A novel approach to predict the effective elastic moduli of matrix composites made from non-circular inclusions embedded in a continuous matrix is proposed. In this approach, those inhomogeneities are substituted by simple equivalent circular-inclusions with modified elastic properties obtained from comparing the dilute solution results. Available simple approximations for the equivalent circular-inclusion medium then can be used to estimate the effective elastic moduli of the original composite. Robustness of proposed approach is demonstrated through the numerical examples with elliptic inclusions.

Glass fiber reinforced polymers (GFRP) is a new material with many advanced features in terms of strength, light weight, anti-corrosion ability on salty environment, which may replace steel. In this work, we present the technology of manufacturing of GFRP in bar form: pultrusion technology. The production line at the factory is imported from abroad. The objective of the research is to step by step mastering the technology and fully master the production line system of GFRP in bar form in Vietnam. We have fabricated successfully a product of high applicability, which has great potential for development (GFRP in bar form with large diameter, 20 mm). Pultrusion is one of technologies to fabricate the polymer composites used in many industries such as in aerospace, automotive and construction ones industries. The high performance pultruded products that are produced by this technique offer high fiber content of at least 70%. In order to produce high quality pultruded profiles, there are variables such as fiber impregnation, resin viscosity, pulling speed and curing temperature that have to be considered and these requests are discussed in this study. The aim of the present work is evaluating elastic properties like Young's modulus and Poisson's ratio from analytical methods such as Rule of mixture, Halpin-Tsai, Nielsen, Chamis and Hashin elastic models and compared with experiment results. The result shows a big difference. The mechanical characteristics of the GFRP D20 bar depend not only on the composition of components (fiber and epoxy) but also on the manufacturing technology. We propose research further direction: optimize the technological element in manufacturing GFRP bar with large diameter.