A process for producing carbon fibers from polyacrylonitrile at low carbonization temperatures was studied. The bulk and surface properties of fibers obtained after reaction with benzoic acid, air and carbonizing in nitrogen or a dilute acetylene atmosphere are discussed. All fiber products had different surface and internal compositions. Samples produced at temperatures up to 950 C and carbonized in nitrogen contained substantial quantities of nitrogen and oxygen at the surface. During carbonization, the surface nitrogen converted into two new forms, possibly nitrile and an azo or a new carbon-nitrogen bond. Samples carbonized in acetylene contained a carbon-rich surface stable to oxidation.
Rods of spherulitic, linear polyethylene were cold-drawn at 60 and 100°C and the morphology of the drawn material, particularly the necked portion, was characterized by light and electron microscopy and by wide- and small-angle x-ray scattering. The drawing proceeded by neck formation and propagation at a draw ratio of 10. Further extension or creep beyond the neck produced draw ratios up to 20. Neck formation was characterized by spherulites deforming essentially in concert with the macroscopic deformation, becoming elongated and oriented and, thereby, defining a gross fibrous structure.
Very early in the process of neck formation, small disruptions appeared within the spherulites. Similar to crazes in amorphous materials, these disruptions measured a few microns long, perpendicular to the direction of deformation, and a fraction of a micron thick. The disruptions increased in size and number as drawing progressed, dominated the structure at the higher draw ratios, and oriented to define a fine, fibrillar structure. These observations are contrasted with the rather different results obtained in an earlier, similar study of the cold-drawing of nylon 66.
Optical analysis of roughness operating on the principle of chromatic aberration and dynamic wetting measurements have been used to investigate the surface properties of polyester fabrics with different woven structures. The results revealed differences in the two basic types of weave — plain and twill — with respect to the penetration behavior of water. Additionally, plain weave fabrics were manufactured using differently profiled fibers — round and cruciform. It was established that fabrics composed of fibers having a cruciform cross section are more hydrophobic than those that are round.
Effective research on the aesthetic characteristies of fabries is difficult because ex plicit definitions are lacking in this field. The most reliable tool is subjective evalua tion: therefore, words ( loft, clammy, hard, etc.) become important research tools. Special meanings of these words become clear if they are logically arranged according to textile frames of reference.
Fabric aesthetic character is defined as a relationship among a minimum of six concepts: STYIE, BODY, COVER, SURFACE TEXIURF, DRAPE, and RESILIENCEE. These con cepts can be described by how they are subjectively perceived, by possible subconcepts (e.g., COVFR can be partitioned into BOTTOM and TOP COVFR). by objective tests when available, and by common word pairs used to communicate their values (e.g., thick-thin, rough-smooth, etc.). To illustrate application of principles, subjective scales, identified by common words, were used for analyzing the COVFR concept in commercial, men's suiting fabries. These were then mathematically related to the aesthetic concept of COVER for specific fabrics.
We demonstrate a physically-based technique for producing draping simulations of a variety of woven fabrics. Our approach employs an interacting-particle model which is based on the microstructure of woven cloth, rather than utilizing a continuum approximation. Empirical data from a fabric testing device is used to tune energy functions within the model. We describe the model, how we convert the fabric test data to energy functions, and two experiments conducted to evaluate the approach. The first experiment produces non-linear mechanical data from the model. The second experiment compares photographs of three different types of draping cloth with visualizations of simulation results. The experiments show that we are able to reliably recover quantitative mechanical information from the model, and to reproduce the unique largescale draping characteristics of a range of fabric types. iii 1 Introduction The drape of woven materials has intrigued humans for centuries. This is evident in...
Copolymers of 1,1-dihydroperfluorooctyl acrylate/methacryloyl chloride acted as multipurpose finishing agents for wool. They provided oil and water repellency; resistance to felting shrinkage; and resistance to acid, alkali, and oxidizing media. The hand and flexural rigidity were altered slightly, whereas wrinkle recovery, fabric break, tear strength, and abrasion resistance were not significantly changed. Grafting of the copolymers on wool is presumed to be due mainly to a reaction between copolymer-acid chloride groups with hydroxy and amino groups in keratin. Aside from rendering the polymer insoluble to dry cleaning solvents, grafting permitted the use of smaller amounts of resin for shrinkage protection than was required with nongrafted polymer. The washfastness of the oleophobic-hydrophobic finish was essentially the same in a comparison of a grafted copolymer fluoroalkyl acrylate and a nongrafted homopolymer fluoroalkyl acrylate.
No significant differences were noted in the washfastness or fastness to dry cleaning of the oleophobic-hydrophobic finish imparted by a commercial fluorinated acrylic resin (FC 208) when the resin was applied on untreated wool, on shrink resistant wool fabrics, or in conjunction with an interfacial polymerization shrinkproofing technique.
