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.