Accelerated Test Methods to Determine the Long-Term Behavior of Composite Highway Structures Subject to Environmental Loading

Research on fiber-reinforced plastic composites has explored the effects of selected aqueous environments on the mechanical and physical properties of these composites. The composite materials tested were produced using the pultrusion process. Resins included in the study were polyester and vinylester. Fibers included were E-glass, carbon, and aramid. Environments considered were air, deionized water, acetic acid at two concentrations, and ammonia at two concentrations. Temperatures considered were room temperature, 50 and 80°C. Mechanical testing included tension, flexure, and short beam shear tests. Weight loss, thermogravimetric, and calorimetric measurements were made to determine whether degradation was taking place in the fiber or matrix phases of the composite. Accelerating factors for the various environments were calculated using the framework outlined in ASTM E 632, Standard Practice for Developing Accelerated Tests to Aid in the Prediction of the Service Life of Building Components and Materials. It was observed that a combination of weight loss and thermogravimetric measurements are useful in determining whether degradation in the composite is due to fiber or matrix degradation. Trends in weight loss closely parallel loss of mechanical properties in polyester/glass rods.