共查询到20条相似文献，搜索用时 0 毫秒
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Michele del Borrello Mattia Mele Giampaolo Campana Matteo Secchi 《Polymer Composites》2020,41(6):2316-2329
The adoption of natural-based fibers in place of inorganic reinforcements is an effective approach to reduce the environmental and economic impact of composite materials. In particular, hemp is an attractive solution due to its mechanical, physical, and growing properties. The present article deals with the manufacturing of thermoset hemp-reinforced composite materials. In particular, the investigation moves into the production by resin transfer molding and by resin powder molding with the use of epoxy polymeric material. To describe the effects of the technological cycle onto the characteristic of realized products, different manufacturing parameters have been combined during the braiding of reinforcement and the polymerization of the final composite. Computed tomography, microscopical analysis, and tensile tests have been used to observe the main effects of the manufacturing process and mechanical properties of the materials. Furthermore, elastic moduli of the materials have been estimated by means of modified rule of mixture and Halpin-Tsai models in order to verify their effectiveness in forecasting stiffness of the hemp-reinforced composites in the early design phase. The article extends the existing knowledge base on hemp-reinforced thermoset composites manufactured with different processes. Results also illustrate relations existing between error introduced by calculation models and the intrinsic variability in mechanical properties. 相似文献
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《Polymer-Plastics Technology and Engineering》2013,52(2):335-350
Abstract: The influences of various fiber amounts and injection molding process conditions on the fracture toughness of injection-molded short fiber-reinforced poly(butylene terephthalate) (PBT) composites were investigated. Three materials of various fiber amounts, neat PBT, 15 wt.%, and 30 wt.% short fiber-reinforced PBT composites, were used in this study. The compact tension (CT) specimens were prepared by various injection molding process conditions, wherein filling time, melt temperature, mold temperature, and packing pressure were design parameters used to measure fracture toughness. The morphology of the specimens, which consisted of frozen, intermediate, and core layers, was evaluated by scanning electron microscopy (SEM) and related to the fracture toughness. The fracture surfaces were also observed by SEM to understand the difference between the fracture mechanisms of neat PBT and fiber-reinforced PBT. It was found that the fracture toughness of neat PBT was significantly increased by the addition of short glass fibers. However, the variation of the injection molding design parameter had little effect on the fracture toughness. The fracture toughness depended on the thickness of the layers where fibers oriented perpendicular to the crack direction. The layer thickness was strongly affected by the fiber amounts. 相似文献
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Gonzalo Barluenga 《Cement and Concrete Research》2010,40(5):802-809
The inclusion of small amounts of short fibers has demonstrated to be an effective solution to control cracking due to drying shrinkage of concretes at early ages. The key point of fiber effectiveness is their capacity to sew the crack sides, preventing crack opening, because cracking of concrete matrix induces fiber actuation. In this paper, fiber-matrix interaction is analyzed considering different amounts (from 600 to 1200 g/m3) and lengths (6, 12 and 18 mm) of alkali-resistant (AR) glass fibers and fiber coating effect. The combination of experimental results previously published and analyses with simple FE models allows for better understanding of early age concrete behavior. As concrete mechanical capacity develops with age, while fibers have full properties before being included in concrete matrix, the interphase between matrix and fibers evolves during setting and hardening, and affects cracking control effectiveness, due to stresses induced by fibers into the matrix during concrete hydration. 相似文献
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During the molding of fiber reinforced plastics, complex behavior of long fibers are observed which lead to significant changes in fiber orientation and fiber content distribution as compared to short fiber reinforced plastics. In earlier publications, a direct fiber simulation approach with a mechanistic model has been presented to display the complex fiber behavior inside simple geometries, which is mainly influenced by fiber interactions during flow. In this article, the prediction with the mechanistic model is evaluated in a complex geometry and compared to commercially available direct fiber simulation as well as traditional simulation tools. In this overview, the fiber parameters of fiber orientation and fiber content distribution are analyzed and compared to experimental data. Conclusively, it is shown that the predictions with a mechanistic model show the most accurate results regarding fiber orientation and fiber content distribution, with the downside of a significantly longer computational time. 相似文献
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本文在研究获得高性能玻璃纤维增强氯氧镁复合材料的基础上，对无机复合材料压力管的成型工艺、产品性能进行分析研究，对比现有的各种材料管，得出无机复合材料压力管是目前性能最好、价格最低的新产品，可以代替钢管、玻璃钢管和预应力混凝土管，其发展前景无限。 相似文献
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采用粘度、凝胶时间及力学性能测试以及示差扫描量热分析和扫描电镜研究了上纬环氧树脂2511-A体系的工艺性能,固化反应行为及其采用西曼树脂浸渍膜塑成型工艺(Seeman Composites Infusion Molding Process,SCRIMP)制成的环氧玻璃纤维复合材料的性能。结果表明:2511-A体系在25～35℃下粘度保持在600 mPa.s以下的时间长达120 min,满足SRCIMP成型工艺要求,其玻璃化转变温度为112℃。复合材料的孔隙率仅为0.19%,且具有良好的力学性能。 相似文献
