The effect of loading rate on the fracture toughness of fiber reinforced polymer composites

This article is a detailed review of the strain rate dependence of fracture toughness properties in polymer composite materials. An attempt is made to draw together all the strain rate studies done in the past and to elucidate the reasons given by the authors of the reviewed papers for the trends resulting from their studies to better understand the strain rate effects on the fracture toughness of fiber reinforced polymer composite materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 899–904, 2005     

短碳纤维增强铝基复合材料

通过化学镀再电镀的方法,在碳纤维表面镀上Cu镀层,制备C/Cu复合丝,并在硼酸的保护下,利用非真空条件下的液态机械搅拌法制备短碳纤维增强铝基复合材料,研究了碳纤维在复合材料中的分散程度,铜镀层存在状态及C/Al复合材料的拉伸性能.实验结果表明：在硼酸存在下,大大降低了铜的氧化程度,碳纤维分散均匀且没有损伤,少量硼酸的加入,对复合材料的力学性能没有影响,该复合材料的抗拉强度随碳纤维含量的增加而增加,其抗拉强度较基体材料提高50%以上,但塑性指标却明显下降.     

Research progress of basalt fiber reinforced polymer composites

玄武岩纤维的综合性能优异,是聚合物复合材料的理想增强体,在高强度、耐高温、耐酸碱腐蚀、耐烧蚀和耐摩擦等特殊领域展示了良好的应用前景。本文对玄武岩纤维聚合物基复合材料研究中的纤维与基体的界面改性、不同聚合物基体的复合材料以及玄武岩纤维与其它纤维的混杂三个方面进行了综述。目前对于玄武岩纤维界面性质的基础研究深度不足,有些复合材料的研究和制备方法还没有应用于玄武岩纤维上,使得玄武岩纤维复合材料的优势还没有得到充分的发挥。因此,应结合玄武岩纤维及其复合材料的特性,开发适用性强的和性价比好的产品,扩大应用范围。     

Measurement of fiber and matrix orientations in fiber reinforced composites

Short glass fiber reinforced polypropylene was employed in a study to determine the effect of molding and mold design variables on the distrubution of fibers and their orientations, and consequently, on the distributions of mechanical properties in the molded article. In this paper, a variety of experimental techniques were employed to evaluate the distributions of fibers and their orientations. Moreover, techniques were developed to evaluate the orientation and crystallization of the matrix. The results yield significant information regarding the development and control of both the microstructure and the properties of short fiber reinforced composites.     

Flammability characteristics of fiber reinforced organic matrix composites

The effect of resin, fiber, and fire retardant additives on flammability characteristics of organic matrix composites was evaluated. Information is presented on the flame spread index, determined by the radiant panel test, the amount of smoke generated, and products of combustion, using the National Bureau of Standards Smoke Density Apparatus, and the amount of oxygen required to support combustion using the Oxygen Index method. These methods were effective in screening the flammability characteristics of organic matrix composites. Of the materials evaluated the polyimide composites were the most resistant to flame spread, exhibited the lowest evolution of smoke and toxic products and had the highest oxygen index. No differences in flame spread and oxygen index were observed for the polyester epoxy glass-cloth laminates. Addition of antimony trioxide and hydrated alumina to the polyester and epoxy resin systems significantly decreased the flame spread index and increased the oxygen index, but showed a marked increase in smoke evolution. Smoke properties depended on resin content whereas the type of reinforcement did not appear to affect flame spread index or smoke properties. The use of protective barriers in selected shipboard areas can reduce flame spread and lengthen the lime for generation of smoke.     

碳纤维增强SiC陶瓷复合材料的研究进展

碳纤维增强SiC陶瓷基复合材料具有良好的高温力学性能，是航空航天和能源等领域新的高温结构材料研究的热点之一．本文回顾了增强体碳纤维的发展，对材料的成型制备工艺，材料的抗氧化涂层研究进展和现有的一些应用做了综述，并展望了碳纤维增强SiC陶瓷基复合材料以后的研究重点及发展前景．     

Micromechanical discrete element modeling of fiber reinforced polymer composites

An analytical model of mechanical behavior of carbon fiber reinforced polymer composites using an advanced discrete element model (DEM) coupled with imaging techniques is presented in this article. The analysis focuses on composite materials molded by vacuum assisted resin transfer molding. The molded composite structure consists of eight‐harness carbon fiber fabrics and a high‐temperature polymer. The actual structure of the molded material was captured in digital images using optical microscopy. DEM was developed using the image‐based‐shape structural model to predict the composite elastic modulus, stress–strain response, and compressive strength. An experimental case study is presented to evaluate the accuracy of the developed analytical model. The results indicate that the image‐based DEM micromechanical model showed fairly accurate predictions for the elastic modulus and compressive strength. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

