Fabric Geometry Research Articles

Shear strengthening of concrete members with TRM jackets: Effect of shear span-to-depth ratio, material and amount of external reinforcement

Abstract An experimental work on reinforced concrete (RC) rectangular beams strengthened in shear with textile reinforced mortar (TRM) jackets is presented in this paper, with focus on the following investigated parameters: (a) the amount of external TRM reinforcement ratio, ρf, by means of using different number of textile layers and different types of textile fibre materials (carbon, glass, basalt); (b) the textile geometry, and (c) the shear span-to-depth ratio, a/d. In total, 22 tests were conducted on simply supported rectangular RC beams under (three-point bending) monotonic loading. The experimental results revealed that: (1) TRM is very effective when the failure is attributed to debonding of the TRM jacket from the concrete substrate; (2) the trend of effective strains for carbon, glass and basalt TRM jackets is descending for increasing values of the TRM reinforcement ratio, ρf, when failure is associated to debonding of the jacket; (3) the effect of textile geometry is significant only for low values of ρf, resulting in variances in the capacity enhancement and the failure modes, and (4) the shear span-to-depth ratio has practically no effect to the failure mode nor to the TRM jacket contribution to the total shear resistance of the RC beams.

Structural mechanic material damping in fabric reinforced composites: a review

Purpose: A review regarding the acting mechanisms of structural dynamic material damping in fabric reinforced composites is presented. Design/methodology/approach: Mechanical acting principles identified by different investigations are considered. Aspects of the determination and calculation of structural mechanical material properties of fabric reinforced composites are described. Approaches intending the description and classification of ondulations in fabrics reinforced single layers are demonstrated. Findings: The mesomechanic geometry of fabrics is not considered sufficiently by relatively simple homogenization approaches. Yet, it significantly affects its structural dynamic material properties, especially the dynamic ones. Research limitations/implications: In each case the different damping mechanisms act coupled and occur at the same time. Therefore a separation procedure is required in any case. Practical implications: Against the background of the comparison and remarks of the presented papers a reasonable further procedure is recommended. Thereby, FE-calculations with a parametrical variation of the mesomechanic geometry in order to identify kinematic correlations due to geometric constraints are suggested. Originality/value: The idea of the representation of the geometric conditions in terms of a degree of ondulation is described. Such a non-dimensional specific value representing the intensity of the ondulation would enable the comparability of the results of different kinds of investigations.

X-ray Imaging of Transplanar Liquid Transport Mechanisms in Single Layer Textiles.

Understanding the penetration of liquids within textile fibers is critical for the development of next-generation smart textiles. Despite substantial research on liquid penetration in the plane of the textile, little is known about how the liquid penetrates in the thickness direction. Here we report a time-resolved high-resolution X-ray measurement of the motion of the liquid-air interface within a single layer textile, as the liquid is transported across the textile thickness following the deposition of a droplet. The measurement of the time-dependent position of the liquid meniscus is made possible by the use of ultrahigh viscosity liquids (dynamic viscosity from 105 to 2.5 × 106times larger than water). This approach enables imaging due to the slow penetration kinetics. Imaging results suggest a three-stage penetration process with each stage being associated with one of the three types of capillary channels existing in the textile geometry, providing insights into the effect of the textile structure on the path of the three-dimensional liquid meniscus. One dimensional kinetics studies show that our data for the transplanar penetration depth ΔxL vs time do not conform to a power law, and that the measured rate of penetration for long times is smaller than that predicted by Lucas-Washburn kinetics, challenging commonly held assumptions regarding the validity of power laws when applied to relatively thin textiles.

Low-velocity impact behavior of weft-knitted spacer fabrics reinforced composites based on energy absorption

Spacer fabrics are prefered to other types of textile fabrics in energy absorption applications due to existence of pile yarns. The particular geometry of spacer fabrics induce to increase resisting out of plane forces such as impact along their thickness. In order to investigate the low-velocity impact behaviour of composites reinforced with spacer fabric, weft-knitted spacer fabrics with different types of pile orientation and pile length were produced using E-glass yarns. Using produced fabrics and epoxy resin, composites samples were provided by hand lay-up method. Low-velocity impact test was carried out on the prepared samples based on a drop-weight method using spherical steel projectile. The indentation at maximum force was extracted as - comparative criteria used to calculate absorbed energy.The results show that the energy absorption of composites increases by increasing the pile density and pile length.

