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1.
K. Gokul T. Ram Prabhu T. Rajasekaran 《Transactions of the Indian Institute of Metals》2017,70(10):2537-2546
In the present work, the natural composites based on sugarcane bagasse fiber and/or coconut shell powder were processed using hand lay-up technique. The matrix selected was polyester. Three different types of composites were considered: polyester matrix + sugarcane fiber, polyester matrix + sugarcane fiber + metal mesh and polyester matrix + sugarcane fiber + coconut shell filler. The sugarcane fibers were used in three forms: (1) chemically treated by NaOH, (2) chemically treated by HCl, and (3) untreated condition. In total, 9 types of composites were developed and studied for tensile, flexural and impact properties. The fracture surface of the tensile and flexural test samples was examined with the aid of scanning electron microscope to understand the bonding characteristics and the mode of failure. The key-findings from the present work are: (1) the composites reinforced with the NaOH treated sugarcane fiber and the metal mesh show superior tensile and impact properties whereas the composites reinforced with the NaOH treated sugarcane fiber show the best flexural properties, (2) NaOH treatment of sugarcane fibres has a significant effect in improving the mechanical properties by surface modification of fibres through OH? functional groups. In contrast, HCl treatment of sugarcane deteriorates the surface of the sugarcane by absorbing the electrons. The damaged surface results in weak bonding causing poor mechanical properties, (3) From the SEM analysis of the surface of the sugarcane fiber, it may be concluded that the surface condition of the sugarcane fibres decide the bonding with the matrix. The fiber pull-outs and porosities are less in the NaOH treated sugarcane reinforced composites. The fiber failure is the main mechanism of failure in the tensile test whereas the fiber debonding from the matrix is the main source of failure in the flexural test. 相似文献
2.
S. Jayabal S. Rajamuneeswaran R. Ramprasath N. S. Balaji 《Transactions of the Indian Institute of Metals》2013,66(3):247-255
The tensile, flexural and impact properties of calcium carbonate particles-impregnated coir fiber-reinforced polyester composites were evaluated. The short untreated green husk coir fibers were used as reinforcement materials in unsaturated polyester resin matrix. The composite fabrications were planned with the three levels of fiber parameters namely fiber length, fiber diameter and filler content as per design of experiments (DOE) and the mechanical properties were tested as per ASTM standards. An artificial neural network (ANN) model was developed to predict the mechanical properties and it was observed that the developed ANN model accurately predicted the mechanical properties within the ranges specified. 相似文献
3.
以短切碳纤维(Cf)和碳化硅纤维(SiCf)为增强相,并用化学气相渗透法对部分纤维进行炭涂层处理,采用热压法制备了4种纤维增强MoSi2基复合材料(SiCf-MoSi2、SiCf/C-MoSi2、Cf-MoSi2和Cf/C-MoSi2),研究了纤维类型及表面炭涂层对MoSi2基复合材料弯曲性能的影响.结果表明纤维的加入明显提高了MoSi2的抗弯强度,加入5%SiCf和5%Cf的复合材料的强度比纯MoSi2分别提高了9.0%和22.8%,Cf增强作用明显优于SiCf;纤维类型相同时,具有炭涂层的纤维增强效果更显著,5%Cf/C-MoSi2复合材料的强度最高,达到了364.7MPa,比纯MoSi2的强度提高了30%;扫描电镜分析表明,无炭涂层的SiCf与MoSi2基体间存在着明显的裂缝,炭涂层改变了纤维与基体的界面结合;有涂层纤维的断裂机制为首先脱粘然后拔出. 相似文献
4.
Two experiments were conducted to determine the effects of dieldrin and calcium on reproductive performance of quail. At 25% egg production the quail received diets containing 0,10 or 25 p.p.m. of dieldrin for 6, 28-day periods in experiment 1 and 0, 5, or 25 p.p.m. of dieldrin for 4, 28-day periods in experiment 2. Pesticide treatments were employed with diets containing 0.5% and 3.0% calcium. The results show that egg shell thickness, cracked eggs, egg production, feed consumption, egg weights, fertility, hatchability and body weights were not affected by dieldrin treatments. However, egg shell thickness, cracked eggs, egg production and hatchability were adversely affected by the lower calcium level. Female body weights were consistently heavier for the low calcium diet. Mortality increased in the presence of 10 and especially 25 p.p.m. of dieldrin. Livability of chicks from hens receiving rations with 10 and 25 p.p.m. of dieldrin was significantly lower than those fed no dieldrin. In summary, dieldrin was without effect on egg shell quality or other reproductive factors but did exert a detrimental effect on adult mortality and livability of progeny. 相似文献
5.
