Methods to generate fibers from hydrogels, with control over mechanical properties, fiber diameter and crystallinity, while retaining cytocompatibility and degradability, would expand options for biomaterials. Here we exploited features of silk fibroin protein for the formation of tunable silk hydrogel fibers. The biological, chemical, and morphological features inherent to silk were combined with elastomeric properties gained through enzymatic crosslinking of the protein. Post-processing via methanol and autoclaving provided tunable control of fiber features. Mechanical, optical, and chemical analyses demonstrated control of fiber properties by exploiting the physical cross-links, and generating double network hydrogels consisting of chemical and physical cross-links.
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3D Fabrics for Technical Textile ApplicationsVIDEO ON THE TOPIC: An Inside Look at BMW's Carbon Fiber Manufacturing Process
Production Engineering. Braiding is an attractive manufacturing method for tubular elements such as hollow shafts and struts. One of the main challenges however is the integration of suitably performing end-fittings. This requires the introduction of protrusions onto the surface of the end-fitting to promote mechanical interlocking with the fibres. However, the lack of accurate modelling tools for the simulation of this manufacturing process means that much empiricism is currently used in the design of such structures.
A novel numerical framework is presented here for the full-scale simulation of the braiding process over structured end-fittings. Nonlinear finite element analysis is applied at the meso-scale, with strands of beam elements representing individual yarns and meshed surfaces modelling the mandrel and tooling. Penalty-based contact formulations are then used to simulate all inter-yarn and yarn-metal interactions, enabling detailed predictions of fibre paths around surface protrusions.
In order to verify and validate this numerical framework, a series of full-scale braiding experiments was conducted using additively-manufactured thermoplastic mandrels. Final braid patterns as well as the occurrence of braid imperfections were investigated and compared to model predictions. It is shown that the proposed modelling strategy reproduces well the trends observed experimentally in terms of final braid quality. A parametric study was then conducted on the effects of initial end-fitting alignment with respect to oncoming yarns, suggesting that better control over this parameter could reduce considerably the occurrence of braid imperfections.
The use of composite materials, such as fibre reinforced polymers FRPs has been increasing rapidly in several industries including aerospace, automotive and renewable energy, due to the superior specific strength and stiffness of these materials over their metallic counterparts. However, because of their limited operation temperatures, poor wear resistance and relatively low through-thickness strength, composites are often used in combination with metals in primary structural components.
This is particularly the case for the manufacture of lightweight struts and shafts in aerospace applications, and more recently also in high-end automotive applications.
The design, manufacture and optimisation of hybrid joints with structured metal surfaces has become the focus of much research in recent years. This is mainly attributed to the rapid development of advanced metal manufacturing techniques such as cold metal transfer, electron beam machining, laser beam welding, and more recently additive layer manufacture ALM , in particular selective laser sintering of metal powders.
They found that macro-scale surface features e. These same authors later characterised the pull-out performance of metal-composite joints with SLM surfaces considering various pin geometries and offset angles [ 10 , 11 ]. Compared to other techniques, ALM offers the greatest freedom of design and homogeneity of material properties, at the expense of high manufacturing costs and some level of porosity in the final product.
The rough surface finish obtained from powder-based ALM—which in most applications is unwanted and requires post-processing steps—is advantageous in the case of hybrid joints as it increases the total surface area of the interface, which in turn improves adhesion [ 12 , 13 ]. The references discussed here so far focused on the characterisation of planar joints. Few studies have investigated cylindrical hybrid joints produced via braiding or winding processes.
Braiding is a mature technique particularly suitable for the manufacture of high-performance rope-like fibre preforms 2D braiding or thick-walled preforms 3D braiding at relatively high production rates. These high rates are possible because large numbers of fibre yarns can be deposited simultaneously, as opposed to the few yarns deposited at once in alternative techniques e.
In standard 2D braiding, yarns are drawn from bobbins attached to carriers which rotate around a stationary circular frame; equal numbers of bobbins rotate in opposite directions, causing yarns to interlace into a braid pattern.
Braiding over structured metal surfaces offers the possibility of incorporating advanced joining mechanisms at high production rates. These authors also compared mechanical properties obtained from different braid patterns and manufacturing processes.
