Hybrid Yarns Research Articles

Commingled yarns – Processing aspects and tailored surfaces of polypropylene/glass composites

Simultaneous spinning of commingled yarns and their investigation in terms of distribution homogeneity, thermal shrinkage, and cross section geometry is described in comparison with those intermingled by air jet texturing. Due to fibre damage avoided in the simultaneous processing and improved distribution homogeneity both hybrid yarn tensile strengths and transverse mechanical properties of unidirectional composites were improved. Nanostructured interfaces introduced by smallest amounts of carbon nanotubes in sizings enable to achieve multifunctional effects such as improved tensile strength of glass fibres, modified morphology of interphases, and new fracture mechanisms.

Microscopic Evaluation of Commingling-Hybrid Yarns

Fibers made of elements such as carbon, aramid and glass have higher mechanical properties than other conventional textile fibers and they enable the production of light weight composites as end products. Furthermore, commingling hybrid yarns generally have a characteristic feature so that their components are distributed homogeneously enough over the yarn cross section. A normal air texturerising machine was modified to produce commingling hybrid yarns for test samples. Different process parameters were applied to produce the hybridized yarn samples. However, these process parameters turned out to have little effect on the filament distribution over the hybrid yarn cross section in terms of homogeneity. The analysis in this paper is focused on the pattern of mixing of filaments over a cross section of hybrid yarns according to different combinations of reinforcement and matrix filament yarns through microscopic view. The volume content of filament in hybrid yarn cross section was maintained at 50% for both reinforced and matrix, and the hybrid yarns count at 600 tex throughout experiments. It was concluded from the experiments that the diameters of reinforcement and matrix filaments have strong effects on the pattern of mixing of filaments over a cross section of hybrid yarns such that the hybrid yarns with more or less equal diameters of reinforcement and matrix filaments showed considerably even distributions over the hybrid yarn cross section.

Commingled Hybrid Yarn Diameter Ratio in Continuous Fiber-reinforced Thermoplastic Composites

Manufacturing of lightweight structures from fiber-reinforced thermoplastic composites is of great benefit. Among various manufacturing methods the usage of semi-finished products is in high demand. To improve the mechanical properties and increase the productivity, the commingled hybrid yarn was developed recently. Among many parameters the fiber volume fraction and was diameters of reinforcement filaments and thermoplastic filaments in hybrid yarn are investigated in this study. The target is to improve the impregnation of reinforcement by molten thermoplastic polymer. Two hybrid yarn samples are illustrated (a) high performance thermoplastic PEEK/CF and (b) standard thermoplastic/glass fibers polypropylene (PP)/GF. The unidirectional (UD) composite samples, manufactured using thinner filaments, show little improvement of mechanical properties within the investigated region. In this study, a new technological approach will be introduced to increase the homogeneity of PP/GF commingled yarns by online hybrid spinning.

Breaking Elongation Properties of Hybrid Yarns by Commingling Process

This paper is concerned the breaking elongation properties of Carbon/Aramid-, Carbon/Glass- and Aramid/Glass- matrix hybridized commingling yarns. The hybrid yarns produced by commingling process were investigated in terms of breaking elongation property. In experiments, carbon (CF), aramid (AF), and glass (GF) filament yarns were combined. In this study, selected matrix materials include Polyether-ether-Keeton (PEEK), and polyester (PES), or polypropylene (PP). The volume content of filament in hybrid yarn cross section was maintained at 50% for both reinforced and matrix, ant hybrid yarns count at 600 tex, respectively. The reinforcement to matrix filament combination was selected as 1:1 proportion. The effect of different air pressures and material combinations was investigated in terms of breaking elongation. In experiments, each type of hybrid yarn sample has been tested 20 times at the testing speed of 10mm/min. under 3 bar of yarn clamping pressure. Since breaking elongation is one of most important properties in textile fiber, it was examined closely with reference to the first breaking point of commingling-hybrid yarns. It was concluded from experiments that hybrid yarns with higher breaking elongation and higher tensile strength tend to show better force-elongation relationship. It was also known from experiments that the combination of two reinforcement filament yarns gives always much better results than a single reinforcement filament yarns in terms of elongation property. GF/AF/matrix is shown very much better elongation properties. PP and PES gives higher elongation than PEEK as a matrix material.

