Structural health monitoring by the piezoresistive response of tufted reinforcements in sandwich composite panels

This paper aims the investigation of the damage monitoring by the piezoresistive effect of the tufting threads in the sandwich structures. This novelty is an additional advantage besides the primary interest for inserting tufts in composite structures that concerns the improvement in the interlaminar fracture toughness. Tufting process reinforced through-thickness the polystyrene foam core and glass fiber sheets. Electrical measurements monitored the specimens through the tufted carbon threads during flatwise compression and low-velocity impact tests for evaluating the strain-sensing and damage response. The irreversible resistance change and infrared thermography (IRT) methods analyzed the damage extent in the tufts after impact tests. IRT characterized the damages from the concentration of temperature on the deteriorated regions of the tufts while injecting electrical current. These results were validated by the ultrasonic C-Scan maps that displayed the major damages in the same zone found on IRT technique. The present study validates the capability of the approach to monitoring strain and damage events by the tufts when subjected to compressive loading. The method also presents efficient to monitor the loading and damage detection, by the irreversible resistance change, under impact tests.