玻纤增强聚脂弯管应变异纳试验研究及其动应力分析

探讨了测定玻纤增强聚脂弯管应变导纳的试验方法。给出了力通道和应变通道的标定曲线。确定了玻纤聚脂弯管的第一、第二阶模态频率和阻尼比以及单位力幅下的动应变值。借助应变导纳的幅频特性和相频特性分析了弯管动应力。还用静态试验验证了动态测试的正确性。     

玻纤增强聚丙烯的三维弯管挤出吹塑

采用摄影技术研究了挤吹中型坯膨胀行为以及使用流变仪分别考察了聚丙烯(PP)、聚丙烯/短切玻纤(PP/SGF)的流变行为;利用扫描电镜观察PP基体中玻纤取向;通过"真空牵拉式三维吹塑设备"成型弯管,PP/SGF弯管比PP弯管在沿轴向方向和周向的壁厚更薄、更均匀.结果表明:PP经过玻纤增强后流变性能、型坯膨胀行为的改变及玻纤取向的方式,可使得其弯管壁厚更均匀.     

土工格栅拉伸速率试验分析

通过对土工格栅(塑料格栅和玻纤格栅)在不同速率下进行拉伸试验,得出拉力—变形曲线及2%,5%应变和峰值拉伸强度、最大断裂力时的延伸率等数据。经过对数据分析和曲线拟合,得出格栅受拉伸速率影响的规律,并最终选定合适的室内拉伸试验速率。结果表明,塑料格栅和玻纤格栅,纵、横向的断裂拉力随着拉伸速率的增加而增大,延伸率随着拉伸速率的增加而减小。塑料格栅和玻纤格栅,纵、横向同等规格时,纵向拉伸强度总体大于横向拉伸强度。     

层合板切口强度和切口敏感性的试验研究

提出了在复合材料板中人工预制尖锐切口的方法。进行了切口呼无切口试样在载荷方向垂直于和平行于纤维面的三点弯曲破坏试验。测定了玻纤／环氧层合板的切口强发口敏感度。探讨了玻纤／环氧层合板的线弹性断裂力学的适用性，借助复合材料的ＷＥＫ断裂模型估计层合板在尖切口前沿的损伤区尺寸。预测了切口强度。结果表明：对于玻纤／环氧层合板，若根据平面应变和小范围屈服的力不条件选择试样尺寸，则其三点弯曲的断裂应力、等效尖     

长玻纤增强聚氨酯复合材料弯曲应力-应变试验研究

针对长玻纤增强反应注射成型聚氨酯复合材料(RRIM-PU)进行了弯曲性能测试试验,研究了玻纤质量分数及玻纤长度对RRIM-PU复合材料弯曲性能的影响,得到了弯曲应力-应变曲线。同时结合扫描电子显微镜(SEM)观察微观组织结构,分析了玻纤在基体中的增强作用及制品弯曲破坏机理。研究结果表明:玻纤质量分数30%,玻纤长度25 mm的复合材料制品具有最佳的弯曲性能。     

玻纤增强热塑性复合材料多尺度建模与各向同性曲线拟合

基于玻纤增强复合材料玻纤取向3D计算的Moldflow旋转扩散(MRD)模型对玻纤增强热塑性复合材料(PA66-G30)的标准1BA样条注塑填充过程中的玻纤取向张量进行计算。以14层玻纤取向张量分布和厚度数据为基础,建立该复合材料多层微观代表性体积元(RVE)模型,采用J2幂乘硬化弹塑性模型来拟合实验测试应力-应变曲线,完成该玻纤增强热塑性复合材料多尺度模型的构建。基于该材料模型生成的45°取向的应力-应变曲线与实验结果吻合良好,验证了本实验材料模型的准确性。基于该模型生成了PA66-G30材料的各向同性应力-应变曲线,用于提高注塑产品力学仿真计算的精度。     

玻纤/环氧三维编织复合材料动态压缩性能研究

本文利用SHPB(split Hopkinson pressure bar)装置对玻璃纤维/环氧三维编织复合材料在高应变率(4000s-1,5000s-1,6000s-1)下的动态压缩性质进行测试.试验结果表明,玻纤/环氧三维编织复合材料是应变率敏感材料.     

玻纤/环氧三维编织复合材料的动态压缩性能

本文利用SHPB（the split Hopkinson pressure bar）装置对玻璃纤维／环氧三维编织复合材料在高应变率（4000s^-1，5000s^-1，6000s^-1）下的动态压缩性质进行测试，试验结果表明玻纤／环氧三维编织复合材料是应变率敏感材料。     

内压载荷下玻璃纤维增强复合软管力学性能研究

对玻璃纤维增强复合软管进行短期爆破压力试验,建立内压载荷下玻纤软管有限元模型进行模拟仿真计算,在此基础上,研究提出了玻纤软管爆破压力的理论求解方法。将三者进行对比分析,结果表明:在一定内压作用下,加强层所受到的力远大于内外层,说明了玻纤软管的加强层承担大部分内压载荷;玻纤缠绕角度大于45°且小于80°时,抗内压能力逐渐增强,59°为玻纤软管设计中最优缠绕角度;适当减小管道的径厚比,可以提高管道承受内压的能力。     

