Treatment of additively manufactured AlSi10Mg surfaces for improved bonding with fiber reinforced composites for sandwich applications

Abstract

The performance of low weight, high stiff multi-materials relies on the interfacial bond quality between the adherends. This study analyses the effect of surface roughness, organosilane treatment and coating with diamond like carbon on the adhesion strength between carbon fiber reinforced composites and an additively manufactured (AM) AlSi10Mg counterpart. Extending applications to sandwich structures, both, bulk and honeycomb structured counterparts were considered. Double-Lap Shear specimens were fabricated in a co-curing process, and further investigated regarding the bond efficiency. Results were compared to the state-of-the-art joints applying an adhesive film layer. It was observed that surface roughness is not pivotal when using such adhesive film. In contrast, higher surface roughness generally tends to promote adhesion strength by promoting mechanical interlocking and increasing the available bond area. Further coating with organosilanes and diamond like carbon increases the surface energy and reduces the contact angle thus improving surface wettability by the matrix resin. In consequence, an improvement of up to 30% in adhesion strength was observed in case of coating the metallic surface with diamond like carbon. Prior surface polishing of the additively manufactured parts does not significantly affect the bond quality and is therefore not recommended.

Carbon and Silane‐based Coatings for Improved Bonding in Hybrid Metal‐Composite Applications

“…Preliminary examinations confirmed the findings made by Zoesmar et al. 24, stating that maximum bonding between CFRP and AM‐parts is achieved when making use of the rough AM‐surfaces (as‐built). Hence, metal surfaces were not mechanically treated prior to further bonding with the CFRP.…”

“…Different concentrations of 5 and 10 wt % for Dynasylan® Glymo and 2 and 5 wt % in case of Dynasylan® Hydrosil 2926 were applied to the metal surfaces by dip‐coating under ultrasonic vibration, as described by Zoesmar et al. 24.…”

“…To assess the interfacial bond strength between the AM surface and the CFRP, metal/CFRP hybrid plates were fabricated in a co‐curing process, and further cut into DLS samples, as described by Zoesmar et al. 24.…”

“…1 summarizes the considered samples and the performed examinations. The wettability of differently coated samples by the resin was assessed on [24], stating that maximum bonding between CFRP and AMparts is achieved when making use of the rough AM-surfaces (as-built). Hence, metal surfaces were not mechanically treated prior to further bonding with the CFRP.…”

“…Prior to coating, the metal surfaces were cleaned using acetone and isopropanol to remove dust, residual powder particles and oxides that weakly adhered to the surface. Different concentrations of 5 and 10 wt % for Dynasylan Glymo and 2 and 5 wt % in case of Dynasylan Hydrosil 2926 were applied to the metal surfaces by dip-coating under ultrasonic vibration, as described by Zoesmar et al [24].…”