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Composites of high‐density polyethylene (HDPE) filled with sintered and nonsintered hydroxyapatite (HA) powders, designated as HAs and HAns, respectively, were compounded by twin screw extrusion. Compounds with neoalkoxy titanate or zirconate coupling agents were also produced to improve interfacial interaction and filler dispersion in the composites. The composites were molded into tensile test bars using (i) conventional injection molding and (ii) shear‐controlled orientation in injection molding (SCORIM). This latter molding technique was used to deliberately induce a strong anisotropic character to the composites. The mechanical characterization included tensile testing and microhardness measurements. The morphology of the moldings was studied by both polarized light microscopy and scanning electron microscopy, and the structure developed was assessed by wide‐angle X‐ray diffraction. The reinforcing effect of HA particles was found to depend on the molding technique employed. The higher mechanical performance of SCORIM processed composites results from the much higher orientation of the matrix and, to a lesser extent, from the superior degree of filler dispersion compared with conventional moldings. The strong anisotropy of the SCORIM moldings is associated with a clear laminated morphology developed during shear application stage. The titanate and the zirconate coupling agents caused significant variations in the tensile test behavior, but their influence was strongly dependent on the molding technique employed. The application of shear associated with the use of coupling agents promotes the disruption of the HA agglomerates and improves mechanical performance. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2873–2886, 2002 相似文献
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Polymers filled with conducting fibers to prevent electromagnetic interference (EMI) performance have recently received great attention due to the requirements of 3C (computer, communication, and consumer electronics) products. In the present article, the effect of fiber content and processing parameters, including melt temperature, mold temperature, and injection velocity, on the electromagnetic interference shielding effectiveness (SE) in injection molded ABS polymer composites filled with conductive stainless steel fiber (SSF) was investigated. The influence of fiber orientation and distribution resulting from fiber content and molding conditions on EMI performance was also examined. It was found from measured results that fiber content plays a significant role in influencing part EMI SE performance. SE value can reach the highest values of approximately 40 dB and 60 dB at 1000 MHz frequency for fiber content 7 wt % and 14 wt %, respectively, under the best choice of molding conditions. Higher melt and mold temperature would increase shielding effectiveness due to a more uniform and random fiber orientation. However, higher injection velocity leading to highly‐orientated and less uniform distribution of fiber reduces shielding effectiveness. Among all molding parameters, melt temperature affects SE performance most significantly. Its influence slightly decreases as fiber content increases. Injection speed plays a secondary importance in affecting SE values, and its influence increases as fiber content increases. Upon examination of fiber distribution via optical microscope and subsequent image analysis, it was found that the fiber becomes more densely and random distributed toward the last melt‐filled region, whereas fiber exhibits less concentration around the middle way of the flow path. This can be attributed to the combined effects of fountain flow, frozen layer thickness, and gapwise melt front velocity. The results indicate that molding conditions, instead of fiber content alone, are very important on the SE performance for injection molded SSF filled ABS composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1072–1080, 2005 相似文献
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Gürhan Kalay Rui A. Sousa Rui L. Reis Antonio M. Cunha Michael J. Bevis 《应用聚合物科学杂志》1999,73(12):2473-2483
This paper describes the process optimization in injection molding of high-density polyethylene (HDPE). Both conventional injection molding and shear controlled orientation (SCORIM) were employed in processing. The process optimization was based on design of experiments and complemented with analysis of variance. Mechanical characterization was carried out by tensile testing. Wide-angle X-ray diffraction and differential scanning calorimetry were used for the structural characterization of the moldings. High-density polyethylene exhibits 7.2 GPa Young's modulus and 155 MPa of ultimate tensile strength following the application of SCORIM processing. These results account for a fourfold increase in Young's modulus and a fivefold increase in ultimate tensile strength compared to conventional injection molding. The maintenance of toughness while enhancing stiffness and strength of the SCORIM moldings is attributable to an oriented morphology developed during shear flow, i.e., shish-kebab structure. The frequency of shearing action has the strongest influence on the morphology development. It is also demonstrated that the studied parameters are very much interdependent. It is possible to achieve substantial gains in mechanical properties of HDPE in SCORIM processing without causing a substantial increase in cycle time. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2473–2483, 1999 相似文献
