Abstract:

This study aims to increase the understanding of the tensile failure of unidirectional hybrid and non-hybrid composite when subjected to tensile loadings. To achieve this goal several models with increasing complexity have been developed and implemented and the effects of tensile loading are studied. A high fidelity three-dimensional multiscale finite element modelling approach for unidirectional (UD) composites was developed to predict the phenomena associated with longitudinal tensile deformation and failure in detail. The approach is based on periodic Representative Volume Element (RVE) on a micromechanical scale, with a random distribution of fibres, to capture the progressive damage and interaction between the fibres and the matrix. The carbon/fibre material AS4/8552 was chosen for the purpose of demonstration of the methodology. The fibres were considered transversely isotropic with linear-elastic behaviour. The brittle fracture of carbon fibres was reproduced explicitly by means of a set of fracture planes whose failure is governed by fibre fracture toughness and a statistical Weibull distribution of fibre strengths. A modified elastic-plastic Drucker-Prager model coupled with tensile damage behaviour was used to model the resin matrix. The fibre-matrix debonding is simulated by means of a cohesive-frictional model coupled with a surface contact algorithm. This numerical methodology was complemented by extensive in-situ experimental characterization of fibres, matrix and fibre-matrix interfaces to generate reliable model inputs.

Besides the detailed simulation of longitudinal fracture mechanisms and their interaction, it will be demonstrated that this approach allows the study important effects on longitudinal failure, such as dynamic loading and residual thermal stresses. Moreover, it allows the determination of important parameters to the development of lower-fidelity but more efficient analysis tools, such as the Stress Concentration Factor (SCF) caused by the dynamic failure of single fibres, which has significant effect on the failure probability of adjacent fibres, and the critical fibre cluster. A 3-D continuum damage mechanics model (CDM) was developed for the prediction of damage onset in FRP is proposed.