This study investigates the effect of voids as manufacturing defects on the matrix-dominated strengths of carbon fiber reinforced plastic (CFRP) by coupon level testing. Specimens were cut from CFRP laminates prepared with different void volume fractions, Vv, by intentionally changing the curing conditions during their fabrication. The transverse tensile strength and the inter-laminar shear strength were evaluated by transverse-tensile testing and short-beam shear testing, respectively, using unidirectional flat specimens. The inter-laminar tensile strength was evaluated by performing four-point bending tests using unidirectional L-shaped curved specimens. The test results showed that these strengths decreased with increase in Vv and the ratio of decrease in strength to the increase in Vv varied according to the loading direction. The X-ray computed micro-tomography of the samples taken from the laminates used for the strength tests revealed the microscopic features of the shapes and the distributions of the voids in the CFRP laminates. The effect of voids on the strengths of CFRP laminates considering the stress concentrations around the voids is discussed based on the microscopic features of the voids and the internal loading directions in the critical regions.
