Materials Science Forum Vol. 1117

Abstract: In recent years, great attention has been paid to the development of porous materials with excellent reactivity and absorbency. The poly(lactic acid) (PLA) microfibers with uniform nanopores were successfully prepared by rotary centrifugal spinning using PLA/chloroform solution. Previous research showed that PLA microfibers have extremely high oil absorbing capacity. In this study, the changes in fiber diameter and nanopore diameter of nanoporous PLA microfibers under different fabrication conditions and the adsorption capacity of Prussian blue nanoparticles were systematically evaluated. The results showed that the fiber diameter increased with increasing PLA/chloroform solution concentration. Furthermore, it was found that the amount of adsorbed Prussian blue nanoparticles increased with the increase in fiber diameter. Prussian blue nanoparticles are known to adsorb radioactive materials such as cesium, and are expected to be applied to the recovery of cesium diffused in the atmosphere and ocean.

Abstract: In this work, TiO₂ was applied to cotton fabric by a sol–gel-hydrothermal process. A combination of 3-(trihydroxysilyl) propyl methylphosphonate monosodium salt solution (TPMP) and (3-aminopropyl)triethoxysilane (APTES) was used as a matrix to enhance the interfacial interaction between TiO₂ and surface of the cotton fibres. During the hydrothermal treatment, silver nitrate (AgNO₃) or reduced graphene oxide (rGO) were added to produce Ag-doped TiO₂- or rGO-coupled TiO₂-coated textiles. The successful application of all investigated components on cotton fabric was confirmed by the analysis of SEM and EDS. The results of UPF determination and self-cleaning activity showed excellent performance of both studied nanocomposite coatings, whereas the use of rGO proved to be better than Ag.

Abstract: Weft-knitted fabrics are used in a wide range of applications. The tensile behaviour, the geometric diversity and the materials to be used are essential structural parameters that are also economically important. To improve this behaviour, the new approach is to integrate warp-stitch threads into a weft-knitted fabric using conventional weft-knitting machine technology, thus significantly increasing the range of binding possibilities for the adjustment of elasticity in wale direction. The characteristics that can be achieved in this way open up new areas of application, for example in compression textiles.

Abstract: In this paper, the sol-gel technique was used to design hybrid phosphorus-doped silica structures for improving the thermal stability and flame retardancy of cotton fabrics. To this aim, diethylphosphatoethyltriethoxysilane (DPTS) was employed as phosphate alkoxysilane in a multistep procedure that involved multiple layers (from 1 to 6) depositions. The multi-layer coatings were applied by padding using sols containing appropriate molar ratios of the precursor, anhydrous ethanol, catalyst, and hydrochloric acid. Moreover, the synergism P-N on flame retardancy of cotton was assessed by introducing 3-aminopropyltriethoxysilane (APTES) as an N-donor precursor in DPTS sols. The effects of the catalyst during the alkoxide reaction and the silica amount applied by sol-gel treatment on the thermo-oxidative behavior of the treated fabrics were deeply studied. The creation of the silica skeleton on the cotton surface and the interactions between the cellulosic fibres and the doped layer were investigated using FT-IR ATR spectroscopy. Moreover, thermal and thermo-oxidative stability, flammability properties, and combustion behavior of the sol-gel treated cotton fabrics were also studied, proving the effectiveness of the sol-gel coating in the fire protection of the cellulosic substrate.

Abstract: Fiber-reinforced plastics (FRP) are a type of composite material consisting of a reinforcing structure and a plastic matrix. When compared to traditional construction materials, FRP has higher strength and stiffness due to the high mechanical properties of reinforcing fibers such as carbon or glass. However, the properties of FRP are dependent on the alignment of fibers within the composite, with deviations leading to reduced strength and stiffness. Eddy current testing is a non-destructive technique used to visualize carbon fibers in the composite and assess the impact of local fiber orientation on the structural properties of FRP. This study aims to understand the influence of local fiber orientation on tensile strength and elastic modulus by producing composites with defined fiber orientations, analyzing them with eddy current testing, and assessing their mechanical properties through tensile tests. The measured fiber orientations are then used to validate a finite element model, in which the actual, measured fiber orientation is applied to the simulation and correlated with the mechanical properties. In contrast to previous published studies measured fiber orientation is used, which as shown in this work, differs from the theoretically implemented fiber orientation.

