Papers by Keyword: Bonded Repair

Abstract: This work focuses on diagnostic methodologies for composite repair patch based on structural health monitoring (SHM) technology. Methodologies based on ultrasonic guided waves (GW) are developed and assessed for monitoring composite scarf repair with piezoelectric transducers. The effectiveness of the RAPID (reconstruction algorithm for probabilistic inspection of defects) algorithm was investigated for adhesively bonded composite patch repair. A composite scarf repair has been weakened by 4-point bending fatigue test and impacted after to generate a Barely Visible Damage (BVID). Both conventional RAPID technique, which requires baseline signals, and the Scaling Subtraction Method (SSM) were applied to detect damage in the bondline. The conventional method showed good performance for defect detection and localization whereas the SSM gives encouraging results for non-linear baseline-free RAPID.

Abstract: A novel strategy is proposed for monitoring of bonded composite repair patch is developed and tested. A specially designed pattern was inject-printed onto the step-sanded repair surface providing real time information about the bondline structural integrity. The obtained results indicated that the proposed methodology was able to detect damage induced by an impact event. Infrared thermography (IrT) and ultrasound inspection were also employed in order to validate the proposed methodology.

Abstract: Bonded repair of composite structures still remains a major concern for the airworthiness authorities because of the uncertainty about the repair quality. This work, investigates the applicability of conventional Structural Health Monitoring (SHM) techniques for monitoring of bonded repair with ring-shaped low profile sensors. A repaired composite panel has been sensorized with two Ring-Shaped Polyvinylidene fluoride piezopolymer Sensors (RSPS) and a piezoelectric (PZT) transducer. An electromechanical impedance (EMI) and Lamb wave analysis have been carried out to check the sensitivity of these sensors to detect an artificially introduced damage simulating a disbond of the repair. The state of the repair have been successfully monitored and reported by both methods.

Abstract: Bonded repair of composite structures still remains a crucial concern for the airworthiness authorities because of the uncertainty about the repair quality. This works, investigates the applicability of Structural Health Monitoring (SHM) techniques for monitoring of bonded repair. Active sensing method has been applied to two case studies: a sensorised panel impacted to cause barely visible impact damage (BVID) and repaired afterwards, the tensile and fatigue testing of a composite strap repair. In the first case, the previous sensors have been used to detect an artificially introduced damage. In the second case the failure of the adhesive during the tensile testing is used as basis of the load levels in the tensile-tensile fatigue test. In both cases PZT transducers have been used to monitor the bonded patch. An electromechanical impedance (EMI) and Lamb wave analysis have been carried out to check the overall integrity of the repair patch between. In both cases the state of the repaired composite was monitored successfully and reported.

Abstract: AA2024-T4 Al substrate with and without bonded E-glass/Epoxy patches were undergone for the experimental study of tensile strength and fatigue behavior. The Al substrates were machined to edge cracked specimens. The strength of the substrate was decreased due to the presence of crack when compared with un-cracked Al substrate. The patches were made in liquid epoxy resin instead of film adhesives and it was discovered that the both static strength and fatigue life were significantly increased for bonded composite patches. Different ply patches were applied on the cracked Al substrates and it was noted that the 9ply patch demonstrated its effectiveness in preventing static failure and increasing fatigue life of the cracked substrates