挤出机头内流场对玻纤取向和分布的影响

本文分析了平直和发散两种挤出机头内的流场,推得发散流道内熔体周向拉伸应变速率的表达式;研究了两种挤出流率下由这两种机头挤出的制品壁内玻纤的取向和分布,并通过流道内的剪切和周向拉伸应变速率,对玻纤取向和分布的形成机理进行解释。结果表明：经平直机头挤出的制品内,玻纤在剪切作用下基本沿流动方向排列。发散机头内熔体受剪切和周向拉伸的共同作用,使制品壁厚方向形成了“表层-次表层-芯层-次表层-表层”的五层结构,并首次发现芯层呈“W”形排列。玻纤的排列不仅受流动过程中的应变影响,更取决于应变速率的大小。     

Influence of chopped strand fibres on the flexural behaviour of a syntactic foam core system

The comparative performance in a three point bending test of syntactic foam comprising epoxy resin and glass microballoons with and without the inclusion of glass fibre in the form of chopped strands is reported. Test samples having a span‐to‐depth ratio of 16:1 were used. The data show that the glass fibre reinforced foam system had a higher strength compared to the unreinforced system. Resorting to light macroscopic and scanning electron microscopic examinations on mechanically tested samples expanded the scope of the work for a structure–property correlation to emerge. © 2000 Society of Chemical Industry     

Enhanced strength of portland cement products via reinforcing polypropylene/fiberglass structures obtained from a novel processing technique

An uninterrupted filament winding process was used to fabricate structures made of polypropylene and glass fiber that provide superior reinforcement to Portland cement structures. Fabricated polypropylene/fiberglass composite tubes were filled with a cement mixture and some were reinforced with internal tapes. Three‐point bending experiments, microscopic observation, and image analysis were used as tools to study various processing variables and their effect on the mechanical properties of the tubes. The temperature of the mandrel and wetting strongly affected the composite's mechanical properties. Increased temperatures diminished the void content within the composite and produced a unique “fuzzy” inner surface for the cylindrical tube. The development of this “fuzzy” inner surface improved the strength and fatigue properties of the cement filled composite tube by providing efficient load transfer to the glass fibres. Also the surface to volume ratio of the steel rebar geometry when compared to that of the polypropylene/fibreglass structure explains the superior load transfer to the glass. It was found that a tube reinforced with 15 internal tapes filled with a cement mixture recorded a maximum tensile stress of 71 MPa (10,000 psi) with excellent damage tolerance, more than a 10‐fold increase over the upper bound value for steel reinforced cement obtained from the rule of mixtures. The tube continued to be load bearing to strains of 0.4, which is more than 40 times the failure strain of glass. These large failure strains are the result of the shear yielding of polypropylene that coats the glass fibres and allows them to move within the cement.     

长玻纤增强丙烯腈-苯乙烯复合材料的研制

采用熔体浸渍工艺制备了长玻纤增强丙烯腈-苯乙烯共聚物复合材料(LGF/AS),研究了不同玻纤含量对LGF/AS复合材料力学、动态力学性能和形态的影响。结果表明:随着玻璃纤维含量的提高,LGF/AS复合材料的力学和动态力学性能逐渐增加;通过SEM证明了玻璃纤维在基体树脂中的具有良好的分散性。     

Creep analysis of fibre reinforced adhesives in single lap joints—Experimental study

In this paper, the effect of reinforcing the adhesive on the creep behaviour of single lap joints was studied experimentally. The reinforcement was in the form of fibre and three types of fibres namely aramid, carbon and glass were used. The test was performed at a temperature above the glass transition temperature of the adhesive. The effect of fibre orientation was also investigated. The failure time and initial strain for all the specimens were evaluated and compared to the un-reinforced adhesive joint. According to the results, adding fibres in the bondline considerably affects both the initial strain and the failure time and these effects are dependent on the fibre type and orientations. The fracture surfaces of the specimens were also studied to investigate the failure mechanisms of the reinforced adhesive in creep. The fibre breakage was observed along with adhesive and cohesive failures.     

Quasi‐static and dynamic experiment investigations on the crashworthiness response of composite tubes

Crashworthiness performance of carbon and glass composite tubes have been comprehensive investigated under quasi‐static and dynamic axial crush testing. In this study, collapse modes and specific energy absorption (SEA) of different ply orientation of carbon fabric composites and unidirectional glass tubes were analyzed. For the weaker tensile strength and bending strength of glass composites, crack propagated approximately perpendicular to the fiber direction when the ply angle was small. Large amount of fibers breakage made the specific energy absorption over 80 kJ/kg under dynamic load. Thickness effect had inverse influence on SEA under different impact rate. The specific energy absorption declined as tube thickness increased under dynamic crush tests, however, increased under quasi‐static tests. Hybridization of glass/carbon tubes and carbon/carbon composites were analyzed by increased the axial fiber content. It was found that hybridization tubes of G803/3234 fabric and G827/3234 axial tapes with higher G827/3234 content present excellent energy‐absorption capability under dynamic and quasi‐static tests for all specimens tested. POLYM. COMPOS., 34:1099–1109, 2013. © 2013 Society of Plastics Engineers     

