Cryogenic mechanics and failure behaviors of CFRP/Aluminum honeycomb sandwich structures

Sandwich structures composed of carbon fiber reinforced polymer (CFRP) and aluminum honeycomb have been widely used in aerospace applications due to their high stiffness and strength. However, the cryogenic reliability of composite sandwich structures remains challenging due to the complex temperature effects on their mechanical performances and failure modes. Herein, the temperature-dependent mechanical behaviors of CFRP/aluminum sandwich structures were investigated through experimental testing, theoretical analysis, and numerical simulation. The failure behaviors were explored through four-point bending and in-plane compression experiments of composite sandwich structures under various temperatures (293 K, 193 K, and 93 K). The effects of dimension and temperature on failure modes were analyzed, and temperature-dependent failure maps were deduced. The results showed an increase in the bending and compression ultimate loads of composite sandwich structures as a function of the decrease in temperature. As the temperature dropped from 293 K to 93 K, the flexural strength of the specimens increased by 33 %, mainly due to the rise in the shear strength of the honeycomb core. Meanwhile, the compressive strength of the specimens rose by 21 % owing to the enhancement of the face sheet. Failure maps showed a more susceptible bending process to the compression failure of face sheet at cryogenic temperatures, while the in-plane compression process was less susceptible to face sheet failure due to the cryogenic reinforcement of the composite. Overall, the proposed approach can efficiently be utilized to analyze the cryogenic bearing performance and failure mode of composite sandwich structures, promising for cryogenic applications.