Reaction products of diethylaminoethyl (DEAE)-cotton and aminoethyl-cotton (aminized) with 1,2-epoxy-3-chloropropane (epichlorohydrin), 1,2-epoxy-3,3-dichloropropane, 1,2-epoxy-3,3,3-trichloropropane, and 1,2-epoxy-4,4,4-trichlorobutane, 1,2-epoxypropane, 1,2-epoxyhexafluoropropane, and 1,2-epoxy-3-bromopropane were studied microscopically. The methacrylate layer-expansion technique was used to evaluate the extent of chemical reaction. Epichlorohydrin appeared to be the most efficient cross-linking agent. The chlorinated epoxides capable of dehydrohalogenation after epoxide ring openings appeared to be good cross-linking agents. Electron mcirographs demonstrate the effects of the above treatments on fiber morphology.
The effect of NaOH mercerization on the crosslinking properties of 1,2,3,4-butanetet racarboxylic acid (BTCA) on ramie yarn is studied, with emphasis on mercerization tension. NaOH at mercerization strength decrystallizes the ramie fibers, resulting in a higher accessibility to BTCA. Due to the change in fiber orientation caused by mercerization, tension mercerized and crosslinked ramie yarn shows a higher tenacity than the crosslinked control, while the low-tension or slack mercerized and crosslinked ramie yarn exhibits more serious tensile strength loss than the crosslinked control.
Prepolymers of tris(1,3-dichloro-2-propyl) phosphate (DCPP) with polyethylenimine (PEI) were prepared, applied to cotton-containing fabrics, and cured at 155°C. The prepolymers imparted flame resistance to all-cotton and cotton/polyester blends. The most effective prepolymers were prepared from 3:1 and 5:1 mole ratios of DCPP: PEI. Practical potentialities for these finishes are limited because their durability to laundering is low.
A new flame retardant for cotton, tetramethylol 2,4-diamino-6-(3,3,3-tribromo-1-propyl)-1,3,5-triazine (TM-DABT), was synthesized. TM-DABT was applied to cotton fabrics from a combination of water and dimethylformamide by a pad-dry-cure process. It polymerized rapidly on fabric at 140°C to give excellent flame retardancy. Flannelette and twill with add-ons of 13.3% and 11.3%, respectively, passed the FF3–71 flammability test after 50 laundering, with char lengths of 4.7 and 3.4 inches. There was evidence of cellulose crosslinking because fabrics had improved wrinkle-recovery angles, and cotton fibers were insoluble in cupriethylenediamine hydroxide. The finish was heat-sensitive, as evidenced by noticeable yellowing when white fabrics were cured at 150°C or above, or when they were laundered repeatedly.
Various physical properties of the fabrics are presented, as well as oxygen index and thermogravimetric analyses.
The dyeing behavior of 1,4-diaminoanthraquinone (1,4-daa), CI Disperse Violet 1 on polyester fibers is investigated in the presence of a double tailed surfactant, dialkyldimethylammonium bromide (dadmab), which is known to form a bilayer. Both dyeing rate and saturation values of 1,4-daa are considerably improved at 110°C in the presence of dadmab compared with those of a dyehouse grade, Miketon Fast Red Violet R. It is likely that the enhanced dyeing properties with dadmab are due to interactions between it and the polyester fibers or between it and the dye.
Various levels of cotton and polyester fibers blended during opening and picking were investigated to determine their effect on carding efficiency and processing performance. A medium staple cotton of average fiber properties and a high-modulus polyester (2.25 denier) were used in the blends.
Shear friction and compression recovery of the blends increased as the percent polyester increased. For the 2.25-den polyester blends, shear friction was slightly lower and compression recovery practically the same as for 1.5-den polyester/cotton blends. Higher polyester content increased friction and cylinder load, thereby reducing carding action so that the short-term sliver variability and neps of the cotton component in the card web increased. Cylinder load and neps in the card web were lower for the 2.25 than the 1.5-den polyester blends. Higher polyester contents slightly improved yarn grade, and the grades for the 2.25-den were higher than those for the 1.5-den polyester blends. Increased friction and length uniformity of the polyester improved drafting so that second-drawing sliver, roving, and yarn uniformity improved when polyester was added to the blend. Carding waste was practically the same whether using 2.25 or 1.5-den polyester; very little polyester was lost in the waste. At constant end breakage, spinning production increased up to a 50/50 blend and then decreased as the percent of 2.25-den polyester was increased.
These findings indicate that for cotton and polyester blended in the opening room, one with a high percentage of cotton can be processed more efficiently than the reverse.
Factory tests for rapid process of ramie bio-degumming by Pectobacterium sp. CXJZU-120 were conducted and evaluated comparing the processes of traditional chemical degumming and bio-chemical degumming. Results revealed that over 90% of the gum in raw ramie could be removed only with Pectobacterium sp. CXJZU-120 in 6 h. The rapid process was not only suitable for the extraction of ramie fibers from different grades of raw material and retaining the inherent morphological structures and textile properties, but also could reduce the production cost up to 20.5%, raise resource utilization by more than 50% and reduce pollution charge by more than 80% compared with the traditional chemical degumming. It is a breakthrough in the degumming of ramie and has great application potential in the extraction of herbaceous fiber materials.
