Study on mechanical properties of powder impregnated glass fiber reinforced poly(phenylene sulphide) by injection molding at various temperatures

The prepreg of continuous glass fiber reinforced poly(phenylene sulphide) (PPS) was prepared using the powder impregnation technique and cut into the pellets, in which the length of glass fibers was the same as the pellets. After injection molding, the mechanical properties were tested and the effects of the pellet length, fiber content, and thermal treatment on the mechanical properties at different temperatures were studied. It is found that the tensile strength and flexural strength of 6‐mm pellet sample are slightly higher than that of 3‐ and 12‐mm pellet samples. The tensile strength, flexural strength, and modulus decrease significantly with increasing the temperature. The notched Izod impact strength at 85ºC is higher than both at 25ºC and 205ºC. At 205ºC, the glass fiber reinforced PPS composites can still keep better mechanical properties. When the fiber content ranges from 0 to 50%, the mechanical properties increase with increasing the fiber contents at different temperatures, except the notched Izod impact strength do not further increase at 145 and 205ºC with raising the fiber content from 40 to 50%. Thermal treatment could improve the mechanical properties of the composites at higher serving temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

黄麻纤维增强聚丙烯的力学性能

本文讨论了注塑成型黄麻纤维增强聚丙烯的制备方法和力学性能.将纤维重量含量分别为10%、20%和30%的复合材料进行比较,分析纤维含量对复合材料拉伸、弯曲和冲击性能的影响;将纤维分别切成约3mm、5mm和10mm长制成复合材料进行比较,分析纤维长度对复合材料拉伸、弯曲和冲击性能的影响.掺入黄麻纤维能使聚丙烯的拉伸和弯曲性能提高,但使其冲击强度降低;随纤维含量的增加或纤维长度的增加,复合材料的强度和模量是递增的,而冲击强度是递减的.     

Effects of A,B, and S components on fiber length distribution,mechanical, and impact properties of carbon fiber/ABS composites produced by different processing methods

Carbon fiber/ABS composites with different acrylonitrile, butadiene, and styrene components were produced via extrusion/injection and long fiber thermoplastic (LFT)/injection molding processes, respectively. The effect of the components on fiber length distribution, tensile, flexural, impact, and dynamic mechanical properties of the composites was investigated. The properties of carbon fiber/ABS composites produced using 12 mm-long LFT pellets were markedly higher than those produced using extruded pellets made with 12 mm-long chopped carbon fibers. Uses of LFT pellets were preferable to enhancing the mechanical properties of carbon fiber/ABS composites. The tensile, flexural, and dynamic mechanical properties were increased in order of ABS750sw > ABS720 ≥ ABS780 > ABS740, whereas the impact strength was increased in order of ABS740 > ABS780 > ABS720 ≈ ABS750sw. Less carbon fiber damages and less carbon fiber length degradation upon LFT processing resulted in longer fiber length distribution and higher fiber aspect ratio in the composites with LFT pellets, indicating a beneficial reinforcing effect, which was responsible for the increased mechanical properties of ABS composites, particularly with ABS750sw. The results were agreed with each other, significantly depending on the A, B, and S components, being supported by fiber length distribution, fiber aspect ratio, and fracture surfaces.     

Continuous glass-fiber reinforced nylon 6 by using a new impregnation die

This paper describes a process for the manufacture of thermoplastic composites reinforced with continuous fibers and the equipment for producing such a product. The process makes it possible to expand and reconsolidate the fibers of rovings by passing them into the impregnation die filled with molten thermoplastic. The die consists of three rollers and numerous pins fixed on the roller surfaces over which the roving is drawn under tension. The material chosen to illustrate the die process is a glass-fiber reinforced nylon-6, PA6. The void content and mechanical properties were measured to investigate the influence of processing variables on properties. These process experiences indicated that poor fiber resin impregnation and fiber damage, due to harsh prepreg fabrication, result in low values for longitudinal tensile strength and impact properties. However, the composites manufactured by this technique show a significant improvement in mechanical properties over conventionally prepared thermoplastic composites.     