Abstract: Textile reinforcements have outstanding load-bearing capabilities due to the excellent tensile properties of high performance multifilament yarns (e.g. carbon fibers). However, in order to take full advantage of their high potential, it is necessary to ensure that the filaments run in a straight line. In order to guarantee this straight filament course, the highly efficient multiaxial warp knitting process is used for the production of 2D non-crimp fabrics (NCF) as textile preforms. In various industrial applications, most structures have complex 3D geometries. Therefore, the 2D textile needs to be shaped for reinforcement, which often results in a rearrangement of the filament orientation. Consequently, the 3D shaping process has to be taken into account during the textile production or in the shaping process itself in order to guarantee the highest mechanical properties. Using the example of lattice girders for concrete reinforcement, a new approach for the fabrication of 3D textile lattice girders in a continous shaping process is presented. The results of the production tests of the developed technology approach show no apparent filament damage and exact roving orientation with no inadvertent deflection, compression or bulging, indicating a precise and gentle shaping process. The developed technology contributes to the future reduction of the production costs of 3D textile reinforcements.

Abstract: The growing use of carbon fibre-reinforced polymers (CFRP) results in an increased amount of CF waste from offcuts or end-of-life components. A promising method to reuse the waste fibre materials in a structural component with excellent mechanical properties is the processing of recycled CF (rCF) and thermoplastic fibres into hybrid yarns. Spinning of friction spun yarns consisting of more than 90% rCF and containing almost no thermoplastic fibres that are suitable for thermoset composites, currently leads to high fibre damage and low yarn quality and is, therefore, addressed in this project. The technology is reported in another paper. One of the limiting factors for drapability of textiles is the stretchability of continuous fibres and draping of the semi-finished textile products for complex geometries is still error-prone. Friction spun yarns exhibit significantly higher yarn elongations due to sliding mechanisms between the fibres. The deformation properties of friction spun yarns are significantly influenced by fibre-fibre interactions and depend on a variety of process and material parameters. In the following, micromechanical finite element models of the spun yarns are created by using beam elements. Monte Carlo method is used to model local variabilities in the yarns. The models are then used to simulate yarn behaviour under deformation and to investigate the influence of various process parameters.

Abstract: The development of different hybrid yarn structures from recycled carbon fibre (rCF) (rCF content approx. 50% by weight) and thermoplastic fibres for thermoplastic composites has been reported earlier. However, manufacturing of yarns with high rCF content (>90%) required for thermoset composites is still not realizable due to high shortening (≥ 70%) in fibre length of rCF, which occurs during different processing steps of spinning. The reason lies in low shear strength, smooth fibre surface, small diameter and high brittleness of rCF. In addition to this, lack of crimp in rCF leads to drafting error during drawing and spinning process. Therefore, there is a high demand on rCF yarns for thermoset composites, as around 70% of composites are produced based on thermoset matrix. In this paper, yarns consisting of staple rCF with high rCF content (>90 weight%) are developed on DREF-friction spinning and wrap spinning technologies. For the production of yarns, slivers with different rCF content are produced using carding and drawing machine. The effect of different spinning parameters suction air pressure for DREF friction spun yarns and yarn twist for wrap spun yarns is investigated and their effect on tensile properties of yarn is analysed. The results show that the tensile properties of yarns can be adjusted to a wide range varying the yarn structure and spinning parameters.

Abstract: Inherent structural stress in a plain weave is induced during the formation process of fabrics, and its evaluation is useful for estimating the mechanical stiffness of weaves. In this study, the effect of inherent stress distributed in a weave fabric was investigated to estimate its mechanical stiffness. Here, a numerical simulation method that imitates the fabrication process of fabrics is proposed to evaluate stiffness. A diagram illustrating the weaving process is defined in this evaluation method. For computational analysis, a unit cell model used in homogenization was developed based on the structural periodicity of the plain weave structure using the finite element method. The weaving state was accomplished by simulating the weaving behavior in this model. The weaving state included the geometric shape and stress/strain data. Subsequently, a model was built to estimate the mechanical stiffness based on the weaving state data. Finally, a uniaxial tensile simulation was conducted using the numerical model. Using this evaluation method, the effect of inherent stress on the mechanical stiffness of weaves was quantified, which indicated that the tensile stiffness improved in a small strain range. The effect gradually decreased as the tension progressed.