An experimental investigation was undertaken to evaluate the mechanical behavior of a soil–cement–fly ash composite, reinforced with recycled plastic strips (high-density polyethylene) that were obtained from postconsumer milk and water containers. The primary motivation for the study was to investigate the innovative reuse of several candidate waste materials in geotechnical and pavement applications. The specific objectives of the research were: (1) to evaluate the compressive, split tensile, and flexural strength characteristics of the material, and (2) to determine the effectiveness of recycled plastic strips in enhancing the toughness characteristics of the composite. Since cement-stabilized materials are weak in tension, the main focus of the experimental program was to conduct a series of specially instrumented split tensile and flexural tests on mixes containing various amounts of cement, fly ash, and plastic strips. For a meaningful comparison of test results, all specimens were prepared at a constant dry density. The standard ASTM C496 procedure for split tensile test was slightly modified by attaching two horizontal linear variable differential transformers (LVDTs) to measure the diametral deformation of the specimen due to compressive loading in an orthogonal direction. This modification enabled the evaluation of the postpeak toughness behavior of the composite. For some specimens, a strain gauge was attached to the middle of the face perpendicular to the loading plane in order to correlate the results with the one found using the LVDTs. All tests were performed with a 90 kN universal testing machine with deformation control. Experimental data show that the soil–cement matrix stabilized with 4% to 10% by weight of fly ash and reinforced with 0.25% to 0.5% (by weight) plastic strips (having lengths of 19 mm or 38 mm) can achieve a maximum compressive strength of 7000 kPa, a split tensile strength of 1000 kPa, and a flexural strength of 1200 kPa. These ranges in strength values are suitable for a high-quality stabilized base course for a highway pavement. To quantify the reinforcing effects in the postpeak region, a dimensionless toughness index is proposed. It is found that the use of fiber reinforcement significantly increases the postpeak load carrying capacity of the mix and thus the fracture energy. It is concluded that the lean cementitious mix containing recycled materials offer a lot of promise as an alternative material for civil engineering construction. 相似文献
6.
通过密炼?注塑成型工艺制备了不同苎麻纤维含量的聚乳酸基复合材料,研究了纤维含量对复合材料性能的影响规律,并揭示了纤维增强机理。研究表明,苎麻纤维的添加提高了复合材料的耐热性能,尤其是当纤维质量分数为40%时,复合材料的热变形温度提高了10.5%。此外,苎麻纤维均匀地分散在基体中,由于纤维与聚乳酸的界面强度较弱,断面上有大量的纤维拔出和纤维孔洞;差示扫描量热仪测试表明高含量的纤维限制了聚乳酸分子链的运动,促进复合材料形成更加致密完善的晶核;同时,流变行为也表明苎麻纤维含量的增加有助于提高复合材料的黏弹响应和复合黏度;最后,苎麻纤维的加入提高了复合材料的拉伸和弯曲强度,且随纤维含量的增加而增大。与聚乳酸相比,当纤维质量分数为40%时复合材料的拉伸和弯曲强度分别提高了30%和21.9%。 相似文献
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8.
采用传统粉末冶金工艺制备了陶瓷颗粒增强Fe?0.5Mo?1.75Ni?1.5Cu?0.7C扩散合金化钢复合材料,选用的陶瓷颗粒为SiC、TiC和TiB2。采用光学显微镜和扫描电子显微镜观察了烧结材料微观结构,并对烧结材料的硬度、强度和摩擦磨损性能进行了测试。结果表明,由于SiC和TiB2与基体的化学相容性好,陶瓷颗粒与基体界面结合良好;由于TiC颗粒具有极高的化学稳定性,TiC颗粒与基体界面结合情况不理想。随着陶瓷相含量(质量分数)的增加,添加SiC和TiC的烧结试样相对密度降低;添加TiB2的烧结试样相对密度先增加后降低,当添加TiB2质量分数为0.9%时达到最大值。随着陶瓷含量增加,添加SiC和TiB2烧结试样的硬度增大,当陶瓷相质量分数超过1.2%时,硬度增加缓慢;添加TiC烧结试样的硬度先增加后降低,当添加TiC质量分数为0.9%时达到最大值。随着陶瓷相含量增加,添加SiC和TiC烧结试样的强度降低,少量添加SiC对强度没有明显损害;添加TiB2烧结试样的强度先增加后降低,当添加TiB2质量分数为0.6%时达到最大值(971.7MPa),比基体提高了14.1%以上。添加陶瓷相对烧结钢性能的积极影响依次是TiB2、SiC和TiC。 相似文献
9.
