Generation of controlled delaminations in composites using symmetrical laser shock configuration

Structural Health Monitoring (SHM) is defined as the process of implementing a damage identification strategy for aerospace, civil and mechanical engineering infrastructures. SHM can be organized into five main steps: detection, localization, classification, quantification and prognosis. Our work considers SHM quantification level and in particular the evaluation of the severity of delamination-type damage in CFRP composite laminates. Prior to quantification algorithms implementation, it is important to properly prepare the supports on which algorithms will be tested. Teflon inserts and conventional impacts are commonly used techniques to generate or simulate delaminations. However, with such rudimentary techniques it is difficult to generate controlled delamination-type damage in a realistic way. In the present work, we investigate symmetrical laser shock approach, as a new method to calibrate delaminations in composites. By tuning the time delay between the two laser beams and laser energy, through-thickness damage position and severity can respectively be adjusted. The effect of multiple contiguous laser impacts was also investigated. Post-mortem analyses using A-scan and C-scan testing as well as penetrant testing were performed in order to characterize laser impact induced damage. Results are encouraging and demonstrate the high potential of symmetrical laser shock for damage calibration in both size and location.