Use Of Electrical Resistivity And Acoustic Emission To Assess Impact Damage States In Two Sic-Based Cmcs

The need to assess damage is essential to accurately predict the degradation of the composite properties such as remaining strength and specimen/component life expectancy. Two methods were used to assess as to their usefulness for damage quantification (acoustic emission) and damage monitoring (electrical resistivity) on two different CMC composites which have undergone impact damage. In particular melt-infiltrated composites with fiber types, SA and ZMI, are examined which were impacted with high velocity projectiles (similar to Mach 1), and tested in tension after high velocity impact. Electrical resistivity was used as both an inspection technique (measured before and after impact testing) as well as a damage monitoring technique in parallel with acoustic emission during tensile testing. The effect of damage was evident from the change in measured electrical resistivity due to impact and during tensile testing. It was also evident from AE activity during tensile testing that crack propagation occurred at relatively low stresses for composites with significant impact damage.