FINITE-ELEMENT ANALYSIS OF POROELASTIC COMPOSITES UNDERGOING THERMAL AND GAS-DIFFUSION

A theory for time-dependent thermal and gas diffusion in mechanically time-rate-independent anisotropic poroelastic composites has been deve loped. This theory advances previous work by fits latter two authors b y providing for critical transverse shear through a three-dimensional axisymmetric formulation and using it in a new hypothesis for determin ing the Biot fluid pressure-solid stress coupling factor, The derived governing equations couple material deformation with temperature and i nternal pore pressure and more strongly couple gas diffusion and heat transfer than the previous theory, Hence, the theory accounts for the interactions between conductive heat transfer in the porous body and c onvective heat carried by the mass flux through the pores, The Bubnov Galerkin finite element method is applied to the governing equations t o transform them into a semidiscrete finite element system, A numerica l procedure is developed to solve the coupled equations in the space a nd time domains. The method is used to simulate two high-temperature t ests involving thermal-chemical :decomposition of carbon-phenolic comp osites. Compared to measured data, tile results are accurate. Moreover , unlike previous work, for a single set of poroelastic parameters the y are consistent with two measurements in a restrained thermal growth test.