The reinforcement of polymer matrices with continuous carbon fibers (CF), giving rise to so-called carbon fiber-reinforced polymers/plastics (CFRP) composites is a major issue in the space, aerospace, naval, wind and oil and gas energy industries because of their need for construction materials that exhibit very high structural efficiency (i.e., exceptional strength/ density and stiffness/density ratios). The improvement in interfacial strength between the polymer matrix and reinforcing fiber system leading to the enhancement of overall mechanical performance of CFRPs has always been sought by materials scientists, since the region separating the bulk polymer from the fiber reinforcement is of utmost importance to load transference and distribution. Kim and Mai [1] and Pegoretti et al. [2] discovered that the shear strength of a fibrous polymer composite is closely related to the shear strength of the fibersurrounding polymer matrix domain. They also noted that the latter property strongly depends upon the mechanical performance of the interphase, which constitutes an intermediate, different phase when compared to the reinforcing fiber and the bulk resin [3]. Many efforts were then devoted to build strong fiber/ matrix interphases by controlling physicochemical interactions and frictional forces acting on this particular region of composite systems [4]. That achievement [1, 2] allowed efficient hierarchical composite structures to be technologically addressed and developed, aiming not only to improve the mechanical strength but also to mitigate interlaminar, intralaminar and translaminar damage, hence enhancing the fracture toughness as well [5][6][7]. For instance, the use of fillers such as monolayer graphene [8][9][10] Abstract. In this paper, a cost-effective and eco-friendly method to improve mechanical performance in continuous carbon fiber-reinforced polymer (CFRP) matrix composites is presented. Unsized fiber fabric preforms are coated with self-assembling sugarcane bagasse microfibrillated cellulose, and undergo vacuum-assisted liquid epoxy resin infusion to produce solid laminates after curing at ambient temperature. Quasi-static tensile, flexural and short beam testing at room temperature indicated that the stiffness, ultimate strength and toughness at ultimate load of the brand-new two-level hierarchical composite are substantially higher than in baseline, unsized fiber-reinforced epoxy laminate. Atomic force microscopy for height and phase imaging, along with scanning electron microscopy for the fracture surface survey, revealed a 400 nm-thick fiber/matrix interphase wherein microfibrillated cellulose exerts strengthening and toughening roles in the hybrid laminate. Market expansion of this class of continuous fiber-reinforced-polymer matrix composites exhibiting remarkable mechanical performance/cost ratios is thus conceivable.

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ResumoO desenvolvimento da tecnologia na produção de painéis e o aumento da demanda por estes produtos, aliado ao encarecimento da madeira maciça de grandes dimensões, contribuíram por motivar o desenvolvimento da indústria de produtos engenheirados de madeira. A partir desta tendência do mercado madeireiro é que se definiu o objetivo do presente trabalho, que consistiu em avaliar as propriedades mecânicas de painéis de partículas orientadas OSB (Oriented Strand Board), OSL (Oriented Strand Lumber) e LSL (Laminated Strand Lumber), produzidos com madeira de Pinus taeda e resina poliuretana à base de óleo de mamona, avaliando-se a influência do comprimento das lascas (inerentes a cada tipo de painel) nas propriedades de rigidez e de resistência. Os ensaios de flexão foram realizados segundo as normas EN 310-2000 e ASTM D 198-09, para a determinação do módulo de elasticidade (MOE) e do módulo de ruptura (MOR) dos três tipos de painéis avaliados. Os resultados do MOE e do MOR, para os três tipos de painéis, atenderam aos requisitos mínimos da norma EN 310-200, e o aumento do comprimento das lascas influenciou positivamente, de forma significativa, nestas propriedades, apresentando os painéis LSL os melhores resultados, seguidos dos painéis OSL e OSB, respectivamente. Palavras-chave:Módulo de elasticidade; módulo de ruptura; Pinus taeda; painéis estruturais. AbstractThe development of technology in panel production and the increased demand for these products, coupled with the increased cost of solid wood with large dimensions, led to the development of engineered wood products industry. Because of this, the aim of this research was to evaluate mechanical properties in static bending of Oriented Strand Board (OSB), Oriented Strand Lumber (OSL) and Laminated Strand Lumber (LSL), produced with Pinus taeda wood and castor oil based polyurethane resin. The influence of the strand lengths (inherent in each type of panel) in its properties of strength and stiffness was evaluated. Bending test was carried out according to EN 310-2000 and ASTM D 198-09 standards for determining the modulus of elasticity and modulus of rupture of the three types of panels. The results of strength (MOR) and stiffness (MOE) in bending for the three types of panels met the minimum requirements of EN 310-2000 standard, and the increase in the length of the strands influenced positively and significantly these properties. LSL panels presented the best results, followed by the OSL and OSB panels, respectively.

Despite the great potential of cellulose wood pulp and cellulose nanofibrils as reinforcing filler in thermoplastics, its use is limited due to its tendency to form agglomerates and due to its high hydrophilic character. Here we describe fiberboard composites with high contents of wood pulp or cellulose nanofibrils, and a resin of poly (styrene-methyl-methacrylate-acrylic acid) used as water-based emulsion. Cellulose wood pulp and cellulose nanofibrils were used directly in the form of water suspensions. The method is based on the flocculation of the polymer emulsion followed by agglomeration of a mixture of the polymer emulsion and cellulose suspension, leading to the co-precipitation of the composite material, which can be easily separated from the water phase. Composites with acrylic polymer/cellulose fibers in the proportions of 75:25, 50:50 and 25:75 wt% were prepared. Composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and water absorption tests. SEM analysis revealed a very good dispersion of the fibers without evidence of agglomeration, which led to superior mechanical properties. These results showed the effectiveness of the methodology and the potential of cellulose wood pulp and CNF as reinforcement fillers in fiberboard composites and any other high fiber-content materials.