Carbon-13 cross polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) has been used to investigate the effect of heat on wool. Increases in the unsaturation of aromaticity of wool occur at about 225 degrees C. In chrome mordanting, the technique shows that paramagnetic chromium appears to act uniformly throughout the bulk of the wool fibre when the fibre is treated in dichromate solution. The technique has shown that the metal is distributed such that proton spin diffusion and relaxation values associated with the various functional groups constituting the wool fibre do not diverge significantly. Therefore no discrete metal binding was detectable under the experimental conditions used.
Thiourea's reaction with hydrogen peroxide in solution under bleaching conditions at three different pH values has been investigated using 13C NMR spectroscopy. Since this reaction is fast and exothermic, it is essential that short total acquisition times be used to accumulate sufficient data to detect different species formed during the reaction. As the abundance of 13C in the reactants in the concentration range studied is very low, 13C-labeled thiourea was used as the starting material. Sufficient data were accumulated in short acquisition times (2–4 minutes) to identify different species formed during the reaction. The results showed that different intermediate products are formed during the reactions, depending on the pH of the medium and the molar ratio of the reactants. The reaction goes through a thiourea dioxide intermediate; this then hydrolyzes under heat and neutral or alkaline conditions to yield sulfonate anion and urea if the initial reaction of thiourea with hydrogen peroxide is allowed to take place in acidic/neutral medium (pH = 4.0–7.0). Because thiourea dioxide hydrolyzes in solution, there is a rapid change in redox potential from a positive value to a high negative value. The species causing the negative redox potential, and hence the species responsible for reductive bleaching, is believed to be the sulfinate anion. The reaction of thiourea with hydrogen peroxide in hydrochloric acid at pH < 1 results in the formation of formamidine disulfide dihydrochloride, which decomposes at pH values greater than 1.
A mathematical model of measuring transmittance of infrared (IR) radiation through fabric is presented here. Combined with a specially made blackbody, a Fourier transform infrared (FT-IR) spectral radiometer was developed to measure the transmittances of polyester (PET) and cotton fabrics within the range of 8—14 µm at different ambient temperatures. The results showed that the influence of cover tightness on transmittance was much in evidence. For cotton fabric, the transmittance was less than 65 %, but for PET fabric, it was less than 75 %. As expected, IR radiation transmitted fabric easily, but it was limited to some extent. The hairiness in the fabric, especially those made of staple yarns, played an important role in the shading parts of IR radiation. The relationship between transmittance and cover tightness was very complicated for different fabrics (the exponential equation for cotton fabric, the linear function for polyester fabric). Similarly, the exponential relationship between transmittance and fabric thickness, the linear relationship between transmittance and area density could be obtained. The blackbody’s temperature did not have an effect on transmittance below 200 °C.
Wool samples were labeled by reaction with aqueous solutions containing [2- ¹⁴ C] iodo acetic acid or [2- ³ H] iodoacetic acid. The counting rate of each sample was measured, firstly, with the 'wool suspended in a liquid scintillation solution (direct method) and, secondly, after oxidizing the same sample and dissolving the products in another liquid scintillation solution. The counting rate determined by the direct method depended on fiber diameter, because of self-absorption of β-particies by the wool, whereas the counting efficiency of the oxidation method was constant. The ratio of the counting rates, direct/ oxidized, for ¹⁴ C-labeled samples decreased linearly from 1.30 to 0.96 as the mean diameter increased from 14 to 35 μ. With ³ H-labeled wool, the inverse ratio, oxidized/ direct, increased linearly from approximately 5.5 to 10.5 with increase in diameter from 14 to 35 μ.
It was also shown that wool samples may be labeled with a known amount of ¹⁴ C by reaction with [2- ¹⁴ C] iodoacetic acid dissolved in a liquid scintillation solution. The results, which show that the reaction occurred uniformly through the fiber, provide the basis for a new method of measuring mean fiber diameter.
A study was made of the migration behavior of filaments in a 3-layer structure of 19 filaments. The filaments were twisted in two distinct forms: (a) ribbon-twisted and (b) cylindrical-twisted. The form of twisting was found to have an appreciable effect on the migration behavior of filaments. The frequency of migration decreases with increase in ribbon width and free length. The experimental results and the observation of yarn formation indicate that, besides the presence of three principal mechanisms, the migration is also caused by the entanglement of filaments. Tensile pro perties of twisted continuous-filament yarns are affected slightly with change in migration behavior.
