Non-destructive testing of structural composites and adhesively bonded composite joints: pulsed thermography

Abstract

Abstract Structural adhesive bonding is an enabling technology for the implementation of composite assemblies in automotive applications. Therefore, the quality and reliability of the composite bond must be assured. An advanced thermal non-destructive test (NDT) method, pulsed thermography, was evaluated for its capability to assess joint quality in an adhesively bonded composite pickup truck box. Pulsed thermography, used under in-plant, pre-production conditions as would exist during process start-up and optimization trials, was shown effective in determining both the quality of the structural adhesive bonds and the quality of the composite itself. With one exception, NDT showed that bonding was performed correctly, i.e. the bond was continuous and properly placed. The exception was a ‘starved’ bond-line that we believe exists due to poor fixturing at that location. Pulsed thermography illustrated the effects of environmental and mechanical exposure on the bonded joints. Finally, the NDT method was able to show mechanical damage to the composite itself, identifying impact damage not visible to the unaided eye.