The fracture properties of a fibre-metal laminate based on magnesium alloy

A range of fibre-metal laminates (FML) based on a lightweight magnesium alloy have been manufactured and tested. Two types of composite reinforcement have been investigated, a woven carbon fibre reinforced epoxy and a unidirectional glass fibre reinforced polypropylene. Initial tests using the single cantilever beam geometry (SCB) have shown that little or no surface treatment is required to achieve a relatively strong bond between the composite plies and the magnesium alloy. Tests on both types of laminate indicated that increasing the volume fraction of composite, V-C in the FML resulted in a significant increase in its tensile strength. Similar tests showed that the addition of the woven carbon fibre/epoxy plies did not have any effect on the Young's modulus of the FML whereas increasing the V-C of the glass/polypropylene plies resulted in a continuous decrease in the modulus of these thermoplastic-matrix systems. Fatigue tests on both types of laminate highlighted the positive contribution of the composite plies in the FMLs. Here, the crack growth rates in centre-notched tension specimens were significantly lower in the FMLs than in the plain magnesium alloy system. Low velocity impact tests on the FMLs highlighted their excellent energy-absorbing characteristics relative to two aluminium-based FMLs. The specific perforation energy of the glass fibre/PP laminate was higher than that offered by a similar aluminium alloy FML and significantly higher than that for a glass reinforced epoxy/aluminium FML. Here, extensive delamination and shear fracture in the outer magnesium alloy plies were found to contribute to the energy-absorbing capacity of these laminates. (c) 2005 Elsevier Ltd. All rights reserved.