Static and fatigue behavior of a carbon‐fiber SMC‐R composite under combined tensile and shear stresses

Abstract Randomly oriented short fiber reinforced sheet molding compound composites (SMC‐R) are among the most commonly used composites for automotive and many non‐automotive structural applications. Many studies have reported the static and fatigue properties of SMC‐R composites under uniaxial stress conditions. However, there are many applications in which they may be subjected to biaxial stress conditions and their biaxial properties have not been reported in literature. The current study considers the static and fatigue characteristics of a randomly oriented carbon fiber SMC‐R under both uniaxial and biaxial loading conditions with various combinations of tensile and shear stresses. A butterfly shaped Arcan specimen was used to conduct the biaxial stress tests. Since both static strength and fatigue life data exhibited significant variability, statistical analysis was conducted using Weibull distribution to analyse the variations in these properties of the material. In biaxial conditions in which a shear stress is imposed along with a tensile stress, the tensile strength of the material decreases with increasing shear stress. A failure envelope drawn based on von Mises equation shows reasonable agreement with the experimental results. As a percentage of the static strength, the fatigue strengths at 1 million cycles in tension and combined equal tension and shear are significantly higher than the fatigue strength in pure shear.