An Air Texturing Process for Hybridization of Different Reinforcement Filament Yarns by Commingling Process

Carbon, aramid and glass fibers are inherently superior to conventional textile fibers in terms of mechanical properties and other characteristics. However, each material has its inherent advantages and disadvantages and it is usually recommended to hybridize them to fully benefit of their high performance in practical applications to many products. This paper is concerned with an air texturing process for hybridization of different reinforcement filament yarns. A normal air texturing machine was selected for process development and modified to suit testing purposes. The modified process for hybridization was introduced mainly in terms of air-jet nozzles employed in experiments. With the proposed air texturing process machine, three types of air-nozzle were applied to the experimental work. Three different filament materials were employed in experiments and they are carbon (CF), aramid (AF), and glass (GF). As matrix materials, polyether-ether (PEEK), polyester (PES), and polypropylene (PP) were selected and experimented. Hybrid yarns produced form the proposed process was evaluated optically in terms of bulkiness, arranging, breaking, and mixing, respectively. The experimental results were also summarized in terms of relationships between applied air pressure and yarn count, and variation in count. As a whole, it was concluded from the experiments that the proposed texturing process could be successfully applied to the practical hybridization of different reinforcement filament yarns. It was also revealed from the experiments that the air pressure in the proposed process is not a significant parameter on the pressing in terms of yarn count.

Ultrasonic evaluation of anisotropic damage in multiaxially textile-reinforced thermoplastic composites made from hybrid yarns

The basic damage and failure models of multiaxially reinforced composites with a thermoplastic matrix are presented and verified. Within the framework of continuum damage mechanics, a phenomenological model is introduced, where the damage is defined as a change in the elasticity tensor. For damage identification, a specific ultrasonic device was developed. A combination of an immersion set-up and a contact coupling device formed a system for an efficient determination of stiffness-tensor components from convenient sets of velocity measurements. Linked to a tensile machine, it allowed us to measure the anisotropic damage of the new materials group caused by tensile loading.

Hybrid Yarns and Textile Preforming for Thermoplastic Composites

In the recent years, the use of textile structures made from high performance fibers is finding increasing importance in composites applications. In textile process, there is direct control over fiber placements and ease of handling of fibers. Besides economical advantages, textile technologies also provide homogenous distribution of matrix and reinforcing fiber. Thus textile performs are considered to be the structural backbone of composite structures. Textile technology is of particular importance in the context of improving certain properties of composites like inter-laminar shear and damage tolerance apart from reducing the cost of manufacturing. Textile industry has the necessary technology to weave high performance multifilament fibers such as glass, aramid and carbon, which have high tensile strength, modulus, and resistance to chemicals and heat into various types of preforms. Depending upon textile preforming method the range of fiber orientation and fiber volume fraction of preform will vary, subsequently affecting matrix infiltration and consolidation. As a route to mass production of textile composites, the production speed, material handling, and material design flexibility are major factors responsible for selection of textile reinforcement production. This opens a new field of technical applications with a new type of semifinished material produced by textile industry. Various types of hybrid yarns for thermoplastic composites and textile preforming methods have been discussed in detail in this issue. Information on manufacturing methods, structural details and properties of different hybrid yarns are presented and critically analyzed. Characterization methods used for these hybrid yarns have been discussed along with the influence of different processing parameters on the properties being characterized. The developments in all areas of textile preforming including weaving, knitting, braiding, stitching and nonwovens techniques are presented and discussed along with the characterization techniques for these preforms. The techniques used for manufacturing composites using hybrid yarns and textile preforms are discussed along with the details on compaction behavior of these structures during consolidation process. The structure of hybrid yarns and the textile preforms have direct influence on the properties of the composite made from them. The reported literature in this aspect is discussed in detail. In the end, the potential application areas and their trends for thermoplastic composites are discussed and analyzed.

Electromagnetic and electrostatic shielding properties of co-weaving-knitting fabrics reinforced composites

The rotor twister successfully fabricated a series of hybrid conductive yarns. Copper wire and polyamide filament were used as the core yarn, and stainless steel wire was used as the wrapping yarn to fabricate the loop yarns for knitting structure. The nonwoven selvedge served as the core yarn, and the conducting wire was used as the wrapping yarn, to fabricate the weft-inlaid yarn. The co-weaving-knitting machine was used successfully in this study to fabricate the conducting co-weaving-knitting fabrics (CWKFs) with the hybrid yarn. The conducting materials of the hybrid yarn were copper wire and stainless steel wire, taken as the wrapping and core yarn, respectively. The CWKFs were laminated with various angles in four layers, and then were heat pressed for 3 mm in thickness. This study examined the surface resistivity, electromagnetic shielding effectiveness and electrostatic discharge attenuation percentage of the CWKFs reinforced composites.