Innovative cellular distance structures from polymeric and metallic threads

Knitting allows a high individual adaptability of the geometry and properties of flat-knitted spacer fabrics. This offers advantages for the specific adjustment of the mechanical properties of innovative composites based on highly viscous matrix systems such as bone cement, elastomer or foam and cellular reinforcing structures made from e. g. polymeric monofilaments or metallic wires. The prerequisite is the availability of binding solutions for highly productive production of functional, cellular, self-stabilized spacer flat knitted fabrics as supporting and functionalized structures.

Anisotropic pore fabrics in faulted porous sandstones

The fabric of pores in sedimentary rocks around fault zones can be subject to significant modification. Knowledge of how pore fabrics vary during and after faulting is important for understanding how rocks transmit fluids around fault zones, and can help to predict mechanical instability due to changes in pore fluid pressure. Datasets detailing the geometry of pore fabrics in faulted porous rocks are lacking. This paper describes pore fabrics quantified from two outcrops of normally faulted sandstone. The porosity and the size, shape and geometry of pores were quantified from core plugs and thin sections. Results were mapped within a framework of the faults to better illustrate how these datasets may be used to improve understanding of fluid flow around fault zones. Results from a mature, quartz-rich arenite show a change in pore fabric from pores oriented horizontally and parallel to laminations to pores oriented at a low angle to σ1. Pore fabrics quantified from a clay-rich, quartz sub-arkose changed from moderate aspect ratio pores with no preferred orientation, to high aspect ratio pores oriented dominantly sub-parallel to the fault surface. Permeabilities measured on corresponding core plugs showed anisotropy of permeability with maximum permeability oriented down fault dip around both faults.

An Application of the Shark Skin Denticle Geometry for Windbreak Fence Design and Fabrication

Windbreak fences in open and urban areas can be used to effectively reduce the wind velocity. In this paper we examine how the geometrical shape of the windbreak fence can optimally mitigate wind velocity. We propose an approach for windbreak fence design based on a bionic parametric model of the shark skin denticle geometry, which improves the reduction of the wind velocity around and behind the windbreak fences. The generative model was used to estimate improvements by variations in the parameters of the fence panel's geometrical shape, inspired by shark skin denticles. The results of the Computational Fluid Dynamics (CFD) analysis indicates that the fence surface inspired by shark skin performs much better than both flat and corrugated surfaces. Taking into account the complex geometry of the surface inspired by shark skin denticles, we propose a fabrication process using an expanded polystyrene foam (EPS) material, created using an industrial robot arm with a hot-wire tool. Creating EPS moulds for the shark skin denticle panels allows for a richer variety material to be used in the final design, leading both to higher efficiency and a more attractive design.

A Review on the Development of Gravitational Water Vortex Power Plant as Alternative Renewable Energy Resources

Gravitational water vortex power plant is a green technology that generates electricity from alternative or renewable energy source. In the vortex power plant, water is introduced into a circular basin tangentially that creates a free vortex and energy is extracted from the free vortex by using a turbine. The main advantages of this type of power plant is the generation of electricity from ultra-low hydraulic pressure and it is also environmental friendly. Since the hydraulic head requirement is as low as 1m, this type of power plant can be installed at a river or a stream to generate electricity for few houses. It is a new and not well-developed technology to harvest electricity from low pressure water energy sources. There are limited literatures available on the design, fabrication and physical geometry of the vortex turbine and generator. Past researches focus on the optimization of turbine design, inlets, outlets and basin geometry. However, there are still insufficient literatures available for the technology to proceed beyond prototyping stage. The maximum efficiency obtained by the researchers are approximately 30% while the commercial companies claimed about 50% of efficiency with 500W to 20kW of power generated. Hence, the aim of this paper is to determine the gap in the vortex power plant technology development through past works and a set of research recommendations will be developed as efforts to accelerate the development of GWVPP.

