Recycling of polypropylene and curaua fiber-based ecocomposites: Effect of reprocessing on mechanical properties

The polypropylene with load of reinforcement of curauá fiber (PP-curauá) is a compound developed to be applied in the process of injection of automotive plastic parts. Polypropylene composites reinforced with mineral fillers (talc) or glass fibers have been widely applied in this segment. However, natural fibers are an important alternative considering the aspects of sustainability, recyclability, abundance and low cost, when compared with glass fibers, and industrial talc. This study was prompted by the growing need for materials that meet the constant cycles of use, disposal and reuse, and avoid the harmful effects on the environment. The mechanical properties of a curaua fiber and polypropylene-based ecocomposite reprocessed one, three and five times were assessed, since reprocessing is known to change the strength of these materials. Pure polypropylene (0%) and ecocomposites with 10 and 30 wt% of fiber were submitted to tensile and three-point bending tests. The results showed that polypropylene ecocomposites with 30% curaua fibers exhibited a higher modulus of elasticity. Moreover, reprocessing did not significantly affect the ecocomposite properties, demonstrating their viability for reuse.

Mechanical and Thermal Characterization of Natural Intralaminar Hybrid Composites Based on Sisal

The main objective of this work was to investigate the effect of hybridization on the mechanical and thermal properties of intralaminar natural fiber-reinforced hybrid composites based on sisal. Ramie, sisal and curauá fibers were selected as natural fiber reinforcements for the epoxy matrix based composites, which were produced by the hand lay-up technique. Tensile, flexural and impact tests were carried out according to American society for testing and materials (ASTM) standards to characterize the hybrid composites, while differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to evaluate the thermal properties. It was found that the mechanical properties are improved by hybridization of sisal based composites. The thermal analysis showed that the hybridization did not significantly affect the thermal stability of the composites. A scanning electron microscopy (SEM) was used to examine the fracture surface of the tested specimens. The SEM images showed a brittle fracture of the matrix and fiber breakage near the matrix.

Mechanical Behaviour of Reinforced Sand with Natural Curauá Fibers through Full Scale Direct Shear Tests

Inclusion of natural fibers (sisal, curauá, coco fiber and others) for soil improvement has been the study object in diverse geotechnical areas and it is a topic of growing interest, within the research area of new geotechnical materials. The state of the art in this subject highlights excellent results as soil strength parameters improve and post-cracking strength (toughness) increase. Soil reinforcement technique with fibers is established in the technology of composite materials, this being a combination of two or more materials presenting properties that the component materials do not possess on their own. The aim of this paper is to study the mechanical behaviour of sand-fiber composite by inserting natural curauá fibers into a sandy matrix, with different fiber contents. The fibers were randomly distributed in the soil mass. The experimental program included physical and mechanical characterization of the composites, using full-scale direct shear tests, with samples measuring 30 x 30 cm and 15 cm high. Direct shear tests were carried out using fibers with 25 mm length and 0.5 and 0.75% fiber content (relative to the soil dry weight). The specimens also presented a relative density of 50% and moisture content of 10%. It was sought to establish a pattern behaviour so that the addition of curauá fiber influence can be explained, thus, comparing with the sandy soil shear strength parameters. Inclusion of natural curauá fibers as soil reinforcement presented satisfactory results, as an increase in the soil shear strength parameters was observed when compared with sandy soil results.

Study of Wet-Drying Cycles on Sisal, Jute and White Curaua Fibers on the Resistance Parameters of Cement-Based Composites

This study presents the results of the mechanical characterization of cement composites reinforced with short fibers of jute, sisal and curauá. Tests of direct tension in flexion and traction, after wetting and drying cycle (5 cycles) to determine the first crack were performed to determine the first crack, the tension and post-peak toughness and strengh of the composites. To ensure the the composite durability, the ordinary Portland cement matrix was modified by adding metakaolin, to consume the calcium hydroxide generated during Portland cement hydration. The composites were produced using short fibers of jute, sisal and curauá (50 mm) at levels of 2%, 4% and 6% of sisal and white curauá, and 3%, 6% and 9% to jute. The fibers of jute and white curauá employed in this study came from the Brazilian Amazon, while the sisal came from the Brazilian Northeast.This fibers have great economic importance in the producing region. Composites with high toughness, strength and multiple cracking processes under bending load were obtained when volume fractions equal to 3% of jute were used as reinforcement and when 6% of sisal and 4% of white curauá were used as reinforcement.