Experimental Investigations on the Influence of Different Notch Designs on the Pullout Performance of Circumferentially Notched Z-pins

Abstract

The results of experimental research on the pullout properties of circumferentially notched z-pins with various notch designs are presented in this paper. Investigations on notched z-pins with four different notch designs—rectangular, circular, triangular, and sinusoidal—inserted into unidirectional (UD) and quasi-isotropic (QI) laminates were carried out in order to assess the influence of notch design and laminate structure on the resulting z-pin pullout properties. It can be shown that the application of circumferential notches at the z-pin surface causes significant increases in pullout forces and consequently, on the resulting pullout energies, regardless of which notch design is considered. The effect of notched z-pins is higher in a quasi-isotropic than in a unidirectional laminate structure. The highest enhancements of the pullout energy were found on quasi-isotropic laminates with circular and sinusoidal notch designs with increases of up to 69%, in comparison to measurements on samples with unnotched z-pins.