Mechanical properties of short fiber reinforced thermoplastic blends

An immiscible thermoplastic component was added to a conventional short fiber reinforced polymer to study its effect on the mechanical properties of the composite. Because of the preferential wetting of the fiber reinforcement a continuous network was formed of fibers ‘welded’ together by the minor component within the matrix polymer.Polyethylene (PE) was used as the matrix, polyamide-6 (PA6) as dispersed polymer phase and glass fibers (GF) as reinforcement. The obtained composite retained unusually high values of the elasticity modulus at temperatures above the melting point of the matrix. The upper limit of the ‘applicability’ of the material is determined by the melting point of the minor component. A simple model was derived to describe the mechanical properties of the composite. The model shows a good agreement with the experimental data. The influence of the model parameters on the predictions of the model was examined.     

Mechanical properties of discontinuous fiber reinforced thermoplastics. II. Random-in-plane fiber orientation

The mechanical properties are presented for a series of discontinuous fiber-reinforced thermoplastic composites made with random-in-plane fiber orientation. The matrix and fiber materials were chosen to provide a wide range of strength, modulus, ductility and adhesive properties. In many cases strong, rigid, yet tough composites were fabricated. Strength levels of over 20,000 psi and modulus values over 1,000,000 psi were reached in several systems reinforced with short Kevlar-49 and graphite fibers. A strong dependence of composite strength and modulus on fiber strength and modulus was noted indicating good transfer of load from matrix to reinforcement. Fiber efficiency factors for modulus and strength were calculated for the experimental composite systems and averaged 0.19 and 0.11 respectively. Data were analyzed using basic composite theory. Properties of the experimental composites could not be predicted from constituent properties.     

Influence of cenosphere on tribological properties of short carbon fiber reinforced PEEK composites

This investigation focuses on the effects of cenosphere fillers on tribological properties of carbon fiber reinforced PEEK composites. Dry sliding wear behavior of 15 wt % short carbon fiber (SCF) reinforced PEEK composites filled with 5, 10, 15, and 20 wt % cenosphere was reported in this study, pure PEEK and 15 wt % SCF reinforced PEEK composites were also prepared for comparative analysis. Friction and wear experiments were conducted on a ring-on-block apparatus under different loads (100–400 N). The experimental results showed that all the composites exhibited lower coefficient of friction and better wear resistance than the matrix resin under different load conditions. It is noted that 10 wt % of the cenosphere particles filled SCF reinforced PEEK composites show superior tribological properties when compared to the other composites in this study. The morphologies of the worn surface and the fracture surface were analyzed by scanning electron microscopy and the transfer film was observed by optical microscope to understand the dominant wear mechanisms. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47245.     

Mechanical properties of short fiber reinforced thermoplastic composites —I. Elastic properties and predictions

Twin roll-mill and compression molding machines were used to process the unidirectional ply of short fiber reinforced thermoplastics (FRTP). FRTP laminates were prepared by compression molding of angle plies with the desired stacking sequences.The fiber length and orientation distributions in FRTP took place after processing. Therefore, a statistical distribution function such as WeiBull distribution function was applied to represent the existing fiber length distribution. The orientation distribution in FRTP was characterized by a single parameter exponential function. Elastic moduli of the unidirectional ply were predicted by the Halpin-Tsai equation where the fiber length distribution was introduced to the estimation. The overall elastic moduli of laminates were estimated based on the simulated laminate-plate method. A comparison of measured elastic moduli with theoretical predicted results from unidirectional ply and laminate was discussed in this study.     

Mechanical and dynamic mechanical properties of epoxy syntactic foams reinforced by short carbon fiber

Epoxy syntactic foams were prepared with diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin, 2.4.6‐tri(dimethylaminomethyl)phenol (DMP‐30), coupling treated microsphere and short carbon fiber. The density of the foam was maintained between 0.56 and 0.91 g/cm³ for all compositions. Compressive, flexural, tensile and dynamic mechanical properties of the foams were investigated with respect to hollow glass microsphere (HGM) and carbon fiber (CF) content. A considerable improvement in the mechanical properties viz. compressive, flexural and tensile strengths was observed for the foams on incorporation of a small quantity of CF. The storage modulus were higher for the foam composites containing CF. The presence of HGM has significant influence on T_g of the syntactic foams, spherical filler diminished the T_g of the syntactic foams due to the plasticizing effect of the coupling treatment of HGM, that is helpful for enhancing damping properties of syntactic foams. POLYM. COMPOS., 37:1960–1970, 2016. © 2015 Society of Plastics Engineers     

