Damage quantification in polymer composites using a hybrid NDT approach

Damage is an inherently dynamic and multi-scale process. Of interest herein is the monitoring and quantification of progressive damage accumulation in a newly developed glass fiber reinforced polymer composite subjected to both tensile and fatigue loading conditions. To achieve this goal, the potential of data fusion in structural damage detection, identification and remaining-life estimation is investigated by integrating heterogeneous monitoring techniques and extracting damage-specific information. Damage monitoring is achieved by the use of a hybrid non-destructive testing system relying on the combination of acoustic emission, digital image correlation and infrared thermography. Full-field strain and temperature differential maps reveal appearance and development of damage "hot spots" at prescribed strain/load increments that also correlate well with distinct changes in the recorded acoustic activity. The use of non-destructive and mechanical testing data further allows the quantification of the observed hysteretic fatigue behavior by providing measurements of the: (i) stiffness degradation, (ii) energy dissipation, and (iii) average strain as a function of fatigue cycles. Furthermore, analysis of the real time recorded acoustic activity indicates the existence of three characteristic stages of fatigue life that can be used to construct a framework for reliable remaining life-predictions.