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Chenkai Zhu Changyong Huang Wuxiang Zhang Xilun Ding Yang Yang 《International journal of molecular sciences》2022,23(15)
Polyvinyl alcohol (PVA) hydrogels are promising implants due to the similarity of their low-friction behavior to that of cartilage tissue, and also due to their non-cytotoxicity. However, their poor mechanical resistance and insufficient durability restricts their application in this area. With the development of biodegradable glass fibers (BGF), which show desirable mechanical performance and bioactivity for orthopedic engineering, we designed a novel PVA hydrogel composite reinforced with biodegradable glass fibers, intended for use in artificial cartilage repair with its excellent cytocompatibility and long-term mechanical stability. Using structure characterization and thermal properties analysis, we found hydrogen bonding occurred among PVA molecular networks as well as in the PVA–BGF interface, which explained the increase in crystallinity and glass transition temperature, and was the reason for the improved mechanical performance and better anti-fatigue behavior of the composites in comparison with PVA. The compressive strength and modulus for the PBGF-15 composite reached 3.05 and 3.97 MPa, respectively, equaling the mechanical properties of human articular cartilage. Moreover, the increase in BGF content was found to support the proliferation of chondrocytes in vitro, whilst the PVA hydrogel matrix was able to control the ion concentration by adjusting the ions released from the BGF. Therefore, this novel biodegradable-glass-fiber-reinforced hydrogel composite possesses excellent properties for cartilage repair with potential in medical application. 相似文献
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Polyester‐ and epoxy‐based composites containing glass and carbon fibers were manufactured using a vacuum‐assisted resin transfer molding (VARTM) process. Fourier transform infrared (FTIR) spectroscopy analyses were conducted to determine the interaction between fibers and matrix material. The results indicate that strong interaction was observed between carbon fiber and epoxy resin. However, weak interactions between remaining fiber‐matrix occur. Scanning electron microscopy (SEM) analysis was also performed to take some information about strength of interaction between fibers and matrix material. From SEM micrographs, it is concluded that the findings in SEM analysis support to that obtained in FTIR analysis. Another aim of the present work was to investigate the influence of matrix on composite properties. Hence, the strengths of composites having same reinforcement but different matrix systems in axial tension and transverse tension were compared. Short beam shear test has been conducted to characterize the interfacial strength in the composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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高性能玻璃纤维的进展与开发 总被引：1，自引：1，他引：1
风电叶片用增强材料的高强、高耐疲劳性为高性能玻璃纤维的发展带了市场机遇,本文结合国内外高性能玻纤的进展,介绍了高性能玻纤多轴向经编织物、基体树脂、真空灌注(导入)工艺等相关技术的进步。通过与传统玻璃纤维进行对比,总结了高性能玻纤的优势和主要应用领域。 相似文献
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The effects of interphase elastic modulus, glass transition temperature, and thickness on interfacial shear strength were investigated both experimentally and theoretically. Single fiber fragmentation tests were performed over a range of temperatures on samples with tailored interphases. Three different types of interphases were investigated: high modulus/high glass transition temperature, low modulus/low glass transition temperature and uncoated (no tailored interphase). A reduction in interfacial shear strength with temperature was observed for all three types of samples tested. The magnitude of this decrease was found to correlate with the glass transition temperature of the interphase. The low Tg interphase samples showed large reductions in IFSS, while samples with a higher Tg coating showed only a small decrease. A three-phase, axisymmetric elasticity solution was developed to predict the sensitivity of the stress state to the interphase material properties and temperatures used in the experimental studies. Predictions which incorporated the change in modulus of both the matrix and interphase with temperature were in good agreement with the experimental trends. Both the theoretical and experimental results supported the existence of an interphase with reduced glass transition in the uncoated samples. 相似文献
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We conducted a feasibility study on the pultrusion of a glass‐fiber‐reinforced urea–formaldehyde (UF) composite using a proprietary method. The UF prepolymer synthesized in this study was prepared from blends of UF monomer and a curing agent (NH4Cl).The process feasibility, kinetic analysis, and dynamic mechanical properties of the glass‐fiber‐reinforced UF composites by pultrusion were investigated. From investigations of the long pot life of the UF prepolymer, the high reactivity of the UF prepolymer, and excellent fiber wet‐out, we found that the UF resin showed excellent process feasibility for pultrusion. A kinetic model, dα/dt = A exp(?E/RT)αm(1 ? α)n, is proposed to describe the curing behavior of a UF resin. Kinetic parameters for the model were obtained from dynamic differential scanning calorimetry scans with a multiple‐regression technique. The dynamic storage modulus of the pultruded‐glass‐fiber‐reinforced UF composites increased with increasing die temperature, filler content and glass‐fiber content and with decreasing pulling rate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1242–1251, 2002 相似文献