TWI Industrial Member Report Summary 226/1983
S A Westgate
Weldbonding, the combination of resistance welding and adhesive bonding, has been studied particularly when joining aluminium alloys for producing both high quality and commercial quality joints. The advantages which are claimed are increased strength and fatigue properties compared to spot welding, combined with joint sealing. Three commercially available single part heat curing structural epoxy adhesives were used in this work when joining 1mm 6009 aluminium alloy with various surface treatments. Limited weldability work was carried out followed by manufacture of spot welded, adhesive bonded and weldbonded mechanical testpieces to commercial quality standards. Static and impact shear properties are reported in this work, plus data on the effect of exposure to humid or salt spray environments.
Static joint strength was more than doubled, almost achieving the parent material strength by employing weldbonding or adhesive bonding compared to spot welding alone, whilst impact energy absorbed could be five times higher. Impact results were, however, more dependent on adhesive type and surface finish.
Twelve weeks exposure to humid or salt spray environments showed substantial reduction in properties of adhesive bonds and weldbonds in as-received material with up to 50% loss in static shear strength and up to 60% reduction in impact energy. Static strength suffered less than 10% reduction when using surface treated material but a more deleterious effect was demonstrated on impact properties with up to 40% reduction in impact energy after 12 weeks salt spray exposure.