In this work, several fabrics with different composition and structure have been used as the substrate for the production of wearable textile-embroidered dipole antennas. The performance of the ...antennas has been determined by measuring their resonance frequency, return loss and bandwidth. To determine their durability as wearable fabrics, the performance has been assessed before and after subjecting the antennas to washing and abrasion cycles. The results revealed that the woven fabrics presented a good washing fastness, even in fabrics having elastic fibers or low-crimp structures. In all cases, a good performance of the antennas was maintained after 30 washing cycles. For the abrasion cycles, the substrates with higher stability (measured as the crimp ratio) presented a higher wear fastness, whereas a higher variability was observed for the substrates with lower stability.
The aim of this study is to develop a process to produce high-performance cement-based composites reinforced with flax nonwoven fabrics, analyzing the influence of the fabric structure-thickness and ...entanglement-on mechanical behavior under flexural and tensile loadings. For this purpose, composite with flax nonwoven fabrics with different thicknesses were first prepared and their cement infiltration was evaluated with backscattered electron (BSE) images. The nonwoven fabrics with the optimized thickness were then subjected to a water treatment to improve their stability to humid environments and the fiber-matrix adhesion. For a fixed thickness, the effect of the nonwoven entanglement on the mechanical behavior was evaluated under flexural and direct tension tests. The obtained results indicate that the flax nonwoven fabric reinforcement leads to cement composites with substantial enhancement of ductility.
•Mechanical performance and durability of OPC/flax nonwovens composites for façade pieces is explored.•The effect of two pozzolanic additions combined with nonwoven treatment is ...evaluated.•Significant improvements in the durability using treated nonwovens.
This experimental research analyzes the mechanical performance and durability of façade pieces based on Portland cement matrix and flax nonwovens as reinforcement. Two types of pozzolanic additions (silica fume and metakaolin) combined with nonwovens subjected to different treatments to decrease their water absorption are analyzed as potential materials for fiber-cement sheets for building envelopes with high strength and durability. For this purpose, on the one hand, the mechanical performance and chemical composition of various ternary compositions were studied. On the other hand, various treatments were performed on the nonwovens and the nonwoven–matrix adherence was also analyzed. Finally, composites were prepared from some selected treated nonwovens and matrix mixtures, and their mechanical properties and durability were evaluated under four-point bending tests after 28days of curing in a humidity chamber and after accelerated aging. The composites developed with the treated nonwovens presented very high performance combined with enough durability to be potential candidates for the development of sustainable materials for building envelopes.
This paper analyses the influence of the addition of low content (0.1 to 0.8 wt%) of nanofibrillated cellulose (NFC) or cellulose nanocrystals (CNC) on the flexural performance, durability and ...microstructure of calcium aluminate cement (CAC) cured at 20 °C or 60 °C. The relationship between the mechanical properties and the microstructure of the cement was evaluated after curing and further after accelerated aging by flexural testing and X-ray diffraction and by backscattered electron imaging, respectively. The addition of 0.1–0.2 wt% of either nanocellulose led to an increase in the modulus of rupture (MOR) and modulus of elasticity (MOE) values. Moreover, CNC was effective to counteract the negative effects of increased porosity of CAC cements before and after aging, significantly improving their mechanical performance and durability. This effect was not observed in Portland cement systems, in which the addition of this low nanocellulose content did not lead to significant changes.
This paper examines the influence of weaving variables such as yarn count, number of layers, warp and weft ratio, materials of the top layer, weft density and interlocking cell shape, and size on the ...thermal performance of multilayer interlocked woven fabrics. A split-plot design was used to construct a total of 64 fabric structures, which were assessed for thermal performance in terms of resistance to convective, conductive, and radiative heat. It was found that, for equal weft density and yarn number, protective performance improved with the number of fabric layers and with the presence of air cells between these layers, especially if air was not trapped within and could rather pass freely between the cells. An optimal combination of factors for the thermal response to the three types of heat was established via a Derringer–a much needed desirability function. The results of this paper are useful for identifying the interaction between configuration parameters and thermal performance, and hence for the design of improved heat protective clothing.
This research analyzes the effects of different treatments on flax nonwoven (NW) fabrics which are intended for composite reinforcement. The treatments applied were of two different kinds: a wet/dry ...cycling which helps to stabilize the cellulosic fibers against humidity changes and plasma treatments with air, argon and ethylene gases considering different conditions and combinations, which produce variation on the chemical surface composition of the NWs. The resulting changes in the chemical surface composition, wetting properties, thermal stability and mechanical properties were determined. Variations in surface morphology could be observed by scanning electron microscopy (SEM). The results of the X-ray photoelectron spectroscopy (XPS) showed significant changes to the surface chemistry for the samples treated with argon or air (with more content on polar groups on the surface) and ethylene plasma (with less content of polar groups). Although only slight differences were found in moisture regain and water retention values (WRV), significant changes were found on the contact angle values, thus revealing hydrophilicity for the air-treated and argon-treated samples and hydrophobicity for the ethylene-treated ones. Moreover, for some of the treatments the mechanical testing revealed an increase of the NW breaking force.
