Numerical analysis of progressive damage in nonwoven fibrous networks under tension

Understanding a mechanical behaviour of polymer-based nonwoven materials that include large-strain deformation and damage can help to evaluate a response of nonwoven fibrous networks to various loading conditions. Here, a nonwoven felt made by thermal bonding of polypropylene fibres was used as a model system. Its deformation and damage behaviour was analysed by means of experimental assessment of damage evolution based on single-fibre failure and finite-element simulations. Tensile tests of nonwoven fabrics were carried out to characterise their damage behaviour under in-plane mechanical loading. It was found that progressive failure of fibres led to localization of damage initiation and propagation, ultimately resulting in failure of the nonwoven felt. To obtain the criteria that control the onset and propagation of damage in these materials, tensile tests on single fibres, extracted from the felt with bond points attached to their ends, were performed. A finite-element model was developed to study damage initiation and propagation in nonwovens. In the model, structural randomness of a nonwoven fibrous network was implemented by means of direct introduction of fibres according to the orientation distribution function. The evolution of damage in the network was controlled by a single-fibre failure criterion obtained experimentally. The proposed numerical model not only captured the macroscopic response of the felt successfully but also reproduced the underlying mechanisms involved in deformation and damage of nonwovens.     

Influence of He/O2 atmospheric pressure plasma jet treatment on subsequent wet desizing of polyacrylate on PET fabrics

The influence of He/O₂ atmospheric pressure plasma jet (APPJ) treatment on subsequent wet desizing of polyacrylate on PET fabrics was studied in the present paper. Weight loss results indicated that the weight loss increased with an increase of plasma treatment time. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) showed an increased surface roughness after the plasma treatment. SEM also showed that the fiber surfaces were as clean as unsized fibers after 35 s treatment followed by NaHCO₃ desizing. X-ray photoelectron spectroscopy (XPS) analysis indicated that oxygen-based functional groups increased for the plasma treated polyacrylate sized fabrics. The percent desizing ratio (PDR) results showed that more than 99% PDR was achieved after 65 s plasma treatment followed by a 5 min NaHCO₃ desizing. Compared to conventional wet desizing, indicating that plasma treatment could significantly reduce desizing time.     

老化丝织品的红外光谱分析研究

古代丝织品老化程度的检测有助于了解丝织品的保存状况及保护方法的选择与改进,通过红外光谱分析对丝织品老化原因及程度进行了研究。样品为经光老化、热老化和水解老化的白色丝织品和出土于湖北、内蒙古、青海的古代丝织品。对这些样品进行了显微红外分析,结果表明,红外光谱分析虽然只是提供半定量分析,但是对于发生了水解老化的丝织品来说,由于羧基含量的增加,红外分析能很容易提供定性及较好的半定量的分析结果,因此对于出土古代丝织品保存状况及老化机理的研究来说很有实用价值。     

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介绍射频辉光放电等离子体改善苎麻织物毛细效应的时效性的实验。分别在充入氩气、氮气、氧气的真空室中对苎麻织物进行射频辉光放电等离子体处理,在每一种处理过程中分别改变其处理时间、放电功率和真空室压强。测试了放置不同时间的经不同等离子体参数处理后的苎麻织物的毛细效应,得出各种参数的等离子体处理对苎麻织物毛细效应时效性的影响。实验结果表明,苎麻织物被等离子体离子体处理后毛细效应得到明显改善,其毛细效应随放置时间的变化为先快速下降,然后变缓,逐渐趋于稳定,这种毛细效应的改善具有良好的时效性,其中100W、40Pa的氧等离子体处理20分钟后的苎麻织物的毛细效应时效性最好。     

Nanocomposite polyester fabrics with in situ generated silver nanoparticles using tamarind leaf extract reducing agent

Using tamarind leaf extract as a reducing agent and various concentrated aq?AgNO₃ solutions as source, the silver nanoparticles (AgNPs) were in situ generated in polyester fabrics. The nanocomposite polyester fabrics were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and antibacterial tests. The size of the generated AgNPs varied between 50 and 120?nm. The X-ray analysis indicated the generation of both AgNPs and AgO nanoparticles in the nanocomposite fabrics. The nanocomposite polyester fabrics exhibited excellent antibacterial activity against both the Gram negative and Gram positive bacteria and hence can be considered for making antibacterial textiles.     

