Fatigue damage characterization in carbon fibre composite materials using an electrical potential technique

Abstract

Changes in electrical resistance during static and fatigue loading of unidirectional and cross ply carbon fibre reinforced polymer composites have been studied. The carbon fibres in the study were T300 and the matrix resins were Hexcel 914 and 920. It was found that changes in resistance during static tensile testing were about three per cent of the original resistance of the samples, while fatigue testing caused resistance changes of up to 10% of the original resistance, immediately prior to final failure. The initial linear portion of the resistance increase on static testing was reversible and could be attributed to reversible elastic strains in the fibres; later non-linear changes were a consequence of fibre fracture and were irreversible. Changes in resistance during fatigue also contained both reversible and non-reversible components. It was found that during fatigue testing the initial changes in resistance caused by the first few thousand cycles could be correlated with the eventual life. Samples with large initial resistance change had reduced lives compared with those with small changes in resistance. Fatigue lives of composite laminates may thus be predicted from monitoring of initial resistance changes. Many of the results could be explained via the parallel resistance model of conduction in composite laminates.

Electrical resistance measurement for in situ monitoring of fatigue of carbon fabric composites

“…This conclusion may also be found in various articles about this subject [1,2,3,4,5,6,7,8,9,10,11]. While doing the literature study, it was noticed that most authors concentrated their work on polymers with unidirectional fibre reinforcement [4,5,6,7,8,9,10,11,12,13]. Occasionally, cross-ply laminates are studied [3,4,5,11,12], but materials reinforced with fabrics were never closely observed using this technique.…”

Real time sensing of structural glass fiber reinforced composites by using embedded PVA - carbon nanotube fibers

“…The resistance measurements were performed in a two-point measurement set-up in the longitudinal direction. Data acquisition of 1 Hz was used for the 20003-p. 3 resistance measurements and stored simultaneously in the P/C of the testing machine. A rubber mat was placed between the specimen and the metal grip of the test machine in order to insulate the specimen from the test machine.…”

“…This enables to fully monitor the structural health of GFRPs with doped resin and establish correlations between internal damage and increase in resistance, e.g. [3,4].…”

“…[3,5]. The idea of monitoring a composite using a unique conductive fiber has been made in [6], where a carbon fiber was embedded into GFRP coupons.…”

Fatigue damage detection of CFRP using the electrical resistance change method

“…The inner couple of electrodes are used to measure electrical voltage change. Irving et al [6] and Seo et al [7] used the electrical resistance change method to detect fatigue damage in a unidirectional CFRP, and in a crossply CFRP. De Baere et al [15] used the electrical resistance method for fatigue damage detection in woven fabric CFRP composites.…”