Design and Maintenance of Aircraft Composite Structures by Advanced Damage Inspection Techniques

This work summarises the outcome of the activities performed in the context of SMAF (Smart AirFrame) project, which is part of PRORA (the Italian Aerospace Research Program). The main goal of SMAF is the enhancement of an integrated offline SHM (Structural Health Monitoring) system, aimed to improve the maintenance and the design approaches of composite primary aircraft structures. The SHM system includes piezoceramic sensors/actuators (PZT) and distributed fiber optic sensors (FOS) for the detection, localisation and measurement, of both the lamination damage and the debonded skin-stringer line extension, induced by low energy impacts. The whole system has been developed and verified through a building block approach; through tests on structural subparts of intermediate and growing size and complexity: from small stiffened panels up to a full-scale stiffened wing panel. Experimental and numerical results are illustrated. Promising reliability of the integrated (PZT + FOS) SHM system has been demonstrated in detecting and measuring the area of the impact/delamination damage and skin-stringer debonding length. This should allow in the future the possibility to make more efficient composite structures, in terms of operating costs, also by improving their static strength with significant weight reduction.