Composite materials are widely used in various structural applications due to their low density, high specific strength and stiffness, corrosion resistance, and good fatigue properties. However composites usually fail in a catastrophic manner and detecting damage, if there is any, prior to final failure has been a significant challenge. This puts limitations on structures comprising such materials as larger safety margins and conservative design envelopes need to be implemented. Sudden failure usually occurs without preceding damage or warning of any kind that is crucial in high volume applications such as in the automotive industry or civil engineering where a sudden collapse or failure could lead to the loss of human life and significant financial costs [1], [2]. It would be desirable if catastrophic failure could be prevented by detecting damage at earlier stages of loading/service. As a result, overload detected in time, can indicate the need for further investigation by more thorough non-destructive testing (NDT) methods and appropriate repair or maintenance can be carried out leading to no excessive/unexpected down-time and enhanced service lives.