Improvements in tribological properties of polyoxymethylene by aramid short fiber and polytetrafluoroethylene

In order to improve tribological properties of polyoxymethylene (POM), the effects of aramid short fibers (ASF) and polytetrafluoroethylene (PTFE) solid lubricants, as two classes of additives, were studied. The appropriate composites of the polymer and the additives were prepared by melt mixing process. Distribution of additives in the polymer matrix was characterized by scanning electron microscopy (SEM). Mechanical properties in tension such as modulus of elasticity, yield stress, and stress-at-break as well as the fracture energy in impact test were studied to explore friction and wear mechanisms of the composites against a smooth steel surface. Tribological measurements showed that both additives reduce friction and wear of the POM. However, both additives reduced fracture energy of POM in impact test, which dismisses the role of abrasive mechanism of wear under applied conditions. On the other hand, tensile results showed that addition of ASF mechanically reinforces POM, while PTFE degrades mechanical properties of this polymer, especially yield stress. Considering the role of yield stress in the adhesive mechanism of friction and wear, this property was used to define tribological behavior of samples. Since ASF induces mechanical stiffening to POM, increase in yield stress improves tribological properties. However, PTFE introduces transfer films at the interface, thus reduction of yield stress is in favor of tribological properties of this composite. Finally, it is shown that frictional heating and contact temperature rise has a significant degrading effect on wear resistance.     

Impact properties of short carbon fiber reinforced nylon 6.6

The impact properties of injection-molded nylon 6.6 composites containing different loadings of short carbon fibers have been studied using an instrumented falling weight impact tester (IFWIT). Analysis of the impact data using linear elastic fracture mechanics (LEFM) has enabled the evaluation of the critical strain energy release rate, G_c. Instrumentation of the impact machine has facilitated the determination of another fracture mechanic parameter, the fracture toughness, K_c. Both parameters are observed to increase with increasing volume fraction of fibers. Examination of fracture surfaces using scanning electron microscopy (SEM) has revealed that the main energy dissipative processes responsible for toughening the composites is the fiber pull-out mechanism.     

Shear and extensional properties of short glass fiber reinforced polypropylene

Shear and extensional properties of a commercial short glass fiber reinforced polypropylene were carefully investigated using commercial rheometers and a novel on‐line rheometer. This on‐line slit rheometer, installed on an injection molding press, has been designed to measure the steady shear viscosity, the first normal stress difference, and the apparent extensional viscosity of polymer melts and composites for high strain rates up to 10⁵ s⁻¹ in shear and 200 s⁻¹ in extension. Our results show that the steady‐state viscosity measurements using the on‐line rheometer are in excellent agreement with those obtained using commercial rheometers. The steady‐state and the complex viscosities of the composites were found to be fairly close to that of the matrix, but the Cox‐Merz rule was not verified for the composites at high rates. The elasticity of the composites was found to be equal to that of the polypropylene matrix. The apparent extensional viscosity was obtained from the pressure drop in the planar converging die of the slit rheometer using the analyses proposed by Cogswell [1] and Binding [2]. The extensional viscosity of the polypropylene was found to be much larger than the shear viscosity at low strain rates with a Trouton ratio of about 40 that decreased rapidly with increasing strain rate down to the value of 4 at 200 s⁻¹. The extensional viscosity of the composites was also found to be close to that of the matrix, with values 35 and 5% larger for the 30 and 10 wt% reinforced polypropylenes, respectively. These results are compared with the predictions of the Goddard model [3], which are shown to overpredict our experimental results. POLYM. COMPOS. 26:247–264, 2005. © 2005 Society of Plastics Engineers.     

Tensile properties of short sisal fiber reinforced polystyrene composites

The tensile properties of polystyrene reinforced with short sisal fiber and benzoylated sisal fiber were studied. The influence of fiber length, fiber content, fiber orientation, and ben-zoylation of the fiber on the tensile properties of the composite were evaluated. The ben-zoylation of the fiber improves the adhesion of the fiber to the polystyrene matrix. the benzoylated fiber was analyzed by IR spectroscopy. Experimental results indicate a better compatibility between benzoylated fiber and polystyrene. the benzoylation of the sisal fiber was found to enhance the tensile properties of the resulting composite. The tensile properties of unidirectionally aligned composites show a gradual increase with fiber content and a leveling off beyond 20% fiber loading. The properties were found to be almost independent of fiber length although the ultimate tensile strength shows marginal improvement at 10 mm fiber length. The thermal properties of the composites were analyzed by differential scanning calorimetry. Scanning electron microscopy was used to investigate the fiber surface, fiber pullout, and fiber–matrix interface. Theoretical models have been used to fit the experimental mechanical data. © 1996 John Wiley & Sons, Inc.     

