Braid Angle Research Articles

Progressive damage simulation of 3D four-directional braided composites based on surface-interior unit-cells models

To accurately predict the longitudinal tensile mechanical properties of 3D four-directional braided composites, parameter modeling for surface and interior unit-cells mesoscopic solid models was implemented and the deviation of yarn spatial traces and squeeze deformation of yarn cross-section were considered in the surface unit-cell model. Voxel mesh was used to discrete models on which appropriate boundary conditions were imposed and damage models for each constituent of composites were added into a user-defined material subroutine (UMAT) in finite element analysis software ABAQUS. By simulation analysis of surface-interior unit-cells models for 3D four-directional carbon fiber/epoxy braided composites with 30° and 45° interior braiding angles respectively, using the volume-weighted average method, longitudinal tensile modulus and strength for braided composites specimens with different thicknesses were predicted. The progressive damage process of composites was studied by counting the number of integration points with the same damage modes. Results show that the longitudinal tensile mechanical properties predicted based on surface-interior unit-cells models for 3D four-directional braided composites agree well with experimental results, and damage analysis results reflect reasonably progressive damage process of surface and interior unit-cells.

Damage and failure analyses of 3D4d braided composite shafts under torsional load and the effects of braid processing parameters on their torsional properties

AbstractThis paper presented the numerical and experimental studies on the torsional properties of 3D braided composite shafts. The torsion test was first conducted, then a parametric tubular unit cell model was constructed based on geometric mapping relations to detail the micro geometries of the shafts. The local yarn orientations were derived using finite deformation theory, and the 3d Hashin failure criterions were adopted to simulate the progressive damage behaviors of the shafts. The predicted results were in good agreements with the experimental ones, which validated the FE model. Based on the FE results, the damage was analyzed in detail, it was found that the transverse shear‐tension damage of longitudinally compressive yarns was critical for the failures of 3D4d braided composite shafts under torsional load. The surface damage initiated first, and then propagated into the internal structure, while the internal damage was much severe in the final failure morphology. The effects of braid processing parameters (M, N, γr, and r1,) on the torsional properties were also reported. A dependency of increasing then decreasing was confirmed by the simulation results for all four parameters, and it was found that the peak values could be achieved when the average braiding angle was around 45o.

Automated braiding of non-axisymmetric structures using an iterative inverse solution with angle control

Braiding reinforcing fibres into a shape using a mandrel is an efficient preforming method to produce composite products. Braiding consists of two yarn groups rotating and interlacing. Mechanical properties of the braided parts are related to the braiding angle, which is controlled by the take-off speed of the over-braided mandrel. This paper presents a novel approach to find the required speed profile to achieve the local targeted braiding angle. The proposed method computes the speed profile iteratively starting from an approximate model and correcting based on the results of the kinematic forward solution and feedback from actual angle measurements following actual braiding. Case studies have shown the validity of the approach for braiding on non-axisymmetric, curved, and variable cross-section mandrels. Implementation results have demonstrated that the proposed model lowers the error of the braid angle in every case, allowing the braid angle to be 1.0° off on average and even 0.7° off without outliers.

Two-scale damage failure analysis of 3D braided composites considering pore defects

Pore defects tend to form in the manufacturing process, and significantly influence the mechanical properties of 3D braided composites. To predict the failure modes and strength properties considering pore defects, a two-scale progressive damage method coupled with representative volume cell (RVC) has been developed due to the periodic feature across different scales of 3D braided composites. Different void generating methods across two scales are established, including the element-model by elements chosen and the void-model by voids explicitly constructed. The user-defined material subroutine (UMAT) is coupled in the nonlinear finite element analysis software ABAQUS to implement the damage model for micro and meso numerical models. Also, the Chamis model considering pore defects are employed and verified. It shows that results by void-model agree well with the Chamis model and the experimental data. And, the void-model is superior to the element-model when predicting the mechanical properties of braided composites. The pore defects weaken the matrix properties, and therefore largely determine the strength and damage mechanism of 3D braided composites with large braiding angle. This two-scale damage failure analysis method by void-model is effective to predict strength and damage failure mechanism of 3D braided composites considering pore defects.

