Study on Failure Criteria and the Numerical Simulation Method of a Coal-Based Carbon Foam under Multiaxial Loading

Abstract

Coal-based carbon foam (CCF) has broad application prospects in aerospace, composite material tooling and other fields. However, the lack of failure criteria limits its promotion. In previous studies, the failure criteria of similar materials were proposed, but there are some limitations. This paper proposes improved failure criteria based on macro-mechanical tests. Furthermore, uniaxial and multiaxial loading tests were carried out to obtain accurate failure criteria of CCF. Finally, 3-points bending tests of the CCF sandwich structure were conducted and their finite element models (FEMs) were established. The CCF test results show that the mechanical properties of CCF are transversely isotropic. The failure criteria in this paper can accurately predict the stress when the CCF fails. The error band boundary formula caused by the dispersion of the material were also given. The maximum load Pmax calculated by the failure surface (3684 N) was only 4.7% larger than the mean value measured by the test (3518 N), and all of the Pmax measured by the test (3933 N, 3640 N, 3657 N, 3269 N, 3091 N) were between the maximum value (4297 N) and minimum value (3085 N) calculated by the error band boundary formula, which means that the failure criteria have good precision.

Keywords

• coal-based carbon foam
• transverse isotropy
• failure criteria
• modified equivalent von Mises stress