Experimental investigation of tensile and bond properties of Carbon-FRCM composites for strengthening masonry elements

Abstract Fabric Reinforced Cementitious Matrix (FRCM) materials are composed of a dry fiber grid embedded in an inorganic matrix, which may contain short fibers. These materials are particularly well-suited for the reinforcement of masonry structures due to their high compatibility with the substrate, vapor permeability and durability against environmental agents. The most important information needed for the characterization of these composite systems, for use as strengthening materials of masonry structures, are the tensile behaviour and the shear bond properties. A Round-Robin Test was organized by the RILEM Technical Committee 250-CSM and the Italian association Assocompositi in order to experimentally characterize different FRCM systems composed of PBO, carbon, glass, basalt, aramid and steel textiles embedded in cementitious or lime-based mortars. The systems were tested at different universities and research centers in Europe in order to investigate the influence of samples preparation, test set-up and instrumentation. In this paper, the experimental tests performed on Carbon-FRCM systems are described and discussed. Important aspects are analyzed herein: differences in the testing procedure and instrumentation, influence of textile geometry and mechanical properties of the constituent materials, importance of specimen preparation and curing conditions. Moreover, a comparison between tensile and shear tests is reported in order to determine a reliable procedure towards the complete characterization of an FRCM material.

Role of ZnO nanowire arrays on the impact response of aramid fabrics

Abstract High performance aramid fabrics are extensively used in personal body armor to provide soft, lightweight, yet effective ballistic protection. Grafting nanomaterials on the surface of aramid fibers is one of the promising methods developed for enhancing and tailoring the performance of the fabrics and their composites. Recently, it was shown that growth of ZnO nanowires on aramid fibers drastically improves fabric interyarn friction, as an energy dissipation mechanism. In this work, the influence of ZnO nanowires on the ballistic response of aramid fabrics is evaluated. Intermediate velocity (22–40 m/s) impact tests are conducted on the fabric targets using a gas gun setup. The setup was equipped with a shock accelerometer for measuring contact force and two photoresistors for accurate velocity measurement of the projectile just before impact. As a result of the integration of ZnO nanowires, the maximum impact force of a single aramid fabric is increased approximately 66% in a specific range of impactor velocity. It is postulated that in this velocity range yarn pullout is the dominant failure mechanism of the fabrics for the specific fabric and projectile geometry used in this study. Furthermore, post-test imaging of the fabric targets confirms the efficacy of ZnO nanowires in enhancing impact resistance of aramid fabrics as a result of increased interyarn friction and limiting yarn mobility.

On the variability of mesoscale permeability of a 2/2 twill carbon fabric induced by variability of the internal geometry

This paper incorporates geometric variability in the determination of permeability, using distributions and spatial correlations of yarn spacing, width and thickness and distortions of yarn centrelines. Variability of a 2/2-twill carbon fabric geometry over a region of ten-by-ten unit cells is characterized based on representation of the yarn path deviations using Markov chains and the correlations between the deviations in the neighbouring yarns using Series Expansion approach. The Stokes equation is solved for the generated stochastic unit cells to predict inter-yarn permeability of each unit cell in principal directions. There is a good agreement between the calculated mean permeability and the values in the Permeability Benchmark II. The predictions show permeability varies over the medium as a function of inter-yarn gaps. Permeability variations show a correlation length of circa 20mm, the size of two-unit cells. Permeability values in x direction have no evident correlation with those in y direction.

O2 Plasma Etching and Antistatic Gun Surface Modifications for CNT Yarn Microelectrode Improve Sensitivity and Antifouling Properties.

