Simulation and Measurement of Cryogenic-Interfacial-properties of T700/modified Epoxy for Composite Cryotanks

Interface between the carbon fiber and epoxy was vital to the mechanical performance of CFRP under cryogenic temperature (-196 degrees C). In this paper, the cryogenic-interfacial-properties of carbon fiber/modified epoxy (T700/M-Epoxy) under -196 degrees C were analyzed by experiment, theoretical analysis and finite simulation method (FEM). Experimental data showed that the interfacial shear strength (IFSS) of T700/M-Epoxy at -196 degrees C was 75.8 MPa, which was increased by 16.1% in comparison with that (653 MPa) under room temperature (RT). For theoretical analysis, the microbond sample could be simplified into a cylindrical model. The increase of IFSS at -196 degrees C derived from contraction deformation of M-Epoxy. FEM was employed to simulate the distribution of interfacial stress and the evolution of debonding in T700/M-Epoxy. Based on the FEM model, both debonding and friction force (148.2 mN, 40.3 mN) at -196 degrees C were much higher than those (112.6 mN, 21.3 mN) under RT because of coefficient of thermal expansion (CTE) mismatch between 1700 and M-Epoxy. The theoretical analysis and FEM simulation made the experimental findings understood well, and they also could be used to predict the interface stress of fiber/resin at cryogenic temperature. (C) 2019 The Authors. Published by Elsevier Ltd.