Mechanical properties of phenolic composites reinforced with jute/cotton hybrid fabrics

Mechanical properties (tensile, flexural, impact, and dynamic mechanical thermal analysis) of novolac type phenolic composites reinforced with jute/cotton hybrid woven fabrics were investigated as a function of fiber orientation and roving/fabric characteristics. Scanning electron microscopy (SEM) was carried out to investigate the fiber‐matrix adhesion. Results showed that the composite properties are strongly influenced by test direction and rovings/fabric characteristics. The anisotropy degree was shown to increase with test angle and to strongly depend on the type/architecture of fabric used, i.e., jute rovings diameter, relative fiber content, etc. It was possible to obtain composites with higher mechanical properties and lower anisotropy degree by producing cross‐ply laminates. Best overall mechanical properties were obtained for the composites tested along the jute rovings direction. Composites tested at 45° and 90° with respect to the jute roving direction exhibited a controlled brittle failure combined with a successive fiber pullout, while those tested in the longitudinal direction (0°) exhibited a catastrophic failure mode. Our results indicate that jute promotes a higher reinforcing effect and cotton avoids catastrophic failure. Therefore, this combination of natural fibers is suitable to product composites for lightweight structural applications. POLYM. COMPOS., 26:1–11, 2005. © 2004 Society of Plastics Engineers.     

短纤维在氯丁橡胶中的应用

研究了短纤维种类、用量及长度对短纤维/氯丁橡胶复合材料的纤维取向、纤维分散、力学性能、耐热性能以及溶胀性能的影响。结果表明,复合材料呈现明显的各向异性;3mm短纤维/氯丁橡胶(CR)复合材料的纤维取向度、拉伸强度、撕裂强度和耐溶胀性能均优于1mm复合材料,短纤维分散性对复合材料耐热性的影响较小。     

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     

Empirical relations of the mechanical properties of polyamide 6 reinforced with short glass fibers

The dependence of the mechanical properties on the length of reinforcing fibers in hydrolytic polyamide 6 (PA 6) Matrix was studied. The fibers create a polydisperse system and the fiber distribution can be expressed by the Tung distribution function. Modulus, tensile strength, and also impact strength measured on test pieces seem to be a linear function of the part of fiber length population (percentile) representing the reinforcing fibers longer than 200 μm (value P²). These were determined not only on test pieces but also in starting pellets. The mutual relations between the individual mechanical properties seem to be linear as well. Consequently, the mechanical properties of these PA 6 composites can be estimated from the known distribution of fiber lengths in pellets and from the P²⁰⁰values, without preparing and testing the test pieces. The fiber length distribution in pellets of the composite can be estimated from the values of mechanical data (modulus, strength, impact strength) measured on test pieces.     

长玻纤增强PET复合材料的力学性能研究

采用自制的浸润装置，以PET浸渍长波纤，经切粒后得到长度为6mm的长纤维增强PET预浸料切片，经一定温度热处理，可得到长纤增强PET复合材料。研究了注塑样条中玻纤含量对其力学性能及玻纤长度分布的影响，并采用SEM观察了长玻纤增强PET注塑样条的断面形貌。结果表明，复合材料力学性能随玻璃纤维含量的提高均有不同程度的提高，当玻纤的质量分数在40％～50％时，力学性能基本达到最佳，且由本方法制备的长玻纤增强PET复合材料的力学性能已达到并超过了国外同类产品的水平。     

