Stitch Pattern Research Articles

Analysis of the mechanical behavior of composite T-joints reinforced by one side stitching

T-joints stiffeners made from carbon/epoxy composites have been increasingly applied in aeronautical structures, however as majority of the carbon fiber reinforced structures, they have faced with delamination problems. Through-the-thickness reinforcements for laminate composites have been studied as manner to increase transversal strength, especially reducing delamination. In the present work, carbon/epoxy T-joints reinforced transversally by one side stitching (OSS) and molded on Resin Transfer Molding (RTM) process have been performed as well as the reference (unstitched T-joints). The stitching position were designed after analysis of the unstitched T-joints by means of strain field on Digital Image Correlation (DIC) under pull-off test to better improve the areas submitted to large strain. Also, the stitched samples were mechanically tested in pull-off mode and were analyzed during tests by in situ microscopy and post-failure on Scanning Electron Microscopy .The energy release was better contained in the stitched structures especially in the critical region (delta-fillet), due to crack bridging that improved the delamination toughness. Otherwise, the stitch pattern generated by OSS process changed the strain fields asymmetrically when analyzed on DIC during tests. The stitched T-joints showed greater ultimate strength (25%) and load recovery post ultimate strength (19%) in comparison to the reference.

Internal structure and fatigue performance of quasi-unidirectional non-crimp fabric reinforced laminates

The aim of this work was to study the effect of stitch pattern and stitch tension on tension-tension fatigue performance of quasi-unidirectional non-crimp fabric reinforced glass-fibre/epoxy laminates. Internal structure variations of the laminates were characterised using cross-sectional microscopy imaging for the evaluation of fatigue test results. Reinforcements for the study were manufactured with three different stitch patterns and two different stitch tensions. Based on the results, the stitch pattern contributes to in-plane and out-of-plane waviness of fibres, as well as on the size and shape of the axial fibre bundles. The fatigue life and slope parameter of the fitted S-N curve were significantly dependent on the stitch pattern, while they were not dependent on the applied stitch tension.

Measurement and Analysis of Drapeability Effects of Warp-Knit NCF with a Standardised, Automated Testing Device

Characterising the drapeability of reinforcement fabrics, is one of the most sought after abilities of those designing composite processes and components. This is not surprising as composite processes are being considered in a greater range of fields and applications. Drapeability effects are formed by the irregular rearrangement of fibres. This displacement can occur within the textile plane and result in fibre disorientations, undulations and gaps or the fibres can be pushed into the third dimension - forming wrinkles or loops. To measure such effects in non-crimp fabrics, the Textechno Drapetest automatic drapeability tester was developed. To show its viability as a tool for composite engineering, a set of fabrics was chosen to show that the influence of textile design parameters on drapeability effects is now quantifiable. The Textechno Drapetest uses a sophisticated digital image analysis system to measure the position and direction of fibres and conclude from this information on the extent and intensity of drapeability effects in the textile surface. To measure effects outside the surface, i.e. wrinkles, a laser triangulation sensor is employed. The textiles were varied in the production parameters of stitch point distance in machine direction (MD) and cross direction (CD), the weight per area, and the stitch pattern (tricot and chain). The measurements showed that the new test method is capable of measuring the effects that were expected from classical test setups as well as a range of additional effects. From the results a significant influence of the stitch yarn on the formation of effects can be deduced. Especially the density of stitch points is a parameter that lets the textile producer control the behaviour of the textile when they are formed into a doubly curved three dimensional shape. To control the gap formation, however, the spacing of the stitch points in machine or in crosswise direction is also of importance with a shorter stitch length decreasing the forming of gaps more than a tighter stitch yarn pitch.

Modeling and testing of a knitted-sleeve fluidic artificial muscle

The knitted-sleeve fluidic muscle is similar in design to a traditional McKibben muscle, with a separate bladder and sleeve. However, in place of a braided sleeve, it uses a tubular-knit sleeve made from a thin strand of flexible but inextensible yarn. When the bladder is pressurized, the sleeve expands by letting the loops of fiber slide past each other, changing the dimensions of the rectangular cells in the stitch pattern. Ideally, the internal volume of the sleeve would reach a maximum when its length has contracted by 2/3 from its maximum length, and although this is not reachable in practice, preliminary tests show that free contraction greater than 50% is achievable. The motion relies on using a fiber with a low coefficient of friction in order to reduce hysteresis to an acceptable level. In addition to increased stroke length, potential advantages of this technique include slower force drop-off during the stroke, more useable energy in certain applications, and greater similarity to the force–length relationship of skeletal muscle. Its main limitation is its potentially greater effect from friction compared to other fluidic muscle designs.

