Effect of laser texturing on mechanical strength and microstructural properties of hot-pressing joining of carbon fiber reinforced plastic to Ti6Al4V

Laser textured TC4 (Ti6Al4V) was connected with CFRP (carbon fiber reinforced plastic) by hot-pressing joining. Influence of textured grid width on tensile-shear force of joint was investigated, and the bonding status at the TC4/CFRP interface with and without laser texturing was compared. Experimental result indicated that laser texturing obviously improved the TC4 surface roughness and wettability of molten CFRP, which increased the interfacial joining area and thus enhanced the shear force of joint. When 0.2-mm-wide grid was adopted, surface roughness of the metal was increased by 14 times and the minimum contact angle of molten CFRP on TC4 was 49.9?. The maximum shear force was 5286 N in this case, which was about three times that of untreated case, and the adhesion ratio of resin-carbon fiber mixture also accomplished the maximum of 49.6 % of overlap area. When grid width became larger, the surface roughness and wettability decreased which caused incomplete filling of molten CFRP in textured grid and decrease of shear force. Interface and cohesive hybrid failure mode was observed from fracture surface. However, the part of oxide layer exfoliated from substrate occurred under the case of laser textured TC4 sheets, which was responsible for the enhancement of mechanical interlocking. Moreover, new chemical bonds between Ti and C were also discovered, justifying a further enhancement of tensile-shear forces.

Automated summary

Using laser textured TC4 surface significantly increases its roughness and wettability, increasing the bonding area with CFRP and enhancing joint shear forces. However, when the texture grid becomes larger, incomplete filling of CFRP leads to a decrease in shear forces. Furthermore, new chemical bonds between Ti and C on laser textured TC4 sheets contribute to further enhancement of tensile-shear forces.