Long fiber reinforcement of polypropylene/polystyrene blends

The recycling of inseparable polymer mixtures usually results in blends with poor mechanical properties. A mixture of PP and PS was taken as a model compound for a recyclate. The effect of adding glass fibers to a mixture of PP/PS (70/30) was studied, with special attention to long glass fiber reinforcement. Test specimens were made in three different ways: by dry blending (direct injection molding), mild compounding with a single screw extruder, and compounding with a twin screw extruder. The fiber concentration was varied from 0 to 30 wt%. The fiber lengths were determined to investigate fiber attrition. The fiber lengths in the samples were 1.09 mm for dry blending, 0.72 mm for single screw compounding, and 0.33 mm for twin screw compounding. The mechanical behavior was studied by unnotched and notched Izod impact and tensile tests. The PP/PS blend had a low fracture strain and low unnotched Izod impact strength compared with a PP homopolymer. With an increasing fiber concentration and fiber length, the modulus, tensile strength, and particularly the impact strength increased. With a 30 wt% glass fiber of the long fiber compound (dry blended), the modulus was raised by a factor of 3.5, the fracture stress by a factor of 2.5 and the unnotched Izod impact strength by a factor of 10. The product quality as judged by the scatter of the data was best for the twin screw compound and poorest for the dry blend. Compounding with a single screw extruder gave fairly constant injection molding product properties, combined with excellent mechanical properties.     

Effect of compounding on the properties of short fiber reinforced injection moldable thermoplastic composites

The mechanical properties of short-fiber-reinforced thermoplastic composites depend on the degree of interfacial bond strength between the fibers and polymer matrix. This interfacial bond strength can be increased by appropriate coupling agents. This study shows, for example, that an amino silane coupling agent improves the bond strength of nylon-aluminum fiber composites, but not polycarbonate-aluminum fiber composites. For cases where appropriate coupling agents are not available it is important to maintain as high a fiber aspect ratio as possible in a molded part. This study shows that a single screw compounder does less damage to glass or carbon fibers than a twin screw compounder under similar processing conditions when the polymer is in the form of pellets. When the polymer is supplied as a powder, satisfactory dry blends can be produced and the twin screw compounder does less damage to the fibers. In both cases, however, fibers initially 6 mm long are reduced to an average length less than 0.5 mm. The greatest degree of fiber size retention was observed when extrusion coated fiber pellets were used in the injection molding machine. The relationship between a fiber's tensile strength and the interfacial shear strength between a fiber and matrix yields a critical fiber aspect ratio below which the maximum reinforcing capability of the fibers are not being utilized. For the polymers investigated in this program, the critical aspect ratio for carbon fibers was found to be between 16 and 25 to 1. The polymers investigated include flame-retardant grades of acrylonitrile-butadiene-styrene (ABS) and poly(phenylene oxide)/polystyrene blend, nylon 6/6 and poly(phenylene sulfide).     

Injection molding of long sisal fiber–reinforced polypropylene: Effects of compatibilizer concentration and viscosity on fiber adhesion and thermal degradation

A two‐step process was used to obtain long sisal fiber‐polypropylene (SF/PP)–reinforced thermoplastic composites, using maleic anhydride grafted polypropylene (MA‐g‐PP) as a compatibilizer. At a first stage, modified polypropylenes (mPP) were used for an extrusion impregnation process, for the preparation of composite pellets containing about 70 wt% of SF. SF/mPP pellets with a large aspect ratio were prepared by continuous extrusion impregnation of a continuous SF yarn, using a single screw extruder and an adequate impregnation die. The mPP used were MA‐g‐PP and regular polypropylene (PP), modified by reaction with different amounts of an organic peroxide. The composite pellets were thus dry blended with regular PP pellets in an injection machine hopper, and injection molded to obtain composite tensile specimens with a minimum quantity of modified polypropylene, minimum fiber breakage and thermal degradation, and excellent mechanical properties. It is shown that the fiber breakage is reduced to a minimum, even for recycled composites, due to the presence of the low‐viscosity polymer layer wetting the SF fibers. The bulk composite effective viscosity and the fiber breakage extent and thermal degradation during the injection‐molding step are found to be closely related. Blending with much less expensive mPP at the impregnation stage optimizes the amount of expensive MA‐g‐PP. POLYM. ENG. SCI., 45:613–621, 2005. © 2005 Society of Plastics Engineers     