Carbon nanotube (CNT) based microelectrodes exhibit rapid and selective detection of neurotransmitters. While different fabrication strategies and geometries of CNT microelectrodes have been characterized, relatively little research has investigated ways to selectively enhance their electrochemical properties. In this work, we introduce two simple, reproducible, low-cost, and efficient surface modification methods for carbon nanotube yarn microelectrodes (CNTYMEs): O2 plasma etching and antistatic gun treatment. O2 plasma etching was performed by a microwave plasma system with oxygen gas flow and the optimized time for treatment was 1 min. The antistatic gun treatment flows ions by the electrode surface; two triggers of the antistatic gun was the optimized number on the CNTYME surface. Current for dopamine at CNTYMEs increased 3-fold after O2 plasma etching and 4-fold after antistatic gun treatment. When the two treatments were combined, the current increased 12-fold, showing the two effects are due to independent mechanisms that tune the surface properties. O2 plasma etching increased the sensitivity due to increased surface oxygen content but did not affect surface roughness while the antistatic gun treatment increased surface roughness but not oxygen content. The effect of tissue fouling on CNT yarns was studied for the first time, and the relatively hydrophilic surface after O2 plasma etching provided better resistance to fouling than unmodified or antistatic gun treated CNTYMEs. Overall, O2 plasma etching and antistatic gun treatment improve the sensitivity of CNTYMEs by different mechanisms, providing the possibility to tune the CNTYME surface and enhance sensitivity.

The Research of Outputting Iges File of Fabric Geometry

The Research of Outputting Iges File of Fabric Geometry

Optimisation of Fabric Reinforced Polymer Composites Using a Variant of Genetic Algorithm

Fabric reinforced polymeric composites are high performance materials with a rather complex fabric geometry. Therefore, modelling this type of material is a cumbersome task, especially when an efficient use is targeted. One of the most important issue of its design process is the optimisation of the individual laminae and of the laminated structure as a whole. In order to do that, a parametric model of the material has been defined, emphasising the many geometric variables needed to be correlated in the complex process of optimisation. The input parameters involved in this work, include: widths or heights of the tows and the laminate stacking sequence, which are discrete variables, while the gaps between adjacent tows and the height of the neat matrix are continuous variables. This work is one of the first attempts of using a Genetic Algorithm (GA) to optimise the geometrical parameters of satin reinforced multi-layer composites. Given the mixed type of the input parameters involved, an original software called SOMGA (Satin Optimisation with a Modified Genetic Algorithm) has been conceived and utilised in this work. The main goal is to find the best possible solution to the problem of designing a composite material which is able to withstand to a given set of external, in-plane, loads. The optimisation process has been performed using a fitness function which can analyse and compare mechanical behaviour of different fabric reinforced composites, the results being correlated with the ultimate strains, which demonstrate the efficiency of the composite structure.

Geometrical Modeling of Woven Fabrics Weavability-Limit New Relationships

Abstract The weavability limit and tightness for 2D and 3D woven fabrics is an important factor and depends on many geometric parameters. Based on a comprehensive review of the literature on textile fabric construction and property, and related research on fabric geometry, a study of the weavability limit and tightness relationships of 2D and 3D woven fabrics was undertaken. Experiments were conducted on a representative number of polyester and cotton woven fabrics which have been woven in our workshop, using three machines endowed with different insertion systems (rapier, projectiles and air jet). Afterwards, these woven fabrics have been analyzed in the laboratory to determine their physical and mechanical characteristics using air permeability-meter and KES-F KAWABATA Evaluation System for Fabrics. In this study, the current Booten’s weavability limit and tightness relationships based on Ashenhurst’s, Peirce’s, Love’s, Russell’s, Galuszynskl’s theory and maximum-weavability is reviewed and modified as new relationships to expand their use to general cases (2D and 3D woven fabrics, all fiber materiel, all yarns etc…). The theoretical relationships were examined and found to agree with experimental results. It was concluded that the weavability limit and tightness relationships are useful tools for weavers in predicting whether a proposed fabric construction was weavable and also in predicting and explaining their physical and mechanical properties.

Petrogenesis and mineral characteristics of the oldest volcanogenic breccia unit from the Himalayan foreland basin, India

Jangalgali breccia unit (JBU), the oldest volcanogenic rock unit in the Himalayan foreland basin, has been studied from five different, however, stratigraphically equivalent localities of Jammu region in NW India. The field and thin section slides of JBU reveal that quartz and plagioclase are the two most common minerals and sanidine, magmatic zircon, rutile, hornblende and biotite are present as accessory phases. Petrographic signatures show that quartz and K-feldspar are set in a fine-grained cryptocrystalline glassy matrix and do not represent any preferred orientation. The euhedral hexagonal dipyramidal quartz phenocrysts, irregularly shaped inclusions having high volatile contents and no signatures of transport/reworking in phenocrysts prior to deposition are the prominent petrographic features of JBU. The mineral grains arrangement varies between tight-fitted fabric geometry to more open-chaotic packing. Overall, the field relationship, texture, mineralogy along with mineral chemistry, and presence of high gas and silica content in the host magma, support the volcanic origin of the JBU litho unit, which has wider implications towards understanding the timing of India-Asia collision as well as geodynamic evolution of the Himalayas.

