Investigation on thermal conduction of graphite film enhanced carbon fiber polymer composite by laser flash analysis

Abstract

Laser flash analysis (LFA) is an advantageous transient method, widely used for measuring thermal diffusivity of solid materials nowadays. In this paper, the thermal conductivity of graphite film enhanced carbon fiber composite was measured by LFA and the results show an unusual size-dependent effect which was considered to be due to violation of homogeneous assumptions. To investigate the size effect, numerical analyses based on the representative volume element (RVE) models were implemented to evaluate the thermal conductivities of composites with periodic microstructures. Transient periodic boundary conditions (PBCs) were proposed and applied to the RVEs for simulating the LFA. Transient simulative results obtained by applying PBCs verify the size effect and are in better agreement with the experimental data than those obtained by applying conventional adiabatic conditions. Moreover, the classical steady-state analyses on RVEs were performed for comparison. The reason for size effect was discussed in details. The present work expands the application scope of LFA to measuring thermal conductivity of complex composite and provides a perception of discreetly selecting specimen size and modifying the general LFA technique.