Peracetic acid can be catalyzed to bleach cotton fibers at temperatures as low as 30°C by incorporating 2,2î-bipyridine in the bleach solution if the appropriate concentration of ferrous ions is present in the cotton fibers. The tris-2,2î-bipyridine ferrous ion complex (trischelate) is the catalytically active species, and sodium lauryl sulfate functions as a stabilizer for the peracid in the presence of the trischelate. The effects of pH, temperature, and concentrations of 2,2î-bipyridine, sodium lauryl sulfate, and ferrous ions on the kinetics and mechanism of peracetic acid decomposition have been investigated. Peracetic acid decomposition in the bleach solution is due mainly to alkaline hydrolysis without added ferrous ions and catalysis by the trischelate complex in solutions containing added ferrous ions. Overall decomposition follows the rate expression
where k 1 is the specific rate constant for alkaline hydrolysis and k 3 is the specific rate constant for catalytic decomposition by the trischelate in the presence of sodium lauryl sulfate.
Peracetic acid can be catalyzed to bleach cotton fibers at temperatures as low as 30°C by incorporating 2,2î-bipyridine in the bleach solution. Treatment of the fibers with HCl prior to bleaching reduces bleaching effectiveness by removing trace transition metal ions from the fibers. Sorption of individual ions (Cr+3 Mn+2, Fe+2, Fe+3 Co+2, Ni+2, Cu+2, and Zn+2) by HCl treated cotton fibers prior to bleaching indicates that the ferrous ion produces the greatest catalytic effect, and it is only effective when the metal ion is in the fiber as opposed to in solution. Ferrous ions in the fibers sorb 2,2î-bipyridine from solution to form the tris-2,2î-bipyridine ferrous ion complex that is associated with the fibers, and it is the trischelate associated with the fibers that catalyzes bleaching. The effects of pH, temperature, and concentrations of 2,2î-bipyridine, sodium lauryl sulfate, and transition metal ions (in the fibers and in solution) on bleaching effectiveness and peracetic acid decomposition have been studied, and a bleaching mechanism is proposed.
Recovery from strain, tensile, and shrinkage are measured for poly(ethylene 2,6-naphtha-late) (PEN), dimensionally stable polyester (DSP PET), and high tenacity polyester (HT PET). The results are considered in the context of an earlier study examining the mechanical properties of poly(ethylene terephthalate) (2GT), poly(trimethylene terephthalate) (3GT), and poly(tetramethylene terephthalate) (4GT). DSP PET and PEN show good recovery from 10% applied strain, at 30% strain DSP PET has the highest recovery overall, and at 60% strain recovery is poor for all types. In the case of HT PET, specimen breakage sometimes occurs before the recovery measurement can be completed. PEN shows the minimum shrinkage in boiling water, and DSP PET is more dimensionally stable than HT PET. However, an interesting observation is that PEN develops a crimped appearance after this treatment, which is not seen in the other two fibers. We associate this with the good recovery behavior of PEN.
Fully hydrolyzed polyvinyl alcohol (FH-PVA) electrospun fibers with uniform diameters of less than 200 nm were fabricated by reducing the viscosity of FH-PVA aqueous solutions. A novel viscosity-modifier (hydrazine monochloride [HMC]) gradually reduced the viscosity of FH-PVA aqueous solution over a period of several days. This phenomenon is counter to the effect of the usual salt addition. After being stored for several days, the viscosity decreased by up to 60% compared with that of an equivalent pure FH-PVA solution. From small angle X-ray scattering (SAXS) and proton nuclear magnetic resonance (1H NMR) spectra observations it is evident that this effect results from the reconfiguration of hydrogen bonding. The viscosity control of FH-PVA solutions with HMC were used to electrospin highly uniform ultrafine fibers (diameter <200 nm).
The efficiency of the device for cleaning the rotor of the BD 200 machine was investigated, the yarn showing no periodic irregularities. However, some trends along the bobbin build were observed. These trends, which were observed earlier, are attributed to bobbin wind.
Organic cotton has become a popular product in recent years due to its environmental friendliness. Different from conventional cotton, the planting of organic cotton does not use pesticides, herbicides, or fertilizer, which can cause degradation in soil fertility, water and natural equilibrium. Organic cotton crop rotation can build strong soil, retain water more efficiently, maintain a balance between pests and their natural predators, and control weed growth. This study presented a yarn spinning process using organic cotton as the raw material. An open-end rotor spinning machine was used in the spinning process. To analyze the processing parameters affecting yarn qualities, the Taguchi method and response surface methodology were used to design an orthogonal array experiment and to find the relationship between controllable input parameters (i.e. feed speed, winding speed, and rotor speed) and output qualities (i.e. strength, unevenness, imperfection indicator/km, and hairiness). To find the optimal parameter combination, two popular optimization methods, particle swarm optimization and genetic algorithm, were used. The results showed that with optimal parameters (0.345 m/min, 34.717 m/min, 82,599 rpm for feed speed, winding speed, and rotor speed, respectively), the proposed method can find optimum values in all observed qualities. A confirmation experiment was conducted to validate the results.