It was shown that the design of such parts requires not only consideration of different materials and braiding configurations, but also the geometry and positioning of surface features with respect to fibre yarns. Optimisation of hybrid braided joints is a very complex task, since it involves maximising the load transfer between metal and fibres while also satisfying several manufacturing constraints related to the braiding process.
Effective optimisation strategies will therefore require a deep understanding of the braiding process, since predicting and controlling the positioning of yarns over structured surfaces is key for both cost and performance. However, there currently are no modelling tools available to simulate the braiding process over complex structured mandrels accurately and efficiently.
The literature on braiding process modelling is limited; yet previous work can be broadly categorised into two types: geometrical-kinematic models, and those based on Finite Element FE analysis. In their work, yarns were assumed perfectly straight and free from interactions with other yarns, so that individual yarns could be analysed independently. Equations for idealised fibre paths at different stages within in the convergent zone were discretised and solved numerically. This approach was later applied to the optimisation of the braiding process [ 19 ].
Braiding simulations based on FE analysis offer several advantages over geometric-kinematic models, including consideration of complex geometries and nonlinear interactions between yarns. In this way, all factors influencing braid quality, such as friction between yarns, sliding contact against the guide ring, and frictional contact against the mandrel are considered as individual variables [ 20 , 21 , 22 ].
The studies however used single chains of beam or bar elements to represent each yarn, and were limited to smooth i. It should be noted that some complex phenomena observed in reality, such as yarn cross-sectional deformation and yarn splitting around surface protrusions, could not be fully captured. In addition, these analyses [ 20 , 21 , 22 ] appear to have been tailored to the manufacture of specific components, and as such would lack the versatility and scalability required for a more general use.
For example, yarns had to be modelled in their entire lengths from the very beginning of the analysis, with several thousands of beam elements stretching out radially away from the guide ring, as if attached to an immense braiding wheel. This may result in great computational cost as well as the possibility of introducing kinematic errors. The approaches proposed in the literature do not seem suitable for virtual braiding trials over structured mandrels.
Numerical modelling cannot be replaced by physical testing either, as it would have to consider an extremely large number of combinations between different braiding parameters and surface patterns.
A modelling framework capable of conducting virtual braiding trials on structured mandrels is therefore in high demand. Moreover, if the model can predict detailed material characteristics such as fibre paths and final yarn cross-sections, then numerical models can be built for the virtual testing of final part performance.
In this paper, a modelling framework is proposed and developed to simulate the process of braiding carbon fibres over structured mandrels, with enough accuracy and resolution to allow studies on the formation of common manufacturing defects, as well as being suitable for future analyses of final part performance. Although the optimisation of hybrid metal-composite joints is the overarching objective, this article focuses on understanding and modelling the braiding process itself, in particular for mandrels containing detailed surface features.
For this reason, the experimental work presented here was conducted using thermoplastic mandrels produced via ALM, instead of metallic ones, so that the modelling techniques could be verified and validated more easily and at a fraction of the cost.
As will be discussed later, all modelling techniques described here can be directly applied to metallic mandrels, as long as the correct geometry, material properties, and surface properties are available.
The structure of the article is as follows. All methods investigated here shared some common features, namely 1 all metal parts i. Different strategies were adopted when modelling yarn feed and cross-sectional deformation, as discussed next.
These components were 1 circumferential counter-rotating motion for weft and warp yarns, and 2 out-of-phase sinusoidal z -direction motion for interlacing. The mandrel was then driven along the z -axis at a constant take-up speed V. Penalty-based contact pairs were defined for yarn-yarn, yarn-ring and yarn-mandrel interactions. Contact penalty stiffnesses were adjusted to avoid excessive interpenetration.
In the absence of more accurate estimates, Coulomb friction coefficients for yarn-yarn and yarn-metal contacts were assumed to be 0. Future work will focus on characterising these coefficients more accurately, e. When employing the FSS method, all beam elements were given a circular cross-section, both for simplicity and consistency with previous work [ 21 , 22 ].
These entities allow for beam elements to be created on demand as the strand is pulled away from the source. New beam elements are created as and where necessary, which reduces simulation run time significantly. Two options have been tested when simulating overbraids.
