Validation of trace-based approach to elastic properties of multidirectional glass fibre reinforced composites

A recent invariant-based theory of composites is re-examined using multidirectional laminates through classical lamination theory applied on experimental data and micromechanical predictions for unidirectional laminates. Initially, the master ply values developed for carbon reinforced polymer composites (CFRP) proved to be inappropriate for aramid and glass reinforced polymer composites (KFRP and GFRP). This led to part the material systems into four classes, According to the type of reinforcing fibre, with dedicated master ply values. By then, GFRP was declared unfit for this theory due to the wide variation of the trace-normalized stiffness parameter with a small variation of longitudinal modulus. Here, the specialization of master ply values for KFRP and GFRP is demonstrated using micromechanical predictions. The invariant-based theory is applied to short beam deflection of multidirectional laminates and cross-ply GFRP laminates. This approach leads to small errors, for all material classes including GFRP. In brief, GFRP composites proved fit for invariant-based theory under the present conditions.