Reductive decoloration of CI Acid Red 27 and CI Reactive Black 5 is achieved by cathodic electron transfer. The stoichiometry of the dyestuff reduction is studied with redox titrations using an Fe(II)-TEA complex as the reducing agent. CI Acid Red 27 is reduced to the corresponding amines at room temperature, while full reduction of CI Reactive Black 5 is observed first at elevated temperatures. In potentiostatic reduction experiments, CI Acid Red 27 is decolorized with an uptake of 4e-. CI Reactive Black 5 can be readily decolorized by cathodic electron transfer. The reaction proceeds via relatively stable hydrazo intermediates. Investigations with cyclic voltammetry and galvanostatic batch electrolysis experiments indicate that the rate of decoloration with CI Reactive Black 5 depends somewhat on transport processes in the diffusion layer of the cathode, but is limited by a preceding chemical equilibrium.
Deflection-force relations for plain weave Kevlar® fabrics have been determined under conditions of uniaxial loading. In these experiments, the loading is stopped at a given level and a portion of the fabric is encapsulated. The fabric is then unloaded, sectioned, and photographed. Measurements on the photographs reveal the changes in weave geometry and yarn cross section with loading. The initial geometrical data are used in a large deformation mechanical model, which couples yarn bending and stretching effects to predict theoretical displacement-force relations for the fabric. Experimental and theoretical deflection-force curves are in good agreement; they show that during initial loading the response is dominated by yarn bending, while for large loads the response is dominated by yarn stretching.
The use of thermoplastic components with a complex three-dimensional (3D) shape, manufactured efficiently with thermo-presses, has been increased steadily. Flat knitting technology using reinforcing hybrid yarns in the horizontal and vertical direction is especially suited for producing near-net-shape or fully-fashion multilayer weft knitted fabrics – MLGs (abbreviated from the German word Mehrlagengestrick, meaning multilayer weft knitted fabric). The other advantages of manufacturing such MLGs, using flat knitting technology, are reduced waste and desired reinforcing fibre alignment to obtain improved mechanical properties for high-performance applications. Before knitting 3D shaped MLGs, it is necessary to transfer the 3D component geometry into a suitable two-dimensional (2D) pattern cut by implementing parting lines. The use of computer-aided design (CAD) programs enables an effective development of complex components preforms. The generated 2D pattern cuts are analyzed with the consideration of net-shape preforming processes on V-bed flat knitting machines. The development of a segmented take-down system for effective production of 3D MLG preforms is also discussed.
A theoretical viscoelastic model based on the four-element Burgers model is devel oped to predict changes in load with time of ISO-301 stitched seams under longitudinal loading subjected to extension/recovery cycling at a constant rate of extension. Param eters calculated from experimental stress relaxation curves are used to determine the theoretical relationship between load and time for tensile cycling. The model gives good agreement with experimental stress relaxation behavior of seams over the range 0-30 seconds. Theoretical predictions of load versus time give the best agreement with experimentally derived tensile cycling curves for seams cycled between the lowest extension limits. The exact solution of the theoretical model consists of a double ex ponential expression, suggesting that two processes are responsible for the change in load of seams with tensile cycling, a result consistent with the statistical model for seam ageing and with visual observations described in Part I of this series.
This paper presents customer participating 3D garment design methods for mass personalization. Complex fashion design is separated into garment surface modeling, pattern designing and texture mapping. Based on the modularization of the garment, we propose a component option sheet to describe the Garment surface Style (GS). Customers can choose components flexibly to construct a basic GS fast. Individual GS can be further modeled by editing the contour curves. Thus, we encode contour curves to save GS information and construct a GS library. The user can drag a favorite GS onto a 3D mannequin model and recover it by decoding the contour curves as a prototype for individual surface design. The users can also draw or drag style curves freely on a 3D triangular garment surface to design individual 3D pattern styles. Total or partial style curves encoding/decoding methods are proposed to store the 3D Pattern Style (PS), and to form a library. Customers can also choose a favorite PS and decode them on another garment surface as a prototype for individual pattern design. Through flexible choices from the garment component library, GS library, PS library, and simply dragging or drawing of contour curves and style curves, customers can easily and conveniently participate in 3D garment design for mass personalization.
