Flexural fatigue performance of hybrid composite laminates based on E-glass and polypropylene fibers

Abstract

An experimental investigation has been conducted to understand the effect of water aging on flexural fatigue performance of unidirectional polypropylene (PP)-glass (G) fiber–reinforced epoxy composites. Test specimens were fabricated using hand lay-up process with a constant total fiber volume fraction. The effects of the reinforcement hybridization, hybrid configuration, and stacking sequences on S–N curves were investigated. Deflection-controlled flexural fatigue tests with a frequency of 25 Hz at zero mean stress have been conducted. A 20% reduction of the initial applied moment was taken as a failure criterion. In the first stage, the flexural fatigue properties of un-aged composite specimens were studied in ambient temperature. In the second stage, flexural fatigue properties were investigated after a preliminary aging step in distilled water for 350 days. The specimen surface temperature rise was measured to ensure that there is no early damage happened in the tested specimens. Results indicated that the hybridization of PP fiber–reinforced composite with G fiber improves its flexural fatigue resistance but increase water uptake. Inter-intraply hybrid laminate with G-fiber layers at the specimen outer faces and PP-fiber layers in the specimen core exhibits the most favorable flexural fatigue behavior, that is, the highest cost ratio and the specific fatigue endurance strength. The water-sorption step induced a significant decrease in fatigue properties of the fabricated specimens. The highest measured temperature rise was observed to be about 9°C for G fiber–reinforced composite.