Hygrothermal aging effects on mechanical and fatigue behaviors of a short- natural-fiber-reinforced composite

• Published in: International journal of fatigue 2018-03, Vol.108, p.96-108
• Main Authors: Mejri, M., Toubal, L., Cuillière, J.C., François, V.
• Format: Article
• Language: English
• Subjects: Aging (natural); Bending fatigue; Chemical composition; Damage mechanisms; Fatigue durability; Fatigue strength; Fatigue tests; Fiber reinforced composites; Fiber reinforced plastics; Fiber reinforced polymers; Fourier transforms; High density polyethylenes; Hygrothermal aging; Infrared analysis; Infrared spectroscopy; Materials durability; Materials fatigue; Mechanical properties; Natural fiber composite; Organic chemistry; Polyamide resins; Residual strength; Residual stress; Static tests; Thermodynamic properties; Thermogravimetric analysis
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2017.11.004

[Display omitted] •We evaluate the monotonic and fatigue strengths of polyethylene and short birch fibers composites.•S-N curves of unaged and aged samples was obtained.•Fatigue behavior defined through the evolution of durability and residual strength.•Hygrothermal aging degrades static mechanical and fatigue properties on composite and loss of the fatigue performance was observed. A new natural fiber composite made of high density polyethylene (HDPE) and 40% wt of short birch fibers (SBF) was developed to replace polyamide (better known under its industrial name “Nylon”) in spur gear manufacturing. The effect of hygrothermal aging on quasi-static and fatigue bending behaviors of this new composite has been studied in this work. Once hygrothermal aging is completed, flexural quasi-static tests have been performed on aged specimens and results compared with those obtained from unaged specimens. It has been observed that hygrothermal aging has no significant effect on flexural mechanical properties of this composite. After characterization, bending fatigue tests have been conducted on aged specimens and results have been compared with those of unaged specimens. These fatigue tests show that hygrothermal aging decreases the high cycles fatigue strength (HCFS) of this composite. The cause of this fatigue durability decrease has been investigated using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and a scanning electron microscope (SEM). These tests show that the chemical composition and thermal behavior of this composite are not affected by hygrothermal aging. On the contrary, these tests show that damage mechanisms of this composite (HDPE/40% wt of SBF) are directly affected by this type of aging.