IMPROVED STRAIN SENSOR

Improved microwire strain sensor elements (20, 40, 52, 62) and corresponding methods are provided, which permit accurate, wireless strain monitoring of a variety of structures, including composite structures, through use of a remote detector (28). The sensor elements (20, 40, 52, 62) have amorphous or nanocrystalline metallic alloy microwire cores (22, 48), which exhibit substantially reduced remagnetization responses when the sensor elements (20, 40, 52, 62) are coupled with a structure to be strain-monitored, and the structures are in an unstrained condition. When the monitored structure experiences a strain above a pre-selected threshold value, the microwire cores (22, 48) exhibit substantially different remagnetization responses as an indication that the monitored structure has experienced a strain above a strain threshold or over a range of strain. In use, the strain sensor elements (20, 40, 52, 62) are coupled with a structure to be monitored by application of the sensor elements (20, 40, 52, 62) to a surface of the structure, or by imbedding the sensor elements (20, 40, 52, 62) within the structure, and the coupled sensor elements are periodically interrogated by the detector (28). Preferably, the microwire cores (22, 48) are placed in compression in order to suppress the inherent remagnetization responses thereof by means of a surrounding body (26) or surrounding layers (44, 46) formed of synthetic resin material which shrinks upon curing. When the sensor elements (20, 40, 52, 62) are strained as a result of a strain experienced by the monitored structure, the remagnetization responses of the microwire cores (22, 48) are substantially increased.