Solid State Phenomena Vol. 333

Abstract: Textile reinforcements have established themselves as a convincing alternative to conventional steel reinforcements in the building industry. Due to their high load-bearing capacities in addition to a smaller concrete cross section required, the bond between textile and concrete is extremely important. In contrast to ribbed steel bars ensuring a stable mechanical interlock with concrete (form fit), the bond force of carbon rovings has so far been transmitted primarily via the coating of the textile, i.e. by an adhesive bond with the concrete matrix (material fit). However, this material fit must be activated over relatively large yarn areas, which does not allow material-efficient utilization of the mechanical load capacity of the textile reinforcement. Solutions involving profiled rovings promise significant improvements in the bonding behavior by creating an additional mechanical interlock with the concrete matrix. In order to achieve a form-fit effect between roving and concrete, a roving geometry inspired by ribbed steel bars has to be created. For this purpose, an innovative profiling process was developed and implemented.

Abstract: Fiber-reinforced plastic (FRP) structures are established in numerous lightweight solutions. Among textile products available for technical applications, flat woven fabrics are commonly used to produce 3D components. In order to convert the flat woven structures into 3D geometries, draping and cutting processes are applied primarily. This leads to structural distortions, yarn interruption and overlaps of the layers. Beside the resulting reduction of mechanical properties, manual work steps are necessary. 3D woven fabrics offer outstanding possibilities for realizing net-shape FRP lightweight structures while avoiding these disadvantages. A current challenge in the manufacture of 3D net-shape structures is the direct generation of desired geometry during the weaving process. The aim of the presented work is the development of a novel weaving technology that enables the creation of spherically curved woven fabrics. Constructive-technological solutions are presented and the required mathematical as well as weaving modelling is shown.

Abstract: Considering the risks facing nature today, the search for sustainable materials has become a necessity. The polyethylene, which is the main waste of the packaging sector, and the cotton fibers, which are among the leading wastes of the textile industry, are increasing day by day and the recycling these wastes by using them as reinforcement materials in composites emerges as a sustainable solution. In this study, 100% recycled composite materials are designed according to the different numbers and sequences of recycled cotton fiber layers and recycled polyethylene matrix plates and produced by hot press method. The physical and thermal properties of the samples are tested to evaluate their usability as a sustainable insulation panel.

Abstract: The aim of this work is to investigate the effect of carbon micro particles used as epoxy resin fillers, for the mechanical properties of reinforced composites unidirectionally oriented carbon fibers. The motivation for this work was expansion knowledge of the possibilities of improving the user properties of these materials at maintaining their weight, thus finding new areas for application recycled carbon fibers from composite waste, which would also contribute to the solution issues of recycling and subsequent use of today's mostly landfilled composites. This work deals with the influence of carbon fillers embedded in epoxy resin on tensile and flexural properties of carbon fiber reinforced epoxy (CFRE) composites. Samples were made from unidirectional carbon multifilaments, and epoxy resin modified with selected carbon fillers in 2.5weight% concentrations. Composites were subsequently examined using flexural and tensile tests. All specimen filled with carbon particles showed increase of both, flexural and tensile properties, if compared to neat epoxy composites.

Abstract: A four node isoparametric shell element (Q4) based on Mindlin/Reissner plate theory and the alpha finite element method (αFEM) was formulated for a nearly exact solution of linear static and buckling analysis of textile-like sheet material. The novel idea of αFEM-Q4 is assumed to be similar to the framework of conventional finite element approaches for Q4, but the gradient of strains is scaled by a factor α ∈ [0, 1]. The numerical examples demonstrate that the αFEM-Q4 can improve the accuracy of FEM solution in static and buckling analysis shell structures of non-woven fabric. However, the αFEM-Q4 cannot provide the nearly exact solution to all elasticity problems. In addition, it also requires a quadrilateral mesh that cannot be fully generated by common geometric algorithms for complicated problem domains.

Abstract: This paper presents an implementation of the node-based smoothed finite element method and Reissner-Mindlin plate theory for a four node isoparametric shell element to improve the numerical precision and computational efficiency subjected to free vibration analysis of textile-like sheet materials. A one smoothing cell integration scheme in the strain smoothing technique is implemented to contrast the shear locking phenomenon that may exists in the analysis for moderately-thick and thick shell models. Various numerical results of free vibration analysis for a multi-layer nonwoven fabric sample are compared with other existing analytical solutions and numerical solutions in literatures to demonstrate the effectiveness of the present method. An advantage of the present formulation is that it can improve the numerical precision without decreasing the computational efficiency.

Abstract: The mechanical behaviour of textile structures is one of their most important characteristics as far as their end use is concerned. Textile structures, fabrics, or yarns are often considered as continuous mediums apart from the fact that they are composed of some discrete elements, individual fibres composing yarns and yarns composing fabrics. This is known as the transition scale, a very important lock to be considered, to evaluate the real structure behaviour. In this context, this work presents some simulations of the mechanical behaviour of a fabric where the yarn is a continuum material. Particular attention was paid to simultaneous loading in uniaxial or biaxial extension and shear loadings. The results of numerical simulations, which show the deformed fabric unit cell under multi-load conditions, are coherent with experimental observations and encourage the authors to continue the present work with parametrical and inverse case studies.