Accurate recognition of the human body is an essential procedure of clothing pattern making, garment fit evaluation, and sizing survey. Over the years, many research efforts have been devoted to define and/or identify features (points and lines) of a human body. However, the neckline, one imperative feature of a human body is still difficult to accurately identify. It is complicated to determine a neckline geometrically due to the large variety of body figures, and the defined neckline must fulfill the requirements of apparel manufacturing and textile properties. The aim of the paper is to propose a new and practical method to identify the neckline from 3D digitized bodies. Firstly, a torso represented by piecewise B-spline curves is generated from a triangulated human mesh model. Secondly, important feature points including front neck point (FNP), back neck point (BNP) and side neck point (SNP) are identified. A cutting-surface is defined and the profile of such cutting surface is construed by those identified feature points. By intersecting the cutting-surface with the piecewise B-spline curve torso, a neckline is then properly determined. The proposed method is verified to be effective for generating necklines for human subjects with varied neck silhouettes. A neckline fitting survey through real subjects’ wear trial is conducted to evaluate and compare the proposed method with the traditional methods.
The uniaxial tensile properties of 4-step 3D braided E-glass/epoxy composites under quasi-static and high-strain rate loadings have been investigated to evaluate the tensile failure mode at different strain rates. The uniaxial tensile properties at high strain rates from 800/s to 2100/s were tested using the split Hopkinson tension bar (SHTB) technique. The tensile properties at quasi-static strain rate were also tested and compared with those in high strain rates.
Z-transform theory is applied to 3D braided composites to characterize the system dynamic behaviors in frequency domain. The frequency responses and the stability of 3D braided composites under quasi-static and high-strain rate compression have been analyzed and discussed in the Z-transform domain. The results indicate that the stress-strain curves are rate sensitive, and tensile modulus, maximum tensile stress and corresponding tensile strain are also sensitive to the strain rate. The tensile modulus, maximum tensile stress of the 3D braided composites are linearly increased with the strain rate. With increasing of the strain rate (from 0.001/s to 2100/s), the tensile failure of the 3D braided composite specimens has a tendency of transition from ductile failure to brittle failure. The magnitude response and phase response is very different in quasi-static loading with that in high-strain rate loading. The 3D braided composite system is more stable at high strain rate than quasi-static loading.
T-joint tube composites have huge potential applications in structural engineering. The paper tries to find an easy way to design and manufacture woven integrated T-joint tube by the theory of ‘flattening-weaving-unfurling’. The difficulty in smoothly unfurling the flattened woven structure lies in the wrinkles formed at the crossing area of the two tubular members, which is analyzed in detail. The key to solve the problem is to increase the extensibility of the structure. A four-layer interlocked hollow woven structure with sandwiched weft wicks in a mini-hole was designed to give the fabric the ability of being extended after part of the wick yarns have dropped out. The parameters of the structure, such as base weave, weft density, number, and thickness of the wick yarns, are investigated to evaluate their effects on the extensibility of the structure. To achieve a higher extensibility, the final structure design should have the following features: coarse wick yarn, relatively higher weft density, 2/2 twill base, and number of wick yarns less than four. By using NedGraphics Jacquard CAD (Computer Aided Design) system, the contour of the crossing area of the T-joint tube was designed, the weaves in different sections of the fabric were assigned, and a JC5 format file was exported to control a normal electronic Jacquard loom to weave the structure. The final experiment indicates that the 3D T-joint tube can be unfurled smoothly and the method of the design is visually verified to be effective.
The aim of this study is to understand the energy absorption mechanism and identified failure modes of the developed multiaxis non-interlaced/non-Z E-glass/polyester and 3D woven carbon/epoxy composite plates with soft backing para-aramid fabric structures.
Two structures, multiaxis non-interlaced/non-Z E-glass/polyester composite plate and soft back layered para-aramid fabric, and 3D woven carbon/epoxy composite plate and multiaxis non-interlaced/non-Z E-glass/polyester composite plate with soft back layered para-aramid fabric, absorbed considerable impact energy when a high speed projectile’s metal jacketed section was stopped.
The damage zones of both structures were investigated after impact. 3D woven carbon/epoxy plate showed a small damaged area compared to that of the non-interlaced/non-Z E-glass/polyester plate. This was because the Z-fiber suppressed the impact load, but the local area was severely damaged in the form of fiber and matrix breakages. There was no intra and inter fiber damage around the impacted area in the 3D carbon/epoxy composite plate, whereas there was intra and inter fiber damage around the impacted area in the non-interlaced/non-Z E-glass/polyester plate. It was thought that the impact load in the E-glass/polyester structure was redistributed around the local impacted area. Fiber damage in the soft back layered fabric extended from the decomposition of the fiber ends, partial and total fiber breakages to yarn pull-out and crimp recovery. Fiber decomposition results in friction between the fabric and the projectile which generates thermal load in the soft structure.
Weaving is one of the key technologies that are used in organising unidirectional fibrous materials into 2D sheet and 3D shaped geometrical architectures for applications such as textile composites. It has been demonstrated that the conventional weaving technology has the potential to produce textile assemblies which have many different types of 3D shaped fabrics, and this approach has obvious advantages in the provision of a sizeable quantity of 3D shaped fabric and in cost reduction. However, the design of such 3D shaped woven fabrics may be complicated especially when the shape and micro structures are complex. This paper reviews the mathematical modelling of different types of 3D weaves which have been successfully used in developing CAD/CAM software for 3D fabrics. The types of weaves described here include single-layer, 3D orthogonal, 3D angle interlock, and 3D cellular. Results from different CAD programmes are also demonstrated.