Transcrystallinity in brominated UHMWPE fiber reinforced HDPE composites: morphology and dielectric properties

Ultra-high-molecular-weight polyethylene (UHMWPE) fibers were treated by photochemical bromination. The analysis of the fibers by XPS and ATR-FTIR showed that this process led to the introduction of C–Br and C–OH moieties and generated CC bonds at the PE fiber surface.Composites were fabricated using either treated or untreated fibers and high-density polyethylene (HDPE) for the matrix. WAXD analysis showed that the treated fibers, through offering a higher concentration of crystallization nuclei, generated a denser transcrystalline layer with higher specific radial orientation with respect to the fiber axis—compared with the untreated fiber. Furthermore, the introduction of polarity onto the fiber surface enabled analysis of the complex relaxation behavior of PE/PE composites by dielectric spectroscopy. It showed the typical α, β and γ-relaxation processes of polyethylene, combined with the effect of the transcrystalline layer, generating—among other changes—a strong β-transition.     

Mechanical dispersion of crosslinked polymers reinforced with randomly distributed short fiber

The dynamic viscoelastic properties of composites reinforced with randomly distributed short glass and carbon fibers were studied in relation to the dependence on the fiber length, the mixing ratio of glass fibers of different length, and the kind of polymer matrix. Although the composite reinforced with glass fiber of 0.05 mm in length shows only one dispersion (α) corresponding to the primary transition of polymer matrix, those reinforced with 3- and 10-mm glass fibers, and those reinforced with the mixture of 10- and 0.05-mm glass fibers are characterized by two additional dispersions (α′ and α″) which appear on the lower frequency side or higher temperature side of the α-dispersion. The composite reinforced with 3-mm carbon fiber does not show the additional dispersions. The α′- and α″-dispersions appear irrespective of the kind of matrix polymer.     

Mechanical properties and tribological performance of alumina matrix composites reinforced with graphene-family materials

This paper introduce the formation of alumina matrix composites reinforced with multilayered graphene, graphene oxide and nickel-phosphorus coated multilayered graphene. The powder metallurgy technique followed by the Spark Plasma Sintering (SPS) method were utilized to fabricate the specimens. The influence of graphene-family material additions on microstructure was investigated, and correlated with measurements of mechanical properties. The emphasis of the research has been placed on the tribological performance conducted with the use of the ball-on-disc method under loads of 10 N and 30 N. Both the wear tracks of composites and the corresponding counterparts were carefully analysed, to evaluate the combined influence of mechanical properties and tribofilm formation on the measured wear rates. All results were compared to pure alumina as a reference specimen.     

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.     

Mechanical and viscoelastic properties of short fiber reinforced natural rubber composites: effects of interfacial adhesion,fiber loading,and orientation

The effect of a two-component dry bonding system consisting of resorcinol and hexamethylene tetramine on the mechanical and viscoelastic properties of short sisal fiber reinforced natural rubber composites has been studied. The studies were conducted with chemically treated and untreated short sisal fibers. Treated fibers impart better mechanical properties to the composites. By mixing with short fibers, the dynamic storage modulus (E') of natural rubber composites was improved. The effects of fiber-matrix adhesion on the mechanical and viscoelastic properties of the composites were investigated. The storage moduli and mechanical loss increased continuously with an increase in fiber loading but decreased with an increase of temperature. The influence of the fiber orientation on the mechanical and viscoelastic properties is discussed.     

纳米硅酸盐与芳纶微米短纤维共补强HNBR复合材料的结构与性能

采用原位改性针状硅酸盐(FS)和芳纶短切纤维(DCAF)与氢化丁腈橡胶(HNBR)机械共混制备HNBR/DCAF/FS复合材料,研究DCAF用量、长度和FS用量对复合材料结构与性能的影响.结果表明,加入DCAF能显著提高复合材料小应变下的定伸应力和压缩模量,增大DCAF长度和用量有利于改善复合材料的拉伸性能及其各向异性;加入FS能明显改善复合材料的拉伸应力-应变特性,提高复合材料的压缩模量.     

