Notched strength prediction of centre-hole carbon/carbon composites

The present work investigates the behaviour of 2D carbon/carbon (C/C) composites containing centre holes and proposes methodologies for the prediction of the residual strength of such C/C laminates. Two different concepts were adopted in order to understand the fracture behaviour of C/C composites in the presence of holes and to evaluate their strength. The first approach is based on the hypothesis of the existence of a damage zone around the hole, which originates during tensile loading. The second uses monitoring of the acoustic emission (AE) activity of the centre-hole specimen, loaded up to a stress level well below its failure strength, as an indication of damage formation, and combines it with a defined calibration curve. Both models predict very accurately the strength of notched laminates for a number of specimens tested.