Effect of Moisture / Liquid Absorption on Mechanical Properties of Composites

Demand for lightweight and strong structures made of composite materials has increased tremendously over the past few years. This necessitates to fully exploit the properties of composite materials. It is important to understand the behavior of composites under different environmental conditions in order to take full advantage of its properties as their behavior is different from conventional materials (metals, nonmetals etc.). Glass fiber reinforced polymer composites are being used in multiple machines from bicycles to aircraft and to space ships. However, certain factors like environmental exposure and moisture absorption effects the mechanical properties of composites, like tensile and flexural strength, which require a thorough investigation. Therefore, in this paper moisture absorption effects on mechanical properties (tensile and flexural) of two categories of glass fiber (9 oz, 18 oz) epoxy laminate composites are analyzed. Fickian model has been used to find out moisture absorption rate and diffusion coefficient. Both configurations were put to three different environmental conditions, which are open environment, water, and kerosene oil, for a specified set time period. One set of specimen of both configurations was tested right after fabrication, and served as benchmark for rest of the specimens, which were put to environmental exposure. After completion of exposure period, specimens were tested and change in mechanical properties (tensile and flexural) were compared with benchmark, and after analysis it was found that 18 OZ glass fiber is less effected in term of environmental exposure and moisture interaction as compared to 9 OZ glass fiber.