An Examination of Failure Criteria for Notched Orthotropic Ceramic Matrix Composite Laminates

Abstract

The purpose of this paper is to further study the Yeh-Stratton (Y-S) failure criterion when applied to the newly developed ceramic matrix composite (CMC). In this study, the failure analysis of notched CMC laminates is investigated by the Y-S criterion and compared to linear elastic stress models including the average stress criterion (ASC), point stress criterion (PSC), and the D criterion.The materials being examined are fiber-reinforced orthotropic composites, which are a new CMC of interest in the aerospace industry, and 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 study results indicate that the Y-S criterion and the linear elastic stress 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 Y-S criterion does not represent the actual damage zone size. The linear elastic stress models appear to predict the actual damage zone size within an order of magnitude. It is apparent that further research on this topic of damage zone size prediction is needed.