Defect formation during preforming of a bi-axial non-crimp fabric with a pillar stitch pattern

To capture the asymmetrical shear behaviour of a bi-axial NCF with a pillar stitch, a non-orthogonal constitutive model was developed and implemented in finite element forming simulations. Preforming experiments indicate that the local distribution of defects is significantly different on both sides of each bi-axial ply, with two different defect mechanisms observed. Correlation with simulation results indicates that one defect type is caused by excessive shear, inducing out-of-plane wrinkling in regions of positive shear (macro-scale wrinkling). The other defect type is caused by fibre compression, inducing in-plane wrinkling in regions of negative shear (meso-scale wrinkling). Local distributions of shear angle and wrinkling strain were used to determine the wrinkling mode and to confirm the corresponding defect mechanism. Results indicate that simulations based on the advanced constitutive model can predict local shear angles within ±5° of experimental values and that predicted wrinkling positions and defect types correlate well with the experiments.

Influence of fabrics’ design parameters on the morphology and 3D permeability tensor of quasi-unidirectional non-crimp fabrics

This research addresses the effects of quasi-UD non-crimp fabric (NCF) design parameters on the fabric architecture and on the permeability tensor. These fabrics are designed for the Liquid Resin Infusion (LRI) of large and thick composite parts. Three fabrics’ parameters intended to bring a flow enhancement to the NCF are investigated: the stitch spacing, the stitch pattern and the weft tow lineal weight. Image analysis is undertaken to characterize the morphology of non-crimp fabric composite. A new continuous permeability measurement method based on compressive tests is proposed to relate the permeability of the quasi-UD NCF to the design parameters during the infusion process. The latter are proven to influence significantly both the fabric architecture and the permeability tensor coefficients.

Image‐based embroidery modeling and rendering

AbstractEmbroidery is a traditional handicraft of sewing stitches into fabric or other materials in different patterns, and this ancient non‐photorealistic art form has not drawn enough attention thus far. In this paper, we present an image‐based method to simulate the traditional embroidery art. The method combines stroke‐based rendering techniques with the Phong lighting model to create picturesque embroidery‐like images. We first build a 3D stitch model and derive some most commonly used stitch patterns from it. Then we preprocess the input image by segmenting it into regions, from which the parameters to specify stitch patterns are obtained. Finally, we apply stitches back onto the desired regions and render them under a virtual light source. Experimental results show that our method, different from the existing schemes, is capable of performing fine embroidery simulations with the effects of lighting and shading based on an input image. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of the fabric construction parameters and roving type on the tensile property retention of high-performance rovings in warp-knitted reinforced fabrics and cement-based composites

In this work, the tensile property retention characteristics of high-performance glass and carbon rovings in warp-knitted reinforced fabrics and cement-based composites used in structural applications were investigated. Three types of warp-knitted fabrics, with differing stitch patterns, and cement-based composites were produced. The tensile strength retention and Young’s modulus retention of the roving in these fabrics and their influence on the properties of cement-based composites were compared on the basis of the stitch type. Samples of warp-knitted fabrics composed of glass fibres and carbon fibres exhibit retention of 76–87% and 65–87.6%, respectively, of the initial strength of the rovings. The highest Young’s modulus retention (∼80%) occurs in the case of the fabric sample composed of glass rovings. The retention of the Young’s modulus in the fabric samples composed of carbon rovings was 37–60%. In addition, the translation of strength from the roving to the fabric and retention of the Young’s modulus in the carbon rovings decreased with increasing strength and modulus, respectively, of the original roving. On the basis of the data presented, we provided guidelines for the possible application of the developed fabrics. As conclusion, it is possible to reduce the cost of the raw materials by using fabrics whose original rovings have low tensile strength and Young’s modulus, but high retention properties.

Tendon Collagen Crosslinking Offers Potential to Improve Suture Pullout in Rotator Cuff Repair: An Ex Vivo Sheep Study.

