A statistical treatment of the loss of stiffness during cyclic loading for short fiber reinforced injection molded composites

Injection molded short fiber reinforced composites (SFRC) have different local fiber orientation distribution (FOD) at every point. SN curves of short fiber reinforced composites are known to depend on the fiber orientation distribution. Such materials also suffer from continuous loss of stiffness during cyclic loading. It is not known whether the loss of stiffness is different for SFRC with different FOD.A statistical analysis of the loss of stiffness curves is presented in this paper. Tension-tension fatigue experiments are performed and loss of stiffness is collected for every data point in the SN curve. A systematic method for comparing the loss of stiffness is developed. It is concluded that the difference in loss of stiffness curves for coupons of SFRC with different FOD is not statistically significant.