Measurement of in-plane thermal diffusivity of carbon composites by periodic heating method using lock-in thermography (Effects of interface thermal conductance and verification by thermal-numerical model)

Abstract

Measurement of thermal conductivity for anisotropic material is difficult or troublesome for conventional measurement techniques. Then periodic heating method using lock-in thermography was proposed as a convenient measurement technique. In this paper, thermal diffusivity distribution of pitch based carbon fiber reinforced plastics (CFRP) was measured by periodic heating method using lock-in thermography. The results showed that thermal diffusivity of several CFRPs depend on heating frequency. Then CFRPs were made using autoclave in various conditions and thermal diffusivities were measured. The results showed that thickness directional thermal diffusivities of CFRPs which were made at low pressurization are smaller than that of CFRPs which were made at standard pressurization, and in-plane thermal diffusivities of CFRPs which were made at low pressurization depend on heating frequency. It means that thermal contact resistance between prepregs causes heating frequency dependencies. Next, numerical model for pitch based CFRP was constructed using control volume method, and parametric study about thermal contact resistance was carried out in order to find the cause of heating frequency dependencies. Numerical results supported the results of experimental study.