Low- and High-Cycle Fatigue Behavior of FRCM Composites

Abstract

This paper describes methods, procedures, and results of cyclic loading tensile tests of a PBO FRCM composite. The main objective of the research is the evaluation of the effect of low- and high-cycle fatigue on the composite tensile properties, namely the tensile strength, ultimate tensile strain, and slope of the stress–strain curve. To this end, low- and high-cycle fatigue tests and post-fatigue tests were performed to study the composite behavior when subjected to cyclic loading and after being subjected to a different number of cycles. The results showed that the mean stress and amplitude of fatigue cycles affect the specimen behavior and mode of failure. In high-cycle fatigue tests, failure occurred due to progressive fiber filaments rupture. In low-cycle fatigue, the stress–strain response and failure mode were similar to those observed in quasi-static tensile tests. The results obtained provide important information on the fatigue behavior of PBO FRCM coupons, showing the need for further studies to better understand the behavior of existing concrete and masonry members strengthened with FRCM composites and subjected to cyclic loading.

Calculation Derivation and Test Verification of Indirect Tensile Strength of Asphalt Pavement Interlayers at Low Temperatures

“…The indirect tensile strength average is about 1.48 times that of the direct tensile strength at 5 • C, and, 1.51 times at 10 • C. The above differential is mainly related to the stress transmission and redistribution in the specimens during the loading period [43]. This effect is more significant for the direct tensile loading due to the longer stress transfer path [46,47].…”

Analytical Modeling of Debonding Mechanism for Long and Short Bond Lengths in Direct Shear Tests Accounting for Residual Strength

“…For the sake of simplicity, in this paper, we derived the expression of the load during debonding only for long bond lengths. The corresponding plot is provided in Figure 13 according to the different models, i.e., by Equations ( 16), ( 27), ( 34), (37) and (45). It is seen that all models except RF estimate a normalized load higher than unity at α = 0, i.e., the effect of residual strength is present also at the onset of debonding.…”

“…On the other hand, for long bond lengths,   eff, the maximum load occurs (e), and its value is achieved by replacing  =   eff into either Equation (34) or E (37). Summarizing, we have: ), 1 39) is plotted in Figure 8 to illustrate the behavior of maximum bond length according to RL for r 0, 0.15   .…”

“…On the other hand, for long bond lengths, λ > λ eff , the maximum load occurs at stage (e), and its value is achieved by replacing α = λ − λ eff into either Equation (34) or Equation (37). Summarizing, we have:…”

“…Recently, a modified double-pull shear setup was introduced by Mukhtar and Shehadah [35] to determine the bond performance of FRP-to-concrete joints. It is worthwhile to note that, recently, the fatigue performance of FRCM composites has been receiving a lot of attention [36,37].…”