On the Mode I Fracture Toughness of Metal-Composite Joints with untreated SLM 3D-Printed Ti6Al4V Substrates

Here we investigate the adhesive properties of Selective Laser Melted (SLM) titanium surfaces in metal-composite co bonded joints without any prior surface treatment, to explore the inherent surface roughness of SLM parts to potentially create strong adhesive bonds. Double Cantilever Beam (DCB) tests were carried out to assess the joints mode I fracture toughness involving untreated SLM titanium and woven Carbon Fibre Reinforced Polymer (CFRP) adherends, co-bonded with an epoxy film adhesive. The same type of DCB joints, but now with sandblasted SLM titanium adherends, were tested to compare the adhesion strength of the untreated SLM surface versus the sandblasted surface. The findings reveal that joints with untreated SLM titanium adherends exhibit similar toughness to those with sandblasted SLM titanium adherends, indicating that the surface morphology of as-printed SLM titanium is suitable for manufacturing robust adhesive joints. The elimination of the surface treatment in the manufacturing of adhesive joints with SLM adherends could increase the interest of many industrial fields towards the use of adhesive bonding over other joining techniques.