The suture-tendon interface is often the weakest link in tendon to bone repair of massive rotator cuff tears. Genipin is a low-toxicity collagen crosslinker derived from the gardenia fruit that has been shown to augment collagen tissue strength and mechanically arrest tendon-tear progression. The purpose of the current study was to evaluate whether genipin crosslinking can sufficiently augment the suture-tendon interface to improve suture pullout strength using simple single-loop sutures and the modified Mason-Allen technique. The study also aimed to assess whether time of genipin treatment is a relevant factor in efficacy. In an ex vivo (cadaveric) sheep rotator cuff tendon model, a total of 142 suture pullout tests were performed on 32 infraspinatus tendons. Each tendon was prepared with three single-loop stitches. Two groups were pretreated by incubation in genipin solution for either 4 hours or 24 hours. Two corresponding control groups were incubated in phosphate buffered saline for the same periods. The same test protocol was applied to tendons using modified Mason-Allen technique stitch patterns. Each suture was loaded to failure on a universal materials testing machine. Suture pullout force, stiffness, and work to failure were calculated from force-displacement data, and then compared among the groups. Median single-loop pullout force on tendons incubated for 24 hours in genipin yielded an approximately 30% increase in maximum pullout force for single-loop stitches with a median of 73 N (range, 56-114 N) compared with 56 N (range, 40-69 N; difference of medians = 17 N; p = 0.028), with corresponding increases in the required work to failure but not stiffness. Genipin treatment for 4 hours showed no added benefit for suture-pullout behavior (46 N, [range, 35-95 N] versus 45 N, [range, 28-63 N]; difference of medians, 1 N; p = 1). No tested genipin crosslinking conditions indicated benefit for tendons grasped using the modified Mason-Allen technique after 4 hours (162 N, [range, 143-193 N] versus 140 N, [range, 129-151 N]; difference of medians, 22 N; p = 0.114) or after 24 hours of crosslinking (172 N, [range, 42-183 N] versus 164 N [range, 151-180 N]; difference of medians, 8 N; p = 0.886). Exogenous collagen crosslinking in genipin can markedly improve resistance to pullout at the tendon-suture interface for simple stitch patterns while the modified Mason-Allen stitch showed no benefit in an ex vivo animal model. Tendon strength augmentation by genipin pretreatment offers the potential to improve suture retention properties. Future studies are warranted for the development of clinically viable intraoperative delivery strategies and in vivo testing for safety and efficacy.

Characterization of shear behavior of warp-knitted fabrics applied to composite reinforcement

Different types of textile fabrics are now widely used for reinforcing composite structural parts. In this work, three types of weft-inserted warp-knitted fabrics differing in stitch pattern and composed of glass roving were produced. The shear behavior of the developed fabrics was determined according to stitch type. Three basic stitch types were chosen: tricot, cord, and pillar. The shear behavior was examined by the picture frame test method. It was observed that the stitch type significantly affects the shear behavior of the fabrics. The deformation phases during the fabric shear test were analyzed. To estimate the changes in the shear stiffness of the fabrics, shear moduli were calculated as a function of the shear angle. In general, the fabric with the tricot stitch has the greatest shear resistance than that of fabrics with the cord and pillar stitches. The results of the characterization of shear behavior of the warp-knitted fabrics are presented and discussed.

Self-Folding Textiles through Manipulation of Knit Stitch Architecture

This research presents a preliminary study on finding predictable methods of controlling the self-folding behaviors of weft knit textiles for use in the development of smart textiles and garment devices, such as those with shape memory, auxetic behavior or transformation abilities. In this work, Shima Seiki SDS-One Apex computer-aided knitting technology, Shima Seiki industrial knitting machines, and the study of paper origami tessellation patterns were used as tools to understand and predict the self-folding abilities of weft knit textiles. A wide range of self-folding weft knit structures was produced, and relationships between the angles and ratios of the knit and purl stitch types were determined. Mechanical testing was used as a means to characterize differences produced by stitch patterns, and to further understand the relationships between angles and folding abilities. By defining a formulaic method for predicting the nature of the folds that occur due to stitch architecture patterns, we can better design self-folding fabrics for smart textile applications.

Experimental compaction characterization of unidirectional stitched noncrimp fabrics in the vacuum infusion process

In this study, experimental test equipment developed in-house was used to study the compaction behavior of stitched quasi-unidirectional (UD) non-crimp fabrics (NCF) during the pre-filling, filling, and post-filling stages of the vacuum infusion (VI) process. The effects of the stitch pattern, stitch tension, and fiber sizing of reinforcements, as well as the effect of nesting of fiber bundles in neighboring layers, were studied. Moreover, the effects of cyclic compaction, resin viscosity, and different post-filling strategies were studied. The developed experimental test equipment provided an applicable measuring method for characterizing the compaction behavior of both the dry and resin-impregnated reinforcements. The effects of the stitching parameters and fiber nesting of reinforcements were found. The stitch pattern and post-filling strategies were noted to have an effect on the preform and laminate thickness. POLYM. COMPOS., 37:2692–2704, 2016. © 2015 Society of Plastics Engineers

Effects of fabric structures on the tensile properties of warp-knitted fabrics used as concrete reinforcements

High-performance textiles are now widely used in civil engineering applications. This work explores the differences between the tensile properties of weft inlay warp-knitted fabrics of high-strength glass and carbon rovings as concrete reinforcements. In this study, 12 types of warp-knitted fabrics with different stitch patterns, including tricot, cord, and pillar stitches, were produced. The effect of the stitch type on the tensile properties of the fabrics was examined. The stitch type was found to significantly affect the tensile properties of the warp-knitted fabrics. The results showed that the tensile strength of fabrics with tricot and cord stitches is greater than that of fabrics with the pillar stitch. The increase in tensile strength was 14% for fabrics made of glass roving and 21% for fabrics made of carbon rovings. A similar gradation was observed for the Young’s modulus of the fabrics. The Young’s modulus was 11% and 25% higher for glass and carbon fabrics, respectively. The structural parameters of the warp-knitted fabrics, including the geometry of the stitch pattern and the yarn cross-sectional shape in a fabric that affect the tensile properties, were analyzed.

Inter-ply stitching optimisation of highly drapeable multi-ply preforms

An efficient finite element model has been developed in Abaqus/Explicit to solve highly non-linear fabric forming problems, using a non-orthogonal constitutive relation and membrane elements to model bi-axial fabrics. 1D cable-spring elements have been defined to model localised inter-ply stitch-bonds, introduced to facilitate automated handling of multi-ply preforms. Forming simulation results indicate that stitch placement cannot be optimised intuitively to avoid forming defects. A genetic algorithm has been developed to optimise the stitch pattern, minimising shear deformation in multi-ply stitched preforms. The quality of the shear angle distribution has been assessed using a maximum value criterion (MAXVC) and a Weibull distribution quantile criterion (WBLQC). Both criteria are suitable for local stitch optimisation, producing acceptable solutions towards the global optimum. The convergence rate is higher for MAXVC, while WBLQC is more effective for finding a solution closer to the global optimum. The derived solutions show that optimised patterns of through-thickness stitches can improve the formability of multi-ply preforms compared with an unstitched reference case, as strain re-distribution homogenises the shear angles in each ply.

Arthroscopic Single-Row Versus Double-Row Repair for Full-Thickness Posterosuperior Rotator Cuff Tears: A Critical Analysis Review.

Over the past two decades, arthroscopic rotator cuff repair has become one of the most popular orthopaedic surgical procedures because of its proven ability to diminish pain and improve function in patients with symptomatic rotator cuff tears. As a result of this increasing demand, arthroscopic techniques have evolved rapidly in an effort to improve structural integrity, biomechanical function, and, ultimately, clinical outcomes. With the increasing number of techniques available for the repair of full-thickness rotator cuff tears, debate has arisen regarding the clinical superiority of any one of these methods over the others. Specifically, this debate has centered on traditional single-row versus traditional double-row repair constructs (Fig. 1). Therefore, the purpose of this article is to present a critical review of the most relevant evidence and to provide clinical care recommendations regarding arthroscopic single-row versus double-row rotator cuff repair constructs. Fig. 1 Traditional single-row suture configuration utilizes two lateral anchors tied in a simple stitch pattern ( Fig. 1 , A ). Traditional double-row suture configuration utilizes an additional medial row of anchors with mattress stitches ( Fig. 1 , B ). The rotator cuff represents a confluence of four tendons that envelop the humeral …