玻璃纤维浸胶纱拉伸破坏模式的研究

介绍了浸胶纱拉伸性能试验的原理、仪器和计算方法。通过对玻璃纤维浸胶纱的拉伸性能试验,研究了玻璃纤维浸胶纱弹性模量及伸长率的试验方法。通过分析玻璃纤维浸胶纱的破坏模式,研究了玻璃纤维与树脂基体的复合性能及机理,有利于促进玻璃纤维更合理的应用。     

Mechanical properties of injection molded long fiber polypropylene composites,Part 1: Tensile and flexural properties

Innovative polymers and composites are broadening the range of applications and commercial production of thermoplastics. Long fiber‐reinforced thermoplastics have received much attention due to their processability by conventional technologies. This study describes the development of long fiber reinforced polypropylene (LFPP) composites and the effect of fiber length and compatibilizer content on their mechanical properties. LFPP pellets of different sizes were prepared by extrusion process using a specially designed radial impregnation die and these pellets were injection molded to develop LFPP composites. Maleic‐anhydride grafted polypropylene (MA‐g‐PP) was chosen as a compatibilizer and its content was optimized by determining the interfacial properties through fiber pullout test. Critical fiber length was calculated using interfacial shear strength. Fiber length distributions were analyzed using profile projector and image analyzer software system. Fiber aspect ratio of more than 100 was achieved after injection molding. The results of the tensile and flexural properties of injection molded long glass fiber reinforced polypropylene with a glass fiber volume fraction of 0.18 are presented. It was found that the differences in pellet sizes improve the mechanical properties by 3–8%. Efforts are made to theoretically predict the tensile strength and modulus using the Kelly‐Tyson and Halpin‐Tsai model, respectively. POLYM. COMPOS., 28:259–266, 2007. © 2007 Society of Plastic Engineers     

Effects of preferential encapsulation of glass fiber on the properties of ternary GF/PA/PP blends

Long fiber molding materials are expected to play an important role in the near future. This paper describes a series of experiments performed to examine properties of ternary blends containing glass fiber (GF), polyamide (PA), and polypropylene (PP). The continuous glass fiber was impregnated with one of the blend constituent polymers by our specially designed impregnation apparatus and cut into chips of 6 mm length. These chips and the other polymer were used to produce various testing specimens in a twin screw extruder or in injection molding machine. The results indicated that the effect of fiber addition on the mechanical and rheological properties is clearly dependent on the order of impregnation process. In the blends containing the GF/PA + PP, the GFs are preferentially encapsulated with PA, and therefore the mechanical properties are superior to the blends with the GF/PP + PA in which the PP phase is located surrounding the GFs. This improved wetting of fibers by sequential impregnation not only resulted in better properties but also protected the fibers from shear action of the screw, thereby allowing significant increase in average fiber length to be achieved in the injection molding process.     

Effect of screw design on fiber damage in extrusion compounding and composite properties

The mechanism of fiber length degradation during twin screw extrusion compounding and methods to reduce it through process and machine design are extremely important in discontinuous fiber reinforced composites. Fiber damage along the screw and the extruder die are determined for three screw designs with different mixing sections. The pellet quality, wet-out, and fiber dispersion in the extruded strands are compared. The fiber orientation distributions in the screw are determined to identify regions of higher fiber interaction. The fiber damage during subsequent injection molding has also been determined. The tensile, flexural, and impact properties of the tensile bars are compared. It is found that the residence time, fill-up, and the intesity of mixing during extrusion compounding have a predominant effect on fiber length degradation. The screw designs were seen to have a greater effect on the fiber damage in the 40 wt% glass-filled polymer than the 30 wt% glass-filled polymer. However, the mechanical properties of the 30 wt% glass-filled polymer showed an increasing trend compared to the 40 wt% glass filled polymer. A screw design that provides a balance of the fiber length, wet-out, and fiber dispersion was noted to give consistent mechanical properties.     

