Effect of resin matrix on the strength of an AZ31 Mg alloy-CFRP joint made by the hot metal pressing technique

Abstract

This study investigated the effect of two types of carbon fiber reinforced plastics (CFRPs) with different matrices, on the strength of a metal alloy–plastic composite joint made by the hot metal pressing (HMP) technique. One set of experiments was carried out with a PAN-type CFRP with a thermoplastic polyurethane (TPU) matrix, and the other with a PAN-type CFRP with a polyamide 6 (PA6) matrix. Both matrices were joined with either as-received or annealed AZ31 Mg-alloy sheets processed at different annealing durations to produce oxide layers on the alloy sheets. Due to the complete suppression of CFRP-resin decomposition at its joint interface, the CFRP with a PA6 matrix exhibited superior joint strength as compared to the TPU-matrix CFRP, which showed partial suppression of the CFRP-resin decomposition and bubble formation, with complete suppression characterized by microcracking at its joint interface. A reaction between C and MgO was observed at the joint interface for the TPU-CFRP but not for the PA6-CFRP. The melting/decomposition temperature of the matrix materials and the influence of the oxide layer on the conduction of heat between the materials were the key determinants of the AZ Mg alloy-CFRP joint strength.