Axial Yarns Research Articles

Multiscale homogenization of thermo-mechanical viscoelastic response of 3D orthogonal composites with time-dependent CTEs

Viscoelastic behavior of the matrix affects the thermomechanical response of polymer composites. This study investigated the structural effects of the time-dependent thermal expansion response of 3D orthogonal woven composite (3DOWC) by combining experiments and finite element modeling (FEM), incorporating the viscoelasticity of its constituents. The deformation characteristics at three orthogonal cross-sections, in the presence of structure-related strain fields at various temperatures, were investigated using digital image correlation method. Findings reveal heterogeneity and localization of the thermal strain, characterized by periodic stripes with alternating high strain regions on the resin and low strain regions on the yarn. This localization intensifies at higher temperatures, but diminishes with increased distance from the interface. Furthermore, the composites exhibit time-dependent thermal expansion behavior derived from the time-independent thermal expansion of its constituents, which cannot be captured in classic elastic material model. FEM reveals that thermal stresses are concentrated at the interfaces between constituents with significant differences in their coefficients of thermal expansion (CTE), particularly at the interface between the resins and axial yarns. The maximum thermal stress occurs in the binder yarns over the considered temperature range due to their low volume content, which should be considered in practical applications.

Exploring in-plane shear characteristics of multilayer biaxial weft knitted fabrics through a micro-scale virtual fiber modeling

The multilayer biaxial weft knitted (MBWK) fabrics and their composites have been widely applied in fields of complex structural products due to their flexible curved deformability. The existence of stitch in MBWK complicates the deformation behavior under the in-plane shear loading. However, it has not been well explored and understood. In this study, a numerical micro-scale virtual fiber modeling was built to investigate the in-plane shear performance of MBWK by considering the micro geometric features and fiber property that are difficult to be characterized solely by experiment. The strain conditions of the stitch that determine the fabric shear behavior are discussed. The deformation behavior leads to local deformation and morphological locking of the stitch. In the early stage of the shearing, the deformability of stitch provides enough space to accommodate the rearrangement of axial yarns. In the shear locking stage, the restriction of stitch and compression within axial yarns at high shear angles restricts the axial yarns from movement in the loading direction. When the theoretical shear angle is 20°, the shear angle located in different shear regions varies. The maximum shear angle near the loading area is 19.1°, while the minimum shear angle near the fixed area is approximately 17°. The results illustrate the deformation mechanism of MBWK under in-plane shearing and provide an excellent guidance for the design of large deformation fabrics, especially for curved surfaces, thus realize the effective utilization of fabrics in engineering applications.

Shape memory behaviors of three-dimensional five-directional braided composites with different axial yarns arrangements

The effect of braided structure on shape memory behaviors of 3D braided composites is critical to design the responses of the composite under external fields. Here we report the effect of axial yarn on shape memory behaviors of three-dimensional five-directional (3D5d) braided shape memory polymer composites (SMPCs) under bending. It was found that the axial yarns will improve bending stiffness and electro-thermal behaviors significantly. The thermomechanical deformation and shape memory effect of SMPCs are influenced by the braiding structural parameters. Specifically, the 3D5d SMPCs exhibits a 53.6% increase in bending recovery force and a faster shape recovery speed than those of 3D four-directional SMPCs. We found from finite element analyses (FEA) that the axial yarns positions influence the inner stress distribution and shape memory behaviors of SMPCs. The axial yarns distributed on both sides of SMPC influence the shape memory behaviors more than those of the middle layer.

Enhancing damage resistance in tubular triaxial hybrid braided composites: Innovative production and tensile modulus prediction with damage analysis

AbstractBraided composite structures, characterized by their inherent brittleness, necessitate precise damage prediction and prevention to ensure structural integrity/reliability. This study introduces an innovative method for enhancing damage resistance in tubular triaxial hybrid braided composites. These composites employ Epoxy resin as the matrix, with polyester serving as the bias yarn, and glass and basalt as the axial yarns, woven at varying braiding angles. Tensile tests reveal a compelling trend: a reduction in the braiding angle correlates with an increase in the failure load, indicative of quasi‐ductile behavior. A model is also derived for predicting tensile elastic modulus, which demonstrates a strong correlation with experimental results. Furthermore, finite element simulations are utilized to analyze damage within the triaxial hybrid braided composite specimens, providing empirical confirmation of progressive damage occurrence. This research offers a promising avenue for designing/manufacturing advanced composite materials with superior damage‐resistance holding immense potential across a spectrum of engineering applications.Highlights The tubular triaxial hybrid braided composites were produced by Epoxy resin as the matrix, with polyester as the bias yarn, and glass and basalt as the axial yarns at different braiding angles. An innovative method was introduced for enhancing damage resistance in tubular triaxial hybrid braided composites. The effect of operating parameters (braiding angle, type of bias yarns, production method) was investigated. Was tried to predict tensile modulus values in tubular triaxial hybrid braided composites by finite element simulation and developed equations. Finite element simulation exhibited excellent performance in the prediction of tensile behavior of structures manufactured by the innovative method.

