20107 フラグメンテーション試験による繊維強度の評価 : 試験速度を考慮した評価方法の提案(界面の強度,OS10 先進材料の力学と強度)

This paper describes a creep rupture model considering the interfacial debonding in broken fibers in unidirectional polymer matrix composites reinforced by glass fibers. Interfacial debonding was accompanied with fiber breaks under the tensile load, depended on the fiber stress at the simultaneous fiber breaks. The interfacial debonding length, fiber strength and an interfacial shear stress were investigated by the fragmentation test. A vinylester/glass fiber interface's properties were investigated by the fragmentation test. Subsequently, the debonding length and a stress recovery length were quantitatively studied and it was found out that the relation between the strength and the length of fiber was linear. The debonding length was calculated by a measure of the distance between the fiber breaking faces. The interfacial debonding length was taken into the Curtin's fracture model. Moreover, the creep test of the unidirectional composites, it was vinylester resin matrix reinforced by glass fibers, was performed to investigate the creep constants. Then, the prediction in the use above parameters of the creep rupture time was discussed.

A technological solution to the testing and data reduction of single fibre fragmentation tests

Strength and adhesion characteristics of elementary flax fibres with different surface treatments

Six short season cotton cultivars (Gossypium hirsutum L.) were crossed in a dillalel crossing system to evaluate inheritance and interrelationship of phenotype and genotype of fiber quality traits (fiber length, uniformity index, fiber strength, micronaire and fiber elongation) and their correlation with earliness and yield traits. The study was carried out from year 2005 to 2008. The experiment design was a randomized complete block design with three replications. Additive, dominance and epistasis effects were analyzed with ADAA model. The results showed that fiber quality traits were mainly controlled by dominant genetic effects and also had a definitely proportion additive genetic effects. Micronaire, fiber length, fiber strength and fiber elongation had the highest broad sense heritability (HB) and by environment interaction (HBE) estimates, 0.618 (HB) and 0.267 (HBE) for micronaire, 0.510 (HB) and 0.287 (HBE) for fiber length, 0.452 (HB) and 0.316 (HBE) for fiber strength, 0.294 (HB) and 0.494(HBE) for fiber elongation, respectively. Narrow sense heritability (HN) was 0.258 for fiber elongation, 0.136 for fiber length, 0.127 for fiber strength and 0.110 for micronaire. Some F1 hybrids (A1×B2), (A2×A3) and (B1×A3) for fiber length, F1 (A2×B3) and (B1×B2) for fiber strength, F1 (B1×A2), (A2×B2), (A2×B3), (B1×A3), (B2×A3) and (B1×B2) for micronaire and F1 (A1×A2), (A1×A3), (A1×B1), (A1×B3) and (B2×A3) for fiber elongation had significant positive heterozygous dominance effects and affected by environment. Some F1 hybrids (A1×A2), (A1×B1), (A1×B3), (B1×A2) and (B2×A3) for fiber length, (A1×A3), (A1×B1) and (A1×B3) for fiber strength, (A1×A3), (A1×B1), (A1×B2) and (B2×B3) for micronaire and (A2×A3), (A2×B2), (A2×B3) and (B1×B2) for fiber elongation had significant positive epistatic effects. Among fiber quality traits, fiber length with fiber strength, uniformity index with fiber strength and micronaire, fiber strength with micronaire showed a positive and significant correlation. Only elongation had a significant negative correlation with fiber quality traits. Fiber quality traits had a negative correlation with earliness traits except micronaire. Fiber length and strength showed a significant negative correlation with lint yield, lint yield before frost, lint percentage and boll number. Uniformity index, micronaire and fiber elongation had a significant positive correlation with yield traits except boll weight and lint percentage. The results showed that the higher the yield and the earlier the maturing and the worse the fiber quality. Therefore, selections of fiber properties and integration of high yield, good fiber quality and early maturing traits should be performed in higher generations in short season cotton variety breeding program.

Fibre quality improvement in Gossypium hirsutum is one of the long thought objectives for sustainability of cotton improvement. The efforts to transfer G. barbadense alleles in to G. hirsutum for enhanced fibre quality is still under process across the world. To meet the future fibre quality demand in India, here we report development of G. barbadense X G. barbadense recombinant inbred mapping population that has huge potential for precise mapping of extra-long staple traits. The two-location evaluation and variability analysis for extra-long staple traits such as fibre length (24.91 to 34.06 mm), fibre strength (25.02 to 35.86 g/tex), micronaire (2.89-4.57), uniformity index (64.08-98.83), fibre elongation (5.37-6.60) and maturity ratio (0.48-0.76) were highly satisfactory. The principal component analysis indicates that the principal component-1 explaining 23.12% variance had maximum values of Eigen vectors explained by fibre strength (-0.464), length (-0.469), elongation (-0.448), maturity ratio (0.312) and micronaire value (0.306) indicating the worth of the population for which it was developed. The correlation analysis indicated that the fibre length and strength could be simultaneously improved without any impact on seed cotton yield since both traits were positively associated with each other and also showed nonsignificant association with seed cotton yield. A total of 255 recombinant inbred lines (RILs) showed normal distribution from both Z-score of skewness/kurtosis analysis and quartile-quartile plots indicating that they can be readily utilized for genotyping with latest available technologies such as genotype-by-sequencing for effective mapping of extra-long staple traits in cotton.

