Abstract
In this paper, the effect of thinning in ply-thickness on improvement of compression after impact (CAI) strength and the mechanisms in carbon fiber reinforced thermoplastics (CFRTP) was investigated. This improvement with thinning in ply-thickness was achieved by reduction of growth of fiber/matrix debondings inside each ply to transverse crack. Higher fracture toughness of matrix resin itself was also expected to contribute arresting the crack growth. By combining thinning in ply-thickness and higher fracture toughness of matrix, internal impact damage in CFRTP was dramatically suppressed. Two kinds of CFRTP laminates, in which one had 40 μm ply-thickness and the other had 120 μm ply-thickness, were prepared in order to observe the difference of morphology in internal impact damage and to evaluate the relation between CAI strength and projected impact damage area. Here, thickness of the both laminates was 3 mm. The projected impact damage area was measured with ultrasonic inspection. The effect of ply-thickness on initiation and propagation of internal impact damage, such as fiber/matrix debonding, delamination, and transverse crack, was discussed based on detailed cross-sectional observation of these internal damage with optical and laser microscope. In this study, polyamide 6 was used as matrix resin of CFRTP. Impact energy applied to CFRTP laminates was 1.5 J/mm.
