Reliability Aspects of Lamb Wave Interaction at Impact Damages in Complex Stiffened CFRP Structures
Abstract »The increasing usage of Carbon Fiber Reinforced Plastics (CFRP) for primary aerospace structures involves dealing with the principal susceptibility of composite laminates to impact loads as well as the occurrence of barely visible impact damages. Therefore the assessment of impact damages in CFRP structures poses an attractive application case for Structural Health Monitoring by Guided Ultrasonic Waves. Wave propagation phenomena at impact damages as well as the utilized signal processing to extract a damage related feature (i.e. damage index) contribute to the sensitivity of SHM system and thus to the reliability of such SHM systems.
This work bases on data from the EU-funded project SARISTU, where a generic CFRP door surrounding fuselage panel with an integrated sensor network has been build and tested by introducing plenty of impact damages.
Wave interaction at delamination and debonding of different size and morphology in Omega-stringer stiffened structures are examined in detail, in order to highlight the factors contributing to the sensitivity. Subsequently criteria for a reliable design are extracted. Common damage indicator formulations for use with imaging algorithms are applied on data from various damage cases and compared to these criteria.