V. V. Berezovskii Yu. O. Solyaev S. A. Lur’e A. V. Babaitsev A. A. Shavnev Yu. A. Kurganova 《Russian Metallurgy (Metally)》2015,2015(10):790-794
The mechanical properties of a composite material with a matrix of aluminum alloy D16 reinforced with dispersed silicon carbide particles have been studied. The physicomechanical properties (density, elastic modulus, ultimate tensile strength, and limiting strains) of the composite material with various filler contents are determined experimentally. The experimental results are compared to the results of a theoretical simulation obtained using elastic and elastoplastic models of the composite material. The experimental and the calculated mechanical properties of the composite material with the volume content of the filler up to 30% agree well with each other. 相似文献
10.
The mechanical properties of bone were modeled in the context of a filled polymeric composite containing a collagenous matrix and a hydroxyapatite filler. The longitudinal and transverse moduli of cortical bone as a composite with perfect alignment of filler particles were calculated to be 34.5 and 5.3 GPa, respectively. When considering that particle orientation is arranged within a distribution about the long axis, moduli close to the experimentally measured values are achieved. The calculated tensile strength of 1.7 GPa is higher than the experimental values, which may be attributable to intrinsic sample flaws and biological heterogeneity. The mode of tensile failure in this model is particle-matrix debonding, which may explain fatigue or stress fractures. Overall, the filled composite model of bone helps explain the roles of mineralization fraction, particle shape and orientation, and other attributes of the constituent phases in understanding the tensile properties. The fundamentals of bone behavior in compression are less well understood. It is proposed that incorporation of an inorganic phase in bone was teleologically necessary for vertebrates to achieve adequate levels of compressive strength. 相似文献
11.
Eggs of Schistosoma mansoni were obtained from livers of mice and hatching was observed under varying conditions of light and ionic composition of the medium. Hatching occurred equally well in light and in darkness. Eggs also hatched readily in 1- to 50-m OsM solutions of urea, sucrose, sodium chloride, and glycerol, but hatching was inhibited at higher concentrations unless the eggs were left in solutions for long periods of time. Hatching readily occurred in deionized water, but the emerged miracidia did not swim longer than 5 to 10 min unless Na+ was added. Histochemistry of the egg showed DNA-positive egg granules and a polysaccharide-positive vacuole matrix. Acid mucopolysaccharides were stained in the vacuolar matrix and in the anterior sac of the miracidium. Longitudinal alignment of constituents of the egg shell is suggested by the predominance of longitudinal rents in the shell at hatching. A mechanism of hatching involving an osmotic stimulus is proposed. 相似文献
12.
The gastrolith of the crayfish Procambarus clarkii contains a small amount of an organic matrix that is mainly chitin and proteins, together with a large amount of calcium carbonate. As the first step to understand the mechanism of calcification, we tried to characterize matrix proteins in the gastrolith. An insoluble matrix protein, referred to as gastrolith matrix protein, was made soluble with 1% SDS containing 10 mM dithiothreitol, and was purified by reverse-phase high-performance liquid chromatography. The protein had a molecular weight of about 50,500 and a blocked amino terminus. By enzymatic digestion and microsequencing, five partial amino acid sequences with a total of 225 amino acid residues were identified and found to include a repetitive sequence not reported previously. 相似文献
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14.
AbstractSilicon carbide reinforced copper matrix composites containing 50–80 vol.-%SiCp were fabricated by hot pressing copper coated SiCp powder. The results show that the densification, thermal expansion coefficients, flexural strength, and thermal conductivity of Cu/SiCp composites reinforced by electroless copper plating and their corrosion resistance in 5%NaCl solution are better than those without electroless plating. Physical properties and flexural strength of the composites decrease with an increase in SiCp content, whereas the corrosion resistance increases with an increase in SiCp volume fraction. By observing the fracture surface after a flexural test, it can be seen there are two types of fracture model: the cracking of Cu/SiCp interface and the pulling out of SiCp particles. The experiment also proved that the bonding strength of the Cu/SiCp interface and the pressure of the hot pressing operation are the two main factors which influence the fracture of these composites. 相似文献
15.
为了避免铬铁矿液相氧化产物中硅、铝和碳酸钾等杂质的循环积累,影响铬酸钾产品的质量,并对生产造成危害,分别研究了氧化钙和氢氧化钙对苛化及脱铝的影响,以及碳酸钾、铁渣的存在对脱硅、脱铝的影响。结果表明,氢氧化钙的脱铝效果要好于氧化钙,而苛化效果劣于氧化钙;碳酸钾和铁渣的存在有利于硅、铝杂质的脱除。脱硅、铝后的溶液在真空度为0.06MPa,蒸发至氢氧化钾的质量分数为30%时,可得到符合质量要求的铬酸钾晶体;在真空度为0.07MPa,蒸发至氢氧化钾质量分数为50%时,溶液中碳酸钾质量分数亦可降到符合工艺要求的5%以下,同时回收了碳酸钾晶体。保证了钾碱的循环。 相似文献
16.
