Constitution and strength of glass fibers

Five characteristic ranges of glass strength are described with respect to the sizes of its associated surface flaw. Particular attention is directed to the substantial difference in behavior between commercial and flawless glass fibers. It has been discovered in the latter case that a surface layer one order of magnitude thinner than normally detected is present, probably as a consequence of the drawing process. Distinct differences in behavior of the two kinds of layers was noted by using ultra-violet light absorption and hydrofluoric acid etching. Basic strength of the flawless glass fibers in vacuum can reach one million pounds per square inch.

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Zusammenfassung Fünf charakteristische Glasstärkebereiche wurden mit Rücksicht auf die Größen ihrer dazugehörigen Oberflächenfehlerhaftigkeit beschrieben. Besondere Aufmerksamkeit wurde auf den wesentlichen Unterschied im Verhalten zwischen kommerziellen und fehlerfreien Glasfibern gelenkt. Es wurde im letzteren Fall festgestellt, daß eine Oberflächenschicht, ein Größenverhältnis dünner als gewöhnlich beobachtet, gegenwärtig ist. Dieses ist wahrscheinlich eine Folge des Ziehungsvorganges. Deutliche Unterschiede im Verhalten der beiden Schichten wurden bemerkt. Man gebrauchte ultra-violette Lichtaufnahme and Fluorwasserstoffsäuere Ätzung. Die fundamentale Stärke der fehlerfreien Glasfibern im Vakuum kann eine Million Psi erreichen.

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Résumé On décrit cinq catégories de fibres de verre et leur resistance en fonction des dimensions des défauts de surface qu'elles comportent. L'attention est particulièrement attirée sur les différences substantielles de comportement que présentent les fibres de verre courantes et les fibres de verre sans défauts.On a pu determiner que ces dernières comportaent une couche superficielle dont l'épaisseur est d'un ordre de grandeur plus faible que celle que I'on détecte habituellement, cette couche étant probablement due au procédé de fabrication par filage.Des différences nettes de comportement de ces deux sortes de couches ont été observées, en mesurant l'absorption des rayons ultraviolets et en recourant à une attaque à l'acide hydrofluorique.La résistance de base de fibres de verre sans defauts pent atteindre dans le vide un million de psi.

     

Tensile strength,ductility and fracture of magnesium-silicon alloys

Tensile tests were performed between 293–573 K in order to investigate the mechanical properties of cast and extruded Mg-Si alloys. For the cast materials, Mg-high Si ( 10 wt%) alloys showed lower values of the highest tensile strength at temperatures up to 373 K, as compared to pure Mg and Mg-low Si (<10 wt%) alloys, whereas the strength at 573 K increased with increasing Si content. The addition of aluminum and zinc to the alloys was effective in increasing the strength. The fact that the Mg-high Si alloys showed lower strength than the Mg-low Si alloys was because a high volume of Mg₂Si embrittled the Mg-Si alloys. Microstructural investigations revealed that the particles of Mg₂Si were coarse for the cast materials and fracture of the particles was caused by deformation. The mechanical properties of the cast materials were improved by hot extrusion. Microstructural refinement by hot extrusion was responsible for the improvement of the mechanical properties.     

Tensile behavior contrast of basalt and glass fibers after chemical treatment

Basalt and glass fibers were treated with sodium hydroxide and hydrochloric acid solutions respectively for different periods of time. Both the mass loss ratio and the strength maintenance ratio of the fibers were examined after the treatment. The morphologies of the fiber surfaces were characterized using scanning electron microscopy and their compositions were analyzed using energy dispersive X-ray spectroscopy. For the basalt fibers, the acid resistance was much better than the alkali resistance. Nevertheless, for the glass fibers, the acid resistance was nearly the same as the alkali resistance. Based on the experimental results, possible corrosion mechanisms are addressed.     

Plasma surface treatment and modification of glass fibers

New helical coupling plasma system for continuous surface treatment and modification (surface processing) of fiber bundles has been developed and tested for glass fibers. The system enables surface processing of single filaments and flat substrates as well. Surface processed glass fibers and their bundles were examined as reinforcements for glass fiber/polyester composite systems. Processing of fibers comprised a surface treatment using argon gas and a surface modification using hexamethyldisiloxane and vinyltriethoxysilane monomers. Interfacial and interlaminar shear strengths of plasma processed glass fiber/polyester systems were compared with those of untreated and commercially sized fibers.     