Single fiber fragmentation test have been conducted to examine the degradation of inner fiber strength surrounded by the resin using E-glass/Vinylestr model composite. Stressed and unstressed specimens under the environmental attack by water and acid have been prepared. The effect of diffusion phenomenon into the resin on inner fiber strength is investigated as a function of immersion time. As a result, the strength of fiber in stressed resin was lower than that in unstressed resin. This result indicates that stressed polymer have the diffusion phenomenon accelerated. In reference to each environment conditions (water and acid), the fiber degradation behavior was unchanged. It seemed that the water would only diffuse into the resin, and the acid would not. These experimental results were explained analytically based on Fickian diffusion analysis. It is expected that water diffusion affect the mechanism of the fiber degradation in the earlier stage than acid diffusion.

Low interface strength is a persistent problem in composite materials and cascades to limit a variety of bulk material properties such as lamina shear strength. Whiskerization has long been pursued as a method to reinforce the interphase and improve both the single fiber interface strength as well as the bulk properties. Recent developments have shown that ZnO nanowire whiskerization can effectively improve the properties of a bulk composite without requiring the high temperatures that previous deposition processes needed. Although the efficacy of a ZnO nanowire interphase has been established, the mechanism for adhesion of the interphase to the fiber has not been identified. Specifically, the addition of the ZnO nanowires to the surface of the fibers requires that the ZnO nanowires have strong chemical adhesion to the fiber surface. This work will create a variety of chemical environments on the surface of the fibers through new chemical functionalization procedures and quantify the surface chemistry through x-ray photoelectron spectroscopy. The effect of fiber surface chemistry on the adhesion of the ZnO is assessed through single fiber fragmentation testing. The interface strength is found to strongly correlate with the concentration of ketone groups on the surface of the fibers.

The role of matrix cracks and fibre/matrix debonding on the stress transfer between fibre and matrix in a single fibre fragmentation test

Statistical fragments and micro-failure modes in the multi-fiber-reinforced micro-composites were investigated by fragmentation test. The specimen consisted of three fibers using carbon fibers (CFs) and glass fibers (GFs), embedded in the epoxy resin with three-dimensional arrangement. Fracture morphology and micro-failure behavior from the progressive fragmentation of fibers and fiber/matrix interfacial adhesion were observed via polarized-light microscope. The interfacial shear strength of CF/epoxy micro-composites is higher than that of the GF/epoxy micro-composites measured by the single fiber fragmentation test. The results show that fragment number on monofilament demonstrates obvious differences between multi-fiber and single fiber systems, and the location of the breakpoint is determined by the CFs that fracture firstly, indicating clustering fracture modes. This is because stress concentration around the breakpoints influences the stress redistribution on the adjacent fibers. Distinct micro-failure modes were observed in three-fiber and the hybrid systems, where matrix cracks around the CFs and interfacial debonding occurs around the GFs. The mixture of CFs and GFs demonstrates distinctive hybrid effect by the changes of the fragment number and initial fracture strain of fibers in hybrid systems.

The primary objective of the study is to investigate the impact of chemical structure at the interface on the interface strength of fiber/matrix composite. A solvent based method was used to deposit trichlorosilane on E-glass fiber surfaces followed by in situ modification of the deposited layer to prepare pure and mixed amine undecyl self assembled monolayer (SAM). The extent of fiber/matrix adhesion was determined by performing single fiber fragmentation test (SFFT). The SFFT data indicate that ≈ 85 % of fiber breaks obtained for epoxy composite occurs at a much lower mass fraction of amine coverage for SAM while a similar number of fiber breaks occur at a much higher mass fraction of amine coverage for aqueous solution deposited coupling agent system.

Influence of kink bands on the tensile strength of flax fibers

Enhancing interfacial shear strength with tailored carbon nanotube orientations: A micromechanical hierarchical model of single fiber fragmentation tests

Effect of annealing and silylation on the strength of melt-spun Ni–Mn–Ga fibres and their adhesion to epoxy

Sheep wool is an eco-friendly, renewable, and totally recyclable material increasingly used in textiles, filters, insulation, and building materials. Recently, wool fibers have become good alternatives for reinforcement of polymer composites and filaments for 3D printing. Wool fibers are susceptible to environmental degradation that could shorten their lifetime and limit applications. This study reports on the mechanical properties of sheep wool fibers under the impact of humid air and UV irradiation. The results of single fiber tensile tests showed a noticeable gauge length effect on the fibers’ strength and failure strain. Long (50 mm) fibers possessed about 40% lower characteristics than short (10 mm) fibers. Environmental aging decreased the elastic modulus and strength of the fibers. Moisture-saturated fibers possessed up to 43% lower characteristics, while UV aging resulted in up to a twofold reduction of the strength. The most severe degradation effect is observed under the coupled influence of UVs and moisture. The two-parameter Weibull distribution was applied for the fiber strength and failure strain statistical assessment. The model well predicted the gauge length effects. Moisture-saturated and UV-aged fibers were characterized by less extensive strength dependences on the fiber length. The strength and failure strain distributions of aged fibers were horizontally shifted to lower values. The results will contribute to be reliable predictions of the environmental durability of sheep wool fibers and will extend their use in technical applications.

A modified single fiber fragmentation test (SFFT) procedure, that permits separation of the fiber break and fiber/matrix (F/M) debond propagation events, was employed to characterize the (F/M) interface toughness of dry and water saturated E-glass/vinylester. By focusing solely on the debond propagation event, and by measuring the critical load for debond propagation, fracture mechanic analysis enabled determination of the fracture toughness of the fiber/matrix interface. After immersion in seawater, the interface was substantially degraded. The fracture toughness was reduced by approximately a factor of two.