Titanium alloy foil-inserted carbon fiber/epoxy composites for cryogenic propellant tank application

Abstract

This paper presents the mechanical and gas barrier properties of titanium alloy foil-inserted carbon fiber/epoxy composites (CFRPs) undertaken to improve gas barrier properties for cryogenic propellant tank applications. A newly developed β-titanium alloy (GumMetal, GM) was applied. A sheet of titanium foil (α-Ti or GM, 0.05 or 0.1 mm) was inserted between cross-plied composite laminates ([0°2/90°2]S) without adhesive. Epoxy resin in the prepreg contributes to bonding between the Ti-foil and CFRP. The Ti-alloy foil insert did not strongly affect the tensile or compressive strength. Transverse cracks in the 90° layer never penetrated into the Ti-alloy foil layer before the final failure under tensile loading. Nonlinear stress–strain behaviors attributable to the pseudo-elastic behaviors of both unidirectional CFRP and β-Ti alloy (GM) were estimated using high-order stiffness and classical lamina theory. The numerical results agreed with the experimentally obtained results. Helium gas leakage under tensile stress was not observed before the final failure of the composites (1.4% of tensile strain). The excellent mechanical and gas barrier properties were successfully demonstrated.