Circular braiding take-up speed generation using inverse kinematics

Circular overbraiding of composite preforms on complex mandrels currently lacks automatic generation of machine control data. To solve this limitation, an inverse kinematics-based procedure was designed and implemented for circular braiding machines with optional guide rings, resulting in a take-up speed profile for a given braid angle distribution on mandrels with complex 3D shapes including non-axisymmetric, optionally eccentric cross-sections that can vary in shape and size along an optionally curved mandrel centerline, allowing a curved machine movement. This procedure reduces the problem size, resulting in a short computation time, fit for CAE process chain integration. Numerical control data was generated for a complex mandrel with a specified braid angle and a triaxial braid. A simulation using this control data yields a braid angle that deviates a few degrees from the specified braid angle. The simulation was validated experimentally, using the generated instructions to control the braiding machine. This showed a deviation from the simulated braid angle of 3 degrees in the centered, non-tapered mandrel regions, up to 10 degrees in tapered regions and an experimental scatter of 7 degrees. The deviation is mainly attributed to the neglect of yarn interaction and guide ring contact friction in the model, leading to an incorrectly modeled convergence zone length.     

塑编袋工艺参数的优选

本文采用方差分析原理，优选了生产塑料编袋的工艺参数，同时改变其原料配比，使塑编袋重量在确保产品质量的产提下有了明显降低，大幅度降低了生产成本。     

Split Hopkinson pressure bar testing of 3D woven composites

Results from a series of split Hopkinson pressure bar (SHPB) tests on 3D woven tetxile composites (3DWC) are presented. These tests were done to determine the rate dependent compression response of 3DWC. Three different configurations of the 3DWC, corresponding to compression response in the plane of the material and through-the-thickness direction (out-of-plane) were studied. The rate dependent responses were compared against quasi-static test results and it was found that 3DWC showed an increase in strength in all three directions studied, however, accompanied by a transition in the failure mechanism. The in-plane orientations showed the largest increase in (about 100%) strength at the elevated rates of loading. A follow-on paper provides finite element based results that correspond to the experimental results presented here.     

汉晋双层斜编织物的编织工艺研究

以新疆营盘出土的方格动物纹斜编组带为编织实验对象,在结构分析的基础上,结合实际的模拟编织,探索汉晋时期双层斜编织物的编织工艺特点。     

Unit yarn-reduction technique and flexural properties of tapered composites based on four-step row and column braiding

Mechanisms of unit yarn-reduction braiding were investigated and preform microstructures were characterized by digital image photography and topological analysis. Flexural properties and failure mechanisms of the unit yarn-reduction composites, cut composites and uniform composites were compared. Results indicated that continuity of the braiding process must be ensured after yarn reduction and distribution of the reduction units should be uniform. A smoothly trapezoidal profile appeared near the unit yarn-reduction cross-section and braiding angles and yarn lengths in the surface or interior yarn-reduction control volumes all increased. Flexural properties of the unit yarn-reduction composites were significantly higher than those of the cut composites and slightly lower than the uniform composites. The damage process of the yarn-reduction composites can be divided into the initial, developing and serious damage stages with yarn breakage being the dominant failure mechanism, while the primary failure mechanisms of the cut composites were matrix microcracking and fiber pulling-out.     

一种新型六角形编织机器的构建与应用

文章首先简单地回顾了传统编织技术,然后阐述新型的六角形编织基本原理,并从编织运动实现原理以及编织控制方面详细讲述基于Labview计算机控制的六角形编织机器的构建方法.最后,通过举例方式展示这种六角形编织的初步应用.可以看出,这种新颖的六角形编织机器的开发,对未来利用精细化微观编织产品的新兴领域来说具有重大意义.     

CRTM(在线编织-拉挤成型)薄壁纤维增强环氧树脂管制造技术

提出一种不同于纤维缠绕、拉绕等现有方法的连续RTM法在线编织成纤维管，旋即在模内浸渍树脂，经拉挤成型薄壁环氧玻璃钢管的工艺方法。     

Sensing of damage and healing in three-dimensional braided composites with vascular channels

With the rise of composite materials as replacements for traditional monolithic materials comes an increase in demand for multifunctionality. Prior studies have demonstrated the ability of an embedded, electrically percolating carbon nanotube network to respond electrically to the onset and progression of damage in composite structures. We build upon this work by incorporating healing functionality into braided composites through the use of a hollow channel resin delivery system. This study demonstrates the ability of a carbon nanotube network to sense crack filling during resin injection, thus providing the scientific basis required for sensing healing in advanced composites. With practical application in mind, a two-part healant system is employed in this study. Two methods for qualitatively assessing healing are employed and compared; these include elastic modulus/strain energy recovery and FTIR spectroscopy.     

Bending and optimisation of an inflated braided beam

Two braided inflatable beams have been made that differ in the number of axial fibres that are placed parallel to the length, and in the angle at which the bias fibres are placed. Each beam consists of a silicone rubber bladder, two end caps and a dry carbon fibre braid placed over the silicone bladder. Experimental and theoretical analysis of the beams have been revealed that due to bending, the beams initially deflect in a linear manner like the Euler–Bernoulli beam model predicts. Once the stress in the axial fibres becomes zero, wrinkling occurs resulting in a significant loss of bending stiffness. The two beams that were tested were optimised for minimum deflection at a constant volume of fibres. The stiffest design has the maximum possible amount of fibres in parallel to the beam.