Compression properties of z-pinned carbon-fibre/epoxy laminates reinforced with circumferentially notched z-pins

Abstract This paper represents results of the investigations on in-plane compression properties of unidirectional carbon-fibre/epoxy laminates with a three-dimensional z-pin reinforcement with circumferentially notched z-pins. Different notch designs - rectangular, circular, triangular and sinusoidal - were examined to identify the impact on the resulting compression strength and modulus. From the determinations it can be concluded that notching of z-pins has a significant impact on the compression strength, no matter of the notch design. Due to the changes in microstructure caused by the implementation of notches at the z-pin surface, eg partially lower in-plane fibre waviness as well as reduced swelling behaviour, the compression strength values are significantly higher compared to those of laminates reinforced with unnotched pins. With increasing notch depth and decreasing notch distances the compression strength values are rising. In contrast, the Young's modulus of the z-pinned laminate is not affected by notching of the z-pins. An influence of the notch design, depth and distance of circumferential notches on the Young's modulus was not found with the investigation carried out.