Steel-CF/PA 6 hybrids manufactured by a laser tape placement process: Effect of first-ply placement rate on lap shear strength for garnet blasted substrates

Abstract This paper investigates the manufacture of selectively reinforced metal/composite hybrids in a laser-assisted automated tape placement process. Unidirectional carbon fibre/PA 6 composite tapes were applied to 1.9 mm hot rolled steel substrates. The bonding of the first ply to the substrate is critical to the success of the metal-composite hybrid. This work investigates the effect of increasing the first-ply placement rate for speeds of 25 mm/s, 50 mm/s and 100 mm/s. The steel substrates were pre-treated by garnet blasting and then coating with a 60 μm layer of PA 6. The garnet blasted surface texture was quantified using white light interferometry. The thermal history for bonding of the first ply was measured with fine wire thermocouples. The interfacial bond strength of the hybrid laminates was assessed by ASTM D 3165 lap shear tests. The lap shear strength increased to the highest value of 22.4 MPa at 50 mm/s. Analysis of the fracture surfaces and thermal history suggest that the lower strengths at 25 mm/s and 100 mm/s are due to lower adhesion of the PA 6 coating to the metal substrate, most probably due to lower levels of crystallization.