An examination of failure criteria for notched orthotropic composite laminates

The purpose of this study is to further develop the Yeh-Stratton (Y-S) failure criterion for the application to orthotropic laminated composite materials. In this study, the fracture analysis of notched composite laminates is investigated by the Yeh-Stratton Criterion, a material strength failure model, and compared to failure models that utilize damage zone size predictions, known as linear elastic fracture models. The linear elastic fracture models of interest in this study are the Average Stress Criterion and Point Stress Criterion proposed by Nuismer and Whitney as well as the D-Criterion proposed by Zhen.; The materials being examined are fiber-reinforced orthotropic composites. The first material in this study is a new ceramic matrix composite (CMC) of interest in the aerospace industry. The second material in this study is a graphite/epoxy AS4/3502. Testing of both fiber reinforced CMC [0/90] and AS4/3502 [0/902/0] laminates containing central cracks and under tensile loading conditions were analytically investigated by the failure criteria and evaluated against the experimental results.; The results of this study indicate that the Yeh-Stratton Criterion and the linear elastic fracture models predict the fracture of orthotropic laminated composites containing a center crack under tensile loading to a similar degree of accuracy. The results also indicate that the damage zone size predicted by the Yeh-Stratton fracture model does not represent the actual damage zone size. The linear elastic fracture models appear to predict the actual damage zone size to a within an order of magnitude. It is apparent that further research on this topic is needed.