A simplified finite element method for failure analysis in adhesive-bonded nozzle diffuser of solid rocket motors

Abstract

The adhesive bond between the nozzle diffuser shell and the insulation layer of solid rocket motors (SRM) is widely used due to its lightweight, simple design, and easy operation. The mechanism of adhesive-bonded failure between them is a concern for designers. In this paper, a simplified finite element method for failure analysis in the adhesive-bonded nozzle diffuser of SRM is proposed. In the method, the diffuser shell, insulation layer, and adhesive between them are considered elastic. The maximum Von Mises stress failure criterion is assumed to be suitable for the adhesive. The adhesive-bonded failure is simulated by using the user subroutine VUSDFLD in the commercial Finite Element Analysis software ABAQUS. The method is verified to be simple but effective based on the comparison with experimental results. The adhesive-bonded failure process under external load can be well simulated, and the critical external load of adhesive-bonded failure can be accurately predicted. In addition, the method is utilized to study the failure of the nozzle diffuser with several kinds of original debonding. It is suggested that the original axial debonding ratio should be less than 60%, and the circumferential debonding angle should be smaller than 30° in the conical section of the nozzle diffuser.