Effects of 3D-printing surface morphologies on interfacial bonding strength between Ti–6Al–4V and CFRTP with PMCs interlayer

In this work, effects of surface characteristics of Ti–6Al–4V sheet manufactured by LPBF on bonding strength and failure jointed with a 3D print carbon fiber reinforced thermoplastic (CFRTP) including polymer matrix composite (PMCs) shell acting as an interlayer were investigated. Hereby, correlations between printing angle of Ti64 sheet, its surface roughness/morphology and bonding strength were established. Lap shear specimens of the printed Ti64 and CFRTP sheets were prepared by a hot press technique using different pressing conditions. It was noticed that the press force of 0.12 MPa and press temperature of 220 °C were appropriate with regard to resulted appearance and maximum bonding strength of joined samples. From surface analyses, decreased printing angle considerably led to higher surface roughness of printed sheets. Different roughness patterns between upper and lower metal surfaces were observed. The printed roughness characteristics were governed by combined contributions of unmelted particles and layer step geometry. It was found that the bonding strength significantly depended on surface morphologies of printed metal, in which the highest bonding strength of 22.2 MPa was achieved at the printing angle of 45° and its maximum difference among all sample orientations was 54.4%.