A methodology for the assessment of residual elastic properties in damaged components made of composite materials

Damage complexity represents one of the main limitations to the diffusion of composite materials in many industrial applications. The objective of this study is to make preliminary steps towards an innovative simplified assessment of the damage sustained by composite materials. A methodology for the evaluation of the residual elastic properties of damaged laminates is proposed and applied. The composite laminate investigated in this study is made of eight twill-wave carbon fabrics impregnated with epoxy resin. Composite plates are subjected to impact tests at different energy levels and residual elastic properties are subsequently assessed through tensile tests. The relationship between the impact energy and the residual elastic properties is used for the individuation of the maximum energy level that induces a negligible damage in the composite laminate (the threshold energy). The value of the Damage Index (DI) obtained from non-destructive impacts at energy threshold is adopted for the prediction of the local residual elastic properties in the damaged area. The proposed methodology is applied and validated on plate specimens. A strict correlation is found between the predicted and the actual residual elastic properties of the damaged composite plate.