Abstract:The nonlinear, anisotropic, and multiscale mechanical behavior of knitted textiles is investigated experimentally in this article. The approach is motivated by recent computational work by the authors that revealed, for the first time to their best knowledge, local‐global mechanical behavior effects related to the hierarchical, three‐dimensional structure of this type of materials. The investigation is carried out on single jersey knitted textile specimens. Mechanical testing consisting of tensile loading alon… Show more
“…Previous researches have investigated the out-of-plane motion 19 but did not exceed a 5% strain range, whereas our work investigated these effects in a deformation range of up to 42%. Figure 12 shows out-of-plane displacement and form in tensile loading in structures a, b, and c. As mentioned in the experimental work, 37 a rapid transition of ordering in the loop geometry occurs up to stretching mode. This verifies that the modeling approach is sensitive enough to incorporate the complex mechanical behavior under in-plane load.Figure 12.Side view of: (a) basic structure, (b) tie structure and, (c) adjusted structure at 18% deformation.…”
Section: Resultsmentioning
confidence: 68%
“…It was demonstrated that this pathway in the wale direction appears to be less wavy, favoring yarn stretching and inter-yarn sliding over-rotation and out-of-plane motion. 37…”
Section: Resultsmentioning
confidence: 99%
“…It was demonstrated that this pathway in the wale direction appears to be less wavy, favoring yarn stretching and inter-yarn sliding over-rotation and out-of-plane motion. 37 Model simulation and validation Mesh analysis. In the case of wale tension loading, as shown in Figure 9, a mesh sensitivity analysis was performed on a structure of nine rows in the wale and nine columns in the tensile wale direction.…”
Section: Experimental Investigation Of Mechanical Behaviormentioning
Three-dimensionally (3D) knitted technology textiles are expanding into industrial and technical applications of textile composites given their geometric, structural, and functional performance. However, there are many challenges in developing computational tools that allow for physics-based predictions while keeping the related computing cost low. The strong interactions between geometrical and physical elements permit determining the behavior of this type of engineering material. In the aim of understanding the specific mechanical behaviors of knitted textiles, a yarn-level simulation model framework was created to predict the nonlinear orthotropic mechanical behavior of monofilament jersey-knitted textiles. The relative contributions of many computational parameters on the global mechanical behavior of knitted fabrics are investigated, specifically, inter-yarn interactions and the boundary conditions effect. The models are saved in a format that can be read directly by Finite Element Analysis FEA software. Yarns are numerically discretized as nonlinear 3D beam components, while input parameters, such as mechanical characteristics of yarns and geometric dimensions of loops in fabrics are established experimentally. Good agreement was relieved by comparing experimental data to simulation results in a wale-wise direction tensile load.
“…Previous researches have investigated the out-of-plane motion 19 but did not exceed a 5% strain range, whereas our work investigated these effects in a deformation range of up to 42%. Figure 12 shows out-of-plane displacement and form in tensile loading in structures a, b, and c. As mentioned in the experimental work, 37 a rapid transition of ordering in the loop geometry occurs up to stretching mode. This verifies that the modeling approach is sensitive enough to incorporate the complex mechanical behavior under in-plane load.Figure 12.Side view of: (a) basic structure, (b) tie structure and, (c) adjusted structure at 18% deformation.…”
Section: Resultsmentioning
confidence: 68%
“…It was demonstrated that this pathway in the wale direction appears to be less wavy, favoring yarn stretching and inter-yarn sliding over-rotation and out-of-plane motion. 37…”
Section: Resultsmentioning
confidence: 99%
“…It was demonstrated that this pathway in the wale direction appears to be less wavy, favoring yarn stretching and inter-yarn sliding over-rotation and out-of-plane motion. 37 Model simulation and validation Mesh analysis. In the case of wale tension loading, as shown in Figure 9, a mesh sensitivity analysis was performed on a structure of nine rows in the wale and nine columns in the tensile wale direction.…”
Section: Experimental Investigation Of Mechanical Behaviormentioning
Three-dimensionally (3D) knitted technology textiles are expanding into industrial and technical applications of textile composites given their geometric, structural, and functional performance. However, there are many challenges in developing computational tools that allow for physics-based predictions while keeping the related computing cost low. The strong interactions between geometrical and physical elements permit determining the behavior of this type of engineering material. In the aim of understanding the specific mechanical behaviors of knitted textiles, a yarn-level simulation model framework was created to predict the nonlinear orthotropic mechanical behavior of monofilament jersey-knitted textiles. The relative contributions of many computational parameters on the global mechanical behavior of knitted fabrics are investigated, specifically, inter-yarn interactions and the boundary conditions effect. The models are saved in a format that can be read directly by Finite Element Analysis FEA software. Yarns are numerically discretized as nonlinear 3D beam components, while input parameters, such as mechanical characteristics of yarns and geometric dimensions of loops in fabrics are established experimentally. Good agreement was relieved by comparing experimental data to simulation results in a wale-wise direction tensile load.
