Ultrasonic damage investigation on woven jute/poly (lactic acid) composites subjected to low velocity impact

An ultrasonic technique is used to investigate the delamination caused by low velocity impact tests, on plates obtained by typical film stacking and compression molding techniques. The square specimens, 100*100 mm, were impacted by a falling dart machine at five increasing impact energy values of 2 J, 5 J, 10 J, 12 J, and 15 J. The delamination is investigated by the very commonly used Ultra Sound technique employing a linear phased array probe. The delaminated area is correlated with both the impact energy and the measured indentation depth. The results showed a threshold energy for the beginning of the internal damage. Moreover, a linear relationship between the delaminated area, the energy and the indentation depth was found.