Prediction of mechanical properties of short kevlar fiber-nylon-6,6 composites

Injection molded short Kevlar (DuPont) fiber/nylon-6,6 composites have been studied. Fiber length and length distribution were measured as a function of processing variables. Critical fiber length was measured by an embedded single-fiber method. Tensile modulus of the molded composites was predicted by an adapted classical lamination analogy. Fiber and matrix orientation factors, derived from X-ray diffraction, were introduced to modify Kelly Tyson equation to estimate the composite tensile strength. It has been found that fiber length is dramatically shortened by the injection molding process, and is affected by processing conditions. Predictions gave reasonable agreement with data for tensile modulus and strength.     

Polymerization compounding composites of nylon‐6,6/short glass fiber

Nylon‐6,6 was grafted onto the surface of short glass fibers through the sequential reaction of adipoyl chloride and hexamethylenediamine onto the fiber surface. Grafted and unsized short glass fibers (USGF) were used to prepare composites with nylon‐6,6 via melt blending. The glass fibers were found to act as nucleating agents for the nylon‐6,6 matrix. Grafted glass fiber composites have higher crystallization temperatures than USGF composites, indicating that grafted nylon‐6,6 molecules further increase crystallization rate of composites. Grafted glass fiber composites were also found to have higher tensile strength, tensile modulus, dynamic storage modulus, and melt viscosity than USGF composites. Property enhancement is attributed to improved wetting and interactions between the nylon‐6,6 matrix and the modified surface of glass fibers, which is supported by scanning electron microscopy (SEM) analysis. The glass transition (tan δ) temperatures extracted from dynamic mechanical analysis (DMA) are found to be unchanged for USGF, while in the case of grafted glass fiber, tan δ increases with increasing glass fiber contents. Moreover, the peak values (i.e., intensity) of tan δ are slightly lower for grafted glass fiber composites than for USGF composites, further indicating improved interactions between the grafted glass fibers and nylon‐6,6 matrix. The Halpin‐Tsai and modified Kelly‐Tyson models were used to predict the tensile modulus and tensile strength, respectively.     

Microstructure and fracture behavior of (co)injection‐molded polyamide 6 composites with short glass/carbon fiber hybrid reinforcement

The mechanical and fracture properties of injection molded short glass fiber)/short carbon fiber reinforced polyamide 6 (PA 6) hybrid composites were studied. The short fiber composites of PA 6 glass fiber, carbon fiber, and the hybrid blend were injection molded using a conventional machine whereas the two types of sandwich skin–core hybrids were coinjection molded. The fiber volume fraction for all formulations was fixed at 0.07. The overall composite density, volume, and weight fraction for each formulation was calculated after composite pyrolysis in a furnace at 600°C under nitrogen atmosphere. The tensile, flexural, and single‐edge notch‐bending tests were performed on all formulations. Microstructural characterizations involved the determination of thermal properties, skin–core thickness, and fiber length distributions. The carbon fiber/PA 6 (CF/PA 6) formulation exhibits the highest values for most tests. The sandwich skin‐core hybrid composites exhibit values lower than the CF/PA 6 and hybrid composite blends for the mechanical and fracture tests. The behaviors of all composite formulations are explained in terms of mechanical and fracture properties and its proportion to the composite strength, fiber orientation, interfacial bonding between fibers and matrix, nucleating ability of carbon fibers, and the effects of the skin and core structures. Failure mechanisms of both the matrix and the composites, assessed by fractographic studies in a scanning electron microscope, are discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 957–967, 2005     

Microstructural characterization of short glass fiber and PAN based carbon fiber reinforced nylon 6 polymer composites

