Design and Validation of a Filament Wound Composite Rocket Motor Case

Filament wound composite structures are widely used in aerospace applications such as motor case of rockets owing to their high stiffness/weight ratio and high strength. However, design and analysis of a filament wound structure is so complex due to the anisotropic nature of the composite material. Variation of the winding angle through the rocket motor case axis and through the thickness, which is also a function of winding angle are the main challenges to the realistic modeling of a filament wound composite rocket motor case. In this study, finite element analysis of a filament wound rocket motor case with unequal dome openings was performed. The finite element model was compared with manufactured motor case in terms of winding angle and thickness to ensure the exact modeling. The finite element analysis was compared with burst tests in terms of fiber direction strain distribution through the outer surface of the motor case to verify analysis. The weak regions of the motor case were determined with finite element analysis to be transition region from cylinder to dome which is subjected to significant bending because of the stiffness difference between these regions. Then, some design improvements were proposed to increase the mechanic performance of motor case. Significant improvement was succeeded in terms of mechanic performance. Important aspects of designing and analyzing a filament wound composite rocket motor case were addressed for designers.