The role of intra-laminar hybridization on the thermo-mechanical behaviour of fibre-hybrid composites using 3D RVEs

Abstract

The effect of intra-laminar hybridisation (i.e., two fibres within the matrix) on the effective coefficients of thermal expansion and thermomechanical behaviour of fibre-hybrid unidirectional composite laminae is investigated in this study. The research focuses on S-glass/epoxy and carbon/epoxy laminae hybridised with a secondary thermoplastic fibre (i.e., polypropylene, PET and PEEK). To conduct micro-mechanical analyses under transverse tensile and shear loading conditions (with and without thermally induced residual stress), three-dimensional representative volume elements (3D RVEs) are developed. The effects of using different microstructures, volume fractions, fibre diameters, and thermal cycles on interfacial and matrix microstress fields are investigated. The predicted homogenised elastic properties are validated against experimental data, while the predicted effective coefficients of thermal expansion of the RVEs models are validated against two well-established analytical models (i.e., Schapery and Mori-Tanaka). The results indicate that intra-laminar fibre hybridisation can alter the lamina’s effective coefficients of thermal expansion and micro-stress fields. Notably, the inclusion of polypropylene (PP) fibres as secondary fibres significantly increases interfacial stresses due to the substantial mismatch in the coefficient of thermal expansion between the PP fibres and the epoxy matrix. The extent of these alterations relies on variables such as fibres’ stiffness and coefficient of thermal expansion, thermal cooling-down cycle, and fibre volume fractions. This facet offers an opportunity for exploration as a method to regulate damage modes and, consequently, the processes of energy dissipation.