Strain-based damage assessment for accurate residual strength prediction of impacted composite laminates

A method for predicting the residual strength of damaged carbon-fibre composites using full-field strain data measured with digital image correlation has been developed and applied to laminates containing barely visible impact damage (BVID). Carbon-fibre coupons containing impact damage were manufactured and then inspected using the novel strain-based damage assessment technique and an ultrasonic technique commonly applied in industry. Predictions of residual strength, with quantified uncertainties, were generated for both the strain-based and ultrasonic measurements using robust Bayesian linear regression. The accuracy of strain-based predictions were found to be significantly higher than those generated using ultrasonic measurements, with the predictions for one set of coupons being over three times more accurate when using the strain-based technique. The use of such a damage assessment technique, capable of accurately predicting the residual strength of a damaged composite structure, could reduce the number of repairs required to ensure the safety of that structure.