Abstract
This study presents a novel hybrid technique for joining composites to metal, employing an array of macro-scale interlocking features on the faying surfaces of adhesively bonded adherends. Single-lap, interlocking adhesive joints (IAJs) and baseline adhesive joints (BAJs), are tested at quasi-static and transient dynamic (0.5 m/s and 3 m/s) loading rates. The joint deformation mechanisms are examined and fractography analysis is performed at the macro and micro scales. Results indicate a 10% increase in lap-shear strength, and 75–120% increase in work to failure for the IAJs compared to the BAJs, at all loading rates. In addition, IAJs exhibit improved damage tolerance compared to adhesive joints, due to reduced joint rotation, more stable adhesive fracture growth, and the ability to sustain load even after cracks have propagated through the adhesive at the ends of the overlap region. The high energy absorption capacity (23–38 J) of IAJs indicates they could be used to significantly improve the crashworthiness performance of multi-material transportation structures.
Highlights
The European Union has a roadmap to realise a competitive, resource‐efficient, and safe transportation system, that will reduce greenhouse gas emissions by 20% and halve the number of road causalities by 2030 [1,2]
Five baseline adhesive joints (BAJs) test repeats and three interlocking adhesive joints (IAJs) test repeats were performed at each test speed to gauge the repeatability of results
Under quasi‐static loading, the interlocking features act to inhibit the growth of the primary crack and allow the secondary crack to grow in a stable fashion, reducing the joint rotation after damage onset, increasing shear deformation and reducing peel deformation, resulting in a significant increase in energy absorption
Summary
The European Union has a roadmap to realise a competitive, resource‐efficient, and safe transportation system, that will reduce greenhouse gas emissions by 20% (based on that observed in 2008) and halve the number of road causalities (based on that observed in 2018) by 2030 [1,2]. The abrupt failure behaviour of bonded structures has led to consideration of hybrid bonded/bolted joints [3,4,5], but these retain the shortcomings of mechanical fastening. Welding is another option for joining metals with thermoplastic composites. None of the above studies addressed through‐thickness reinforced joints between aluminium and thermoplastic composites, despite the obvious advantages for the automotive industry of such a material combination. The IAJs are compared to baseline adhesive joints (BAJs) which have no interlocking features
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