Fracture Mechanics of Coilable Ultra-thin Composite Shell Structures

In recent years, ultra-thin composite shell structures have been implemented into origami-inspired deployable spacecraft designs due to their ability to be tightly coiled to meet the volume constraints of a rocket and support structural loads when deployed and in operation. During these processes, the coilable shells undergo large curvature changes which may induce the formation of localized cracks. To understand and model the fracture phenomenon, new approaches are proposed to characterize the fracture mechanics of geometrically nonlinear, anisotropic shells under flexure. This includes the development of new experiments to measure the bending mode fracture toughness. Preliminary results from these experiments will be presented. Additionally, fracture problems of the coilable composite longerons of the Space Solar Power Project (SSPP) spacecraft will be discussed. Results from X-ray μCT imaging of microstructural defects and their contribution to failure during coiling will be presented. The goal of this study is to understand the effects of manufacturing induced microstructural defects across different length-scales in causing failure in the longerons.