LAUSR

Abstract This paper presents the results of experimental investigations on the pullout properties of circumferentially notched z-pins in carbon-fiber/epoxy prepreg laminates with unidirectional (UD) and quasi-isotropic (QI) fiber orientation. Four different notch depths between 10 and 25 μ m and three different notch distances between 100 and 300 μ m were investigated to determine the influence of notches with rectangular shape incorporated at the pin surface on the characteristic z-pin bridging forces and the resulting pullout energies. At UD-laminates the highest increase of the maximum debonding force Pd and maximum friction force Pf could be determined with notched z-pins with a notch depth of 10 μ m and a notch distance of 100 μ m. This is also reflected in the specific pullout energy, which shows an increase of 40%, compared to samples with unnotched pins. For QI-laminates, the increases are higher and can be quantified with an increase in pullout energy of 55% at a notch depth of 15 μ m. A variation of the notch distance at a constant notch depth of 20 μ m shows linear dependencies of the pullout energy and achieves improvements of up to 29% for UD-laminates and 42% for QI-laminates at the highest notch distance of 300 μ m.