Weibull distribution-based prediction model for compression after impact (CAI) strength of CFRP laminates

The aim of this research was to assess the appropriateness of the two-parameter Weibull distribution-based model to predict the compression after impact (CAI) strength and to develop both efficient and secure prediction scheme for laminated composite. Four levels of impact energy were considered (10 J, 25 J, 40 J and 55 J) and CAI tests were conducted. The scanning electron microscope were used to evaluate the representative damage pattern. Two-parameter Weibull function was utilized for statistically evaluating the CAI strength results. Experiment results showed that the wildest variance was observed at the impact energy range of 25–40 J for both layups. It was found fiber damage accompanied with high variance while the matrix and delamination damage corresponded to lower variance. To predict the CAI strength more efficiently, the time to first failure (TTFF) concept was used to draw CAI strength versus impact energy graphics under different reliabilities for reference. It was verified that the safe design strength curve under 0.99 reliability level was capable and secure enough to predict the residual strength in actual application considering the variance of composite.