Variation of the mechanical properties of E-glass/epoxy composites subjected to hygrothermal aging

In this study, the effects of hygrothermal aging on the mechanical properties and impact behavior of glass-epoxy composites were investigated experimentally. The vacuum-assisted resin infusion molding was used to manufacture composites. In manufacturing of composites, unidirectional E-glass fabrics with areal density of 300 g/m(2) and a resin system (Araldite LY 564/Aradur 3487 BD) were used. In order to determine mechanical properties such as modulus of elasticity, longitudinal and transverse strengths, shear strength, and Poisson's ratio, the composite samples were prepared according to the ASTM standards. Then, the samples were conditioned at a constant temperature (95 degrees C) and a constant humidity (70%) for different periods of times, ranging from 0 h to 1200 h. The conditioning temperature was chosen due to the glass transition temperature (T-g) of the intact composites which is determined as 78 degrees C. It is noted that the most affected mechanical property via material degradation is modulus of elasticity in transverse direction (E-2) while the least affected one is shear modulus (G(12)). The perforation threshold of the composite materials also decreases with increase of conditioning time.