Evaluation of Fiber Orientation in Carbon Fiber-Reinforced Polymer Composites Using a Simple, Low-Cost Infrared Measurement System: Application to Unidirectional Carbon Fiber Composites

Carbon fiber-reinforced polymer (CFRP) composites exhibit higher strength in the longitudinal direction than in the transverse direction of the fibers, making fiber orientation evaluation crucial. In this study, a method for evaluating fiber orientation using halogen spot-periodic heating and a non-lock-in-type infrared camera is employed and applied to a unidirectional carbon fiber composite—a CFRP composite with unidirectional continuous fibers. Consequently, the in-plane thermal diffusivity in the fiber direction is significantly higher than that in other directions. Therefore, the employed method successfully evaluates fiber orientation in unidirectional carbon fiber composites.