No abstract

The progress in establishing new classes of biocomposites has led to potential applications in the automotive, aerospace, and construction industries because of their life cycle properties, low cost, lightweight, nonabrasive, and moderate mechanical strength. The heterogeneity of natural fibers plays an important role in the fiber-matrix adhesion, therefore affecting the mechanical performance and the durability of the composites. This work has described the manufacturing, characterization, and testing of hybrid composites reinforced with sisal fibers and silica nanoparticles. A full factorial design was performed to identify the effects of fiber treatment, fiber orientation and nanosilica inclusion factors on the physical and mechanical properties of hybrid composites. Composites made with unidirectional untreated fibres and silica nanoparticles (2 wt%) provided higher impact resistance. In contrast, the highest strength and stiffness values and the lowest overall porosity were achieved when unidirectional treated fibres with 2 wt% of silica inclusions were considered. POLYM. COMPOS., 39:146-156, 2018.

The study describes a design of experiment analysis performed on hybrid polymeric composites reinforced with unidirectional banana fibres and silica microparticles. Maleic anhydride was also evaluated as a chemical additive to improve the adhesion between phases. A full factorial design (2 2 3 1 ) and the analyses of variance were performed to identify the significance of the microstructure constituents against different mechanical and physical properties in a total population of 120 biocomposites samples. The microstructure parameters considered were fibre volume fraction (30% and 50%), silica addition (0%, 20 wt% and 33 wt%) and maleic anhydride addition (0% and 2 wt%). The mechanical and physical properties of the composite considered as factorial and analyses of variance responses were the apparent density, apparent porosity, water absorption, modulus of elasticity and mechanical strength under tensile and flexural loading. The design of experiment analysis has shown that the volume fraction of the fibres significantly affects all responses, with the composite made from 30% of banana fibres exhibiting superior mechanical strength and modulus of elasticity. While the addition of silica has featured a statistically noticeable contribution to the porosity and the water absorption, the presence of the particles did not provide any significant enhancement to the composites mechanical strength. Maleic anhydride showed a significant contribution to the apparent density, water absorption and flexural modulus, not improving the adhesion between phases, with a consequent decrease of the Young's modulus and increase of the water absorption within the composites.

The use of composite materials in construction has grown considerably in recent years, such as cementitious matrices and concrete reinforced with fibers. The vegetable fibers have become an alternative due to its abundance, low cost and low energy consumption for its production, and appropriate properties mechanical. Curauá fiber is a plant native from Amazonas harvested manually in commercial farming and it is used in the manufacture of ropes and baskets or as reinforcement in composite with organic matrix of components for cars, buses and trucks. On the other hand, the extrusion process can produce composites with high-density matrix with fibers, low permeability and good interface between fiber and matrix. This process is also compatible with the use of vegetable fibers as raw materials in the production of cost-effective construction elements such as ceiling panels and drywalls. The objective of this research was use the analysis of variance (ANOVA) for evaluating the content and length of curauá fibers on the mechanical behavior of the extruded cementitious composites. Composites without fibers and reinforced with 1% and 2% by mass of fibers as well as 6 mm and 10 mm of length these curauá fibers were evaluated. The composites with fibers of 10 mm have showed better mechanical results. Besides, the composites with fibers curauá after 200 accelerated aging cycles were better than one non-aging.

The work describes the manufacturing and testing of novel hybrid epoxy/carbon fibre composites with silica micro and poly-diallyldimethylammonium chloride-functionalised nanoparticles. A specific chemical dispersion procedure was applied using the poly-diallyldimethylammonium chloride to avoid clustering of the silica nanoparticles. The influence of the various manufacturing parameters, particles loading, and mechanical properties of the different phases has been investigated with a rigorous Design of Experiment technique based on a full factorial design (2 1 3 1 ). Poly-diallyldimethylammonium chloride-functionalised silica nanoparticles were able to provide a homogenous dispersion, with a decrease of the apparent density and enhancement of the mechanical properties in the hybrid carbon fibre composites. Compared to undispersed carbon fibre composite laminates, the use of 2 wt% functionalised nanoparticles permitted to increase the flexural modulus by 47% and the flexural strength by 15%. The hybrid carbon fibre composites showed also an increase of the tensile modulus (9%) and tensile strength (5.6%).