Strain-rate dependence of the tensile strength of glass fibers

It is well known that the strength of glass fibers increases with increasing strain rate. Consequently, impact strength of glass fiber is competitive with that of carbon fiber. This strengthening phenomenon is well recognized for bulk glass. Strain-rate dependence of the strength for bulk glass was described by considering slow crack growth in glass. The analytical model that considered the slow crack growth of glass is proposed to predict the strength of glass fibers. The proposed model considered the stress corrosion limit and a constant crack velocity region. Calculations showed almost same results with the previous model, however, some differences were confirmed. To discuss the validity of the analysis, tensile tests of E-glass fiber bundles were conducted at various strain rates. It was observed that the fracture behaviors differ with the strain rates. Experimental results showed that the strength of E-glass fibers increased with increasing strain rate. Furthermore, we confirmed that the analytical results were in good agreement with the experimental results. The strain-rate dependence of the strength of glass fibers was successfully predicted by considering the slow crack growth in glass.     

基于断裂韧性预报复合材料层合板的开孔拉伸强度

开孔层合板的强度预报往往取决于孔边的临界长度,它不仅与材料性能,而且与铺层、孔径都有关。本文基于线弹性断裂力学,提出了一种预报对称铺层层合板开孔拉伸强度的新方法,只需提供正交层合板的断裂韧性和无缺口层合板的拉伸强度,显著降低对实验数据的依赖性。首先,将临界长度表作为层合板断裂韧性和无缺口拉伸强度的函数,再通过正交层合板[90/0]_8s的紧凑拉伸试验和虚拟裂纹闭合技术,确定出0°层断裂韧性,进而计算得到任意对称铺层层合板的断裂韧性。本文测试了T300/7901层合板[0/±45/90]_2s和[0/±30/±60/90]_s的开孔拉伸强度,孔径分别为3 mm、6 mm和9 mm。理论预报结果与试验值吻合较好,最大误差为15.2%,满足工程应用需求。      

Study on interfacial adhesion strength of single glass fibre/polypropylene model composites by altering the nature of the surface of sized glass fibres

Polypropylene (PP) compatibly sized glass fibres (GFs) were treated with boiling water and toluene, respectively, to reveal the interactions of water and toluene with different components in the sizing of sized GF and their influences on the interfacial adhesion strength of GF/PP model composites. Compared to control GF/PP model composites, about 30% increase of interfacial adhesion strength was achieved for composites with water-treated GF, whereas a small decrease of interfacial adhesion strength was revealed for composites with toluene-treated GF. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Zeta-potential measurement, and water contact angle measurement demonstrated that the boiling water-treated GFs posses a more polar and hydrophilic surface with homogeneously distributed derivatives of 3-aminopropyltriethoxysilane, which is related to a higher interfacial adhesion strength for water-treated GF/PP model composites. In contrast, hot toluene-treated GFs led to a more hydrophobic surface with low molar mass PP and surfactants enriching on the outermost surface.     

新型高强度玻璃纤维制备与性能研究

研究了一种新的高强度玻璃纤维(NEWHS),其主成分为SiO2、Al2O3、MgO,总含量96%(质量分数),其余为助熔剂、澄清剂和不可避免的杂质;经过熔制得到玻璃实验样品,对各试验样品进行高温粘度、析晶上限、新生态强度、软化点、耐酸性等性能检测,得到新型高强度玻璃纤维的各性能数据:新生态强度为4600～4800MPa、软化点温度为965～970℃、耐酸性质量损失率5.25%;新型高强度玻璃纤维的力学性能、耐温性能、耐酸性能皆高于现有高强度玻璃纤维产品(HS2、HS4),也高于AdvantexTM、Hiper-texTM玻璃纤维,接近美国S-2TM,可以投入生产。     

Tensile behaviour and fracture toughness of EPDM filled with untreated and silane-treated glass beads

The Essential Work of Fracture (EWF) theory has been applied to study the fracture behaviour of untreated and silane-treated glass bead-filled EPDM composites. The experimental values of both Young's modulus and tensile strength have been compared with those predicted by the main theoretical and semiempirical models, and the influence of the composite processing temperature on the tensile properties has been studied, noticing a marked drop of stiffness and strength from a processing temperature of 200 °C. A good adhesion between EPDM matrix and glass beads was achieved with the silane Z-6032, resulting in higher tensile strength, and it has been observed that glass bead presence induces plasticity in the EPDM matrix. No differences of the specific essential work of fracture were found in the three filled samples, although results show that the higher adhesion degree between matrix and particles, the higher value of the specific plastic work of fracture, and also the higher final instability in crack propagation.     

