Bonding of continuous SiC fiber reinforced Ti-6Al-4V composites using interlayers

In the present work, we have investigated the role of interlayers in bonding continuous SiC fiber reinforced Ti-6Al-4V composites and have applied step joint forms and scarf joint forms to bond the composites. The composites were successfully diffusion bonded to themselves using a matrix interlayer. The joint strengths increased with thickness of the interlayer. In a composite with a fiber volume fraction (V-f) of 30 vol%, the joint strengths of 800 to 850 MPa, which were equivalent to a strength of the composite to the Ti-6Al-4V joint, were obtained using interlayers more than 80 mu m in thickness. Although the joint strengths decreased with increasing V-f of the composites, they were 150 to 200 MPa higher than the values simply calculated form area fractions of the matrix at bonded interfaces. This is thought to be caused by triaxially constraining plastic deformation of the matrix near the fibers. Pseudo-step joints of a 10-ply composite (V-f=30 vol%) were fabricated with a varying number of steps and those strengths increased with the number of steps. A step joint with 10 steps showed 90% tensile strength of the composite. Scarf joint forms were applied to diffusion bonding of the composites to a Ti-6Al-4V plate and to themselves. The composites (V-f=30 vol% and 45 vol%) to Ti-6Al-4V joints were fractured in the Ti-6Al-4V Plate. The composite (V-f=30 vol%) to composite joints had a maximum strength of 1380 MPa corresponding to approximately 80% tensile strength of the composite.