Fabrication and characterization of jute fabrics reinforced polypropylene-based composites: effects of ionizing radiation and disaccharide (sucrose)

Composites were prepared successfully by compression molding technique using jute fabrics (reinforcing agent) and polypropylene (matrix). Jute fabrics were treated with disaccharide (sucrose) solution and composites were fabricated with the treated fabric and polypropylene. The fiber content of the prepared composites was 40% by weight. It was found that the sucrose (2% solution) decreased the tensile strength (TS) and elongation at break about 6% and 37%, respectively, but tensile modulus and impact strength improved about 27% and 32%, respectively. When gamma radiation was applied through the untreated and treated composites the mechanical properties were improved much higher in non-treated Jute/PP-based composites than that of sucrose treated composites. For 5.0?kGy gamma dose the highest mechanical properties were observed for non-treated composites. At 5.0?kGy gamma dose the improvement of TS was 14% and 2% for non-treated and sucrose treated composites, respectively. The water uptake property of the sucrose treated composites was performed up to 10 days and composites absorbed 18% water. The functional groups of the both composites were analyzed by Fourier transform infrared spectroscopy machine. The scanning electron microscopic images of the both composites were taken for the surface and fiber adhesion analysis.     

Action of a finishing product in the improvement of the ultraviolet protection provided by cotton fabrics. Modelisation of the effect

The Ultraviolet Protection Factor of a fabric is a quantitative measurement of the effectiveness of the fabric to protect the human skin against ultraviolet radiation. The protection provided by uncoloured cellulosic fabrics is, in general, too low, but can be improved by the finishing treatment with UV-absorbers. In the present paper cotton fabrics with different compactness, and hence with different initial Ultraviolet Protection Factor values, are treated with several concentrations of an UV-absorber, according to a predefined experimental plan. The influence of each variable as well as their interaction on the response of Ultraviolet Protection Factor is analysed and a statistical model for predictions is proposed.     

Synthesis of some 4-arylazo-3-hydroxythiophene disperse dyes for dyeing polyester fabrics

A series of novel 4-arylazo-3-hydroxythiophene disperse dyes was synthesized by heterocyclization of ethyl 2-arylhydrazono-2-phenylthiocarbamoyl acetates with a variety of α-halogenated reagents. The structures of the synthesized dyes were confirmed by UV-Vis, IR, ¹H NMR, and MS spectroscopic techniques and elemental analysis. The dyes were applied to conventional polyester fabric by high temperature exhaust dyeing. These dyes were found to give orange to reddish-violet shades with very good depth, levelness, and brightness on polyester fabric. The dyed fabric showed moderate to good light fastness and very good fastness to washing and perspiration. Also the position of color in CIELAB coordinates (L^*, a^*, b^*, H^*, and C^*) was assessed. Correspondence: Ehab Abdel-Latif, Department of Chemistry, Faculty of Science, Mansoura University, 35516 Mansoura, Egypt     

Induction technique in manufacturing preforms

The prepreg technology is a state-of-the-art method to produce high-performance CFRP parts. Due to the high material prices, the restricted process rate, and limitations to the component complexity, in future, more and more parts will be assembled by using liquid composite moulding. Especially in the case of series larger than 100 parts per year, the LCM technology offers the best cost-effectiveness. This technology is based on resin injection into dry multilayer fibre textiles (preforms). The Institute of Joining and Welding (TU, Braunschweig), together with the Institute of Composite Structures and Adaptive Systems (DLR), has elaborated a new technology to speed up the preform process, which is the most labour-intensive step within the LCM process chain. A novel concept to consolidate binder-coated fabrics is under development. By applying the high energy transfer rate of induction technology, it is possible to heat up a preform with rates up to 50 K/s to melt the binder and consolidate the preform. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 5, pp. 747–756, September–October, 2008.