• Fibers and Polymers
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• v.4 no.3
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• pp.124-128
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• 2003

Dark brown Alpaca fiber was reduced in shade via selective bleaching with peroxide. Two selective oxidative bleaching methods were tested on alpaca top to assess their effectiveness for color removal and fiber quality properties. Color change, bundle strength, weight loss, fiber diameter, surface modification, dye-ability and dye wash fastness were assessed for both methods and compared with the original brown top. Bleach method 1 (BL-I) showed little surface modification, 5.8% weight loss and 2.4% strength loss. D1925 yellowness index was reduced to 74.3 from 83.1 and provided a good base for the dyeing of medium to deep shades. Bleach method 2 (BL-II) displayed considerable surface modification, 7.8% weight loss and 18% strength loss. BL-II also resulted in a mean diameter reduction of 1.9 micron during bleaching. Yellowness was reduced to 64.5 from 83.1 and provided a very good base for the dyeing of medium to deep shades. BL-I showed better exhaustion of the premetallised dye Lanaset Violet B than BL-II. Wash fastness for BL-II was 1 grey scale unit poorer than BL-I. BL-II showed far better color clarity at pale depths however the wash fastness of the finished product was not good enough to maintain the depth or clarity of the color. BL-I showed poorer clarity of color but exhibited better wash fastness results.

• Macromolecular Research
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• v.10 no.5
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• pp.282-285
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• 2002

In this paper, we report a modified technique for the production of oriented continuous nanofibers instead of non-woven mats using a rapidly rotating collection device. We are interested in retaining physical properties such as electrical conductivity of fiber bundles in their axial direction. The experiments were performed using polyethylene oxide (PEO) and its blend with polyaniline (PANI). According to the results, a typical fiber with a uniform diameter of about 100 nanometer was produced. The fibers from the PEO/ CHCl$_3$ solution show high crystallinity and good orientation whereas the fibers from the blend solution of PEO/PANI/m-cresol and CHCl$_3$ show no preferred orientation. However, the fibers of the blend exhibit high electrical conductivity of 33 S/cm for a fiber bundle at a PANI level of 50 %.

• Composites Research
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• v.30 no.6
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• pp.365-370
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• 2017

Mechanical properties of carbon fiber reinforced thermoplastic composites (CFRTPs) are affected by various factors. One of the them are poor compatibility of the epoxy sizing layer on the carbon fiber surface with thermoplastic matrix, which causes the inferior interfacial strength between fibers and matrix. In addition, the high molten-viscosity of thermoplastics attributes to the poor impregnation state. Consequently, many voids in the composite materials were generated, which leads to poor mechanical properties of the thermoplastic composites. In this study, the epoxy sizing on the carbon fiber surface was removed and the polyamide 6,6 solution was coated on the de-sized carbon fiber surface to improve the impregnation state and mechanical properties. Interlaminar shear strength (ILSS) of CFRPTs was estimated by implementing short beam shear tests. In addition, flexural strength was measured and the impregnation state of the composites was evaluated by calculating void content.

• Fibers and Polymers
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• v.6 no.3
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• pp.263-268
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• 2005

Alpaca fibers have some distinct properties such as softness and warmth, which have not been fully understood in combination with the fiber internal structures. In the present investigation, the internal structures of alpaca fibers have been closely examined under the scanning electron microscope (SEM), especially in the longitudinal direction. The results showed that numerous pigment granules reside loosely inside pockets in brown and dark-brown alpaca fibers. These pigment granules were mainly distributed inside the cortical cells, the medullation regions as well as underneath the cuticles. Their size in the brown alpaca fibers was smaller and more uniformly round than in the dark-brown fibers. These granules in colored alpaca fibers loosen the bundle of cortical cells, providing many crannies in the fibers which may contribute to the superior flexibility, warmth and softness of the fibers. Moreover, there are no heavy metal elements found in the granules. The mordant hydrogen peroxide bleaching employed could eliminate the pigment granules and create many nano-volumes for further dyeing of fibers into more attractive colors.

• Composite Materials and Engineering
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• v.3 no.3
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• pp.221-239
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• 2021

This paper presents a multiscale modeling method for sheet molding compound (SMC) composites through a novel bundle packing reconstruction algorithm based on a micro-CT (Computed Tomography) image processing. Due to the complex flow pattern during the compression molding process, the SMC composites show a spatially varying orientation and overlapping of fiber bundles. Therefore, significant inhomogeneity and anisotropy are commonly observed and pose a tremendous challenge to predicting SMC composites' properties. For high-fidelity modeling of the SMC composites, the statistical distributions for the fiber orientation and local volume fraction are characterized from micro-CT images of real SMC composites. After that, a novel bundle packing reconstruction algorithm for a high-fidelity SMC model is proposed by considering the statistical distributions. A method for evaluating specimen level's strength and stiffness is also proposed from a set of high-fidelity SMC models. Finally, the proposed multiscale modeling methodology is experimentally validated through a tensile test.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.38 no.3 s.116
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• pp.29-37
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• 2006

