Long-term sea water effect on the failure behaviour of adhesively strap joints

In this study, the effects of seawater on the failure behavior of lap-jointed composite plates were investigated experimentally. Glass fiber/epoxy composite plates were bonded with epoxy-based adhesives using single- and double-face patches. The prepared specimens were kept in seawater at room temperature for 9, 12, 15, and 18 months. The failure loads of the seawater-soaked joints were determined by static tensile tests. In the experimental study, the effects of time variation, patch fiber reinforcement angle variation ([0°] 8 , [15°] 8 , [30°] 8 , [45°] 8 ), and lap length variation (20 mm, 30 mm, 40 mm) on the joint strength were investigated. According to the results of the experimental study, the failure load decreased as the ageing time in seawater increased. The reduction ranged between 10.83%–33.49% for single-face connections and 4.08%–32.91% for double-face connections. Increasing the lap length increased the failure load by 33.37% to 108.03%. When the effect of patch fiber angle was examined, the highest increase was observed at [15°] 8 patch with 17.98%.