A finite element investigation on design parameters of bare and polymer-covered self-expanding wire braided stents

Self-expanding covered braided stents are routinely used across a diverse range of clinical applications, but few computational studies have attempted to replicate their complex behaviour. In this study, a computational framework was developed to predict the functional performance of bare and covered self-expanding wire braided stents, with a systematic evaluation on the effect of various braid and cover parameters presented. Simulated radial force and kink deformation tests show good agreement to experimental data for covered braided stents across a range of braid angles and cover thicknesses. Our results demonstrate that braid angle is a key governing parameter that dictates the radial and kink performance of both bare-metal and covered wire braided stents. It was also demonstrated that addition of a polymeric cover to a wire braided stent causes a stiffer radial response across all braid angles, particularly when thicker and/or stiffer covering systems were considered. This study represents the first experimentally-validated computational model for covered wire braided stent systems and has excellent potential to be used in future design of these devices for a range of applications.

Study on the simulation of annular axis braiding process and braiding angles’ prediction method

A common braiding machine cannot perform continuous braiding using closed annular axis mandrels. To solve this problem, a modified vertical braiding machine was made to braid composite preforms with irregular cross-section mandrels. The finite element method was used to simulate the braiding process, and an efficient method was also derived to predict the braiding angles. The results show that the predicted braiding angles are basically consistent with the actual braiding angles, and the braiding angles at distinctive locations on the braided preform recorded differences of up to 10° or more than 30%. Braiding process simulation via the finite element method can thus effectively and vividly reflect the yarn path on the preform. As such, the braiding angles on the braided preforms can be realized through projection and surface flattening with much better accuracy. It also resolves the difficult problem often faced in measuring the braiding angles at the corner of the mandrel and provides a solid basis for continued research on the performance of its composite reinforcement.

Robot trajectory optimization control of braiding for three-dimensional complex preforms

The quality of composite preform has great influence on its mechanical properties. Aiming at the problems of difficulty in robot teaching and unstable braiding angle in the process of braiding three-dimensional complex component, a control method of robot is proposed. Firstly, the mandrel is discretized to ensure that the axis of each discrete mandrel is perpendicular to the braiding point plane, and the orientation and direction of the tool center are calculated. Then, the take-up speed of the robot is calculated, so that the self-adjustment of the braiding angle can be realized in the braiding process. The experimental results show that the control method can effectively reduce the braiding angle error of variable cross-section mandrel within 2°, and can improve the quality of composite products in actual production.

Investigations of defect effect on dynamic compressive failure of 3D circular braided composite tubes with numerical simulation method

This paper numerically investigated the effects of manufacturing defects and braiding angle on the impact compressive properties of three-dimensional (3D) carbon fiber/epoxy resin circular braided composite tubes. Based on the realistic geometrical architecture of 3D tubular braided preform, the full-size microstructural finite element analysis (FEA) models of the braided composite tubes with different braiding angles were established for the axial impact compression behavior at the split Hopkinson pressure bar apparatus. The manufacturing defects including fiber breakages and voids in the resin matrix were generated with Monte Carlo method in fiber tows and resin, respectively. The numerical results show the effects of defects in fiber tows and resin on the compressive strength, initial modulus, and failure strain of the braided composite tubes are both dependent on the braiding angle. The random defects have a negative influence on compressive failure mechanisms of the braided tubes. Comparing the failure morphologies of FEA models with experimental results, we found the non-ideal models containing random defects of appropriate content in fiber tows are more accurate than ideal models to simulate the dynamic compressive failure evolution process of 3D braided composite tubes.