To use bamboo in the pulp industry, the anatomical characteristics of 60-day-old, 1-year-old, 2-year-old, and 3-year-old moso bamboo (Phyllostachys pubescens Mazel), and the characteristics of fiber and sheet of alkali pulp made of moso bamboo were investigated. Moso bamboo is composed of metaxylens and parenchyma cells in the inner part of the wall, and thick-walled small bundle sheathes near the outer walls. Moso bamboo showed the heterogeneity in anatomical structure. The longest fibers were shown in the middle part, and the widest width in the inner part. The lignin contents were 14.4% in 60-day-old bamboo, which was not lignified yet. The lignin contents in bamboo above 1 year were approximately 35%. The yields of alkali pulp of moso bamboo were in the range between 41 and 47%, and the yields tend to decrease with the increase of ages. The lignin contents of 60-day-old bamboo were 2.1% and those of bamboo above 1 year showed approximately 4% to 5% increment. The length, width, and curl index of fiber in alkali pulp appeared to be similar in all ages. However, coarseness increased slightly with the increase of bamboo ages. The distribution of long fiber was shown much in 60-year-old bamboo. The optical and mechanical properties of moso bamboo tended to decrease with the increase of bamboo age.

• Polymer(Korea)
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• v.33 no.5
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• pp.420-428
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• 2009

In this study, the composites containing carbon black (CB) or carbon fibers were prepared, and the microwave absorbing properties and the absorption mechanism of them were investigated and discussed in the frequency range of 2-18 GHz, respectively. The optimum mass fraction of CB has been found as 6%, and the carbon fibers were discovered to absorb radar wave either under parallel or vertical polarization, the suitable gap distance between each bundle of which was 5 mm. According to the results of the single constitute absorber samples, the structured composites with the two kinds of absorbers combination were fabricated and studied at 2-18 GHz. The top layer absorbers affect the absorption performance a lot; the maximum reflection loss of composites with CB as top layer absorbers was -31.8 dB with the frequency range of 2.4 GHz below -10 dB, and the other type with CFs as the top layer absorbers obtained the reflection loss peak value of -31.4 dB with 2 GHz below-10 dB.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.91-94
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• 2003

Laminated composites are liable to fatal damage under impact load due to the fact that they have no reinforcement in the thickness direction. To overcome the inherent weakness, three dimensional (3D) textile reinforcements have drawn much interests. In this paper, impact performance of 2D and 3D textile composites has been characterized. For 2D composites, fiber bundle size and fiber pattern have been varied. For 3D composites, orthogonal woven preforms of different density and type of through-thickness fibers have been studied. To assess the damage after the impact loading, specimens were subjected to C-scan nondestuctive inspection. Compression after impact (CAI) were also conducted in order to evaluate residual compressive strength.

• Composites Research
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• v.26 no.3
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• pp.160-164
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• 2013

In this study, the effect of phosphoric acid (PA) as a fiber spinning aid on the strength increase of polyacrylonitrile (PAN) nano-fibers by using modified mechano-electrospinning technologies has been analyzed. The medium carbonization temperature of $800^{\circ}C$ has been selected for the future economic production of these new materials. The concentration of PAN in dimethyl sulfoxide (DMSO) was fixed as 5 wt%. The weight fraction of PA was selected as being 2%, 4%, 6%, and 8% in comparison to PAN. These solutions have been used to make the nanofibers. The mechano-electrospinning apparatus installed in KRICT was made by our own design. By using this apparatus the continous and highly aligned precursor nano-fibers have been obtained. The bundle of 50 well aligned nano diameter continuous fibers with the diametr of 10 microns with 6 wt% phosphoric acid for addition showed maximum mechanical properties of 1.6 GPa as tensile strength and 300 GPa as Young's modulus. The weight of final product can be increased 19%, which can improve the economical benefits for the application of these new materials.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.205-210
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• 2019

Bioactive glass (BG) finds limited use as a bone replacement material owing to its low mechanical properties. In order to solve this problem, the micro-sized 13-93 BG was prepared as a fabric composite with SiC microfibers, and its mechanical properties and biocompatibility were investigated in this study. The tensile strengths of BG-SiC fiber-bundle composites increased in proportion to the number of SiC fibers. In particular, even when only one SiC fiber was substituted, the tensile strength increased by 81% to 1428 MPa. In the early stage of the in-vitro test, a silica-rich layer was formed on the surface of the 13-93 BG fibers. With time, calcium phosphate grew on the silica-rich layer and the BG fibers were delaminated. On the other hand, no products were observed on the SiC fibers for 7 days, therefore, SiC fibers are expected to maintain their strength even after transplantation in the body.