Uniaxial tensile behavior of sheet molded composite car hoods with different fibre contents under quasi-static strain rates

Abstract

Composite materials have recently been of particular interest of the automotive industry due to their high strength to weight ratio and versatility. Among different composite materials used in mass-produced cars are sheet molded compound (SMC) composites, which consist of random fibres making them inexpensive candidates for non-structural applications in future vehicles. In this work, SMC composite materials were prepared with varying fibre orientation and volume fraction and put through a series of uniaxial tensile tests at varying strain rates. Tensile strength was found to increase with increasing volume fraction and increasing strain rate, but strain rate was the less sensitive of the two. The two material orientations used, longitudinal and transverse, had vastly different results in reference to tensile strength and fracture strain. Yield and ultimate tensile strengths were higher in the transverse direction. The experimental results were used to develop a general predictive analytical model including the effects of strain, strain rates, and volume fraction of fibres. The analytical model was found to accurately predict the composite deformation in majority of cases, while some error was found in tensile properties of SMC composites with lower volume fractions and high strain rates. This constitutive model can describe the deformation behavior of an SMC composite to aid in determining the feasibility of integrating these materials into the automotive industry.