Modelling of Tensile Behaviour of Sheet Moulding Compounds

An original approach to compute the longitudinal tensile break stress of multiphase composite materials with short fibers reinforcement is presented. The most obvious mechanical model which reflects a multiphase composite material is a pre-impregnated material, known as prepreg. We may include in this class of prepregs, Sheet-and Bulk Moulding Compounds. The model is seen as consisting of three phase compounds: resin, filler and fibers, model that is reduced to two phase compounds: substitute matrix and fibers. The Sheet Moulding Compounds reinforced with discontinuous and almost parallel fibers, subjected to longitudinal tensile loads, presents a specific note by the existence of a shear mechanism between fibers and matrix. This shear mechanism transfers the tensile load through the fibers. The Young's moduli for the substitute matrix and for the entire composite are computed and a comparison between the theoretical approach and the experimental data is accomplished.