This article is focused on the study of the contribution of aramid fibers in a hybrid carbon-aramid fiber twill weave used to reinforce epoxy resin. To evaluate the influence of the aramid fibers, a comparative study between carbon and carbon-aramid woven-reinforced composites, considering the mechanical behavior of both materials under several loading conditions, is performed. The tests used in this study are meant to analyze the effect of aramid reinforcements on the composite stiffness, strength, impact, and fracture performance. Higher values of energy absorption and fracture toughness were exhibited by the carbon-aramid composite. The mechanical tests performed indicated that the aramid phase present in the hybrid carbon-aramid composite induced an important enhancement on the impact (37.9% in energy absorption) and fracture resistance (12.7% for fracture initiation and 43% for steady state regime), compared to small reductions on the material stiffness. In addition, the ultimate strain and the through thickness compression strength were favorably affected, with an increase up to 19.5% and 8.3%, respectively, by the presence of aramid fiber that presents a more ductile response with respect to the carbon reinforcement.

There is a lack of commercially available low-cost technologies to assess gait clinically in non-controlled environments. As a consequence of this, there has been poor massification of motion measurement technologies that are both objective and reliable in nature. Advances about the study of gait and its interpretation in recent years using inertial sensors have allowed proposing acceptable alternatives for the development of portable and low-cost systems that contribute to people’s health in places and institutions that cannot acquire or maintain the operation of commercially available systems. A system based on a custom single Inertial Measurement Unit and a mobile application is proposed. Thus, an investigation is carried out using methodologies and algorithms found in the literature in order to get the main gait events and the spatial-temporal gait parameters. Twenty healthy Chilean subjects were assessed using a motion capture system simultaneously with the proposed tool. The results show that it is possible to estimate temporal gait parameters with slight differences respect gold--standard. We reach maximum mean differences of -2.35±5.02[step/min] for cadence, 0.03±0.04[sec] for stride time,0.02±0.03[sec] for step time, ±0.02[sec] for a single support time, 0.01±0.02[sec] for double support time and 0.01±0.03[m] for step length. As a result of experimental findings, we propose a new technological tool that can perform gait analysis. Our proposed system is user-friendly, low-cost, and portable. Therefore, we suggest that it could be an attractive technological tool that healthcare professionals could harness to objectively measure gait in environments that are either within the community or controlled. We also suggest that the tool could be used in countries where advanced clinical tools cannot be acquired. Therefore, we propose in this paper that our system is an attractive, alternative system that can be used for gait analysis by health professionals worldwide.

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Woven fabrics used in composite materials are designed to fulfill specific manufacturing or structural requirements. Knowledge of the influence of the weave structure on the mechanical properties of the composite is essential to properly optimize the design of structural components. The focus of this work is to investigate the influence of the type of weave used for fabric reinforcement in polymers particularly on the in-plane shear mechanical performance. The selected materials are carbon fibers and epoxy resin. The laminates are manufactured by vacuum infusion. Three woven structures are selected for manufacturing the composite laminates: (a) a plain weave with unidirectional orientation in the warp direction, (b) a plain weave with balanced properties in the warp and weft directions and (c) a 2/2 twill weave with balanced properties in the warp and weft directions. The laminates are tested according to the ASTM D 4255 standard by a two-rail shear test under quasi-static monotonic and cyclic loading conditions. The resulting stress–strain curves are used to study the initial in-plane shear modulus and its evolution (which directly correlates with material damage) and the hardening produced by plastic strain. The results show that for vacuum infusion manufacturing, the weave structure has an influence on the resulting fiber and void volume fractions and, consequently, on the mechanical performance. However, for similar fiber volumes, the weave structure is found to have little effect on the experimental results.

The global demand for products manufactured with carbon fibers (CFs) has increased in recent years; however, the waste generated at the end of the product lifetime has also increased. In this research, the impact of the addition of carbon nanotubes (CNTs) on the interlaminated resistance of recycled carbon fibers (RCFs) was studied. In this work, a recycling process of the composite material was applied via thermolysis to obtain the CFs, followed by the growth of CNTs on their surface using the Poptube technique. The recycling temperature were 500 °C and 700 °C; and ferrocene and polypyrrole were used to grow CNTs on CFs surface. CNTs were verified by Raman spectroscopy and scanning electron microscopy (SEM). Finally, to determine the interlaminar resistance, a double cantilever beam (DCB) test was performed. The results indicate that with Poptube technique, CNTs can be grown on RCFs using both impregnations. Thermolysis recycling process at 500 °C allowed CFs without resin residues and without visible damage. The DCB tests showed a decrease in the fracture resistance in mode I loading of 34.9% for the polypyrrole samples and 29.3% for the ferrocene samples compared with the virgin carbon fibers (VCFs) samples with a resistance of 1052.5 J/m2.