Effect Mechanism of Plain Woven Structure of Carbon Fiber on CFRP Cutting

Carbon fiber-reinforced plastic (CFRP) is increasingly employed as structural components for aircrafts in aerospace. The plain woven CFRP is more commonly used than the UD-CFRP. The machining-induced damages are easy to occur. The influence of the plain-woven structure on the cutting mechanism and the defects occurrence mechanism are seldom studied in detail. In this paper, the three-dimensional FEM model of plain woven CFRP is established. The occurrence and propagation of the delamination are investigated. The results indicate that the stress concentrations are easy to occur at the junction of warp and fill bundles near the cutting position. The plain-woven structure can block the transfer of stress and the crack propagation. When θ=90°, the damages of the fill fibers and the crack of the interface are easy to occur. When θ=45°, the step-like fracture is formed in both of the warp and the fill bundles, especially in the fill bundles. Under the same cutting conditions, the exit delamination of the plain-woven CFRP is obviously less than that of the UD-CFRP. The delamination greatly increases with the increase of the feed speed. The delamination decreases with the increase of the cutting speed. The delamination is closely related to the instantaneous cutting position of the cutter.

Mechanical properties of the surface membrane of lattice spacer-fabric flexible inflatable composites

The surface membrane plays a vital role in bearing loads of flexible inflatable composites. In this work, the mechanical properties of the upper and lower surfaces of inflatable composites and spacer fabrics were studied. It focused on the changes in mechanical properties of surfaces of spacer fabrics with different structures after coating and damage characteristics. The results show that the PVC resin improves the mechanical properties of the surface, which penetrates into the structure to make the yarns bond to each other and adhere to the resin on the surface. And compared with knitted structures, composite membranes with a woven structure have the characteristics of specific strength. This provides data accumulation for performance research of flexible inflatable composites, finite element calculation analysis, and the experimental reference for broadening the application in military pontoons and marching tents.

WAYS TO INCREASE THE LIGHTNING PROTECTION OF CARBON FIBER PLASTICS

Based on the previously conducted analytical study of the destruction of conducting composites by lightning currents, methods for increasing their lightning resistance are considered. To substantiate these methods, an analysis of the current distribution at different ratios of transverse and longitudinal resistivity was carried out. One of the methods using conductive additives in the composition of the binder material allows you to influence the anisotropy of the conductive medium of carbon fiber. The parameters of the range of the degree of anisotropy of carbon fiber are proposed to achieve uniform current spreading and reduce the radius of destruction of the composite by lightning currents. The formula for the fracture radius in the absence of anisotropy is obtained and estimated calculations are performed. The method of reinforcing carbon fiber with thin wires to increase its lightning resistance is considered. Calculated expressions are found for estimating the weight, the number of delays per unit area, and the absence of overheating. Comparisons of weight characteristics for various reinforcing materials are carried out and a conclusion is made on their effectiveness. The advantages and disadvantages of this method of protection are considered. The third way to increase the lightning resistance of the composite suggests using a carbon fiber material with a woven structure as a protective coating. This protection reduces the energy release in the material and the size of the damage. It is concluded that it is necessary to control the lightning protection parameters and choose a coating with the required characteristics. The principles and criteria of lightning protection for real carbon fiber plastics will be considered in subsequent works.

Polyurethane Electrospun Fiber Biomimetics Membrane for Constructing the Structure of Grain Layer with Good Breathability for Cattle Split Leather

