Experimental and numerical analysis of mode II fracture between propellant and insulation

The reliability of the bonding between propellant and insulation plays an important role in estimating Solid Rocket Motor (SRM) structural integrity. In this paper we use experimental and numerical methods to analyze the Mode II fracture properties of the interface debonding between propellant and insulation. An adhesive-adherend sandwich of Hydroxyl-Terminated Polybutadiene (HTPB) propellant and HTPB based insulation is bonded by the HTPB adhesive, providing Single-Lap Joints with revised supports to analyze the shear behavior of the interface debonding. A bilinear model is used to construct the Finite-Element (FE) model and simulation. The estimated Cohesive Zone Model (CZM) parameters calibrated from experiments are optimized by an inverse analysis based on the Hooke-Jeeves optimization algorithm. Good agreement is found which indicates that the estimated CZM values were precise. The study presents a simplified way to test the shear behavior of the adhesive layer between propellant and insulation with ductile properties. The result may offer a contribution to optimizing the interface structure in SRM, to analyzing the structural integrity of SRM, and for conducting numerical analyses of SRM.