BONDING PERFORMANCE OF MAGNESIUM TO CARBON-FIBER COMPOSITES

Advanced materials including magnesium (Mg) alloys and carbon fiber (CF) reinforced composites are of interest for automotive components due to their lightweight characteristics. Mg alloys have low density (1.7 g/cc), high ductility, superior damping capacity, high machinability and thermal conductivity. Despite having potential in the automotive industry for weight savings, the use of Mg in an average vehicle is relatively less. This is because Mg is difficult to join or repair when used in a multi-material system. Carbon Fiber/Magnesium (CF/Mg) hybrid system has the advantage of lowering the material cost(s) while maintaining high structural integrity. This study uses chemical etching to enhance the surface energy of AZ31 magnesium alloy for optimal bonding to carbon fiber composites. Chromium Oxide (CrO3) based etching agents were used in various concentrations to optimize treatment on the Mg surface. Sandwich panels were compression molded with Mg as the substrate, and carbon fiber composite as the skin. Flexural strength of ~593 MPa was observed for polyamide (PA6)/Mg hybrids compared to ~527 MPa for epoxy woven prepreg/Mg hybrids. Flexural modulus of ~40 GPa was observed for PA6/Mg hybrids and ~38 GPa for epoxy woven prepreg/Mg hybrids. Failure mode under bending did not exhibit major delamination between substrate and skin, indicating strong interfacial bonding. The manufacturing approach, testing/characterization, and mechanisms of failure are discussed. The work has value for automotive and a broader range of multi-material systems.