The assembled beam section ABS approach consisted of converting single beam elements into bundles of beams which together represent a single yarn. The number of beams to be added was defined by the user, and a good balance between geometrical accuracy and computational cost had to be found, leading to the baseline number of 12 beams per bundle. This is obviously far less than the number of fibres in real yarns, so each beam still represents thousands of fibres.
Yarn cross-sections were represented by meshes of three-dimensional 8-node solid elements, as shown at the bottom-right corner of Fig. Typically 12 solid elements were used to represent a yearn cross-section, with element lengths along yarns equalling the original beam element length. As before, yarn cross-sections were assumed to be elliptical, with dimensions controlled by user-defined input parameters.
Likewise, a dynamic relaxation step could be added to produce more realistic braid geometries. Every new strand of beams added to the model increases computational cost in proportion to the number of yarns in the braid.
In order to minimise computational overhead, parametric studies were conducted by varying the number of strands per yarn. Although more strands resulted in more realistic deformed cross-sections, it was found that three strands per yarn enabled satisfactory predictions of manufacturing defects while still offering acceptable run times.
This observation further supports the use of three strands per yarn. An example of the IMS modelling approach is shown in Fig. Manufacturing defects captured by an IMS model; a yarn splitting, b splitting and twisting.
As discussed in Sect. Since the braiding process itself results in relatively small loads being applied to the mandrel, thermoplastic pinned sleeves produced by ALM were used in this work, since their wide availability and low cost meant that several braiding trials could be conducted quickly during the early stages of model development.
The use of thermoplastic inserts also facilitates characterisation via X-ray computed tomography CT , which will be useful when verifying internal layers in overbraids. Apart from the aluminium tube, all other components were fabricated via ALM.
The end cap also contained small pins to facilitate initial alignment and to prevent slippage during the initial stages of braiding.
Single and multiple overbraid trials were conducted. Dimensions of pinned sleeves; a pin height h and pin width a , b baseline sleeve with 54 pins, and c high pin density sleeve with pins. The performance of hybrid joints is believed to be strongly influenced by the shape of surface protrusions, as well as their areal density and spatial arrangement. Higher protrusion densities are expected to promote a more direct load transfer between metal and fibres, as well as greater reinforcement in the through-thickness direction.
However, protrusion geometry and arrangement also influence the braiding process, especially the formation of manufacturing defects e. Their setup, shown in Fig. The different modelling strategies discussed in previous sections were first verified against experiments using mandrel assemblies similar to that shown in Fig.
Braiding convergence zone as seen from viewpoint 1; a experiment, b IMS model both figures share the same scale.
Braiding convergence zone as seen from viewpoint 2; a experiment, b IMS model both figures share the same scale. Again, very good qualitative agreement is obtained, with a more regular interlacing pattern being predicted by the FE model in comparison to real observations, which may be again attributed to local variations in yarn geometry and frictional properties. Quality of braid over pinned mandrels; a low pin density and b high pin density.
Fibre paths predicted by the IMS model; a low pin density and b high pin density. The IMS model provided good qualitative agreement with experimental observations; full quantitative agreement can only be checked once parameters such as coefficients of friction have been fully identified. When the baseline friction coefficient of 0. This suggests that the surface roughness created by ALM processes contributes to the occurrence of bridging defects, and that artificially high friction coefficients may be required in FE models to compensate for their perfectly smooth surfaces.
Local braid angle, as predicted by the IMS model, for a unpinned sleeve, b pin sleeve and c pin sleeve. In order to gauge the accuracy of the model when predicting the occurrence of braiding defects, the number of pin-led imperfections was counted over each braided sleeve, in experiments and models.
Bally Ribbon Mills provides production, manufacturing, dyeing and finishing in-house. In this […]. Cut your research time in half by downloading our Webbing Guide. Inside, we highlight topics such as:. Equipment and Materials. Shuttle loom A shuttle containing the filling yarn passes through the shed opening of warp yarns to produce the desired weave.
EP0528336A2 - Braided shaped filamentary structures and method of making - Google Patents
A surgical suture is used to close the edges of a wound or incision and to repair damaged tissue. There are many kinds of sutures, with different properties suitable for various uses. Sutures can be divided into two main groups: absorbable and non-absorbable. An absorbable suture decomposes in the body.
