Experimental investigation on hole bearing behavior and failure mechanism of double-lap hybrid composite/titanium bolted joints

In this paper, a new co-curing process for hybrid titanium alloy foils into composite laminates was put forward. Meanwhile several pull-out specimens were tested to obtained the bonding response between titanium alloy and composites. And the size of titanium alloy foils in double-lap hybrid composite/titanium bolted joints were designed according to the response. Then these double-lap bolted joints were fabricated and tested. The test results revealed that hole bearing responses of hybrid specimens were significantly better than composite specimens. Moreover, the hole bearing strengths of hybrid specimens with 33% titanium content were more 40% higher than composites specimens. And the degree of bearing strength enhancement exceeded the degree of weight gain of the specimen. Meanwhile, the hole damage morphologies of these double-lap specimens were characterized. It could be found that the edge length had a significant effect on the failure form of the double-lap bolted joints, and the area affected by hole failure could be significantly reduced by increasing the edge length appropriately. The structure of hybrid titanium alloy foils within a bolted joint area of composite laminates will provide a reference for improving hole bearing strength. Highlights: A new co-curing process for hybrid titanium alloy foils into composite laminates was created. Hole bearing strengths of hybrid composite/titanium bolted joints are higher than composite specimens. Increasing the edge length can effectively reduce the area of the hole failure affected zone.