Thermal Diffusivity Imaging of CFRP: Spatial Correlation Between Lock-in Thermography-Based Measurement and Synchrotron X-ray CT Simulation on Identical Region

With the increasing adoption of wide-bandgap semiconductors such as SiC and GaN in high-power electronics, the thermal management of semiconductor devices has become critical. High thermal conductivity thermal interface materials (TIMs) are essential to minimize thermal contact resistance.
While advanced fillers such as graphene, diamond nanosheets, and hexagonal boron nitride (h-BN) have been proposed, their effectiveness strongly depends on the spatial continuity and orientation of the filler network. Excessive filler loading, on the other hand, degrades mechanical strength and
flexibility. Visualizing the spatial distribution of thermal conductivity is thus essential to optimize the filler structure.
This study investigates the correlation between the spatial thermal diffusivity distribution and the internal filler structure in composite materials using both experimental and numerical approaches. A lock-in thermography-based laser periodic heating method was used to image the thermal diffusivity
of a CFRP (carbon fiber reinforced plastic) specimen. The internal fiber-resin structure was visualized using synchrotron X-ray computed tomography (CT), meshed using GeoDict, and used to perform transient heat conduction simulations in ANSYS. The thermal diffusivity distribution obtained from simulations was compared with that measured by the lock-in thermography method. Good agreement between the two results validated the capability of the method to visualize anisotropic thermal transport associated with the fiber structure. Additionally, the effects of filler content and chain-like carbon fiber configurations on thermal diffusivity were discussed. The findings provide valuable insights for the structural design of high thermal conductivity composite materials.