ABSTRACT

Aerospace structures are subjected to high-design loads under complex operational and environmental conditions as well as discrete damaging loads such as impacts. Although maintenance constitutes a significant part of aircraft life cycle cost, the existing paradigm for ensuring structural safety may allow an undetected damage to grow to a critical size between major inspections (schedule-based maintenance) and cause catastrophic failure. In addition, the use of composites for aircraft structures is increasing rapidly due to several advantages such as lighter weight, fewer joints, improved fatigue life, and higher resistance to corrosion. However, composite 396structures have several forms of damage such as delamination between plies, fiber–matrix debonding, fiber breakage, and matrix cracking. These damages often occur below the surface due to fatigue, foreign object impact, and so on, and may not be visible.