碳纤维增强树脂基复合材料的应用研究

碳纤维增强树脂基复合材料以其优异的综合性能成为当今世界材料学科研究的重点。本文介绍了的碳纤维增强复合材料的性能，简述了增强机理、成型工艺及其应用领域和发展趋势。     

Damage modeling of oxide/oxide ceramic matrix composites under cyclic loading conditions

Ceramic matrix composites exhibit optimal high temperature property and complex nonlinear behaviors including irreversible deformations and stiffness degradation under different mechanical loading conditions. In the present work, the damage evolution of the material under multi-axial loads considering effects of loading-unloading cyclic was studied and a novel continuum damage constitutive model was proposed. The material degradation was decomposed into monotonic damages and cyclic damages. The anisotropic hardening behavior of the material was considered by taking orientation dependence into account. Compared to the experimental results, the constitutive model could accurately predict the stress-strain response and stiffness degradations of the oxide/oxide ceramic matrix composites for monotonic loading and cyclic loading.     

Crack closure stresses in fiber reinforced brittle matrix composites

The fracture toughness of an alumina ceramic and a continuous SiC fiber reinforced alumina composite processed by pressureless sintering was studied in situ in a Scanning Electron Microscope (SEM). The applied stress intensity factor was obtained as a function of both applied load and crack extension. Closure stresses across crack surfaces imposed by grain-bridging and fiber-bridging, and hence fracture resistance from bridging were studied by both stress intensity factor and J-integral considerations. Theoretical calculations agree with experimental results. An average fracture resistance of ≈40 J m⁻² per fiber and a corresponding toughness of ≈1·6 MPam^1/2 per fiber was obtained for fiber elastic bridging before fiber failure. Fiber-matrix interfacial properties were examined and a technique for evaluating interfacial frictional shear stress was developed.     

Dynamic mechanical analysis of fiber reinforced composites

Dynamic mechanical and thermal properties were determined for unidirectional epoxy/glass composites at various fiber orientation angles. Resonant frequency and relative logarithmic decrement were measured as functions of temperature. In low angle and longitudinal specimens, a transition was observed above the resin glass transition temperature which was manifested mechanically as anadditional damping peak and thermally as a change in the coefficient of thermal expansion. The new transition was attributed to a heterogeneous resin matrix induced by the fiber. The temperature span of the glass-rubber relaxation was found to broaden with decreasing orientation angle, reflecting the growth of fiber contribution and exhibiting behavior similar to that of Young's modulus. The change in resonant frequency through the glass transition was greatest for samples of intermediate fiber angle, demonstrating behavior similar to that of the longitudinal shear modulus.     

The elastic properties of random-in-plane short fiber reinforced polymer composites

Four types of random-in-plane short fiber reinforced polymer composites were manufactured by the prepreg route using carbon or glass fiber tissue and 913 or 924 epoxy resin. The in-plane Young's modules and in-plane shear modulus of the composites were measured over the temperature range − 100 to + 200°C by dynamic mechanical analysis using three point bend and rectangular torsion testing geometries. Theoretical predictions of the elastic properties of the composites were determined over the same temperature range and compared with the experiment. Of particular interest was the use of the “S mixing rule” of McGee and McCullough to determine a single theoretical estimate for the composite elastic properties. Excellent agreement between experiment and theory was found for the four composites over the majority of the measured temperature range.     

Stiffness and strength of flax fiber/polymer matrix composites

Flax fiber composites with thermoset and thermoplastic polymer matrices have been manufactured and tested for stiffness and strength under uniaxial tension. Flax/polypropylene and flax/maleic anhydride grafted polypropylene composites are produced from compound obtained by coextrusion of granulated polypropylene and flax fibers, while flax fiber mat/vinylester and modified acrylic resin composites are manufactured by resin transfer molding. The applicability of rule‐of‐mixtures and orientational averaging based models, developed for short fiber composites, to flax reinforced polymers is considered. POLYM. COMPOS. 27:221–229, 2006. © 2006 Society of Plastics Engineers     

A review on machining of carbon fiber reinforced ceramic matrix composites

Carbon fiber reinforced ceramic matrix ceramic/polymers composites have excellent physical-mechanical properties for their specific strength, high hardness, and strong fracture toughness relative to their matrix, and they also possess a good performance of wear resistance, heat resistance, dimensional stability, and ablation resistance. It is a choice for thermal protection and high temperature structural materials. However, this kind of composites owning characteristics of high hardness and abrasion is difficult to machine which impedes the large-scale industrial application of manufacturing. This paper mainly reviews the research on machining status of carbon fiber reinforced ceramic matrix composites including carbon fiber reinforced polymer matrix composites from the aspects of conventional machining and unconventional machining method. The machining trends, problems existing in various machining methods and corresponding solutions are generalized and analyzed.     