Three-point flexural performance of tailor-braided thermoplastic composite beam structures

This work investigates the potential of improving the mechanical performance of braided composite beams through the introduction of local braid angle variations. Tubular braided beams with a 45°/60°/45° length-wise (axial) braid angle variation were manufactured and tested in quasi-static three-point flexure and their performance was compared with beams having a layer-wise (radial) [±60°/±45°/±45°] variation. Compared to beams having uniform braid angles, axial braid angle tailoring resulted in equivalent flexural performance with a 24% reduction in part weight. In contrast, tailoring in the radial direction did not yield any improvement in mass-specific performance. Deformation analysis of the beams using an extensometer and digital image correlation showed that an axial braid angle variation in each layer resulted in a comprehensive shift in deformation characteristics. Changing the braid angle in the outer layer across the whole beam showed partial change in deformation mode, but did not match the modification observed through axial variation.

Circular braided glass fiber/epoxy composites with helical architecture (coil spring) fabricated by plaster‐sacrificial compression molding for structural automotive applications

AbstractVarious approaches to reduce the weight of electronics and automobile devices have been explored. For instance, an alternative polymer was utilized to replace metals. In the present study, a new circular braided glass fiber/epoxy composite (braid angle: 45°, fiber: 48 vol%) with a helical structure was fabricated as a model coil spring for weight reduction. A plaster‐sacrificial compression mold was especially designed to fabricate helical composites without voids. The spring design was validated by the experimental results of torsional tests. Plastic deformations of the epoxy resin were measured using creep tests to eliminate high‐temperature plastic deformation (HTPD) of the composites. Pre‐strain applied thermal aging was utilized to remove HTPD. Mechanical properties of the composites were also investigated. The mechanism of mechanical failure was found to be the interfacial failure. For preparation of uncured prepreg, resin permeability was measured to a range of 10−10 m2. Resin transfer in the glass fiber‐braided textiles occurred due to the combination of viscous and diffusional flow mechanisms. Based on the results in this study, the facilely designed coil spring composite can be used for various applications, especially automotive parts.

Characterization of polypropylene (PP) and poly(ethylene terephthalate) (PET) multifilament braided textile structures for Achilles tendon partial substitution

When tendon injuries present a too large damage extension, the conventional treatment options do not result, so a new prosthetic device needs to be developed to partially replace a tendon. Therefore, in this study, different braided textile structures based on polypropylene (PP) and poly (ethylene terephthalate) (PET) multifilament yarns were developed, using a textile technology-based technique, in order to mimic the fibrous structure of tendons. Structures with different architectures were developed using different PP or PET yarns number and different braiding take-up rates, which consequently leads to different braid angles. The braids architecture influenced the porosity level, swelling profile, wicking ability and mostly their mechanical behavior. It was observed that the load at failure of the braids was mainly controlled by the number of yarns, but the strain level was mostly influenced by the take-up rate and consequently by the braid angle. Regarding the stiffness level, it results from a combination of the yarns number and braid angle. The structure based on 16 PET yarns, produced with the highest take-up rate, revealed a very promising creep and force-relaxation behavior for the final application, as well as a very interesting fatigue resistance.

On the behaviour of flattened tubular Bi-axial and Tri-axial braided composites in tension

The effect of braid angle and number of axial tow insertions on the behavior of flattened tubular braided composites (carbon fibre/epoxy resin) has been investigated. Two type of braids i.e. bi-axial and tri-axial (i.e. 6 and 12 inserted axial tows), for three braid angles (35°, 45° and 55°), have been studied. The stress–strain curve for the bi-axial braided composites is pseudo-ductile in nature, with a smooth transition into a plateau region at low strains, accompanied by necking of the composite. By contrast, the tri-axial braided composites show an initially high peak stress, related to the deformation and fracture of the axial tows, and subsequent plateau-like behaviour accompanied by neck formation, the extent of which appears to be determined by the strain-to-failure of the composite. For the bi-axial braids, an increase in braid angle produced decreased strength, axial modulus and specific energy absorption, but an increase in strain to failure. Inserted axial tows produced increased strengths and Young’s moduli, but a decrease in specific energy absorption (except for 55°) and strain to failure. In all cases, the braided composites outperformed the specific energy absorption of aluminium.

