Short-beam shear fatigue behavior of round curved pultruded composite

• Published in: Mechanics of advanced materials and structures 2022-10, Vol.29 (26), p.5579-5587
• Main Authors: Tonatto, Maikson L. P., Tarpani, José Ricardo, Amico, Sandro C.
• Format: Article
• Language: English
• Subjects: carbon fiber; Carbon fiber reinforced plastics; Curved beams; Curved composite; Cyclic loads; Damage; Epoxy matrix composites; fatigue; Fatigue strength; Fatigue tests; Heat treating; Laminates; Low cycle fatigue; Polymer matrix composites; pultrusion; Residual strength; Shear stress; Shear tests; short-beam test; Stiffness; Strengthening
• ISSN: 1537-6494; 1537-6532
• DOI: 10.1080/15376494.2021.1959968

Short-beam shear test has been used to evaluate the fatigue strength of round curved pultruded carbon fiber - epoxy matrix composite specimens in three point bending test of a convex-beam. The specimens were cyclically loaded at peak stresses from 50 to 80% of the quasi-static short-beam strength, and load ratios of 0.1 to 0.5, and damage evolution was monitored using the apparent stiffness method. Basquins' law was used to fit the experimental S-N data. The results showed that the fatigue strength of curved pultruded composites is lower than for conventional thin flat unidirectional laminates, and less sensitive to load-ratio effects. Residual strength of pre-fatigued specimens was determined by quasi-static short-beam tests, and it sometimes exceeded the pristine material performance due to fatigue-induced strengthening phenomenon. Stress redistribution and residual manufacturing-induced stress relief due to the previous cyclic loading were found the main responsible for mitigating damage growth under quasi-static loading. Fractographic survey indicated that stress redistribution and stress relief governed the strengthening process under high-cycle and low-cycle fatigue regime, respectively.