Comparison of fracture models to assess the notched strength of composite/solid propellant tensile specimens

Modifications are made in the well-known inherent flaw model as well as in the stress fracture models for accurate prediction of notched tensile strength of composite laminates containing holes or slits. To examine the adequacy of these modifications, fracture data on different composite materials reported in the literature are considered. The notched strength estimates from the present fracture models are found to be close to the existing test results. An attempt is made to correlate the fracture data of center crack tension specimens made of nitramine and HTPB-based propellant materials. The present analysis results from the above simple models are found to be in good agreement with test results. This study confirms the applicability of the above three fracture models to solid propellant materials having relatively low stiffness and strength. Since the notched strength estimates of composite/solid propellant tensile specimens are close to the test results, any one of them can be utilized while evaluating the notched tensile strength of specimens.