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•Two strategies to improve P3HB4HB’s foaming have been studied.•The system of study revealed high complexity due to multiple factors’ influence.•Chain extender additive played a key ...role in the final properties of the foams.•Cooling system was only relevant when chain extender was not used.•Density reduction was improved due to the use of the chain extender.
Bacterial polyesters such as polyhydroxyalkanoates (PHAs) are of great interest for a large number of applications both because of their properties and because they come from renewable resources, despite having a higher cost than commodity polymers. Their foaming—although it presents some difficulties—could be an option to increase their competitiveness. In this work, two strategies have been studied to enhance the poly(3-hydoxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) foamability by extrusion foaming. The effect of the cooling system (water-quenching or air-cooling), chain extender (CE) addition and chemical blowing agent (CBA) amount were evaluated. Density, cellular morphology, mechanical and thermal properties were studied. Optimal density reduction was achieved with use of CE and 3–4wt.% of CBA masterbatch. The most effective strategy on density reduction was the addition of CE, while the water quenching had only a slight influence on the samples in which CE was not present. CE addition decreased the viscosity and the degradation rate of the polymer, thus leading to lighter foams with larger cells but with equal or even slightly better resistance to compressive and tensile stress, in general terms.
The aim of this study is to propose and explore a novel approach for the production of cellular lightweight natural fibre, nonwoven, fabric-reinforced biocomposites by means of gas dissolution ...foaming from composite precursors of polyhydroxybutyrate-based matrix and flax fabric reinforcement. The main challenge is the development of a regular cellular structure in the polymeric matrix to reach a weight reduction while keeping a good fibre-matrix stress transfer and adhesion. The viability of the process is evaluated through the analysis of the cellular structure and morphology of the composites. The effect of matrix modification, nonwoven treatment, expansion temperature, and expansion pressure on the density and cellular structure of the cellular composites is evaluated. It was found that the nonwoven fabric plays a key role in the formation of a uniform cellular morphology, although limiting the maximum expansion ratio of the composites. Cellular composites with a significant reduction of weight (relative densities in the range 0.4⁻0.5) were successfully obtained.
With the substantial growth of the smart textiles market, electrical properties are becoming a basic requirement for most of the advanced textiles used in the development of wearable solutions and ...other textile-based smart applications. Depending on the textile substrate, the test method to determine the electrical properties can be different. Unlike smart fibers and yarns, the characterization of the electrical properties of fabrics cannot be tested between two connection points because the result would not represent the behavior of the entire fabric, so the electrical properties must be related to an area. The parameters used to characterize the electrical properties of the fabrics include resistance, resistivity, and conductivity. Although all of them can be used to indicate electrical performance, there are significant differences between them and different methods available for their determination, whose suitability will depend on the function and the textile substrate. This paper revises the main parameters used to characterize the electrical properties of conductive fabrics and summarizes the most common methods used to test them. It also discusses the suitability of each method according to several intervening factors, such as the type of conductive fabric (intrinsically or extrinsically conductive), its conductivity range, other fabric parameters, or the final intended application. For intrinsically conductive woven fabrics, all the methods are suitable, but depending on the requirements of conductivity accuracy, the contact resistance from the measuring system should be determined. For intrinsically conductive knitted fabrics, two-point probe, Van der Pauw, and eddy current methods are the most suitable. And for intrinsically conductive nonwoven fabrics, two-point probe and four-point probe methods are the most appropriate. In the case of extrinsically conductive fabrics, the applied method should depend on the substrate and the properties of the conductive layer.
The main objective of this paper is to study the effects of the processing parameters of the needle-punching machine and the interactions between them on some physico-mechanical properties of ...interest of nonwoven (NW) fabrics. For this purpose, a fractional factorial design has been planned with two levels for each factor: feeding speed, delivery speed, stroke frequency, penetration depth and gap between plates. Sixteen NW fabrics were obtained from polyester fibre and characterized by tensile strength and stiffness for mechanical behaviour and air permeability as physical properties of interest in some technical applications. The results have been subjected to statistical analysis in order to find the effects of the processing variables and the interactions between them on the fabric properties. It was possible to find the effects of the five processing parameters studied on the thickness, fabric mass, stiffness, tensile strength and air permeability of the obtained needle-punched fabrics.
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