load direction. The magnitude of the redistributed stresses in the simulated composite is small in relation to the quasistatic strength with a maximum amount of 0.26%.