Unsaturated polyester composite reinforced with Caroá fiber (Neoglaziovia Variegate): water sorption and mechanical properties

Abstract

Aiming to minimize the environmental pollution and reducing the production costs of the composite materials, the use of plant fibers improves their physical and mechanical properties. On the other hand, fibers have high water absorption, which may increase their volume and weaken the fiber/matrix interaction, affecting the mechanical features of the composites. Concerned with this problem, this research had the objective of making 3 and 10 millimeter-thick specimens, containing 23% (m/m) of Caroa fibers and 73% (m/m) of unsaturated polyester. Samples were withdrawn after 0, 2, 4, 7, 12 and 21 days of exposure at room temperature water (ASTM D570 − 98). Then, the test of tensile (ASTM D 3039), flexural (ASTM D 790-03) and impact (ASTM D 256) was realized and the mechanical properties were analyzed. The samples subjected to humidity had their fibers degraded and presented loss of mechanical properties, more significant in composite with 3 mm. For example, the reduction of the strengths tensile, after 21 days of test were 80% for composites with 3 mm and 60% for composites with 10 mm. Studies like this are important for long-term applications of such composites in humid environments.

Physical and mechanical properties of polyurethane thermoset matrices reinforced with green coconut fibres

“…The results observed in this study are similar to the ones found by Bezerra, 61 who obtained mean impact strength values varying between 50 and 250 J/m in composites produced with polyester resin and coconut fibre content between 13 and 40%. As for the study performed by Luz et al., 34 the values obtained in this work are far higher than the ones obtained by the authors, who found 111 J/m for composites produced with 30% coconut fibre and epoxy.…”

“…This behaviour was also observed by Pereira et al., 59 who noticed a tendency to reduce mean values for bulk density, as more eucalyptus fibres were added to the composites. Bezerra 61 observed that the bulk density of the composites decreased about 15% in composites produced with 40% of coconut fibres, thus resulting in a decrease of the composite mass. The results observed in this work for bulk density are slightly lower than those of Wiedman, 1 whose author reported average values of bulk density of 0.53 g.cm −3 in composites produced with coconut fibres and urea-formaldehyde adhesive.…”

“…Less dense composite materials have advantages in the use of light structures, in that, regarding final performance of the product, lightness is a determining factor for the conception of new material. 61 Moreover, composites made with natural fibres, because there are lighter, are preferred for interior design applications, such as panels, cabins and furniture, in addition to sea vessels and automobiles.…”

“…This behaviour occurs because, with the increase in the volumetric amount of fibres, the main mechanisms for energy absorption are enhanced, which result in more energy for the rupture. 61…”

Study of the Moisture Absorption in Polymer Composites Reinforced with Vegetal Fiber Using Langmuir’s Model

“…The kinetics shows higher absorption of moisture at initial times of the process and for long timer exists a tendency to reach the equilibrium moisture content (saturation point). These results are consistent with those reported to polymer composites reinforced by other kind of vegetable fibers [15][16][17][18] .…”