Synthetic hydroxyapatite particles of two median sizes and different morphologies have been used to manufacture hydroxyapatite reinforced high density polyethylene composites (HAPEX) for medical applications. The effects of hydroxyapatite particle size on properties of the resultant composites were investigated using various techniques. It was found that composites with smaller hydroxyapatite particles had higher torsional modulus, tensile modulus and tensile strength, but lower strain to failure. Examination of fracture surfaces revealed that only a mechanical bond existed between the filler and the matrix. It was shown that dynamic mechanical analysis is useful in studying the viscoelastic behaviour of the composite. 相似文献
17.
Flexural Behavior of an Ultrahigh-Performance Concrete I-Girder 总被引:1,自引:0,他引:1
Benjamin A. Graybeal 《Canadian Metallurgical Quarterly》2008,13(6):602-610
The flexural behavior of an ultrahigh-performance concrete (UHPC) was investigated through the testing and related analysis of a full-scale prestressed I-girder. A 28?ksi (193?MPa) compressive strength steel fiber reinforced concrete was used to fabricate an 80?ft (24.4?m) long AASHTO Type II girder containing 26 prestressing strands and no mild steel reinforcement. Intermediate and final behaviors, including cracking, flexural stiffness, and moment capacity, were investigated. Test results are compared to predictions based on standard analytical procedures. A relationship between tensile strain and crack spacing is developed. The uniaxial stress-strain response of UHPC when subjected to flexural stresses in an I-girder is determined and is verified to be representative of both the stress and flexural stiffness behaviors of the girder. A flexural design philosophy for this type of girder is proposed. 相似文献
18.
Plastic deformation under uniaxial longitudinal tension and compression is investigated for pure aluminum reinforced with
a high volume fraction of parallel alumina fibers. The matrix substructure is also examined in transmission electron microscopy.
The aim is to study thein situ room-temperature mechanical behavior, particularly the work-hardening rate, of pure aluminum when reinforced with a high
volume fraction of chemically inert ceramic reinforcement. The matrix substructure prior to deformation, composed of cells
about2 μm in diameter, is similar to that of highly deformed unreinforced aluminum. Measured compressive composite elastic moduli
agree with rule of mixture predictions; however, no elastic regime is found during tensile loading. As tensile deformation
proceeds above a strain around 0.05 pct, a constant rate of work hardening is reached, in which the matrix contribution is
negligible within experimental error. Upon unloading from tensile straining, Bauschinger yielding begins before the composite
reaches zero load, as predicted by the rule of mixtures. The matrix substructure after load reversal retains a2- μm cell size but with greater irregularity in the dislocation configurations. Using the rule of mixtures,in situ stress-strain curves are derived for the reinforced aluminum matrix and described by a modified Voce law.
Formerly with the Department of Materials Science and Engineering, Massachusetts Institute of Technology 相似文献
19.
采用熔融共混法用双螺杆挤出机制备了长支链聚丙烯(LCB-PP)/有机蒙脱土(OMMT)纳米复合材料,并对其结构、流变和力学性能进行了研究.透射电镜(TEM)测试结果表明,大部分OMMT在LCB-PP中发生剥离.流变行为研究发现,当OMMT的填充量达到一定临界值后,制备的纳米复合材料呈现出在低频处储能模量增加、剪切变稀行为明显等线性黏弹性行为,表明LCB-PP/OMMT内部形成了紧密和稳定的网络结构,从而抑制了大分子链的松弛和运动.力学测试结果表明,OM-MT显著提高了LCB-PP的拉伸强度、缺口冲击强度和弯曲模量,但降低了其弯曲强度. 相似文献
20.
Crab-shell chitin, which is inherently high in calcium carbonate and nutrients, was tested as a multifunctional, fractional amendment to improve the effectiveness of spent mushroom compost (SMC), which is a low-cost, frequently used, but often underperforming substrate for treating acid mine drainage (AMD). Batch and continuous-flow column tests were used to evaluate different crab-shell/SMC mixtures for their ability to neutralize acidity, reduce sulfate, and remove metals in field-collected AMD. Alkalinity generation and the removal of manganese and sulfate were strongly correlated to the fraction of crab shell in the substrate: the treatment capacity increased from 36.7 L/kg for the traditional 90% SMC/10% limestone substrate up to 428 L/kg for 100% crab shell. The costs associated with adding crab shell to SMC were found to be minimal relative to the resulting improvement in water quality. Based on these data, it appears that a small fraction of crab shell (5–15%) does not provide a significant benefit over traditional compost and limestone substrates, but that larger fractions (50–100%) are much more efficient than traditional SMC substrates, especially for the removal of metals. 相似文献