Compressive behavior of triaxially braided metal-CFRP hybrid lattice structures

Cellular approaches facilitate the flexible design of materials with desirable properties that may be manufactured from single polymers, metals, and, recently, fiber-reinforced composites. This paper describes cellular materials with metal and carbon fiber-reinforced plastic (CFRP) struts. Composite lattice tubular structures were automatically braided, and the effects of axial CFRP yarns on the compressive behaviors of braided lattices were studied. Metal wire-reinforced plastic and metal rods served as axial yarns when preparing hybrid triaxially braided metal-CFRP lattices. The effects of the axial yarns in polyurethane (PU) foam-filled samples were also assessed. Ten braided structures were manufactured, and their compressive behavior and energy absorption were evaluated by axial compression tests. Finite element (FE) simulations were used to investigate deformation, buckling, and damage. Addition of axial CFRP yarns improved the compressive properties; the specific absorbed energy (SAE) increased by 16%. Hybridization further enhanced the SAE by 62%.

Transition from folding to splaying failure of braided composite tubes subjected to axial compression hybridized by bi-axial and tri-axial laminate

The failure mode is a dominant factor of mechanical performance of braided composite tube subjected to axial compression. The failure mode was modified by tailoring stack-up sequence of composite tubes hybridized by bi/tri-axial braided laminate. The thermal photographing and micro-CT scanning methods were employed to monitor the in-situ damage progression and post-mortem specimen, respectively. The results show that the delamination was easy to be induced at the interface nearby tri-axial braided laminate. It attributes to the combination between the crack caused by local buckling of the axial yarns and the crack caused by shear deformation of braiding yarns. By the illumination of this behavior, delamination is controlled to occur at the different position along thickness direction of braided tube by adjusting the stacking sequence of braided laminates. When delamination position transfer from the inner/outer sides to the middle of tube wall, the failure mode transfer from the progressive folding to splaying, which increase the specific energy absorption by 45.77%.

Numerical Prediction of Three-Point Bending of Braided Composite Tubes With Axial Yarns

Numerical Prediction of Three-Point Bending of Braided Composite Tubes With Axial Yarns

X-ray microtomography analysis of the damage mechanisms in 3D circular braided carbon fiber/epoxy resin composite tubes under axial impact compression

The dynamic behavior of three-dimensional (3D) circular braided composite tubes with different braided parameters was experimentally investigated subjected to axial impact compression using a Split Hopkinson Pressure Bar (SHPB). The damage characterization of the post-impacted tubes was examined using scanning electron microscope (SEM) and X-ray micro-computed tomography (micro-CT). The influence of braided parameters and strain rate, including braided angle, the number of braided layer and axial yarn, on the dynamic mechanical properties, progressive crush characteristics and failure mechanism of 3D braided composite tubes was analyzed in detail. It was found that the smaller braided angle and the larger numbers of braided layers contributed to better axial dynamic properties. The compressive strength, stiffness and specific energy absorption (SEA) of 3D five direction (3D5D) tubes with axial yarn were larger than those of 3D four direction (3D4D) tubes without axial yarn. Meanwhile, the dynamic mechanical response and damage patterns of braided tubes exhibited significant strain rate effects. The impact compression failure mechanisms of braided tubes were mainly fiber tows crushing, fiber breakage, fiber buckling, shear fracture, resin cracking, interfacial cracks, fiber-matrix debonding, etc.