The effect of braid angle on the flexural performance of structural braided thermoplastic composite beams

Thermoplastic braided composite tubular beams were manufactured using commingled hybrid yarn with braid angles 30°, 45° and 60° and tested in static three-point flexure. Two principal deformation modes were observed during the flexural loading: global flexure and localised crush. The extent of each mode occurring in the three braid angle variants was measured using a linear deflectometer as well as 3D digital image correlation. Localised crushing was found to decrease significantly with increasing braided angle, accounting for 63%, 45% and 19% of the total applied deflection for the 30°, 45° and 60° beams respectively. Further, surface strain measurements obtained from 3D DIC showed increasing the braid angle led to a global flexure-dominated deformation. In addition, the stiffness and peak load increased with increasing braid angle. The observed differences in deformation modes were due to a combination of multiple braid angle-dependent properties of braided composites such as modulus, thickness etc.

Free vibration responses of 3D braided rotating cylindrical shells based on third-order shear deformation

3D braided composite has achieved attractiveness over the laminated composite due it some unique properties such as higher impact resistance, fatigue strength, stiffness in the thickness direction, anti-delamination capability, etc. In this study, the equivalent material properties of the composites are computed using bridging models base on a volume averaging method (VAM). Four steps 1 × 1 braided technique are introduced to manufacture the 3D braided rotating cylindrical shells panels. A third-order shear deformation (TSDT) with twelve degrees of freedom per node is used in the present eight nodded isoparametric 3D-finite element formulation (FEM). This theory has more capability compared to the other shell theories to predict the accurate results of the 3D braided shell. The generalized dynamic equilibrium equation of the present models is derived from Lagrange’s equation of motion. For moderate rotational speeds, the Coriolis effect is neglected. The correctness of the present finite element code is investigated by verifying with the existing results. The modals result of the rotating cylindrical shells (CYS) is computed at a different braided angle, braided volume fraction, aspect ratio, thickness ratio, curvature ratio, twist angle, blade setting angle, pre-cone angle, and rotational speeds, etc.

Effects of Micro-Braiding and Co-Wrapping Techniques on Characteristics of Flax/Polypropylene-Based Hybrid Yarn: A Comparative Study.

Micro-braiding and co-wrapping techniques have been developed over a few decades and have made important contributions to biocomposites development. In this present study, a set of flax/polypropylene (PP) micro-braided and co-wrapped yarns was developed by varying different PP parameters (PP braiding angles and PP wrapping turns, respectively) to get different flax/PP mass ratios. The effects on textile and mechanical characteristics were studied thoroughly at the yarn scale, both dry- and thermo-state tensile tests were carried out, and tensile properties were compared before and after the braiding process to study the braidabilities. It was observed that PP braiding angles of micro-braided yarn influenced the frictional damage on surface treatment agent of flax roving, the cohesive effect between PP filaments/flax roving, and the PP cover factor; PP wrapping turns of co-wrapped yarn had a strong impact on the flax roving damage and the PP coverage, which further influenced the characteristics. Micro-braided yarn and co-wrapped yarn with the same flax/PP mass ratio were compared to evaluate the two different hybrid yarn production techniques; it was proven that micro-braided yarn presented better performance.

An experimental study on the interaction between braiding structural parameters and their effects on ropes mechanical properties

Braided rope configuration and properties are the main key factors to consider on choosing it for various industrial applications. Rope's structure is characterized by high axial tensile strength combined with flexibility. The mechanical properties of ropes are greatly influenced by braiding process settings which have crucial effects on their functional performance. In this study, 27 types of braided polyester ropes were produced and divided into three groups according to their structural parameters and braiding settings, which include take-up and tension rates, yarn count, braid pattern, number of spindles and carriers' settings. The effects of changing these parameters on braid angle, repeat length, linear density, and mechanical properties such as tensile stress, strain and tensile modulus were investigated. Statistical analysis was conducted to evaluate the results using multiple regression analysis, F-test, surface and contour plots to illustrate the relation and the interaction between variables that have significant effects on the ropes' properties and to assess their performance. The results indicated that increasing the take-up rate leads to increase the ropes' braid angle. Whereas, increasing the tension leads to obtain ropes of low linear density with high stress and modulus. Ropes of lower strain were attained by increasing the take-up and decreasing the tension rates. Furthermore, the rope sample produced with pattern 2/2 using the high take-up and medium tension rate achieved the highest mechanical properties of high stress, modulus with low strain among all rope samples in the three groups.

