Effects of Changing Environment and Loading Speed on Mechanical Behavior of FRP Composites

Abstract

Durability of fiber reinforced polymer composites (FRP) are controlled by the durability of their constituents: reinforcement fibers, resin matrices, and the status of interfaces. A great deal of research has been focused on attempting to assess the relationship between interfacial structure and properties of fiber-matrix composites. It is at the interfacial area where stress concentration develops because of differences in the thermal expansion coefficients between the reinforcement and the matrix phase. A significant mismatch in the environmentally induced degradation of matrix and fiber leads to the evolution of localized stress and strain fields in the FRP composite. The present investigation aims to study the effects of changing hygrothermal conditioning cycles (either by changing relative humidity and temperature is kept constant, or by changing temperature but relative humidity is maintained same) on moisture gain/loss kinetics and on interlaminar shear strength (ILSS) of varied weight fractions glass fiber reinforced epoxy and polyester matrices composites. The mechanical assessment is extended to evaluate the loading rate sensitivity of hygrothermally shocked glass/epoxy and glass/polyester laminates at 2mm/min and 50mm/min crosshead speeds. Observations on absorption/desorption kinetics are noticed to be dependent on nature of hygrothermal shock cycle and on weight fraction of fiber reinforcement. Results of mechanical performance are statistically significant at different stages of conditionings. Shear values are found to be greater at higher crosshead speed for all undertaken situations. Mechanical responses are observed to be dependent on matrix resin and type of hygrothermal shock cycle. Very little and limited literature is open to address the important interactions of polymer composites with this kind of realistic environmental situations.