Abstract: In order to study the failure mode of carbon fiber/poly-ether-ether-ketone (CF/PEEK) single lap welded structure in elevated temperature wet condition and the influence of elevated temperature wet condition on its performance, the shear tests were carried out in the room temperature dry condition and the elevated temperature wet condition, respectively. At the same time, three different cohesive force models were used to predict the shear failure load of the structure. The test results show that CF/PEEK single-lap welded specimens in the elevated temperature wet condition show the same three failure modes as those in the room temperature dry condition, namely interface failure, mixed failure and laminate tearing failure. In the range of test error, compared with the room temperature dry condition, the single lap shear strength of welded joints with the same failure mode in elevated temperature wet condition has no obvious change, but the resin at the end of the lap plate has obvious plastic deformation in the elevated temperature wet condition, the average structural stiffness decreases by about 22%, and the average failure displacement increases by about 88%. The numerical results show that the strength prediction results of the exponential cohesive model in the three cohesive models are more consistent with the experimental results for the welded joints with only delamination failure in the room temperature dry condition.

Key words: thermoplastic composites, welding structure, shear failure, failure mode, elevated temperature wet condtion, cohesive zone model