Abstract

The accurate determination of interlaminar fracture toughness at cryogenic temperatures is critical for understanding the performance of composite materials in extreme environments, such as those encountered for liquid hydrogen storage applications. However, traditional measurement techniques, such as the Double Cantilever Beam (DCB) test, face significant challenges at cryogenic temperatures. One of the primary difficulties is the inability to directly measure the crack length during the test due to the immersion of specimens in cryogenic fluids, which is necessary to maintain the desired temperature.

In this study, we propose and validate an alternative methodology for estimating the crack length indirectly based on compliance calibration. Using a pre-characterized relationship between specimen compliance and crack length at ambient conditions, we develop a compliance-based approach that eliminates the need for direct crack length optical measurement during the cryogenic test. This method is applied to carbon fiber-reinforced epoxy composites, and its accuracy is evaluated by comparing results obtained at room temperature using both the standard method and the compliance-based approach.

Results demonstrate that the compliance-based method provides reliable fracture toughness measurements at room temperature, with good agreement with the standard approach. Extending the method to cryogenic conditions, we present interlaminar fracture toughness measurements at 77 K.

Our findings establish the compliance-based approach as a robust and practical solution for characterizing fracture toughness in cryogenic environments, overcoming experimental limitations associated with direct crack length measurements. This work contributes to the development of advanced testing protocols and enhances our understanding of composite material performance under cryogenic conditions, paving the way for their reliable use in liquid hydrogen tanks for the next generation of hydrogen-powered aircraft.