Damage detection using Terfenol-D

Delamination is one of the predominant forms of failure in laminated composites due to lack of reinforcement in the thickness direction. Fiber composites often consist of layers that are bonded together as part of the curing process. The strength of this bond is limited by the matrix strength. Delamination results in severe loss of bending stiffness and strength of the composite structure.

One method to design against delamination failure is to calculate the interlaminar stresses and compare these with allowable interlaminar stress. Another way of assessing the reliability of laminates with respect to delaminnation is to adopt fracture mechanics approach by assuming the presence of crack like flaw as initial delamination and to determine the stress that will lead to propagation of this initial delamination crack. Though the structure is not usually designed with an initial delaminaton, it can arise from loadings such as accidental impact or from initial imperfections in the structure. In this lecture, an effort has been made to formulate a model to sense delamination in fiber composite laminates using MS layer of Terfenol-D, thus to establish magnetostriction as an effective method of real time integrity monitoring of composite structures.