Tensile properties of short sisal fiber-reinforced polyethylene composites

Sisal fibers (Agave-Veracruz) have been used as reinforcements in low-density polyethylene (LDPE). The influence of the processing method and the effect of fiber content, fiber length, and orientation on tensile properties of the composites have been evaluated. The fiber damage that normally occurs during blending of fiber and polyethylene by the meltmixing method is avoided by adopting a solution-mixing procedure. The tensile properties of the composites thus prepared show a gradual increase with fiber content. The properties also increased with fiber length, to a maximum at a fiber length of about 6 mm. Unidirectional alignment of the short fibers achieved by an extrusion process enhanced the tensile strength and modulus of the composites along the axis of fiber alignment by more than twofold compared to randomly oriented fiber composites. © 1993 John Wiley & Sons, Inc.     

Mechanical properties of glass fiber/organic fiber mixed–mat reinforced thermoplastic composites

The purpose of this study is to investigate the influence of different types of fibers on the mechanical properties of hybrid composite materials. Long and short glass fibers (GF) and different types of organic fibers, viz. aramid fiber, DuPont Kevlar‐49 (KF), liquid crystalline polymer (LCP), and vinylon (VF) in hybrid composites, were used to reinforced the high density polyethylene (HDPE) matrix. The long fiber hybrid composites were prepared in a “fiber separating and flying machine,” while the short fiber hybrid composites were prepared in an “elastic extruder.” The total amount of fibers used in both long and short fiber hybrid composites was fixed at 20 vol%. The influence of fiber content, length, and mixing ratio on mechanical properties, such as tensile, bending, Izod and high rate impact strength, as well as viscoelastic propertics in the solid state, was studied. Fracture surfaces of the materials were also examined using a scanning electron microscopy.     

Preferred orientation of chopped fibers in polymer-based composites processed by selective laser sintering and fused deposition modeling: Effects on mechanical properties

The orientation of reinforcing fibers in polymer-based composites greatly affects their mechanical features. It is known that different orientations of continuous fibers in the stacked layers of a laminate play a crucial role in providing an isotropic mechanical behavior, while the alignment of chopped fibers in injection molding of composites results in a degree of anisotropy. Recent additive manufacturing techniques have offered a way of controlling the fiber orientation. This article aims to investigate the effect of fiber orientation on the mechanical properties of polyamide/carbon fiber composites processed by fused deposition modeling and selective laser sintering. Tensile samples which had different fibers and layer interface with respect to the sample axis (and therefore to the tensile load) were produced. Tensile tests were performed at different strain rates; the tensile properties and the fracture surface morphology were correlated with the processing method and the sample microstructure. The best strength and stiffness were observed when the fibers and the layer interfaces were parallel to the sample axis.     

短切CF增强TPEE热塑性复合材料的注射成型及力学性能研究

以热塑性聚酯弹性体(TPEE)为基体材料,8 mm短切碳纤维(CF)为增强材料,制备CF/TPEE复合材料。材料通过双螺杆挤出系统混合塑化、挤出造粒后,再经过注塑成型制备成标准拉伸试样,通过力学性能测试及微观结构观察,系统研究了碳纤维含量和等离子表面处理对CF/TPEE复合材料拉伸性能的影响。结果表明,当碳纤维含量为20%时,CF/TPEE复合材料的拉伸强度最大,为39.08 MPa;相比于纯TPEE,其拉伸强度提高了217%;经过等离子表面处理后,拉伸强度进一步提高了5%。结合拉伸后断面的SEM图发现,注塑试样表层碳纤维取向度高,而近中区和中心层取向度相对较低,这是注射CF/TPEE复合材料拉伸性能提高效应不明显的主要原因。