Shear modulus G(12) of unidirectional composites: a boundary element evaluation

The early micromechanical modelling techniques for describing composite beh aviour considered the material as a two-phase medium with a perfect bonding between the components. At present, the development of modelling technique s is slightly more complex as there are some studies that consider that the re is a zone surrounding the fibre with different properties from either th e fibre itself or the matrix. Normally, this zone is artificially introduce d as a thin coating. In cases of very thin coating, the thickness can be ne glected, but the effect is taken into account using an appropriate coeffici ent of interface h. With this approximation, the evaluation of shear modulu s G(12) can be obtained by solving the boundaries of two bodies only. As sh own in this paper, the BEM is a very efficient method for this purpose. The analysis is based on the analogy between the longitudinal shear loading an d the transverse heat conduction in the unidirectional composite. Two model s of boundary elements are proposed. The simpler model uses constant bounda ry elements. The second one uses two types of elements: linear elements, at the external boundaries, and cubic elements (with only two nodes), at the interface boundaries. All the results obtained can be compared with a simil ar model using MEF. A classic model is used for comparing under certain hyp othesis. In all cases the results are in agreement. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.