The traditional thick coating on split leather does not have the ability to breathe like full grain leather. The air and water vapor permeabilities of full grain leather are well known properties due to its fiber woven structure. Simulating the fiber morphology and weaving structure of the dermis or grain layer is very important to construct a top surface layer for split leather. In this paper, a PU (polyurethane) foam layer is put first on the split to enhance the adhesion of a second application of a superfine fibrous PU resin. This foam uses well-known waterborne polyurethane foaming technology. This dried foam has good breathability because of high porosity. A superfine fiber membrane is next put atop of the foam layer by using an electro-spun polyurethane resin. This second resin imitates collagen fibers in the network structure of the leathers’ grain layer. Thus, this resultant electrospun fiber biomimetics membrane simulated the grain layer of natural leather. SEM showed the morphology and structure of this electrospun fiber biomimetic membrane to be like that of the grain layer of natural leather. The porosity and apparent density were basically the same as the grain of leather, which were 63.65% and 583.878 kg/m3 respectively. The air and water vapor permeability of the biomimetics membrane were also as high as 2250 mL·cm-2·h-1 and 8753.02 μg·cm-2·h-1 respectively. Therefore, the biomimetics membrane largely restored the ability to breathe of split leather. Thus, this method simulates the performance and structure of full grain leather and is a novel method for industrial production

Investigating the Performance of Sewn Seams from Woven Fabrics

Seam performance ensures the durability, attractiveness, strength etc. of the sewn garments. Fabric types, fabric densities, fabric strength, seam types, sewing thread count, thread strength, stitch densities and stitch types influence the performance of a sewn seam. This paper investigates the performance of sewn seam of various structure of woven fabric. The variables of this research are stitch densities (SPI), sewing thread count, seam types and woven structures. We conduct our research over plain, twill 2/1, twill 2/2, oxford and poplin woven structure. Firstly, we apply lockstitch (301) to produce superimposed, lapped and bound seam on the woven sample by using thread count 27 Tex, 30 Tex, 20/2 Tex, 40 Tex, 40/2 Tex, 40/3 Tex having stitch densities (SPI) 8, 10 and 12. Then according to ASTM D1683 standard, we measured the tensile strength test and recorded the seam breaking strength (N). We apply error bars over each diagram to investigate the standard deviation. Finally, we discuss four hypothesis to conclude our research work. We found higher seam breaking strength with the increase of thread count and SPI. The bound seam samples has shown superior seam breaking strength than superimposed and lapped seam; poplin structure surpassed to others. The seam efficiency of the samples varies from 60–90% and do not exceeds 100%. Finally, we found some significant alternatives hypothesis of the population since F values exceeded F critical values for the sewn seam.

Effect of Parameters on the Runoff Erosion Control Performance of Structurally Modified Jute and Coir Geomeshes over Loamy Sand

Soil erosion is a serious environmental problem that can be controlled using bioengineering techniques. In using a bioengineering technique, temporary reinforcement is performed with geomeshes until vegetation takes root. In this study, structurally modified jute and coir geomeshes were tested for runoff erosion control and runoff volume over loamy sand at different slope angles. The laboratory results revealed that all parameters (slope angle, type of weave and type of material) had a significant effect on the erosion control performance of geomeshes. The slope angle contributed most (52.34%) to runoff erosion control, followed by weave type (25.79%) and type of material (12.28%). At lower and medium slope angles (of 15o and 30o, respectively) the twill-woven structure of coir geomeshes provided better erosion control than plain- and satin-woven structures, while plain-woven jute geomeshes demonstrated better erosion control at all slope angles. To understand the overall impact, a germination test was also conducted. According to the germination test results, the twill weave of jute geomeshes provided the highest rooting length. In general, plain-woven jute geomeshes are preferred for better erosion control on a high slope angle, while plain and twill can be used on a low slope angle.

Force kinematic analysis of the process of needle punching of woven preforms

Описан процесс трансверсального армирования плетеных преформ иглопробивкой. Определен процесс взаимодействия иглы с оплеточными жгутами с учетом деформационных процессов изменения амплитуды переплетения и проскальзыванием жгутов плетеной структуры материала при введении иглы. Приведены экспериментальные данные сопротивления проникновению иглы в преформу и подложку. The process of transverse reinforcement of woven preforms with needle punching is described. The process of interaction of the needle with the braiding cords is determined, taking into account the deformation processes of the change in the weave amplitude and the slippage of the cords of the woven structure of the material when the needle is inserted. Experimental data on resistance to penetration of the needle into the preform and substrate are presented.