Stress relaxation effect on fatigue life of biaxial prestressed woven E-glass/polyester composites

In this study, the stress relaxation effect on the fatigue cycles-to-failure of the biaxial elastic fibre prestressed woven composite (E-glass/polyester) was investigated. The fibre pretension load was applied prior and during matrix cure, and then it has been released to induce compressive residual stresses within the matrix. The longevity of these stresses is questionable, and it needs investigation. The time of residual stress redistribution or relaxation was estimated experimentally for the E-glass fibre prestressing level be equal to 50 MPa. Residual stresses within the polyester matrix have declined by (27%) throughout 110 days leading to reduce the improved fatigue life by about 14% due to the stress relaxation process within the polyester matrix material. The study showed that even though the stress relaxation in the matrix reduced the improved fatigue cycles of the biaxial elastic prestressed E-glass fabric/polyester resin system, some improvement still is possible for long-term performance.