Damage evolution of CFRP laminates subjected to cryogenic flexure loading using in situ X-ray computed tomography

Studying the damage evolution and leakage behavior of carbon fiber-reinforced polymer (CFRP) composites subjected to complex loading in cryogenic propellant tanks has been challenging for the research community. The development of a novel in situ cryogenic flexure test for monitoring the damage evolution of plain woven CFRP composites using X-ray computed tomography (CT) is presented in this study. In situ flexure testing was conducted at temperatures of room temperature (RT), −100 °C and −180 °C. The defects were extracted and quantified from in situ CT images. The effects of the stress state and temperature on cryogenic damage evolution behavior are discussed. CT, optical microscopy and scanning electron microscopy characterization revealed the damage evolution and failure mechanisms of CFRP composites under flexural loading. Intralaminar cracks and interlaminar delamination were induced under cryogenic mechanical loading, and leakage paths formed. The leakage properties of the CFRP composites under various pressures at RT, −100 °C and −180 °C were measured by permeability testing.