Off‐axis creep rupture prediction of pultruded glass‐fiber reinforced polymer unidirectional lamina

Abstract Limited research on the creep behavior of glass‐fiber reinforced polymer (GFRP) composites has constrained their broader adoption in civil engineering applications. This paper investigates the off‐axis creep rupture behavior of pultruded GFRP unidirectional lamina. The mechanical properties of the GFRP unidirectional lamina were determined through static tests conducted on specimens at six different off‐axis angles. Based on the strength criterion for composite materials, a method for predicting in‐plane shear strength via off‐axis static tensile tests is established. Considering the influence of the fiber nominal angle error and the test measured strength error, the optimal off‐axis angle and the ideal off‐axis angle range for predicting the in‐plane shear strength are calculated. Based on the short‐term creep rupture test results of specimens at 0°, 90°, and within the ideal off‐axis angle range, the longitudinal tensile, transverse tensile, and in‐plane shear creep strength functions (CSF) were established. The creep rupture times of the unidirectional lamina at various off‐axis angles were predicted using the CSFs. The uneven distribution of fibers resulting from the pultrusion process further exacerbates the dispersion of creep rupture times. Therefore, according to the normal distribution model, a probability interval calculation method for creep rupture time is established, and the prediction interval under different probabilities is estimated. The results of the creep rupture tests verify the reliability of the method in the prediction interval. Highlights The in‐plane shear strength is predicted by the off‐axis tensile test results. The ideal off‐axis angle calculation for shear strength prediction is proposed. The shear CSF is predicted using creep test results with ideal off‐axis angles. The creep rupture time at various off‐axis angles is predicted using CSFs. A probability interval prediction method for creep rupture time is established.