Loss of Mechanical Properties by Water Absorption of Vinyl-ester Reinforced with Glass Fiber

ABSTRACT: The effect of water absorption on the mechanical properties of the composites has been studied. The matrix used was vinyl-ester. Different arrangements of glass fibers were used to reinforce vinyl-ester matrix: mat, unidirectional, and bidirectional cloth. The samples were immersed in distillated water at 80C. The flexural modulus was measured as a function of immersion time. The decrease in the glass transition temperature, Tg, was correlated with the water absorption and flexural modulus. The composite flexural modulus was fitted by means of a modified rule of mixture, which included an interfacial coefficient. The relationship between the directionality of the fiber in the composite material and the water absorption was also analyzed. KEY WORDS: composites, ageing, water absorption, vinyl-ester, mechanical properties