Innovative Approaches for Evaluating Interlaminar Tensile Strength of Ceramic Matrix Composites (CMCs) at Elevated Temperatures

Hot structures fabricated from CMCs are an attractive design option for specialized components of future military aerospace vehicles and propulsion systems to reduce weight and increase survivability. However, thermal-structural components fabricated from CMCs suffer from inadequate interlaminar strength, thereby increasing their vulnerability to delamination when subjected to high through-thickness thermal gradients, acoustic/high cycle fatigue, impact damage, and/or applied normal loads. Although there are Industry standards for Interlaminar Shear strength testing, no such consensus exists for Interlaminar Tension [ILT] strength testing – particularly at elevated temperatures. Better test methods are needed to characterize the interlaminar strength of CMCs to facilitate the design of efficient structures, reduce the risk of premature hardware failures, and support production Quality Assurance. Hyper-Therm HTC is proposing an innovative approach for measuring the elevated temperature ILT strength of CMCs. The test configuration directly applies an interlaminar tension force to the midplane of the laminate thereby creating a clean, ILT stress state in the specimen that does not require knowledge of the interlaminar properties in order to calculate the failure stress. Specimens can be fabricated inexpensively from flat plate stock, and because the test method does not require adhesive bonding, it can be used at temperatures up to 4000°F.