Prediction of effective mechanical properties of 2D triaxially braided composites using a geometrical model incorporating flat portions of composite yarns

This study aims to predict the effective mechanical properties (EMPs) of a 2-D triaxially braided composite (TBC) using an analytical model and to investigate the effects of various geometric parameters on them. The 2-D TBC, a type of braided textile composite, consists of an axial yarn and two braider yarns that are oriented in different diagonal directions within a plane, alternating between running below and above each other. A geometrical model is built considering the flat portion of the composite yarn to adjust the fiber volume fraction of the 2-D TBC while keeping other parameters constant. The prediction method is verified by comparing it with experimental and predicted results reported in various references, demonstrating good agreement. A parametric study indicates that geometric parameters affect the undulation path of a braider yarn and the volume content or each composite yarn, resulting in significant impacts on EMPs. The proposed prediction method is competitive in terms of computing time compared to finite element-based methods and can contribute to the design and improvement of composite structures.

Thermo-mechanical behavior of 3D multi-directional braided composites based on a two-scale method

Two-scale modeling is adopted to investigate the thermo-mechanical behavior of 3D four-directional (3D4D), 3D five-directional (3D5D), and 3D full five-directional (3DF5D) braided composites. Based on the stress-strain relationship considering thermal expansion and the periodic boundary conditions, the elastic constants and the coefficients of thermal expansion (CTE) of the three types of braided composites are predicted by a two-scale homogenization method. The micro stress under free expansion and thermo-mechanical coupling is also simulated. The calculated results are in good agreement with experimental results from relevant references. The numerical results show that the longitudinal elastic and thermal expansion properties are gradually improved with the increase of axial yarn content from 3D4D to 3D5D and then to 3DF5D braided composites. The braiding angle corresponding to the zero longitudinal CTE of each braided structure is basically about 40°. Furthermore, with the increase of temperature, the longitudinal micro-stress in yarns increases gradually, but that in matrix drops. These conclusions will provide a reliable basis for the structural optimization design and safety evaluation of 3D multi-directional braided composites in a thermal environment.

Impact and post-impact flexural property of 3D five-directional braided carbon/glass hybrid epoxy composites

The impact property and residual flexural property of three-dimensional (3D) five-directional braided carbon/glass hybrid epoxy composites were studied. Four kinds of arrangement for carbon fiber and glass fiber in the axial yarn were designed. Taking pure carbon fiber composites (C/Ca) as the control, the rest of arrangements were that glass fiber and carbon fiber alternately arranged at the width direction (C/G1), glass fiber and carbon fiber alternately arranged at the thickness direction (C/G2), and only glass fiber appeared at the axial yarn (C/G3). Results showed that the C/G2 composite has higher impact energy absorption capacity, and the C/G1 composite has higher impact stress. The flexural properties of C/Ca composite are the best and that of C/G3 composite are the worst before impacting. This study is helpful for the structural design of composites in specific occasions.

Silk Fibroin/Silk Braiding Fabric Composite Grafts via Layer-by-Layer Self-Assembly: Water Permeability and Cytocompatibility

ABSTRACT Stent grafts play an important role in sealing vessel perforations, ruptures or aneurysms for remodeling vascular access, but maintaining long-term patency remains a major challenge after implantation. Silk fibroin (SF) is an ideal vascular graft material with excellent biocompatibility and physicochemical properties. In this study, we developed a series of composite grafts consisting of regenerated SF (RSF) and silk fabric, prepared using braiding technology and layer-by-layer (LBL) self-assembly, and investigated morphology, water permeability and cytotoxicity. The results showed that silk fabrics were covered effectively and tightly by RSF films, and the anti-water permeability of grafts was closely related to fabric structural parameters and self-assembly layers, in which the braiding angle of 90° and number of axial yarns above 60 threads/10 cm obtained very low water leakage. In particular, the graft prepared by 1 × 2 silk yarn had a thinner and more uniform thickness (70–80 μm), and showed lower water permeability (8.8 mL/min·cm2). Tests on L929 fibroblast cells showed that grafts had no significant cytotoxicity, and unreacted substances could be removed by LBL rinsing. These composite grafts may be promising biomaterials for the repair and regeneration of vascular access.

