Internal Strain Analysis of Fibre Break Interactions in Carbon Fibre Composites using Digital Volume Correlation and In situ Synchrotron Radiation Computed Tomography
Topic(s) : Experimental techniques
Co-authors :
Yeajin LEE (UNITED KINGDOM), Partha PAUL , Mark Noel MAVROGORDATO , Simon Mark SPEARING (UNITED KINGDOM), Ian SINCLAIRAbstract :
The tensile failure of unidirectional carbon fibre reinforced polymer composites is critically determined by the load redistribution around fibre breaks in 0-degree plies. To date, a comprehensive understanding of the load redistribution in practical composites has largely relied on modelling efforts; a recent study by AhmadvashAghbash et al. [1] developed a finite element model to predict how various parameters involving interfacial debonding influence stress redistribution in both a broken single fibre and the adjacent intact fibres. A tougher interface, characterised by higher interfacial strength and fracture toughness, was reported to restrain debonding propagation, resulting in shorter recovery lengths in the broken fibre (i.e. a shorter ineffective length). On the other hand, the shortened debond length also leads to increased load localisation on neighbouring fibres, contributing to their failure. However, this study requires experimental validation for ineffective length measurement and a deeper understanding of stress redistribution around coplanar and non-coplanar (i.e. diffused) fibre breaks, recognising that the stress localisation on intact fibres is expected to vary depending on interfacial strength differences.
The present work, a combination of Digital Volume Correlation (DVC) and in situ Synchrotron Radiation Computed Tomography, presents 3D volumetric fibre-level strain field assessment longitudinally from single and coplanar/non-coplanar breaks to understand the intricacies of load redistribution that varies with fibre break types and interfacial strength differences. To enable local Digital Volume Correlation analysis on the self-similar microstructure of conventional carbon fibre reinforced polymer composites [2], epoxy resin was filled with industrial-grade silicon dioxide particles of spherical geometry with a nominal size of 500nm [3]. By using two different treatment types for the surfaces of the carbon fibres, we investigate how differences in interfacial strength contribute to local load transfer and, accordingly, the occurrence of cluster formation with increasing load. Internal strain mapping is used to understand stress localisation on nearby intact fibres, which varies depending on the presence of intact fibres between broken ones, and their influence on load redistribution around fibre breaks (Fig. 1). The effect of local fibre volume fraction on DVC-based strain transfer length measurement is also be taken into account.
The present work, a combination of Digital Volume Correlation (DVC) and in situ Synchrotron Radiation Computed Tomography, presents 3D volumetric fibre-level strain field assessment longitudinally from single and coplanar/non-coplanar breaks to understand the intricacies of load redistribution that varies with fibre break types and interfacial strength differences. To enable local Digital Volume Correlation analysis on the self-similar microstructure of conventional carbon fibre reinforced polymer composites [2], epoxy resin was filled with industrial-grade silicon dioxide particles of spherical geometry with a nominal size of 500nm [3]. By using two different treatment types for the surfaces of the carbon fibres, we investigate how differences in interfacial strength contribute to local load transfer and, accordingly, the occurrence of cluster formation with increasing load. Internal strain mapping is used to understand stress localisation on nearby intact fibres, which varies depending on the presence of intact fibres between broken ones, and their influence on load redistribution around fibre breaks (Fig. 1). The effect of local fibre volume fraction on DVC-based strain transfer length measurement is also be taken into account.