The warp knitting parameters are important to determine the knitting process and the mechanical properties of warp knitting mesh fabric. In this work, the relationship between different knitting parameters (mesh side length and the let-off value) and the mechanical properties were studied. The effect of knitting parameters on the tensile strength and elongation was investigated by experiment. As a result, the relationship between the mechanical properties and the two parameters was found, and the optimization values of two parameters which could improve the isotropy of mesh fabric were given.
Processes of the Liquid Composite Molding (LCM) are widely used in composites produced by impregnation of a dry preform with liquid resin. The resin flow through the preform is usually described by Darcy’s law and the permeability tensor must be obtained for filling process analysis and characterizing the ability of a porous material to be impregnated by a resin fluid. In generally, resin flow in the thickness direction can be neglected for thin parts, but the resin flow in the transverse direction is important for thicker parts. In this study, the transverse permeability measurement device using ultrasound method was developed, the transverse flowfront could be calculated, and global effective permeability and transverse were studied.
For industrial applications, many of the damage of textile reinforced flexible composites are due to growth of the defects coming from manufacturing process or generation by static or dynamic load prior to failure. Hence, this work attempt to investigate on tensile behavior and damage initiation mechanisms in woven fabric reinforced flexible composite with single edge notch (SEN) subjected to mono-axial loading. Tensile tests were conducted with a notch depth of 0, 5, 10, 15 and 20mm, respectively. Damage mechanisms have been described and tensile strength, energy absorption was also expressed. Experimental results indicate that the failure progressive in the textile reinforced flexible composite was quite complex and tested material demonstrated significant notch sensitivity.
In textile techniques, woven, knitted, non-woven and braiding techniques all can be used to weave tubular fabrics as intraluminal stents. The radial force is the most basic mechanical property of intraluminal stent. In this study, the influence of braiding parameters such as braided materials, diameter of stents and gear ratio on the radial compressive property of braided stents were studied.
In the past decade, natural fibre composites with thermoplastic matrices had attracted many composites manufactures for the superiority of lightweight and low-cost. A major challenge for natural fibre composites was to achieve high mechanical performance at a competitive price. Composites constructed from yarn and fabric structure preforms were better than composites made from random nonwoven mats. However, the twist structure of conventional ring spun yarns prevented the full utilization of fibre mechanical properties in the final composites. In this paper, the wrapped yarns were produced by wrap spun method with flax and polypropylene (PP), in which all flax fibres were twistless, then woven to be fabric preforms. The PP fibres served as a carrier for flax fibres during processing and became the polymer matrix in the final composites. The homogenous distribution of fibre and thermoplastic matrix in preforms could be achieved before hot pressing, so that not lead to impregnate difficultly, and prevented damage to the reinforced nature fibres during processing. Composites made from the wrapped yarn demonstrated significant tensile and peeling properties. The fabric structures (include plain, twill, and basket weave) and yarn tensile orientation (in 0°, 90°, 45°), had great influence on tensile strength and elongation of preforms. The cavity thickness of hot pressing mould had different influence on the tensile strength and peeling strength of thermoplastic composites, and the mechanical properties were superior when the thickness was 0.8-1.2 mm. The microstructure of thermoplastic composites showed uniform infiltration between layers, and had good bonding interface between flax fibre and PP matrix in composites.
This study aims to develop a new hybrid strengthening approach for reinforced concrete beams by integrating near‐surface mounted shape memory alloys (SMAs) and externally bonded carbon fiber reinforced polymers (CFRPs). Due to the superelasticity and shape memory effect of SMAs, the proposed strengthening can enhance the flexural strength of concrete beams without compromising ductility. The recovery behavior of deformed SMA wires was studied to determine the optimal prestrain level that can achieve the highest recovery stress. Afterward, the flexural performance of concrete beams strengthened with SMA, CFRP and both was investigated by performing three‐point tests. The results show that integrating SMA and CFRP has more influence on increasing the ultimate moment than the cracking moment and leads to a more significant improvement in the ultimate moment than individually utilizing SMA and CFRP. Besides, the effect of the integrated approach on enhancing the ductility is more notable than increasing the ultimate moment. The ultimate moment was analytically calculated, and the calculations show reasonable agreement with experimental results. The effects of the SMA and CFRP amount on the ultimate moment were also clarified through a parametric study.
In order to investigate the effects of lager notch ratio (2α/W) and loading rate on the tensile behavior of woven fabric reinforced flexible composites, in this study, fracture mechanism and tensile strength of finite woven fabric-reinforced flexible composite materials with a through-the-thickness symmetrical located double edge notches is experimentally investigated, and the effects of notch size, loading rate on the tensile properties of notched specimen are analyzed. The results show that the woven fabric reinforced flexible composites exhibit notch sensitivity and loading rate dependent. These results play an important role in predicting strength and evaluating the lifetime of textile reinforced flexible composite materials with double edge notches.
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