Torsion damage mechanisms analysis of two-dimensional braided composite tubes with digital image correction and X-ray micro-computed tomography

This paper investigates the torsion progressive damage and failure mechanism of two-dimensional (2D) braided carbon/epoxy composite tubes. Four kind of samples with four braiding angles, 30°, 45°, 55°, and 60°, are experimentally tested on the static torsion machine. Three-dimensional digital image correlation (3D-DIC) is utilized to monitor the progressive torsional strain and the crack propagation. Also, Micro-computer tomography (Micro-CT) is employed to describe the volume of damages and the torsional damage morphologies inside the specimens. Results indicate that the braiding angle has a significant effect on the torsional mechanical behaviors. Furthermore, the damage modes of 30° and 60° specimens are mainly influenced by the accumulation of the matrix damage, whereas those of 45° and 50° ones are largely dominated by the fiber tows breakage.

Modeling and analysis of an electro-pneumatic braided muscle actuator

The present study deals with static modeling and analysis of a novel electro-pneumatic braided muscle (EPBM) actuator. The EPBM actuator is a hybrid McKibben-type actuator, made of a dielectric polymeric bladder enclosed in a braided mesh sleeve. A continuum mechanics-based electromechanical model is developed to predict the response of the actuator for a combined pressure and voltage loading. The model also incorporates braid-to-braid frictional effects. The model agrees well with existing experimental results for the special case of zero input voltage. Parametric studies are subsequently performed for varying braid angle, input pressure, and voltage. Finally, the model is utilized to study the impact of fiber-reinforcement in the bladder on the actuator performance.

Numerical investigation of mesoscopic volumetric ablation of 3D braided charring composites

Owing to the complex mesoscopic structures, 3D braided charring composites for the thermal protection system (TPS) have the multi-scale and multi-physical high-temperature responses. The mesoscopic features can significantly affect the volumetric ablative behavior of the braided composites, which will be essential for the TPS design. To take into account the effect of mesoscopic structures on the volume ablation response, the thermo-physical properties of constituents within the braided composites are predicted using asymptotic averaging method. The volumetric ablation model of the braided composites considering the mesoscopic structures is proposed, which is calculated by finite volume method with a tightly coupled solving process. The effect of braid angles on the volumetric ablation responses of the braided composites are investigated. The maximum back temperature and the peak inner pressure of the braided composites decrease with the increase of the braid angle. The isothermal and isobaric surfaces of the braided composites under volumetric ablation exhibit complex characteristics and are not perpendicular to the heating direction, which may induce the complex thermal stress field within the composites. The study on mesoscopic volume ablation may be helpful to accurately predicting the ablation responses and guiding the material design of the braided charring composites.

Experimental study on compressive fatigue behavior and failure mechanism of 3D five-directional braided composites

The purpose of this research is to study the fatigue behaviors of 3D five-directional braided composites with different braiding angles subjected to longitudinal and transversal compression loads. Compressive fatigue tests were conducted under cyclic stress ratio of R = 0.1 with frequency at f = 5 Hz to study fatigue characteristics by establishing cyclic creep curves, hysteresis loop curves, peak stress ratio curves. The results show that parameters of braiding angle, load direction and stress level affected the fatigue behaviors of braided composite. With evolution of hysteresis loops, permanent strain increased gradually and deformation resistance ability of composites decreased, damage was further increasingly accumulated, the stiffness degradation characteristics was observed. The failure modes and damage evolution were identified by analyzing the evolving damage processes. Generally, the damages got serious with cracks propagation, matrix cracking, fibers breakage, interface debonding between fibers and matrix, which finally resulted in the structure damage.