A strength of materials and elasticity approach was used in this study to determine the stiffness of fiber-reinforced composites, by taking into account the concept of boundary interphase. Theoretical expressions for longitudinal transverse and shear moduli, as well as for longitudinal Poisson's ratio, were derived by use of this model. Results derived from these expressions were compared with others, to observe the discrepancies and evaluate their validity

No abstract

In this work, the effect of moisture absorption on the mechanical properties of particulate composite materials is studied. Moisture absorption constitutes a main parameter affecting the thermomechanical behaviour of composites, since it causes plasticization of the polymer matrix with a concurrent swelling. In the present work, the influence of water absorption on the flexural properties of particle-reinforced composites was thoroughly investigated. It was found that during the process of moisture absorption there exists a variation of the flexural properties closely related to the degradation of the mechanical behaviour of the composite, as well as the percentage amount of moisture absorbed. Experiments were carried out with composite made of epoxy resin reinforced with low-content iron particles. The variation of ultimate stress, breaking strain, deflection, elastic modulus and Poisson ratio due to water absorption was examined.

SYNOPSISIn this article an experimental study to determine the longitudinal (or in-plane) shearing stress-strain response of a unidirectional fiber-reinforced composite material is presented. The test method used is the four-point bending of a 245" off-axis glass-fiber-reinforced laminate. Although a laminate is used for the investigation of the shearing stress-strain response, it is shown that unidirectional shear properties can be found from the laminate test data following a procedure analogous to that used in previously. Also, the 45' off-axis test of the unidirectional composite in bending was carried out to obtain the in-plane shear modulus and compare it with that obtained by the f 4 5 " off-axis method. Finally both values were compared with the theoretical value of the in-plane shear modulus obtained from a theoretical formula where the concept of boundary interphase between fiber and matrix was introduced. 0 1995 John Wiley & Sons, Inr.