A Modal-based Contribution to Damage Location in Laminated Composite Plates

The need for damage detection on complex structures at an early stage, has led to the development of techniques that evaluate changes on vibration parameters, since the dynamic response of a structure is dependent on its particular characteristics. The generality of the vibration based damage detection techniques are based on the fact that damage will induce a local reduction on the component stiffness. However, no single approach has proven appropriate for all situations. Composite materials, which are receiving an increasing attention in the aeronautical and other industries, namely Carbon Fibre Reinforced Polymers (CFRPs), are very sensitive to impacts of medium and low energy. Typically, Barely Visible Impact Damage (BVID) will occur, constituting an unsafe failure of difficult assessment. To assess (detect, locate and quantify) damage in this kind of material is still a challenge, especially if a huge amount of sensors or expensive equipments are not available. In this work, a methodology that makes use of a reduced amount of conventional sensors is explored, with the aim of locating damage on laminated components that are subjected to impacts during service for a low cost. This represents a considerable benefit, namely for the assessment of damage in aeronautical components, when compared to most methods used today. This work can also give a major contribution to the research community since uncommon approaches will be used to model damage in composite materials, namely the modal damping factor as feature for damage location.