碳纤维增强树脂基复合材料的最新应用现状

介绍了碳纤维增强树脂基复合材料的性能特点,结合碳纤维增强树脂基复合材料的优异性能,讨论了其在新能源(风力发电、钻井采油和天然气储存)、汽车(外覆盖件、刹车片和涡轮增压)和航空航天(民用飞机、战略导弹)领域的最新应用。最后对碳纤维增强树脂基复合材料未来的发展方向进行了展望。     

Manufacturing and testing of long basalt fiber reinforced thermoplastic matrix composites

In this work, long basalt fiber reinforced composites were investigated and compared with short basalt fiber reinforced compounds. The results show that long fiber reinforced thermoplastic composites are particularly advantageous in the respects of dynamic mechanical properties and injection molding shrinkage. The fiber orientation in long basalt fiber reinforced products fundamentally differs from short basalt fiber reinforced ones. This results in more isotropic molding shrinkage in case of long basalt fiber reinforced composites. The main advantage of the used long fiber thermoplastic technology is that the special long fiber reinforced pellet can be processed by most conventional injection molding machines. During extrusion compounding the fibers in the compound containing 30 wt% fibers are fragmented to an average length of 0.48 mm (typical of short fiber reinforced thermoplastic compounds), this length decreases further during injection molding to 0.20 mm. Contrarily using long fiber reinforced pellets and cautious injection molding parameters, an average fiber length of 1.8 mm can be achieved with a conventional injection molding machine, which increased the average length/diameter ratio from 14 to 130. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Carbon fiber reinforced ultra-high temperature ceramic matrix composites: A review

Recent studies on carbon fiber-reinforced ultra-high temperature ceramic matrix (C/UHTC) composites fabricated by hot-pressing, chemical vapor infiltration, polymer impregnation and pyrolysis, and melt infiltration (MI) are reviewed. Various efforts have been made to improve these preparation processes and to combine two or more of these because they have both the advantages and disadvantages in terms of the processing time, operating temperature, and the porosity of the resulting C/UHTC composites. In addition, the parameters governing the fracture toughness, thermal conductivity, and recession behavior (in oxidizing environments) of these composites have been discussed. This review demonstrates that C/UHTC composites with Zr- or Hf-based UHTC matrices fabricated via MI are potential candidates for advanced heat-resistant structural materials.     

Mechanical properties of high ductile alkali-activated fiber reinforced composites incorporating red mud under different curing conditions

Red mud (RM) is an industrial by-product created during the production of alumina/aluminium that has engendered severe environmental concerns arising from its improper disposal. To mitigate the negative environmental impact of RM waste and produce a sustainable material having high mechanical performance (particularly ductility) for a variety of applications, this study developed an alkali-activated fiber reinforced composite (AAFRC) using RM, ground granulated blast-furnace slag (or slag), and silica fume as the precursors. The effects of two different curing conditions (ambient-curing and heat-curing) on the mechanical properties and microscopic characteristics of the material were systematically investigated. The heat-cured RM-derived AAFRC exhibited excellent tensile strain capacity (or ductility) of up to 5.6%, which was significantly higher than that of its counterpart that was cured under ambient condition. Despite the reduction in strength caused by heat-curing, AAFRC retained adequate tensile and compressive strengths of 4.0 and 75 MPa, respectively. The results of three-point bending, single crack tensile, and single fiber pullout tests provided reasonable explanations for the tensile behaviors of the studied material. Scanning electron microscopy revealed that a less compacted matrix was formed in the RM composite due to heat-curing. The combined results from energy dispersive spectroscopy and nanoindentation tests indicated that adding red mud did not alter the types of reaction products for the material, which were similar in composition to conventional alkali-activated slag while also including C-A-S-H and N-A-S-H gels in addition to a type of layered double hydroxide. These findings can serve as theoretical guidelines for the future design and application of eco-friendly, high-ductile cementless composites prepared from RM waste.     

Reuse of natural fiber reinforced eco‐composites in polymer mortars

In this article, the results of the design of recycling–reuse facilities for transformation of solid–polymer composite waste into polymer mortars and concrete structures for the low‐cost building industry have been presented. Thermoplastic polymer matrix composites based on polylactic acid (PLA) reinforced with natural fibers (rice husks and kenaf fibers) have been recycled and reused as reinforcement. Polymer mortars with unsaturated polyester resin as a binder (commercially available orthophthalic liquid polyester with 35% monomer content) have been prepared by mixing foundry sand and milled recycled eco‐composites (milled size of 0.050 mm) in mix proportions of 40/20/40 ^%/_% wt. The obtained materials have been analyzed with standard test methods (mechanical tests, thermogravimetrical analysis (TGA), dynamic‐mechanical analysis (DMTA), differential scanning calorimtery (DSC), and scanning electron microscopy (SEM)). POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers