Braided Fabrics Research Articles

Application of Braided Fibre Reinforced Composite Rods in Concrete Reinforcement

This paper describes the work that is being done at the University of Minho concerning the development of braided rods for concrete reinforcement. A preliminary research study has been conducted to understand the mechanical behaviour of braided fabrics. Various samples have been produced varying the type of fiber (glass, polyester and aramid), the type of braided fabric (simple, hybrid and core reinforced) and in the latter case, the number of core reinforcing yarns. The tensile properties of these samples have been evaluated and the results presented. The influence of each factor on the tensile properties of braided fabrics has also been analysed and discussed. In order to produce braided reinforced composite rods to use as a concrete reinforcement, a special technique has been developed using a standard vertical braiding machine. The braided reinforced composite materials have been produced in rib structure to improve adhesion between them and the concrete. Special samples have been prepared and tested to evaluate the adherence between both materials involved. The tensile and bending properties of braided reinforced composite rods have been evaluated and the results obtained presented and discussed.

Effect of braid angle on fatigue performance of biaxial braided composites

Biaxial braided fabric is gaining popularity in primary structural application in small business jets because of its natural ability to conform to complex shapes. This research addresses the effect of braid angle on in-plane mechanical properties and fatigue performance. The carbon/epoxy braided composites were fabricated using low cost vacuum assisted resin transfer molding (VARTM) with different braid angles (25°, 30° and 45°). The static tests were performed to evaluate tensile strength, modulus, and Poisson’s ratio. It is observed that as braid angle increases the tensile strength, modulus, and Poisson’s ratio decreases significantly. The load controlled tension-tension fatigue tests ( R = 0.1) were conducted at 10 Hz frequency with constant amplitude. The endurance limit was defined as the fatigue load that results in a fatigue life of one million cycles. The endurance limit for 25° and 30° braided composites was 40% of UTS whereas for 45° braided composites it was 50% of UTS. However, braid angle did not significantly affect the failure mechanism under fatigue loading. It was very crucial to control the braid angle within a test specimen, as tensile strength is significantly affected by braid angle variation. The special form of biaxial braided fabric termed slit sleeves assures the constant braid angle while handling and processing. It was observed that, a Sigmoidal function could be used effectively to represent the fatigue life behavior. Braided composites exhibited substantially different fatigue failure behavior as compared to conventional angle-ply laminated composites. The major difference being that the failure is sudden. There were hardly any noticeable matrix cracks or delaminations in the first 90% of the fatigue life at all fatigue load levels. There is rapid damage accumulation in the last 10% of the fatigue life.

Characterization of a Novel Polymeric Scaffold for Potential Application in Tendon/Ligament Tissue Engineering

Unlike braided fabrics, knitted scaffolds have been proven to favor deposition of collagenous connective tissue matrix, which is crucial for tendon/ligament reconstruction. But cell seeding of such scaffolds often requires a gel system, which is unstable in a dynamic situation, especially in the knee joint. This study developed a novel, biodegradable nano-microfibrous polymer scaffold by electrospinning PLGA nanofibers onto a knitted PLGA scaffold in order to provide a large biomimetic surface for cell attachment. Porcine bone marrow stromal cells were seeded onto either the novel scaffolds by pipetting a cell suspension (Group I) or the knitted PLGA scaffolds by immobilizing in fibrin gel (Group II). Cell attachment at 36 hours, cell proliferation and extracellular matrix synthesis at 1 week, and mechanical properties over 2 weeks were investigated. Cell attachment was comparable and cell proliferation was faster in Group I. Moreover, cellular function was more actively exhibited in Group I, as evident by the higher expression of collagen I, decorin, and biglycan genes. Thus, this novel scaffold, facilitating cell seeding and promoting cell proliferation, function, and differentiation, could be applied with promise in tissue engineering of tendon/ligament.

Tensile, flexural and impact properties of jute fibre-based thermosetting composites

The present study reports static and impact mechanical properties of jute fibre-based thermosetting composites using woven and flat braided jute fabrics. Tensile, three-point flexural and low-to-medium energy drop-weight impact tests were conducted and mechanical properties were evaluated to study their dependence upon surface modifications of the fibre materials due to bleaching and coating treatments. Full-bleaching (longer and rigorous) treatments improved interfacial bonding and tensile strength properties of the woven jute composites compared to unbleached and half-bleached counterparts. Bleaching treatments did not seem to improve the flexural strength of composites. Unbleached (natural) jute composites have relatively better flexural strength due to reduced microstructural waviness or fibre crimping to facilitate flexural failure. With coated jute yarns, the tensile properties of the resultant flat braided composites slightly degraded, whereas the flexural properties showed clear improvements. The changes in the mechanical properties were broadly related to the accompanying modifications and to the state of microstructural imperfections, namely fibre/matrix interfacial adhesion, severity of resin matrix shrinkage during the curing process, fibre/matrix debonding and distribution of disbonds within the matrix region, and also to the relative fibre filament density along the loading axis, in the cured composite structure. There was a clear indication that natural woven jute composites could be more effective in applications requiring better impact damage resistance, energy absorption capability and improved progressive crushing behaviour.

A novel device for left atrial appendage exclusion

The left atrial appendage is a frequent source of thromboemboli in patients with atrial fibrillation. Exclusion or excision of the left atrial appendage may reduce the risk of stroke in patients with atrial fibrillation. We evaluated the ability of a novel device to exclude the left atrial appendage during early and intermediate follow-up periods in a canine model. Eight mongrel dogs (mean weight 29.1 +/- 4.0 kg) were used in this study. The occlusion device, constructed from 2 stainless steel strips covered with a knit braided polyester fabric, was implanted at the base of the left atrial appendage through a left thoracotomy on a beating heart. Dogs were evaluated at 7 days (n = 2), 30 days (n = 2), and 90 days (n = 4) by epicardial echocardiography, left atrial angiography, histologic inspection, and gross pathology. Device implantation was performed without complications in all animals. Complete exclusion of the left atrial appendage from the circulation was confirmed acutely and chronically by echocardiographic and angiographic evaluations. There was no device migration or damage to adjacent structures. This novel device enables rapid, reliable, and safe exclusion of the left atrial appendage. The device provides a new therapeutic option for reducing the risk of stroke in patients with atrial fibrillation.

A Model To Study Slit DamagedBraided Fabric Structures

A micromechanical model has been developed that will allow the study of a slit-damaged braided fabric air-beam structure. As such, the relevant system of non-dimensional ordinary differential equations is derived and solutions are given for the stress concentration near the broken yarns. This knowledge will contribute to the prediction of damage growth and the ability to compare different fabric materials for their damage tolerance. A simplification of the analysis has been shown to be possible when a parameter, e , the ratio of yarn tensions due to inflation to the yarn stiffness is small, approaching zero. In such a case, the equations for the braided fabric can be reduced to those of the plain weave fabric, so that the stress concentrations are the same as those for woven fabrics. As it turns out, an important result of the present analysis is that the stress concentration factor is, in fact, independent of the parameter, e , and the helix angle of the braided fabrics. This means that much of what has been learned in the study of damage in woven fabrics can be used for braided fabrics.

Evaluation of the Physical and Mechanical Properties of Braided Fabrics and their Composites

This study aims to evaluate the permeability and the basic mechanical properties of braided fabrics intended for hollow composites to be manufactured by resin infusion processes. A simple procedure has been devised to obtain flat specimens for the required permeability and mechanical tests. Permeability measurements have been performed on 2-D biaxially braided glass fabrics at three braiding angles. The change of the braiding angle affects the fiber volume fraction, which in turn affects the permeability. Tension, compression, and shear tests have also been conducted on unidirectional (UD) and braided glass-epoxy composites. From the experimental UD properties, the lamination theory (LT) has been used to predict the properties of angle ply () laminates equivalent to the braided composites tested. From the comparison of the predicted and experimental results, the effects of the fibers’ intertwining and undulation on the mechanical properties have been derived. The undulation of the fibers is responsible for the compression strength reduction, mainly at low braiding angles, but has no effect on the tensile strength. For all angles, the braided composites have a higher modulus than the predicted angle ply laminates. The Iosipescu shear method is not suitable for the characterization of composites containing braided fabrics because of their high shear stiffness and strength.

Geometric and algebraic algorithms for modelling yarn in woven fabrics

This paper presents geometric and algebraic algorithms and relevant optimizing operators for 3D computer modelling of yarns in fabric. New algorithms and approaches are successfully employed to create more realistic and flexible geometry models with consideration of the differential and topological structure of yarns. By using asymptotic iterative approximation, we have developed a new algorithm for creating B-spline curves using periodic interpolation, where the actual curve shape passes through the control points of B-spline. The generator for irregular cross-sections of yarn in complex fabric structures is created with variability in both shape and size along the yarn path represented by combined spline curves, which allows the complicated shapes of yarn cross-sections in fabrics as the yarns are flattened by the compression at the crossovers. An algorithm of differential geometry is employed to track the vector of tangent orientation of the yarn path in 3D space to get the normal plane of yarn for creating the correct cross-section of yarn. The method described is demonstrated by the visualization of woven fabrics. The approach established can then be further generalized for more different and complicated fabrics (including braided fabrics and knitted fabrics) and 3D fabric.

A Micromechanical Model for Slit-damaged Braided Fabric Air-beams

A micromechanical model has been developed that will allow the study of a slit-damaged braided fabric air-beam structure. As such, the relevant system of non-dimensional ordinary differential equations is derived and solutions are given for the stress concentration near the broken yarns. This knowledge will contribute to the prediction of damage growth and the ability to compare different fabric materials for their damage tolerance. A simplification of the analysis has been shown to be possible when a parameter, e, the ratio of yarn tensions due to inflation to the yarn stiffness is small, approaching zero. In such a case, the equations for the braided fabric can be reduced to those of the plain weave fabric, so that the stress concentrations are the same as those for woven fabrics. As it turns out, an important result of the present analysis is that the stress concentration factor is, in fact, independent of the parameter, e, and the helix angle of the braided fabrics. This means that much of what has been learned in the study of damage in woven fabrics can be used for braided fabrics.

Fatigue Behaviour of Multilayer Braided Fabric Reinforced Laminates

In this paper, the fatigue behaviour of the laminated composites made from an epoxy matrix and four layers of flat regular braided carbon fiber fabrics of different braiding angles was investigated experimentally. Three laminate lay-ups were used. They are: [100/100/100/100], [280/100/100/280], and [280/280/280/280], where 100 within the bracket indicates that the single layer braid lamina had a braiding angle of 100 inclined with the longitudinal (loading) direction. The static tensile and tension-tension fatigue tests were conducted for those laminates, and detailed fatigue data are reported in the paper. Failure mechanisms of the tested laminates were also characterized. The stiffnesses and strengths (including static tensile and fatigue strengths) of the [100/100/100/100], [280/100/100/280], and [280/280/280/280] laminates were the highest, intermediate, and the lowest respectively. However, different failure mechanisms were recognized. It was found that under the uniaxial tensile or a high-level fatigue load, the [280/280/280/280] laminate failed catastrophically as a result of fiber breakage nearly across the cross section of the specimen. Delamination was seen only when a low-level fatigue load was applied to the laminate. In the case of the [100/100/100/100] laminate, a laminate longitudinal splitting was the main failure mode. No delamination accompanied the laminate failure. For the [280/100/100/280] laminate, significant delamination was found with any applied load (whether static or tensile fatigue of any load level). Splitting, both across the cross-sectional breakage and longitudinal, were involved in the failure of this combined laminate. These findings provide a useful insight into understanding the fatigue behaviour of braided fabric reinforced laminates.

Effect of braid structure on yarn cross-sectional shape

The effect of braid construction parameters on yarn cross-sectional shape is presented in this paper. The location of the yarn within the braid unit cell is quantified by a compaction factor. A range of braided fabrics were produced and optically measured for actual yarn cross-sectional shape. A comparison of the theoretical and experimental values shows good correlation. Design curves can be produced with the developed model to allow selection of appropriate braid process parameter to create yarns with desired cross-sectional geometries.

Stiffness and strength design of composite bone plates

Although the potential of composites used for bone plate implantation has been realized for a long period of time, not much literature has addressed optimal design of composite bone plates upon variation in reinforcing fiber structures, plate thicknesses, and so on. In this paper, we present a preliminary but critical design procedure for composite bone plate with target on both its stiffness and its ultimate strength. While the material system used is the same, i.e. carbon fibers and PEEK matrix, three kinds of fibrous preforms namely unidirectional (UD) prepregs, braided fabrics, and knitted fabrics are considered as reinforcements, constituting six different candidate laminated plates. They are UD [0°] ns , angle plied [±20°] ns , multidirectional [0°/±20°/0°] ns , two braiding angle diamond braid fabrics [5°] ns and [15°] ns , and plain weft knitted fabric laminates. By varying the number of layers ( n) in the lamination, different plate thicknesses can be attained. The structure–property relationship of the composite plates is realized through the use of a micromechanics bridging model. A clinically used stainless steel plate is taken as a design benchmark. It has been found that the composite bone plates with all the considered lamination patterns except for the knitted fabric reinforcement and having a thickness near to that of the stainless steel plate can exhibit required properties of bending rigidity and maximum bending moment. The plate thickness is more controlled by strength rather than by stiffness requirement. However, the 5° braided fabric composite bone plate shows an overall superiority as compared to the other lamination forms, and is thus recommended as the first choice.

Fabrication and Mechanical Properties of PE/PE Interface-less Composites using Micro-braiding

An interface-less PE/PE composite has been fabricated using a micro-braiding technique. With braided fabrics, additional non-braiding yarns can be inserted, within the intertwining yarns (this type is called the middle-end fibre) and at the centre of the micro-braided yarn (this type is called the axial fibre). The effect of moulding conditions on the tensile properties was examined, followed by the effect of the diameter of the reinforcement fibre bundles, which we have called the impregnation distance. Middle-end fibres are more effective in improving the tensile strength than axial fibres because the permeation of the matrix resin into the reinforcement fibre of the middle-end fibre is easier than that of the axial fibre, although the modulus of middle-end fibre was lower than that of axial fibre because the reinforcement fibre bundles of the middle-end fibres were slightly wavy compared to that of the axial structure.

ＰＥ／ＰＥ織物複合材料の成形と物性

A interface-less composite of PE/PE with a sandwich structure was fabricated using UHMWPE woven fabrics and L-LDPE sheets. The effect of fabrication temperature and compression time on the tensile properties was studied. At high fabrication temperature, the woven fabric was melted. For long compression time, the braided fabric was damaged by heat and shrunk. As a result, the suitable fabrication condition was found. Then, the effect of the emulsion treatment before molding to the tensile properties was examined. Nevertheless no increase of the strength, the tensile modules became large with increase of the emulsion condensation. Finally, the tensile properties of the PE/ PE composites was compared to that of the PE/Epoxy composites. The strength of the PE/PE composites is the same as that of the PE/Epoxy composites. The strength of the PE/PE composites is three times larger than that of the PE matrix. The strength of the PE/Epoxy composites is three times larger than that of the Epoxy matrix. It shows that the effect of composing the PE fabric with the PE matrix on the strength is the same as that with the Epoxy matrix. The same tendency was found for the modulus. On the other hand, PE matrix is good peerless to PE fabric compared to Epoxy matrix. The PE/PE composite exhibits good performance of composites. That is the bonding strength between the PE fabric and the PE matrix is larger than that between the PE fabric and the Epoxy matrix. It is effective to choose the PE for the matrix from the point of view of the interface reinforcement.

Compression Properties of Square Braided Fabric-Concave Compression Properties-

Concave compression properties of square braided fabric were investigated. From the observation of the cross section with optical microscopy, the mechanism of deformation under concave compressive loading was clarified. The deformation involved change in crimp ratio and braiding angle of fiber bundle. Inside structure of braided fabric and deformation properties were extremely changed at first compression and then tended to converge to stable structure; compression ratio decreased and recovery ratio increased. The change in structure of braided fabric was resulted from change in braiding angle and change in crimp of fiber bundle because of bending deformation.

Compression Properties of Square Braided Fabric-Recovery properties after flat compression-

In this study, recovery properties of square braided fabric after flat compression were focused. The observation of the cross section with optical microscopy was performed and the mechanism of recovery deformation was clarified. Inside structure of braided fabric and recovery properties were extremely changed at first compression and then tended to converge to stable structure. Recovery ratio kept almost constant value after 2nd cycle. Recovery of braided fabric was resulted from change in braiding angle of fiber bundle ‘a’ and ‘b’ and decrease in crimp of fiber bundle.

Development and application of innovative triaxially braided ductile FRP fabric for strengthening concrete beams

In this paper, an innovative triaxially braided ductile fiber reinforced polymer (FRP) fabric has been developed for strengthening reinforced concrete beams. The fabric was designed to potentially avoid most of the drawbacks experienced by currently available FRP strengthening systems. The ideal characteristics of a strengthening material for reinforced concrete beams were first investigated. Then, an analytical study was conducted to investigate the undulation effect of diagonal yarns on their loading behavior. Based on these investigations, the fabric was designed, manufactured, and its mechanical properties were experimentally evaluated. The effectiveness of the fabric as a strengthening material for reinforced concrete beams has been investigated by testing four reinforced concrete beams strengthened in flexure and shear using the new fabric. The test results showed that the fabric met its design objectives.

Resin flow monitoring in resin film infusion process

The resin film infusion is a promising and low cost technique for the manufacturing of high performance polymer-based composite materials. The processing cycle is usually performed in the autoclave where, under temperature and pressure application, a bagged dry fiber mat is infiltrated by a thermoset polymer resin which is pre-shaped in film form under the fibers. After complete infusion, the consolidation step behaves as in the conventional autoclave process. The infusion process is strongly affected by the permeability of the fiber mat that determines processing issues, such as the cycle time and the complete fiber impregnation and, as a consequence, the performance of the final part. Therefore, the permeability measurement represents one of the most crucial requirements for the design and the optimization of the composite manufacturing by RFI. In this study, a non-conventional technique, based on a fiber optic sensor, has been used to guess the permeability of braided carbon fiber fabrics infiltrated with an epoxy resin by reproducing experimental conditions similar to the RFI industrial manufacturing. The fiber optic sensor, placed through the reinforcement, is able to detect the resin advancement during the infiltration by recording the light intensity drop which takes place as the resin reaches the optical fiber location. This technique represents a valid alternative to the common permeability measurement methods based on flow visualization and in addition, it can be easily used for the real time monitoring of the resin flow advancement during the real processing.

Multi-chain digital element analysis in textile mechanics

The concept of multi-chain digital element analysis is established. This new approach is a general numerical tool for textile mechanics. It can be used for textile process design and for fabric deformation, strength and failure analyses. In multi-chain digital analysis, fabric is considered as an assembly of yarns; furthermore, a yarn is considered as an assembly of fibers. Each fiber is modeled as a frictionless pin-connected rod element chain, defined as “digital chain”. Once the length of these rod elements approaches zero, the digital chain becomes a fully flexible one-dimensional entity with a circular cross section. It imitates the physicality of the fiber. Since a yarn is composed of many fibers, it is modeled as an assembly of digital chains. Contact between digital chains is modeled by contact elements. A procedure, similar to finite element analysis, is adopted. Displacement of fiber inside a fabric is derived based upon the global stiffness matrix and the boundary conditions. As a result, both detailed yarn paths and cross-section shape can be traced during the textile forming process or fabric deformation. In order to describe the new concept, two numerical examples are presented. The multi-chain digital element approach is used for the simulation of the two-dimensional weaving and three-dimensional braiding processes. One can observe, section-by-section, the yarn cross-section shape inside the woven and braided fabric.

An Experimental and Numerical Study of the Mechanical Properties of 3-D Braided Structural Textile Composites

An Experimental and Numerical Study of the Mechanical Properties of 3-D Braided Structural Textile Composites