An experimentally validated model for predicting the tensile modulus of tubular biaxial and triaxial hybrid braids

AbstractBraiding is a versatile and cost‐effective approach to generating various composite structures for mechanical, sports, and biomedical engineering applications, which are different from each other. For example, a stent is a braided structure and blood penetration in it is essential as much as the right function. Predicting the tensile responses is a prerequisite for the success of implementation of braided structures, and it is usually performed via destructive mechanical testing that might be costly and/or time‐consuming. Therefore, it is essential to provide a model that can accurately predict the tensile modulus. In this research, a theoretical model is developed using the simplification of a braided structure and is validated via testing of biaxial and triaxial braids composed of polyester, glass, and basalt yarns on a 16‐carrier vertical braiding machine. Experimental results not only are used for the model validation but also show the effectiveness of axial yarn presence, hybridization, and the presence of high‐performance yarn in the braided structures on the tensile properties. A good correlation between theoretical values and experimental results is observed approving the high accuracy of the proposed model. This paper is likely to fill a gap in the state of the art and provide pertinent results that are instrumental in the design of hybrid‐braided structures with minimum computational/experimental effort. The research innovation centers on the use of two different yarns to make hybridization, simplicity of the model to be used for biaxial and triaxial braided structures, and a start to omit destructive tests.

Effect of axial yarn distribution on the progressive damage behavior of braided composite tube subjected to three-point bending

The effect of axial yarns on progressive bending damage of braided composite tubes is studied in this paper. Four specimens with different number and distribution of axial yarns were experimentally tested by quasi-static three-point bending. At the same time, infrared thermography was used to observe the damage in-situ. Combined with the cross-section morphology of Ultra-Depth 3D Microscope, the damage evolution and distribution characteristics of braided tubes were identified. It is found that axial yarns enhance the mechanical properties of braided composite tube. The detected changes of infrared maximum temperature have a good correlation with the damage initiation and failure mechanism of the specimen. The abrupt changes of the maximum temperature indicate the occurrence of local fiber breakage, especially the axial yarn breakage. If there are axial yarns on the compression side of the tube, the maximum temperature increases by 0.5 °C in the linear elastic stage, and two initial damages of debonding and fiber breakage will occur. The debonding started at the interface of the axial yarn. The axial yarns increased fiber crimp, resulting in obvious wavy delamination between layers of the specimen, and the axial damage range was expanded. In addition, the mixed structure with axial yarns only on the compression side can inhibit the damage from spreading down the braided tube wall.

Impact compression damages of 3D braided composites with/without axial yarns after thermo-oxidative ageing

Ageing conditions and braided structures will affect dynamic damage and failure mechanisms of 3D braided composites. Here we report the influence of thermo-oxidative ageing on impact compression behaviors of 3D braided composite with and without axial yarns, i.e., four directional (3D4d) and five directional (3D5d) braided composites. We found a significant difference in mechanical properties between epoxy resins and composites after ageing. The impact compressive strength of epoxy resins declined rapidly and then slowly, while the composites decreased continuously, with the increase of ageing days. The interfacial debonding is main degradation mechanism for both braided composites at the later ageing stage. Thermo-oxidative ageing accelerates the inner damage evolution which propagates from surface cracks. Compared with 3D4d braided composites, the 3D5d braided structure has higher strength retaining level after ageing. In addition, the 3D5d braided samples have higher resistance to impact deformation and lower crack propagation. Finite element analysis (FEA) results revealed that 3D5d composites showed higher load carrying capacity and less damages than 3D4d composites.

Distribution of axial yarns on the localized deformation and damage mechanism of triaxial braided composite tubes

Localized deformation and damage mechanism of triaxial braided composite tubes, with different quantities and positions of axial yarns, were experimentally studied under transverse low-velocity impact. A high-speed infrared thermography was applied to analyze the transient thermo-mechanical failure process and afterwards verified by the external and internal damage characterization. It is found that the distribution of axial yarns has a significant effect on the mechanical behavior of braided composite tubes. The bending stiffness and peak force of the tubes were enhanced with the increased quantity of axial yarns, while the impact lasting time and displacement presented an opposite trend. And the more axial yarns assembled at the impact side, the greater force oscillatory of the tubes under low-velocity impact, accompanied by the decreased heat generation in small-angle braided tubes and the alleviated fiber tows fracture, delamination and in-plane shear cracks inside the wall of large-angle braided tubes. On the premise of the same quantity of axial yarns, the position effect plays a key role. Axial yarns concentrated at the impact side could restrain the damages spreading to the non-impact side by changing the damage mode of large-angle braided tubes. If a larger force is needed at the early stage, axial yarns could be inserted at the local position most probably to be impacted; Otherwise, it is highly suggested to braid at least one axial yarn in each layer at the impact side and non-impact side respectively to reinforce localized strength and prevent the impact-side indentation and non-impact-side delamination.