On the role of material architecture in the mechanical behavior of knitted textiles

Direct numerical simulations based on three dimensional finite element analysis were performed to investigate the mechanical behavior of knitted textiles at the scale where their manufactured material architecture can be simulated and assessed. A numerical investigation of the effects that the material architecture has on deformation localizations, as well as both in- and out-of-plane displacements is presented. To achieve this, a procedure to numerically synthesize and modify knitted textile geometries is investigated which takes into account yarn-to-yarn interactions, while it further allows meshing used in finite element analyses. Appropriate boundary conditions are applied to avoid unnecessary constraints, while a specific type of interaction definition between yarn surfaces is enforced to remove the effect of contact and friction. Furthermore nonlinear analysis is used to capture the geometrically significant yarn position changes resulting from the flexural motion of the looped knitted textiles. The observed anisotropic effects are explained by examining the load transfer as a function of local material architecture. In addition, both linear and nonlinear material laws are used to study the role of material nonlinearities in the mechanical behavior of this type of material at the length scale of their architecture.

Study regarding the physical-mechanical properties of knits for garments – pilling performance

The effect of the pilling degradation results is an important decreasing in garment quality and a negative influence on the user’s comfort to wear. There are a lot factors, such as the yarn spinning system, fabric geometry and finishing operation, which affect the pilling performance. This research paper presents the investigation of fabric surface concerning pilling formation, especially knits, influenced by the fibrous composition. As samples were used knitted fabric panels, obtained from carded yarns, with fibers composition like cotton, wool or mixed one. Regarding fabric geometry 3 types were used – single jersey, 2x2 rib and moss stitch. In order to establish which of the yarns are most appropriate for knitting garments from the point of view of pilling resistance were realized tests using the standard SR EN ISO 12945-2.The tests were performed with the Nu-Martindale – Abrasion and Pilling Tester, Model 864.For assessment were used two methods – the first one is a comparison with visual standards, tested fabrics or photographs of fabrics, to find the degree of pilling on a scale from 5 (no pilling) to 1 (very severe pilling) and the second one by determination of mass loss percent.

Research Regarding the Influence of Raw Material and Woven Fabric Geometry on the Air Permeability of Mattress

Properties of woven fabrics are influenced by many factors: the nature of raw materials, woven fabric geometry and density, technological parameters of the weaving operation and finishing. The main purpose of this research paper is to increase the performance of woven process during mattress manufacturing by choosing the right woven fabric geometry and raw material. The variation in air permeability depends on the area density, linear density, loop length and thickness of yarns. To obtain woven fabric samples were used several types of classic yarns, also ecological yarns like organic cotton and bamboo viscose.On the other side, tests results show the fabric resistance regarding air permeability, like one of the main requirement for this type of textile material.

Role of Fabric Geometry in Ballistic Performance of Flexible Armour Panels

Energy absorption behavior of flexible armour materials treated with Shear Thickening Fluids (STF) was studied. Five different structures were prepared with varying thread densities of p-aramid yarns, followed by treatment with 60% w/w STF. In untreated condition, plain woven fabrics show highest impact resistance in low velocity impacts, followed by 3/1 twill, 2/2 twill, 5-end satin and 2/2 matt weaves. Ballistic impact mitigation behavior improves with increase in thread density in case of plain woven fabrics. Addition of STF significantly improves both low and high velocity impact behavior of the panels. Low velocity behavior of STF treated fabrics have been published previously [12]. This paper brings together both low and high velocity impact behavior of various geometries of fabrics. It was seen that both primary and secondary yarns are engaged during impact which improves impact mitigation behavior of STF treated fabrics. However, fabrics get jammed at thread densities beyond 32×32 per inch. As was observed earlier in low velocity impact conditions, addition of STF did not enhance performance of fabrics with high thread density in high velocity impact as well.