| The work presented here focused on the effect of various hot and humid environments on the mode I fracture toughness of bonded composite Double Cantilever Beam (DCB) specimens and bonded sandwich Single Cantilever Beam (SCB, also known as "Cracked Sandwich Beam", CSB) specimens.;For SCB specimens, GIC was identically affected by exposure of the specimen to 95% relative humidity or liquid salt water, the result being a decrease of about 20% in the propagation G IC compared to unconditioned specimens. All these specimens suffered cohesive failure within the core.;Fracture tests were performed on the specimens after 3-4 months of exposure to the environments and it was found that conditioning DCB specimens resulted in reductions of at least 22% in the initiation value of GIG The propagation value was not affected by conditioning in high-humidity environments, but reduced by approximately I5% and 6% when conditioning by immersion at 82°C and 70°C water, respectively (salt concentration had no effect). In terms of failure mode, all DCB specimens failed I00% cohesively (within the bond line) when unconditioned, and all had a relatively large proportion of adhesive failure (between the adhesive and the composite laminates) after any type of conditioning. |
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