In this paper, the low velocity impact characteristics and impact damage of sandwich composites, produced at four different core thicknesses from 3-dimensional (3D) integrated sandwich fabrics, with and without foam filling, have been examined. The 3D sandwich fabrics have been produced using the same yarn and weaving densities. Thus, the impact characteristics are only affected by the core thickness and whether foam filling is used or not. Low velocity impact tests have been conducted at 32 and 48 J energy levels. The impact behavior has been determined as a function of the peak load, the energy to peak load, the time to peak load and the absorbed energy. The impact damage and the change in the compressive strength after impact have been analyzed. The findings obtained indicate that core-skin delamination on 3D sandwich composites has been fully prevented. Impact tests carried out on integrated 3D sandwich structures have shown that impact damage is limited to the vicinity of the point of impact and does not affect the integrity of the structure. This indicates that such damage can be easily repaired and the service life of the product can be sustained.
Geometrical modelling for tubular braids of different structures is studied and a simple versatile three-dimensional model is proposed after considering the crimp of the braiding yarn together with the tubular curvature of the tubular braid structure. The proposed model is versatile and suitable not only for different braid structures, but also, with the changes in the structural parameters such as braid angle, number of yarns in a set, yarn and mandrel diameter the model is still applicable. Application and 3D drawings of the model for diamond, regular and triaxial braids are given with the aid of Visual Basic and 3DSMax Studio.
The 4,5-dihydroxy-2-imidazolidinone system, with methyl and/or methylol substituents in the 1,3-positions, has been studied with respect to the geometry of the hydroxyls in the 4,5-positions and with respect to the textile properties of cotton cross-linked with these agents. In addition, some of the impurities and byproducts expected in this system are discussed. Fabrics finished with the cross-linking agents have been compared with respect to acidic and basic hydrolysis of the finish, wrinkle recovery angle, chlorine damage, discoloration, and formaldehyde release.
In the reported experiments, photochemical aging of yarns from two similar Kevlar 49 fabrics, and unwoven Kevlar 49 yarns and filaments, was studied by changes in mechanical and molecular properties. The warp and weft yarns from each fabric showed different susceptibilities to photo-induced deterioration, as indicated by their respective tensile properties. Unwoven yarns were less susceptible to photodegradation than the fabric yarns. The degradation rates remained unaltered on solvent extraction of yarn surface finish and after abrasion damage (which may occur during the weaving process). Although radiation self-screening occurs within the yarns, it is not sufficient to account for the differences in their photodegradation rates. The reduction in mechanical properties was not accompanied by any appreciable molecular weight changes and is therefore unlikely to be due to molecular chain scission reactions; however, the lower the initial strength of the yarn, the more rapid is the reduction in tensile strength.
The dispersion behavior of C.I. Disperse Yellow 54 under dyeing conditions is assessed by the turbidity ratio, which increases with decreasing dye particle size. Two different dye dispersions are prepared by milling presscakes for 1 and 25 hours. The sizes of small dye particles are more likely to increase than larger ones during dyeing at elevated temperatures; this enlargement is attributed to crystalline growth. Dyes excluded from adsorption on polyester fibers are enlarged during the dyeing process. At first, dyes of small particle size show lower exhaustion values than larger ones, but eventually they show higher values at temperatures above 130°C.
The effects of covalent, intermolecular cross-linking resulting from the introduction into cellulose of thio (SH) groups which are subsequently oxidized to form disulfide (S—S) linkages between the cellulose chains are discussed. When the reactions described herein are carried out on cotton fabrics, there is enhanced wet and/or dry wrinkle recovery, depending upon the mode of thio group oxidation. The results of oxidation in aqueous, nonaqueous, and gas-phase systems are compared. The relation between the degree of cross-linking and wrinkle recovery is described in quantitative terms. The effects of intermediate reactions and disulfide cross-linking on strength as well as on wrinkle recovery are also described.
Methods are described for measuring parameters of the tensile recovery of animal fibers. The effects of fiber crimp on these measurements, and the interpretation of the data obtained with crimpy fibers, are discussed.
Data are presented on the fiber-to-fiber variation in tensile recovery and on the effects of various chemical treatments.
For wool fibers from a common source there is very little fiber-to-fiber variation in tensile recovery.
We investigated the correlation between crystallinity and plasma susceptibility for PET and nylon 66 fibers. Plasma susceptibility is measured by the weight loss observed when fibers of varying crystallinity are exposed to air plasma. We varied the crystallinity of samples by annealing fibers at different temperatures. Plasma susceptibility and dyeability as a function of the crystallinity of fibers showed a striking resemblance: both decreased with increasing crystallinity up to a threshold crystallinity, above which there were appreciable increases. Plasma susceptibilities of these fibers, under the conditions used in this investigation, are believed to be proportional to the dyeable non-crystalline region, but not to the total noncrystalline phase of fibers.
