Thermophysical Properties Mapping of Composites by Lock-in Thermography: Applications on Carbon Fiber Reinforced Plastics

We propose a versatile method for measuring the thermophysical properties of composites by means of lock-in thermography (LIT) technique. The method is based on analyzing the thermal response distribution induced by periodic laser heating, which enables simultaneous high-spatial-resolution mapping of the effective out-of-plane thermal diffusivity, thermal conductivity, and volumetric heat capacity over the surface of the material. We validate the method using a reference material and demonstrate its capability in visualizing the effective properties of laminated carbon fiber reinforced plastic and carbon fiber reinforced thermoplastic with discontinuous fibers. The results showed that the LIT-based approach has high reproducibility and sensitivity, which allows observing the effect of fiber orientations on the effective properties. The proposed method will be useful for thermal research in composites, defect detection, and for investigating component geometric arrangement effects on the thermophysical properties.