Experimental and numerical analyses of the tensile strength and mixed-mode fracture behavior of sheet molding compound plates

Polymer matrix composites are the most prevalent ones among all the composite materials because they offer high specific strength to weight ratio, toughness, and ease of processing. These composites own most of their properties to the high-strength reinforcement materials as carbon, glass, and aramid fibers. The mass production method of such composites is basically the sheet molding compound (SMC) compression molding technology. However, regarding the inherent defects of SMCs, such as porosities and internal cracks, the current trend of improving their performance requires a thorough understanding of mechanical and fracture properties of such products. Therefore, in this work, the commercially available chopped glass-fiber reinforced polyester SMC has been subjected to uniaxial tensile and mixed-mode fracture experiments, along and perpendicular to the rolling direction. The results of these experiments were employed as input data in a finite element model to determine the fracture toughness (KIC and KIIC) and critical strain energy release rate (GIC and GIIC) of material under mixed-mode loading conditions. Overall, although the reinforcing material were in the form of strands of glass fiber, SMC specimens exhibited lower mechanical properties and fracture toughness in transverse direction as compare with that of the longitudinal (rolling) direction under all modes of loadings.