Life prediction and life extension of composite specimens using acoustic emission technique

Abstract

This paper discusses a proof test procedure for estimating and extending the fatigue life of composite coupons. The estimates were based on the acoustic emission data collected during the described proof test procedure. A group of coupon specimens that included both undamaged as well as damaged ones were tested to verify the ability to estimate the fatigue durability. For majority of the specimens tested the fatigue life of the coupons is inversely proportional to the cumulative AE energy collected during the proof test procedure. Based on the trend that was established, a new group of specimens AE based proof test was performed and using the acoustic emission response, the life was estimated. If one could estimate the fatigue life, it would be possible to identify those specimens, which are likely to fail prematurely. For such specimens it may be possible to extend the fatigue life by appropriate reduction in the cyclic load amplitude. This hypothesis was tested on the last group of specimens. The results obtained during the life extension phase actually show that it is possible to identify the specimens, which are likely to have short life and extend the fatigue life by subjecting them to less demanding load history.

Health monitoring of composite structures based on acoustic emission measurements

“…Although the class presumed to consist of matrix-crack-induced AE events bore no useful conclusions, classes representing interface debonding and fibre failure were correlated with 'consumed' fatigue life. Nkrumah et al (2005) used a static proof-loading to estimate remaining life after fatigue on a limited experimental data set. A more elaborate approach is encountered in the work of Caprino et al (2005), using specimens subjected to constant-amplitude (CA) loading at one particular stress level.…”

Acoustic emission monitoring of unstable damage growth in CFRP composites under tension

“…Mizutani [9] compared data with generated waveforms to find relation between Lamb wave properties and fracture modes. Nkrumah [10] found that total AE energy during the proof tests were a good indicator of fatigue life of impact damaged woven glass-epoxy composite specimens. Jacques [11] showed that bonded sensors can detect AE signals with high fidelity by comparing these signals with signals from a Laser interferometer.…”

Using acoustic emission to assess shear strength degradation in FRP composites due to constant and variable amplitude fatigue loading

“…These classes were shown to correspond to the three main failure mechanisms, each being dominant at a particular stage of fatigue life. Nkrumah et al [12] used a static proof-loading to estimate remaining life after fatigue. Nevertheless, developed procedures relied on limited experimental data sets and no robust, validated predictive models were proposed.…”