A modular modeling approach for describing the in-plane forming behavior of unidirectional non-crimp-fabrics

Various commercially available unidirectional (UD) non-crimp-fabrics (NCFs) are currently used for manufacturing carbon fiber reinforced plastic (CFRP) parts. These UD NCFs can differ significantly in their forming behavior. For optimizing and ensuring the manufacturability of the forming process of CFRP parts manufactured from UD NCFs these differences have to be taken into account. This motivates developing an efficient and universally applicable modular modeling approach for describing the in-plane forming behavior of various UD NCFs. The first component of this modular approach is a hyperelastic material model that accurately predicts the fiber orientation of UD NCFs during forming. This material model is implemented via a user-defined material subroutine in the commercial finite element package LS-DYNA. The second component is a simple truss structure that allows modeling the various stitch patterns of the different UD NCFs. This modular model can be calibrated via simple tensile tests. To demonstrate the versatility of this approach, the in-plane forming behavior of three different UD NCFs is validated by comparing experimental data and simulation results of the common picture frame test.

Impact and post impact (CAI) behavior of stitched woven–knit hybrid composites

In this study, the effect of stitch pattern on the impact and post impact (CAI) behavior of eight ply woven–knit hybrid composite plates consisting of 2D woven fabrics as outer layers and rib knitted fabrics as inner layers was investigated. Layers of the woven–knit hybrid composite plates were sewed in circular, square and diamond shape through thickness in order to prevent delamination and slippage between the layers. Impact and post impact testing were carried out in order to determine the impact and post impact resistance of three different stitched composite structures. Results showed that the impact strength of composite laminate increased 5.5%, 11% and 22% in the case of square, diamond, and circular stitching, respectively. It was also found that the woven–knit hybrid composites with square pattern have the highest CAI strength.

Cable Crossings: The Aran Jumper as Myth and Merchandise

This article considers the Aran jumper as a cultural artefact from an anthropological perspective. As an internationally recognized symbol of Irishness that comes with its own myth of origin, the Aran jumper carries emotionally charged ideas about kinship and nativeness. Whether read as an ID document, family tree, representation of the landscape or reference to Christian or pre-Christian spirituality, the Aran jumper’s stitch patterns seem to invite interpretation. Emerging at a particular period in the relationship between Ireland and America, this garment and the story that accompanies it have been shaped by migration and tourism, but may be understood very differently on either side of the Atlantic. The resilience of the myth of a fisherman lost at sea, whose corpse is identifiable only by designs his relatives have stitched into his clothing, is explained in light of its resonance with diasporic narratives and transnational longings.

Influence of Stitching Parameters on Tensile Strength of Aramid/Vinyl Ester Composites

Stitching process is used to provide structural integrity and through-the-thickness reinforcement in the composite materials. In this study, the effect of sewing parameters on tensile strength in stitched composite laminates was examined. In the production of composite laminates, Twaron T-750 type plain weave fabric was used as reinforcement material and a Polives 702 Bisphenol-A type epoxy based vinyl ester as resin. The effects of stitch density and stitch direction or stitch pattern on tensile strength of composite samples were studied and, as a result of the experiments, it was observed that higher tensile strength occurs with low stitch densities in stitched laminates.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3829

Formability Evaluation of Non-Crimp Carbon Fabric by Non-Contact 3D Deformation Measurement System

Non-Crimp Carbon Fabric (NCF) consists of unidirectional plies which are kept together by stitching yarns arranged in a number of different orientations relative to the fabric production direction. It is reported that NCF possesses excellent drape performance compared to woven fabrics. However there is not a clear criterion of a drape evaluation on the drape characteristic of the NCF. In addition, it is not clarify that stitch pattern and stitch tension influence on the drape characteristic of the NCF. Moreover, in existing bias extension test, measurement of shear angle is based on the pin-jointed net (PJN) approximation. The PJN approximation doesnt takes into consideration the fiber sliding and the effect of the stitched parameters of the NCF. In this study, the bias extension test based on the measurement of shear angle by non-contact 3D deformation measurement system was conducted to evaluate the drape performance of the NCF. We made a proposal of the formability evaluation index based on the measurement results. Moreover, the 3D draping tests were conducted onto hemisphere geometry and regular tetrahedron, in order to verify availability of the formability evaluation index. The availability of the formability evaluation index was verified.