“…Subsequently water was applied which allowed the removal of the transfer paper's backing leaving the speckles on the surface. While there are many methods to transfer patterns onto a specimen including manual markers [53], micro stamps [54], lithography [55] and stencils [52], this method was chosen for ease of use and good fidelity to pattern the speckles at the given length scales and printing parameters. Fig.…”
Section: Physical Experiments -Scalability and Error Analysismentioning
Background Digital Image Correlation (DIC) is a length scale independent surface pattern matching and tracking algorithm capable of providing full field deformation measurements. The confident registration of this pattern within the imaging system becomes key to the derived results. Practically, conventional speckling methods use non-reliable, non-repeatable patterning methodologies including spray paints and air brushing leading to increased systematic and random errors based on the user's experience. Objective A methodology to develop a speckle pattern tailored to the imaging and experimental conditions of the given system is developed in this paper. Methods In this context, a novel bio-inspired speckle pattern development technique is introduced, leveraging spatial imaging parameters in addition to frequency characteristics of speckle patterns, enhancing the results obtained through DIC. This novel technique leverages gradient parameters in the frequency spectrum obtained from patterns fabricated using a bio-templating manufacturing technique. Results The analysis presented shows that optimized gradient features alongside tailored spatial characteristics reduce errors while increasing the usefulness of DIC results across the entire region of interest. With this new approach, gradient information is derived from the bio-templated pattern, extracted, optimized and then convolved with spatial properties of a numerically generated 2D point clouds which can then be transferred onto actual specimens. Numerical error analysis shows that the optimized patterns result in significant reduction in root mean square error compared to conventional speckling methods. Conclusions Physical experiments show the scalability of this optimized pattern to allow for varying working distances while consistently maintaining a lower error threshold compared to conventional speckling techniques.
“…Our initial focus has been on representing fabrics that can be manufactured by weft-knitting machines consisting of two flat beds of needles and a single yarn. Since it has been shown that the structures formed by yarns and their interactions dominate the mechanical behavior of knitted textiles [2,3,4,5], TopoKnit represents these types of fabrics with yarns and the neighborhoods where they contact each other. The goal of our work is to define a low-level representation of knitted fabrics that has the properties of both completeness (i.e.…”
Machine knitted textiles are complex multi-scale material structures increasingly important in many industries, including consumer products, architecture, composites, medical, and military. Computational modeling, simulation, and design of industrial fabrics require efficient representations of the spatial, material, and physical properties of such structures. We propose a process-oriented representation, TopoKnit, that defines a foundational data structure for representing the topology of weft-knitted textiles at the yarn scale. Process space serves as an intermediary between the machine and fabric spaces, and supports a concise, computationally efficient evaluation approach based on on-demand, near constanttime queries. In this paper, we define the properties of the process space, and design a data structure to represent it and algorithms to evaluate it. We demonstrate the effectiveness of the representation scheme by providing results of evaluations of the data structure in support of common topological operations in the fabric space.
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