Combination Effects of Open-End Rotor Spun Hybrid Yarns

We have developed a mechanical hybrid yarn spinning system that produces different yam types on a modified open-end rotor spinning frame. In order to improve yam properties and produce novel yams, we investigate the effects of combinations with typical hybrid yams by inserting two filament yarns with varying filament over-feeds. The results are a new rotor spun loop (RSL) yam made by combining two aspects of typical hybrid yarn production into one process, and an RSL yam where a filament yam, fed with a core filament over-feed (CFOF), is located in the center of one yarn and the other filament yam, fed with the effect filament over-feed (EFOF), makes a loop on the yarn surface. The stable conditions of RSL yam production are within a range of EFOF ≧ 4 (m/min) and -6.0 << CFOF << -4.0 (m/min).

Electromagnetic and electrostatic shielding properties of co-weaving-knitting fabrics reinforced composites

Abstract The rotor twister successfully fabricated a series of hybrid conductive yarns. Copper wire and polyamide filament were used as the core yarn, and stainless steel wire was used as the wrapping yarn to fabricate the loop yarns for knitting structure. The nonwoven selvedge served as the core yarn, and the conducting wire was used as the wrapping yarn, to fabricate the weft-inlaid yarn. The co-weaving-knitting machine was used successfully in this study to fabricate the conducting co-weaving-knitting fabrics (CWKFs) with the hybrid yarn. The conducting materials of the hybrid yarn were copper wire and stainless steel wire, taken as the wrapping and core yarn, respectively. The CWKFs were laminated with various angles in four layers, and then were heat pressed for 3 mm in thickness. This study examined the surface resistivity, electromagnetic shielding effectiveness and electrostatic discharge attenuation percentage of the CWKFs reinforced composites.

Commingled and Air Jet-textured Hybrid Yarns for Thermoplastic Composites

Hybrid yarns have reinforcing and matrix-forming filaments combined together in order to reduce the problems associated with high melt viscosity of thermoplastic matrices. Among hybrid yarns, commingled and air-textured yarns, which are produced with air jets have demonstrated high flexibility and good mixing of constituent filaments. Many research findings have been reported on the structure and properties of intermingled and air-textured yarns having low-modulus apparel-grade filaments. The relationships between air jet, filament yarn, and the processing parameters are critically reviewed. It is emphasized that there is an immediate need to study the mixing behavior of combination of high- and low-modulus filaments in air jet, which has not been investigated in detail in the published literature, in order to improve the mixing of these filaments. The methods used to characterize hybrid yarns are discussed. The need to study and improve the stability of the hybrid yarns in terms of maintaining the level of mixing of constituent filaments across the cross section is also established.

Study on thermal treatment of hybrid technical yarns

The present paper reports the impact of thermal treatment on the characteristics of core-sheath type hybrid technical yarns. The core-sheath type hybrid yarns are prepared using DREF-III technology. Polyester and glass multifilaments are used as core components whereas the cotton and polyester staple fibers are the sheath components wrapped around the core filament with different proportions to form a hybrid structure. The thermal treatment is carried out both in dry and in wet state under relaxed condition and the thermal shrinkage, sheath-slipping resistance and tensile and bending properties of hybrid yarns have been studied. Thermal treatment markedly increases the thermal shrinkage and sheath-slipping resistance of hybrid yarns with polyester multifilament in core, but insignificant effect for yarns with glass multifilament in core. Breaking elongation of hybrid yarns with polyester multifilament in core increases with treatment temperature. The hybrid yarns with glass multifilament in core are least affected by thermal treatment.

DSC investigations of polyamide 6 in hybrid GF/PA 6 yarns and composites

Glass/PA 6 composites were manufactured from specially designed hybrid yarns. The hybrid yarns were produced by three different spinning systems: friction spinning, ring twisting and pneumatic texturing. Each of these systems gives a different structure of the yarn and a different level of blending of the reinforcing and thermoplastic fibres. The crystallization and melting behaviour of PA 6 in the yarns and the composites were studied by differential scanning calorimetry. The different structure of the hybrid yarns leads to differences in the crystallinity of PA 6 in the yarns and the composites. The mechanical properties of the thermoplastic yarns and the composites are influenced, among other factors, by the crystal structure of the polymer.

Melt spinning of fine and ultra-fine PEEK-filaments

Hybrid yarns of PEEK and Carbon fibres are attractive as reinforcing materials. In an optimized hybrid yarn PEEK and Carbon fibres possess similar diameters. But the melt spinning of fine and ultra-fine thermoplastic filaments is a processing technique which makes great demands on the polymer and its elongational flow. The paper deals with theoretical and experimental investigations of the melt spinning process of fine and ultra-fine PEEK filaments up to finenesses of 1 dtex and lower. With a special spinning equipment finest filaments of lower than 0.1 dtex were reached.