Nylon 66 yarn was exposed to near-ultraviolet radiation in a dry oxygen atmosphere for exposure periods up to 240 hr. Dye take-up, viscosity, and density measurements, DSC thermograms, and wideline nmr spectroscopy were employed to assess the effects of the irradiation. Measureable changes were observed with each analytical technique. It was concluded that exposure of nylon 66 to the above conditions caused considerable chain scission in the defect regions, there was no detectable crosslinking, and the newly freed chain ends relaxed resulting in a more highly ordered fiber structure.
Texturing conditions were systematically varied in a factorial experiment, and the resulting yams characterized for crimp, relative dyeability, and propensity to form streaks in two-ply saxony carpets. The streaks were highly correlated with crimp rather than dye variations, with high and low crimp yarn implants producing light and dark streaks, respectively. The crimp level was also quantitatively correlated with texturing changes and a novel carpet tuft compression measurement. This analytical tool allows, for the first time, confirmation. of crimp-related carpet streaks.
Longitudinal swelling in water of nylon 66 multifilament yarn and fabric has been measured before and after heat setting. It is shown that relatively large increases in longitudinal swelling of the nylon occur as a result of setting. The swelling produced is to a large extent of reversible nature, which results in considerable stresses being produced in heat-set specimens dried at constant extension.
Previous experimental investigations of cold drawing have employed two different techniques, (i) a study of load-elongation curves obtained on a constant-rate-of-elongation apparatus, and (ii) the operation of a two-roller drawing machine. In the first case, the length of yarn is fixed and the travel of the neck is followed along this length. In the second case, the neck is fixed in space by adjusting the speed and draw ratio applied to the traversing fiber.
A third experimental method is to apply a constant load to an undrawn fiber and measure the increase in length with time (creep). In this experiment, cold drawing is observed by a marked yield region on the logarithmic time scale. Prior to the yield point, there is a region of uniform extension or pre-yield creep. Following the yield point, there is also a region of uniform extension or post-yield creep.
These creep curves can be used to predict cold drawing behavior on both a two-roller drawing machine and a constant-rate-of-elongation apparatus. In particular, the location of the neck between feed and draw rolls, the drawing tension, and the speed dependence can be understood. These concepts are illustrated using results on nylon 66 monofilaments.
Soiling of nylon 66 carpets was studied to investigate the effect of spin finishes with and without fluorocarbons finishes; and, in addition, the use of a secondary extraction process was examined to determine the effect of removing residual spin finish oils. Two types of residential carpet of intimate blend trilobal fibers with two modification ratios were evaluated: one had fluorcarbons in the spin finish with an additional topical mill-applied fluorocarbon. The second carpet had no fluorocarbons in the spin finish, but had a topical mill-applied fluorocarbon finish so that both carpets had a target of 250 to 300 ppm fluorine. Acetone extraction was used to remove the spin finishes from the carpets. Both carpets with and without extraction were soiled with particulate soil in the laboratory. Visual ratings and color difference measurements indicated more soiling on the carpets that had been extracted. Fluorine analysis showed that fluorcarbons were removed from both carpet types with the acetone extraction. Electron microscopy indicated the deposition of soil in the V-groove of the filaments with the higher modification ratio. Furthermore, fiber surfaces near the face of the carpet exhibited higher levels of soil than surfaces located near the carpet backing.
In order to test the applicability of the phenomenological theory of linear viscoelasticity to semicrystalline polymers, creep measurements were performed on oriented nylon 66 filaments. Stresses used were 0.10, 0.35, and 0.50 g/den; the temperature range was 25° to 150° C; and the samples were maintained in an anhydrous atmosphere. Under these conditions, Boltzmann's superposition principle was found to apply. By employing time–temperature superposition and the stress relaxation data of Dunell, Joanes, and Rye , the creep compliance at 25° C over 26 decades of time can be obtained. Three dispersion regions are indicated; however, there is only a tenfold variation in compliance. The shift factors log aT, which give the temperature dependence of the master compliance curve, are linear in temperature from −100° to +150° C. These results on nylon 66 agree in general with the behavior of other semicrystalline polymers studied by Nagamatsu . Although no molecular interpretation is given, the glass-to-rubber transition, common to amorphous polymers, is seen to be quite unlikely as a possible mechanism.
A method employing a linear variable displacement transducer has been adapted to measure the thermal shrinkage of oriented yarns of nylon 66. The thermal shrinkage of this material has been found to be viscoelastic in that nonlinear functions of time, temperature, and stress are required to describe the shrinkage. The activation energy has been estimated to be 40 kcal per mole, which is partly explainable by a dissociation of the hydrogen bonds in the amide groups.