短玻璃纤维增强聚丙烯复合材料的制备及其力学性能的研究

采用双螺杆挤出机通过熔融共混的工艺路线制得短玻璃纤维增强聚丙烯(PP)复合材料,通过激光粒度分布仪对复合体系中的玻璃纤维的长度进行了测试,同时对复合材料的主要力学性能进行了表征。结果表明:随着短玻璃纤维含量的增加,复合材料中短玻璃纤维的长度平均径有所减小;随着短玻璃纤维含量的增大,复合材料的拉伸强度、冲击强度都大幅度增加,硬度有所增加;当短玻璃纤维质量分数为40%时,短玻璃纤维增强PP复合材料拉伸强度为64.39 MPa,与纯PP相比提高了74%,冲击强度为5.8 kJ/m~2,与纯PP相比提高了174%,硬度为85,与纯PP相比提高了11%。     

Parameters regulating interfacial and mechanical properties of short glass fiber reinforced polypropylene

The performance of thermoplastic composites is known to depend on the intrinsic properties of the two composite components, the quality of the fiber–matrix interface, and the crystalline properties of their matrix. The objective of this work is to characterize the effect of the addition of modified polypropylene (PP) and silane coupling agent on the mechanical and interfacial properties of short fiber reinforced PP composites. Differential scanning calorimetry (DSC), single fiber composite fragmentation tests (SFC), and mechanical testing are used to understand the different parameters regulating the interfacial properties of composites. No influence of the modified PP on the level of crystallinity is observed. Some differences in the size of the spherulites are observed for acrylic acid grafted PP (PP‐g‐AA). Those samples also show lower mechanical properties in spite of good interfacial interactions. Maleic anhydride grafted PP (PP‐g‐MAh) leads to better mechanical performances than PP‐g‐AA. A high MAh content PP‐g‐MAh grade with low viscosity is the best polymeric additive used in the present work. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2047–2060, 2000     

玄武岩短纤维增强硅橡胶复合材料的制备及性能

采用玄武岩短纤维(BF)增强硅橡胶,制备了BF/硅橡胶复合材料,考察了硅烷偶联剂的种类、BF用量以及硫化条件对复合材料力学性能的影响,并用扫描电子显微镜观察了复合材料的微观形貌。结果表明,用KH 550对BF进行表面处理,所得复合材料的力学性能优于以Si 69处理的材料;当BF用量为20份时,BF/硅橡胶复合材料的力学性能最好;制备复合材料的最佳硫化条件为10 MPa×175℃×25 min;用KH 550处理BF,BF与硅橡胶的相容性比用Si 69处理的好。     

短碳纤维增强碳化硅基复合材料的制备

短纤维的分散均匀性一直是短纤维复合材料应用受限的主要原因．采用固相球磨分散和熔融渗硅工艺,可得到均匀分散的短碳纤维增强碳化硅基复合材料．并利用金相显微镜见察复合材料微观形貌,测试复合材料的抗弯强度和断后韧性．     

Mechanical and tribological properties of electrospun PA 6(3)T fiber mats

The mechanical and tribological properties of electrospun fiber mats are of paramount importance to their utility as components in a large number of applications. Although some mechanical properties of these mats have been reported previously, reports of their tribological properties are essentially nonexistent. In this work, electrospun nanofiber mats of poly(trimethyl hexamethylene terephthalamide) (PA 6(3)T) with average fiber diameter of 463 ± 64 nm are characterized mechanically and tribologically. Post-spin thermal annealing was used to modify the properties of the fiber mats. Morphological changes, in-plane tensile response, friction coefficient and wear rate were characterized as functions of the annealing temperature. The Young's moduli, yield stresses and toughnesses of the nonwoven mats improved by two- to ten-fold when annealed slightly above the glass transition temperature, but at the expense of mat porosity. The coefficient of friction and the wear rate decrease by factors of two and ten, respectively, under the same conditions. The wear rate correlates with the yield properties of the mat, in accord with a modified Ratner–Lancaster model. The variation in mechanical and tribological properties of the mats with increasing annealing temperature is consistent with the formation of fiber-to-fiber junctions and a mechanism of abrasive wear that involves the breakage of fibers between junctions.