Twisting Mechanisms of Open-End Rotor Spun Hybrid Yarns

We have developed a mechanical hybrid yam spinning system that produces different kinds of yam on a modified open-end rotor spinning frame. In order to understand the characteristics of hybrid yam and produce novel yarns, it is necessary to investigate yarn formation and the twisting mechanism in the spinning rotor during yam production. Our results reveal that the rotor revolution generally results in combining the filament yam and the staple fiber strand. The fiber twist angle of the strand in a hybrid yarn is smaller than that of a rotor spun single yam with the same spinning conditions. Although a fed filament yam has a false twist inserted by increasing the filament over-feed, the filament yarn in the hybrid yarn has a smaller level of fiber twist angle in the same direction as the twist of the staple fiber strand due to untwisting of the false twist.

Preferable Filament Diameter Ratios of Hybrid Yarn Components for Optimized Longfiber Reinforced Thermoplastics

Abstract The mechanical properties of hybrid (commingled) yarn based reinforced thermoplastics depend on many parameters of the fiber components as well as of the different technological conditions during the commingling and the hot press molding. Among the fiber parameters the diameter ratio of the matrix and the reinforcing yarn components are most important to obtain best mechanical properties of the reinforced thermoplastics. The paper treats theoretical considerations in order to reach a high probability of coating each reinforcing filament with the thermoplastic material during the hot press molding. The calculations include the filament ratios and the achieved volume ratios of both hybrid yarn components of the finished reinforced thermoplastics. It is demonstrated that under different optimization criterias (same filament numbers for both components or the same surfaces of the reinforcing yarn filaments and the matrix yarn filaments before the hot press molding) a more or less small range of filament ratios seem to be valid for manufacturing a homogeneous faultless reinforced thermoplastic. Quantitative calculations for two hybrid yarn systems PEEK/carbon fibers and PP/glass fibers, presented in diagrams, are demonstrated. Technological conditions for the spinning of micro fibers like PEEK-filaments complete the presentation.

Processing and mechanical properties evaluation of a commingled carbon-fibre/PA-12 composite

A carbon-fibre/PA-12, hybrid yarn, woven fabric material has been processed into laminates and mechanically tested to evaluate its suitability for high performance applications. The processing technique used was compression moulding. A process parameter investigation was carried out to determine the most suitable values of pressure, temperature and time at temperature required to economically produce laminates of high quality. Laminates were subsequently produced for a detailed material-testing programme. It was found that the hybrid yarn material exhibits excellent mechanical properties, particularly tension, open-hole tension, fracture and impact properties.

The Influence of Structure of Hybrid Yarns Glass/PA6 on Mechanical Properties of Composites

The fabrication process of thermoplastic composites using hybrid fabrics composed of yarns made of glass and PA6 fibres as prepregs is presented. The influence of the structure of hybrid yarns produced using commingled, texturising, twisting and friction spinning technology on the mechanical properties of composites is discussed. The results of the investigation indicate that the best tensile and bending properties of composites were achieved using fabrics made from texturing yarns produced under optimal conditions. These optimal conditions should ensure the minimum destruction of filaments during the blending process.

Pultrusion of Micro-Braided GF/PA6 Yarn

The present paper reports about experimental investigations on a new type of thermoplastic intermediate material (TP-prepreg). Today, most processes for producing fibre reinforced composite parts with thermoplastic matrices require expensive prepregs like pre-impregnated tapes or hybrid yarns (commingled yarns or powder impregnated yarns). The microbraiding technique offers some advantages compared to existing prepregs: Microbraided yarns can be produced directly by the user by a microbraiding process requiring only glass rovings and polymer rovings, and at the same time, the user is free of any restrictions on fibre/matrix combinations or reinforcement fibre content. Glass Fibre/Polyamide 6 (Nylon 6) microbraided yarn was compared to commercially available GF/PA6 tape concerning the use in a pultrusion process. For mechanical characterisation, shear strength and bending strength were determined. The processing parameters such as preheating temperature, heated die temperature and pulling speed were varied.

Effect of hybrid yarn structure on the delamination behaviour of thermoplastic composites

Abstract Continuous-glass-fibre-reinforced polyamide-matrix composites have been manufactured on the basis of hybrid yarns with different arrangements of the reinforcing glass and polyamide matrix fibres. In addition, glass fibres with different sizings were used. To characterize the delamination behaviour of composites made with these semi-finished products, mechanical and fracture mechanical tests were performed, including longitudinal and transverse tensile, compression shear, double cantilever beam, single-edge notched and end-notched flexure tests. The results demonstrate the significant influence of the different hybrid yarn structures and glass fibre coatings on fracture toughness. The best mechanical and fracture mechanical properties have been obtained for composites manufactured with air-textured commingled yarns containing glass fibres only with aminosilane as coupling agent.