Microstructural characterization of nylon 6/short glass fiber (SGF) and nylon 6/polyacrolonitrile based carbon fibers (PAN‐CFs) of 10 to 40 wt% has been performed by positron lifetime technique (PLT). The positron lifetime parameters viz., o‐Ps lifetime (τ₃), o‐Ps intensity (I₃), and fractional free volume (F_v) of nylon 6/SGF and nylon 6/PAN‐CF composites are correlated with the mechanical properties viz., tensile strength and Young's modulus. The F_v shows negative deviation with the reinforcement of 10 to 40 wt% of PAN‐CF and show positive deviation in nylon 6/SGF from the linear additivity relation. The negative deviation in nylon 6/PAN‐CF composite suggests the induced molecular packing due to the chemical interaction between the polymeric chains of nylon 6 and PAN‐CF. The positive deviation in nylon 6/SGF composite indicates the formation of interface between the polymeric chains of nylon 6 and SGF. The increased crystallinity of nylon 6/SGF and nylon 6/PAN‐CF composites shows the improved mechanical properties of the composites. The hydrodynamic interaction parameter (h), which shows more negative values in nylon 6/SGF than nylon 6/PAN‐CF composites. However, the extent of chemical interaction in nylon 6/SGF is less compare to nylon 6/PAN‐CF composites. This is evident from Fourier transform infrared spectrometry studies. POLYM. ENG. SCI., 58:1428–1437, 2018. © 2017 Society of Plastics Engineers     

Short glass fiber reinforced ABS and ABS/PA6 composites: Processing and characterization

In this study acrylonitrile‐butadiene‐styrene (ABS) terpolymer was reinforced with 3‐aminopropyltrimethoxysilane (APS)‐treated short glass fibers (SGFs). The effects of SGF concentration and extrusion process conditions, such as the screw speed and barrel temperature profile, on the mechanical properties of the composites were examined. Increasing the SGF concentration in the ABS matrix from 10 wt% to 30 wt% resulted in improved tensile strength, tensile modulus and flexural modulus, but drastically lowered the strain‐at‐break and the impact strength. The average fiber length decreased when the concentration of glass fibers increased. The increase in screw speed decreased the average fiber length, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength were affected negatively and the strain‐at‐break was affected positively. The increase in extrusion temperature decreased the fiber length degradation, and therefore the tensile strength, tensile modulus, flexural modulus, and impact strength increased. At higher temperatures the ABS matrix degraded and the mechanical strength of the composites decreased. To obtain a strong interaction at the interface, polyamide‐6 (PA6) at varying concentrations was introduced into the ABS/30 wt% SGF composite. The incorporation and increasing amount of PA6 in the composites broadened the fiber length distribution (FLD) owing to the low melt viscosity of PA6. Tensile strength, tensile modulus, flexural modulus, and impact strength values increased with an increase in the PA6 content of the ABS/PA6/SGF systems due to the improved adhesion at the interface, which was confirmed by the ratio of tensile strength to flexural strength as an adhesion parameter. These results were also supported by scanning electron micrographs of the ABS/PA6/SGF composites, which exhibited an improved adhesion between the SGFs and the ABS/PA6 matrix. POLYM. COMPOS. 26:745–755, 2005. © 2005 Society of Plastics Engineers     

A study of the mechanical properties of randomly oriented short banana and sisal hybrid fiber reinforced polyester composites

The mechanical performance of short randomly oriented banana and sisal hybrid fiber reinforced polyester composites was investigated with reference to the relative volume fraction of the two fibers at a constant total fiber loading of 0.40 volume fraction (V_f), keeping banana as the skin material and sisal as the core material. A positive hybrid effect is observed in the flexural strength and flexural modulus of the hybrid composites. The tensile strength of the composites showed a positive hybrid effect when the relative volume fraction of the two fibers was varied, and maximum tensile strength was found to be in the hybrid composite having a ratio of banana and sisal 4 : 1. The impact strength of the composites was increased with increasing volume fraction of sisal. However, a negative hybrid effect is observed when the impact strength of the composites is considered. Keeping the relative volume fraction of the two fibers constant, that is, banana : sisal = 0.32 : 0.08 (i.e., 4 : 1), the fiber loading was optimized and different layering patterns were investigated. The impact strength of the composites was increased with fiber loading. Tensile and flexural properties were found to be better at 0.40 V_f. In the case of different layering patterns, the highest flexural strength was observed for the bilayer composites. Compared to other composites, the tensile properties were slightly higher for the composite having banana as the skin material and sisal as the core material. Scanning electron micrographs of the tensile and impact fracture surfaces of the hybrid composites having volume fraction 0.20 and 0.40 V_f were studied. The experimental tensile strength and tensile modulus of hybrid composites were compared with those of theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1699–1709, 2005     