Debonding strength of bundled glass fibers subjected to stress pulse loading

This paper reports experimental results of the debonding propagation of bundled-fibers specimens subjected to a tensile stress wave. In addition, the paper also presents a dynamic debonding model for the problem on the basis of the cohesive zone model, and verifies the model by comparing the predicted debonding to the experimental data. The established numerical model is used to study the propagation mode of the debonding, and the result suggests that in this particular specimen design and loading condition, the debonding initiated in a mixed mode condition. However, the mode II quickly increased and dominated the mode I during an early debonding propagation up to certain extend where the mode mixity became constant.     

Tensile fracture behaviour of microstructurally engineered Cu bearing high strength low alloy steel

Abstract

An attempt has been made to highlight the influence of precipitation and microstructural constituents on tensile fracture behaviour in Cu bearing HSLA 100 steel. Variations in the microconstituents have been incorporated in the steel by engineering the microstructures through thermal treatments consisting of solutionising, water quenching and aging at various temperatures. The microstructure in quenched condition consists of mainly lath martensite, bainite and acicular ferrite besides little amount of retained austenite, carbides and carbonitrides. Aging up to 500°C facilitated fine coherent ?-Cu precipitation that lost its coherency at >550°C. Simultaneously, recovery and recrystallisation of martensite and acicular ferrite occurred at higher temperatures. The formation of new martensite islands occurred on aging at >650°C. Carbides, carbonitrides and retained austenite remained essentially unchanged. Tensile tests were conducted at a slow strain rate to study the tensile fracture behaviour of the steel. Microstructural and fractographic evidences indicating that coherent Cu precipitate causes the brittleness in the material in initial stages of aging whereas loss of coherency of Cu precipitate in later stages results in the reappearance of ductility in the material.     

Effect of surface finish on strength degradation of glass ceramics

The processing of components manufactured from ceramics, such as machining, induces cracks on or beneath the surface leading to strength degradation. Usually, four-point bending tests are used for measuring the strength of ceramic materials. In this paper, a new approach is proposed to evaluate the loss of strength due to machining. First, beam specimens of glass ceramics are prepared by milling. The surface profile of representative areas of the specimens is determined using a laser profilometer. The surface topography of the representative area is reconstructed to characterize the surface irregularities after machining. A finite element program is then employed to analyze the stress distribution on a rough surface of a beam in four-point bending. A performance index—the stress concentration factor, is introduced to quantify the effect of surface irregularities on determining the critical crack depth related to the machining-induced damage. The flexural strength of machined ceramic specimens is predicted using the fracture mechanics. The strength degradation is compared with the experimentally determined values. A close correspondence between the predicted and measured strength is observed. The potential of using a computer-based evaluation to study the strength degradation of glass ceramics by machining induced surface damage has been established.     

玻璃纤维增强环氧复合材料上超疏水表面层的制备

先采用真空袋压法制备含CaCO3/环氧树脂表面功能层的玻璃纤维增强环氧树脂复合材料,再通过化学刻蚀与表面修饰,在玻璃纤维增强环氧树脂复合材料上制备出超疏水表面。采用扫描电镜和动/静态接触角分析仪,表征表面的形貌和疏水性,结果表明,在复合材料表面构建了具有微-纳米尺度二元粗糙结构;采用1%(质量分数)的硬脂酸修饰后,其表面与水的接触角最高达160.03°;制备的超疏水表面结构在室温环境下具有长期的稳定性。     

Tensile performance of carbon-fibre-reinforced glass

The tensile behaviour of unidirectional and [±]_s angle-ply HMU carbon-fibre-reinforced borosilicate glass was determined as a function of the angle between the fibre and the applied load. Both the longitudinal and transverse strain of the composite are reported and discussed relative to the microstructural features responsible for the observed composite behaviour. Stress-strain behaviour for static and cyclic loading conditions is presented. The experimentally determined values of the composite elastic modulus and strength are also compared with those predicted from classical laminate theory. The composite tensile strength is accurately predicted by the Tsai-Hill failure criterion. The elastic modulus measurements indicate that the shear modulus of the uniaxially reinforced composites is higher than that of the multiaxially reinforced composites. This observation is attributed to more extensive matrix microcracking being present in the multiaxially reinforced composite as a result of fabrication. The failure modes present in the composite are also documented.     

Thermal history and tensile strength determination from fracture surface analysis

Aluminum alloys are used in various critical aerospace applications that require properties to be obtained from very specific heat treatments. This study shows that the fracture surface can indicate details of the thermal history and strength of the material. This is a novel technique to characterize the material from an analysis of the fracture surface features. This study evaluated the effect of varying the cooling rate and aging time on the fracture surface of an aluminum alloy.