Papers / Articles
Production Engineering. Braiding is an attractive manufacturing method for tubular elements such as hollow shafts and struts. One of the main challenges however is the integration of suitably performing end-fittings. This requires the introduction of protrusions onto the surface of the end-fitting to promote mechanical interlocking with the fibres. However, the lack of accurate modelling tools for the simulation of this manufacturing process means that much empiricism is currently used in the design of such structures. A novel numerical framework is presented here for the full-scale simulation of the braiding process over structured end-fittings.SEE VIDEO BY TOPIC: 7 Tips to Start Small Scale Manufacturing - Business Ideas for Product Makers
Handbook of Advances in Braided Composite Materials: Theory, Production, Testing and Applications focuses on the fundamentals of these materials and their associated technology. It provides a one-stop resource that outlines all the significant issues about structural braiding, providing readers with the means by which to produce, test, and design braided composite material structures. It documents the latest research findings into these advanced materials and provides new ideas to encourage greater use of the technology. Jason P. His composite material-based research has led to numerous critical findings translated in over 30 peer-reviewed high impact, top-ranked journal and conference papers. His research team focus on understanding the fundamental behaviour of braided composite materials for biomedical to structural applications. Woodhead Publishing ,
3D braided fabrics
Braiding , in textiles, machine or hand method of interlacing three or more yarns or bias-cut cloth strips in such a way that they cross one another and are laid together in diagonal formation, forming a narrow strip of flat or tubular fabric. The word plaiting is generally applied when such materials as rope or straw are employed. Braids are frequently used as trimming or binding. Flat braid may be used to produce a decorative border effect on garments or home furnishings or may be folded over raw fabric edges as a finishing method.
Two dimensional 2D woven, braided, knitted and nonwoven fabrics have been used for the fabrication of soft and rigid structural composite parts in various industrial areas. However, composite structure from biaxial layered fabrics is subject to delamination between layers due to the lack of through-the-thickness fibers. It also suffers from crimp which reduces the mechanical properties. Triaxial fabrics have an open structure and low fiber volume fraction. However, in-plane properties of triaxial fabrics are more homogeneous due to bias yarns. A 3D woven fabric has multiple layers and is free of delamination due to the z-fibers. However, 3D woven fabric has low in-plane properties. Three dimensional braided fabrics have multiple layers and they are without delamination due to intertwine type out-of-plane interlacement. However, they have low transverse properties.
Braiding & narrow width fabrics
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A braiding machine is a device that interlaces three or more strands of yarn or wire to create a variety of materials, including rope , reinforced hose , covered power cords , and some types of lace. In a horn gear braider, bobbins of thread pass one another to the left and right on pseudo-sinusoidal tracks. The bobbins are mounted on spool carriers that are driven by a series of horn gears. A horn gear is a notched disk driven by a spur gear below on the same shaft; bobbins are transferred between notches of adjacent gears. These gears lie below the track plate that the bobbin carriers ride on. The gears must be driven at multiple points on machines that use two or more bobbin sets and cross-shafts. On a vertically oriented machine, the braided thread is taken up above the machine. The height and diameter of a guide ring affects the characteristics of the braided product. On horizontal machines, the braiding track plate and associated bobbins are rotated 90 degrees and the braided product is produced parallel to the ground.
George C. Sih , Alberto Carpinteri , G. The last decade has seen a significant growth in the processing and fabrication of advanced composite materials.
He studied for his PhD at the University of Glasgow from —, prior to gaining a research assistant post until December Malcolm has diverse research interests, with activities spanning space and aerospace technology, including mission and system design, astrodynamics, and swarm and disaggregated system engineering. He also has interests in technology foresight, horizon scanning and roadmapping, and is a fellow of the Royal Aeronautical Society. His mainstream scientific contributions consist of about papers and several books related to statistical physics, thermodynamics, the physics of semiconductors, the various aspects of terrestrial and space solar energy applications and other energy-related issues.
Three-dimensional braiding is among the oldest and most important of textile processes, transforming small natural fibers into more functional forms. Fabrics used in 3D braiding, such as rope , have been used since 4, BC.
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