The Influence of Embedded Optical Fibres on the Fatigue Damage Progress in Quasi-Isotropic CFRP Laminates

Abstract

Embedded optical fibre sensors have in the last decade been introduced as possible candidates for continuous damage monitoring in loaded composite structures. However, incorporation of foreign bodies like optical fibres in laminated structures can lead to substantial microstructural disturbances, stress concentrations and degradations in mechanical properties. Optical fibres were embedded in the different interfaces of a quasi-isotropic CFRP laminate which was subsequently tested in interrupted tension-tension fatigue. During each interruption the damage state of the samples was quantified by using penetrant enhanced microfocus radiography. The results were compared to earlier results obtained during continuous fatigue testing is which the number of cycles to fracture and the stiffness degradation were monitored. The main conclusion is that some optical fibre configurations can affect the fatigue properties by weakening the 0°-plies or accelerating the damage evolution. These results are the first to demonstrate a faster damage evolution caused by embedded optical fibres.