Influence of Moisture on the Mechanical Properties of <i>Rhecktophyllum camerunense</i> Vegetable Fiber

Abstract

Plant fibers are become an environmentally friendly substitute to glass fibers for the reinforcement of composites, particularly in automotive and civil engineering. The fundamental difference between these two types of fibers is their behavior to the humidity. Plant fibers absorb moisture when they are used as reinforcement in composite materials and drawback their mechanical properties. It is important to analyze hygromechanical behavior of plant fibers in order to treat them before using in composite material as reinforcement. The treatment can be electrically, physically, chemically and other. Indeed, the RC fibers used in this study come from the roots of RC collected in central Cameroon. Fresh ones have been selected for this purpose. Some samples were submitted to hygroscopic ageing in an environmental enclosure of 23%, 54% and 75% relative humidities at 23±1°C and others immersed in distilled water (100%). Hygroscopic ageing is noted by the saturation of the fibers after several weighing on a balance until the constant mass is obtained. This experiment followed steps described by NF EN ISO 483: 2006-01 standard. After that tensile test was done on those saturated individual fibers according to ASTM D 3397-75 standard. Twenty specimens were used to evaluate elastic properties of RC at each hygroscopic condition. The qualitative analysis of behavior curve shows that no matter the relative humidity, the RC fiber presents a toughness behavior and elastic material, characterized by a relatively prevalent viscoelastic area and a great elongation at break. However, we note a decrease of the stress at break and decrease of the elastic modulus for all humidities.