Effects of ferromagnetic & carbon-fibre Z-Pins on the magnetic properties of composites

This paper investigates for the first time the effects of Z-pins on the magnetic properties of composite laminates. In-plane and out-of-plane M-H curves of IM7/8552 laminates with and without Z-pins have been characterised by an MPMS3 SQUID magnetometer. Two kinds of pin materials (T300/BMI composite and ferromagnetic Ni/Fe alloy) have been studied at three different volume fractions (nominally 0.5%, 2% and 4%). The unpinned and carbon-fibre pinned laminates were found to be diamagnetic. The carbon-fibre pin had no significant influence on the global magnetic properties of the laminates. The Ni/Fe alloy pin increased the laminate linear-part magnetic volume susceptibility up to 1.87 and 0.13 for the out-of-plane and in-plane directions, respectively. Numerical modelling has been conducted to support the investigation of the effect of the pin volume fraction on the overall magnetic susceptibility and saturation magnetisation. The laminate out-of-plane susceptibility exhibits a nonlinear behaviour dependent on pin volume fraction, due to interactions between adjacent pins. The saturation magnetisation is proportional to the pin volume fraction and independent of field direction.