The effect of fiber orientation on creep behavior of sisal/epoxy composites

The mechanical performance of a polymeric composite reinforced with fibers, as tensile properties and creep behavior, is strongly influenced by fiber orientation. Although several studies have conducted creep tests on polymeric composites, none have performed creep analyses on sisal/epoxy under actual working stress conditions. In this work, Findley's and Burger's models were utilized to describe the creep behavior of sisal/epoxy composites with different orientations [0°, 90°, and cross-ply (0°/90°)]. They were evaluated under three distinct stress levels (10, 40, and 60% ultimate stress) at 27 °C, under constant tensile for 8 h. Also, the tensile test was performed on the final stress levels and Young's modulus. As a result, by fitting experimental data with Findley's and Burger's models, the creep behavior of sisal/epoxy [0°] composites was superior to other composites and epoxy matrices. According to the data obtained, the parameters A and E0 from Findley's equation and EM, EK, and Nk from Burger's equation were extremely stress-dependent. In addition, the tensile test showed the sisal/epoxy [0°] (175 ± 0.9 MPa) and cross-ply (70 ± 1.9 MPa) composites had a tensile strength higher than the epoxy matrix (35 ± 0.6 MPa). To conclude, the characterization of tensile creep behavior has great application potential in predicting the long-term performance of sisal/epoxy composites. This study suggested the creep modeling could adequately predict the short-time creep behavior of the sisal/epoxy composites since Burger's and Findley's models prolong the structures ‘service life and reduce maintenance effort and cost for long-term applications.