A three-dimensional densely packed particle model has been created using the discrete element method (DEM) [1,2] to represent the fibre reinforced composite. Through changing the distribution of particle size and parallel bonds properties, different mechanical characteristics of fibres and matrix can be recreated in the DEM model. Both the anisotropic behavior of the fibre and the isotropic behavior of the matrices were calibrated through measuring respective axial compressive deformation from the DEM results. For the matrix material, random packing method was used for the assembly of the particles. A compressive pressure was applied to obtain the elastic modulus of matrix. For a fibre material, a useful method was proposed to define the transverse and longitudinal directions. A longitudinal and a transverse compressive pressure are applied respectively to obtain its longitudinal and transverse modulus.
Good agreement was observed from the comparisons between the numerical tests and the test results from WWFE-II . From these simple comparisons, the contact properties between matrix particles and between fibre particles are respectively calibrated. These contact properties were then introduced into the DEM simulations of the IM7/8551-7epoxy laminate (WWFE-II Info Pack). It can be found that the material properties of the individual fibre and matrix materials obtained from DEM simulations agree very well with the experimental measurements. The comparisons for the laminate are not satisfactory at the moment. Problems have been identified in the model, including that shear contacts between particles were not properly calibrated and the contact properties between particles with different materials were not calibrated. In the current model, a rigid contact was assumed. Obviously future research is needed.
The particle simulation can also be employed to study the process of microscopic failure within the laminates, which is very difficult, if not impossible, to be recorded in experiments. The preliminary studies have validated the capacity of the analysis of the microstructures of the laminated composites, and also revealed potential applications in studying the failure mechanism of fibre reinforced composites at microscopic level.