Effect of styrene on properties of vinyl ester resins,I

The paper describes the effect of styrene on the properties of bis(methacryloxy) derivatives of epoxy resins (vinyl ester resins). The styrene concentration in the resin was systematically varied between 20–60 wt.-%. The curing characteristics of vinyl ester resins changed only marginally on dilution with styrene. Dilution with styrene resulted in a decrease in tensile modulus and increase in elongation of neat resin castings and glass fibre reinforced laminates. The glass transition temperature of laminates was determined by dynamic mechanical analysis and was found to decrease with increasing styrene content.     

Evaluation of dynamic modulus measurement for C/C-SiC composites at different temperatures

The determination of elastic properties at application temperature is fundamental for the design of fibre reinforced ceramic composite components. An attractive method to characterize the flexural modulus at room and high temperature under specific atmosphere is the nondestructive Resonant Frequency Damping Analysis (RFDA). The objective of this paper was to evaluate and validate the modulus measurement via RFDA for orthotropic C/C-SiC composites at the application temperature. At room temperature flexural moduli of C/C-SiC with 0/90° reinforcement were measured under quasi-static 4-point bending loads and compared with dynamic moduli measured via RFDA longitudinally to fibre direction. The dynamic modulus of C/C-SiC was then measured via RFDA up to 1250°C under flowing inert gas and showed an increase with temperature which fitted with literature values. The measured fundamental frequencies were finally compared to those resulting from numerical modal analyses. Dynamic and quasi-static flexural moduli are comparable and the numerical analyses proved that bending modes are correctly modeled by means of dynamic modulus measured via RFDA. The nondestructive RFDA as well as the numerical modeling approach are suitable for evaluation of C/C-SiC and may be transferred to other fibre reinforced ceramic composite materials.     

树脂基纤维增强复合材料高应变率下力学性能的研究进展

综述了国内外在树脂基纤维增强复合材料的动态力学性能测试的实验技术、高应变率下力学性能和动态本构模型方面所开展工作的研究进展,指出了研究中应注意的问题。     

Experimental study of the influence of adhesive reinforcement in lap joints for composite structures subjected to mechanical loads

The paper deals with experimental investigations on reinforcing the adhesive in single lap joints subjected to mechanical loads such as tensile, bending, impact and fatigue. The adhesive used for bonding was an epoxy reinforced with unidirectional and chopped glass fibres as well as micro-glass powder. The adherends were glass reinforced composite laminates. The bonding surfaces were prepared before joining. In the case of unidirectional fibres in the adhesive region, the fibre orientations considered were 0°, 45° and 90°. The volume fraction of fibres in the adhesive layer in all the cases was 30%. The volume fractions of micro-glass powder were 20%, 30% and 40%. The tensile, bending, impact and fatigue tests on the prepared specimens were conducted according to ASTM standards. The results show that except the 90° unidirectional orientation, reinforcing the adhesive with glass fibres or powder increases the joint strength. The use of volume fraction of 30% of micro-glass powder gave the best performance in the above loading conditions. The fatigue life increased by 125%, the ultimate joint strength in tension increased by 72%, the bending ultimate joint strength increased by 112% and the impact joint strength increased by 63%. The microstructure of the debonded area was examined and three modes of failure could be observed namely cohesive failure, light fibre-tear failure and thin layer cohesive failure.     

Influence of the Film Former on Fibre-Matrix Adhesion and Mechanical Properties of Glass-Fibre Reinforced Thermoplastics

The film former is in mass percentage the main component in most glass fibre sizes. Its influence on the fibre-matrix adhesion and the compound properties is studied in two thermoplastic matrices, i.e. polypropylene (PP) and rubber-modified styrene-co-maleic anhydride. The composition of the size is varied by changing the chemical nature and molecular mass of the film former and by leaving out the silane. The size's morphology on the glass fibres is studied with scanning electron microscopy and X-ray photoelectron spectroscopy. The effect on fibre-matrix adhesion is inferred from 0° bending and interlaminar shear strength measurements of unidirectional, continuous fibre reinforced composites. The possible effect of the film former on matrix crystallinity in PP is studied with differential scanning calorimetry and polarized-light microscopy. The same sizes are also tested in injection moulded, short fibre reinforced compounds by measuring their mechanical properties. In addition, the diffusion of the size into the matrix is studied by confocal scanning laser microscopy. The main conclusion of this study is that the film former plays a crucial role in the level of fibre-matrix adhesion because it does not diffuse away from the fibre-matrix interface into the matrix. Its effect may be larger than that of the silane. In addition, most mechanical properties of short fibre reinforced compounds improve with increasing fibre-matrix adhesion.