Effects of laser processing microgrooves on the shear strength of Ti6Al4V adhesively bonded joints
Chong Zhang, Yongkang Zhang, Lingyu Chen, Jie Jin
Abstract
Laser processing has been used as a surface preparation before adhesive bonding, which significantly improves the adhesion between the adhesive and the substrates. In this work, a pulsed fiber laser was used to process different microgrooves in the bonding region of a Ti6Al4V substrate. First, the pulse energy was optimized, and then the effects of the microgroove parameters (groove pattern, depth, and distance) on the surface roughness of the substrate and on the shear strength and failure mode of the adhesive joints were studied using a single factor experimental design. The results show that when the pulse energy is greater than 63 μJ, a significant amount of molten residue is generated around the groove. The parallel groove is the most beneficial to improve the shear strength when the groove direction is 90° (when the groove is perpendicular to the loading direction). In contrast, cross grooves easily form pores that are not filled with adhesive, which weakens the shear strength. The shear strength was observed to decrease for greater groove distances and increase with the groove depth. The maximum shear strength of the adhesively bonded joint after laser processing is about 29.71 MPa, which is an increase of 140% compared with that by surface grinder polishing.