Lap Splice Length and Fatigue Performance of Frp Laminates

In this paper, the lap splice length and the long-term (fatigue) performance of lap-spliced carbon FRP laminates were investigated. Lap-spliced CFRP coupon specimens were fabricated with a splice length of 12.7, 25.4, 38.1, 50.8, 76.2, and 101.6 mm. To eliminate the bending on the lap splice joint, a symmetric specimen configuration was adopted. The width of the specimens was 38.1 mm. These specimens were tested to failure under tension. The ultimate load, failure mode, and strain distribution on the surface of both the non-lapped and lapped areas were monitored. It was found that a length of 38.1 mm was sufficient to develop the static ultimate strength of the CFRP laminate. Tension-tension fatigue tests were performed on 101.6-mm lap-spliced specimens to investigate the long-term performance. A stress ratio versus number of cycles curve was constructed using the test data and compared with theoretical results. It was shown that 101.6-mm lap-spliced CFRP laminates can sustain more than 2.0 million load cycles with no effect on residual strength, if the maximum applied stress does not exceed 40% of the ultimate static strength. A 101.6-mm lap splice length is recommended for field use as presently adopted in standard practice.