An experimental investigation into flexural properties of hybrid carbon-basalt triaxially braided composite lamina

Here, an investigation was conducted to evaluate the effect of intralayer hybridization with basalt fibers on the flexural moduli of triaxially braided carbon/epoxy composite lamina (3AXB). Four 3AXB preforms were produced using a circular braiding machine and were fabricated into a composite lamina via vacuum bag assisted resin transfer technique using epoxy resin. Then, three-point bending tests were performed on the prepared four specimens according to ASTM D790 with a large span-to-depth ratio in both longitudinal and transverse directions to determine their flexural moduli. Test results showed that hybrid 3AXB composites with carbon fibers as axial yarns and basalt fibers as braid yarns showed similar flexural performance in longitudinal direction in comparison to all-carbon 3AXB composite. Similarly, hybrid 3AXB composites with basalt fibers as axial yarns and carbon fibers as braid yarns showed similar flexural performance in transverse direction in comparison to all-carbon 3AXB composite. These indicate that, under specific circumstances, there is a possibility to reduce the overall cost of all-carbon 3AXB composite without compromising its flexural performance. Besides, a multi-scale finite element model was performed to predict the flexural stiffness of 3AXB composites.

Study on in-plane compression properties and numerical modeling of three dimensional five-directional braided composites

Delamination phenomenon often occurs on traditional laminated composites while 3D five-directional braided composites (3D5dBC) could avoid this defect in practical application. In this work, the mechanical properties and failure mechanisms of 3D5dBC with different braiding angles are investigated at room temperature under transversal and longitudinal compression via experiments and finite element analysis (FEA) simultaneously. Meanwhile, the compression properties at elevated temperature are also researched. It is found that mechanical properties of composites under longitudinal compression are superior to those under transversal compression. Composite with small braiding angle possesses higher strength and modulus comparing to those of large braiding composite. Moreover, at room temperature, 3D5dBC exhibits 45º shear crack failure mode under transversal compression originated from matrix cracking, fiber failure along Z-direction obtained from FEA, and interfacial debonding; Under longitudinal compression, the structure shows shear expansion failure feature due to thorough fracture of axial yarns along L-direction, braiding yarns fracture along L-, T- and Z-direction, and matrix cracks obtained from FEA. With temperature increasing, interfacial debonding of fiber/matrix gets obvious. The microscopic failure modes and process at room temperature are well explained by FEA method.

Numerical analysis of crimping behaviour of triaxial braided structures

The mechanical properties of tubular braided structures influence their inherent performance during application as biomedical materials. In their use as stents, braided structures are forced to conform to the topology of the host tissues. Triaxial braided structures have had limited use in tissue repair and organ support even though they have the potential of offering equal if not better performance compared to bi-axial braided structures. A study of the mechanical dynamics of tri-axial braids would be crucial in the potential design of customised structures for advanced tissue repair and organ support. This study therefore uses Finite Element Methods (FEM) to design and develop triaxial braided structures and investigate their crimping behaviour using parametric modeling and numerical analysis in their potential application as biomedical materials. The results in this study portrayed that the presence of axial yarns in tubular braided structure offers improved performance in terms of stability of the structure.

Parametric characteristics analysis of three cells in 3D and five-directional annular braided composites.

On the basis of analyzing the movement law of 3D circular braided yarn, the three-cell model of 3D five-direction circular braiding composite material is established. By analyzing the node position relationship in various cell models, the calculation formulas of braiding angle, cell volume, fiber volume and fiber volume content in various cell models are obtained. It is found that there are four different braiding angles in four internal cells, and the braiding angles in internal cells gradually increase from inside to outside. The braiding angles of upper and lower surface cells are approximately equal. With the increase of the length of the knuckles, the braiding angles of each cell decrease, and the braiding angles of the four inner cells decrease greatly, while the braiding angles of upper and lower surfaces decrease slightly. The results of parametric analysis showed that with the increase of the length of the knuckles and the inner diameter of cells, the mass of cells increased proportionally, while the total fiber volume content of cells decreased. With the increase of braiding yarn number and axial yarn number, the unit cell mass decreases in direct proportion, and the unit cell total fiber volume content increases. Through the research results of this paper, the geometrical characteristics of the cell model under different braided parameters can be obtained, which greatly improves the analysis efficiency.