Residual tensile strength of CFRP scarf joints with impacted internal damage

This paper is separated into two main sections focusing on different topics regarding composite repair methods. The first of these topics is the influence of scarf angle on various characteristics, namely tensile strength, damage after impact, and tensile after impact (TAI) strength. Such influences were investigated experimentally by using three variations of scarf angles of 3-, 4.5-, and 6-degrees. As the results of the tensile test, it was found that the tensile strength decreases as the scarf angle increases. As the results of cross-sectional observation and TAI test, it was found that the TAI strength of the scarf joints was much affected by the fact that the debonding length of the adhesive layer varies depending on scarf angle. The second topic is based on experiments done on test specimens closer to conditions actually used in practical application. Because aircrafts are repaired using smaller scarf angles, this infers that the scarf angle has been reduced to 2-degrees on specimens, and tensile tests as well as TAI were repeated. Furthermore, specimens were also prepared that were reinforced with CFRP doublers at the same scarf angle. As the results of TAI test, it was found that the TAI strength of the scarf joint specimens (2-degree scarf joint specimen and 2-degrees scarf joint specimen reinforced with CFRP doublers) was almost the same as that of the CFRP laminates.