EP/BMI树脂基碳纤维复合材料的制备与性能表征

以环氧树脂(EP)、双马来酰亚胺(BMI)、4,4’-二氨基二苯砜(DDS)和短切碳纤维(SCF)等为主要原料制备了EP/BMI/DDS/SCF复合材料,并研究了SCF添加量对复合材料力学性能和热性能的影响。结果表明,当SCF添加量为0.25 %(质量分数,下同)时,EP/BMI/DDS/SCF复合材料的力学性能提高最大,其拉伸强度、弯曲强度、弯曲模量和缺口冲击强度比未添加SCF时的EP/BMI/DDS复合材料分别提高了48.52 %、32.15 %、25.77 %以及150.91 %;此外,SCF的加入有助于提高复合材料的热性能。     

Optimization of Mechanical Characteristics of Short Glass Fiber and Polytetrafluoroethylene Reinforced Polycarbonate Composites via D-Optimal Mixture Design

This paper deals with the application D-optimal mixture design (DMD) integrating response surface methodology (RSM) to discuss variation of mechanical characteristics depending on injection molding during production of short glass fiber (SGF) and polytetrafluoroethylene (PTFE) reinforced polycarbonate (PC) composites. Planning of experiments was based on a D-optimal mixture design (DMD). By applying RSM analysis, a mathematical predictive model of the tensile strength and flexural strength properties was developed in terms of the mixture ratio of PC, SGF, and PTFE. In addition, analysis of variance (ANOVA) and response surface graphs were applied to identify the effect of mixture ratio of SGF and PTFE reinforced PC composites for the tensile strength and flexural strength.     

Structure and properties of UHMWPE fiber/carbon fiber hybrid composites

Ultrahigh molecular weight polyethylene (UHMWPE) fiber/carbon fiber hybrid composites were prepared by inner‐laminar and interlaminar hybrid way. The mechanical properties, dynamic mechanical analysis (DMA), and morphologies of the composites were investigated and compared with each other. The results show that the hybrid way was the major factor to affect mechanical and thermal properties of hybrid composites. The resultant properties of inner‐laminar hybrid composite were better than that of interlaminar hybrid composite. The bending strength, compressive strength, and interlaminar shear strength of hybrid composites increased with an increase in carbon fiber content. The impact strength of inner‐laminar hybrid composite was the largest (423.3 kJ/m²) for the UHMWPE fiber content at 43 wt % to carbon fiber. The results show that the storage modulus (E′), dissipation factor (tan δ), and loss modulus (E″) of the inner‐laminar hybrid composite shift toward high temperature remarkably. The results also indicate that the high‐performance composite with high strength and heat resistance may be prepared by fibers' hybrid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1880–1884, 2006     

短切碳纤维对天然橡胶/顺丁橡胶复合材料性能的影响

以天然橡胶(NR)和顺丁橡胶(BR)为基料,以短切碳纤维(SCF)为添加剂,制备了SCF/NR/BR复合材料,考察了SCF用量对NR/BR的摩擦性能及力学性能的影响。结果表明,SCF可增强NR/BR基体的强度,增大其硬度。在NR/BR混合胶中加入15份SCF可以降低混合胶的摩擦系数,减少混合胶的磨损量,提高混合胶的耐磨性能。SCF增强的NR/BR在摩擦过程中发生了磨粒磨损和黏着磨损,形成了卷曲磨屑。     

Strength -Composition relationships of random short glass fiber -thermoplastics composites

Twelve polymers and copolymers reinforced with random short glass fibers are used for the study of the strength -composition relationship. Six of these reinforced systems are new and have not been reported elsewhere. The effect of fiber volume fraction on tensile and flexural strengths is related to the Kelly and Tyson equation. For each composition the strengthening factor, F, is calculated and discussed with respect to the structure of the polymer. One factor pertaining to the actual performance of fiber glass, fiber efficiency, K, has been extrapolated for the fiber glass used for this study. The effects of fibers on toughness and the Izod notched impact strength are discussed. It is the impact strength ratio and not the toughness which is used to describe the net result of reinforcement. The deviations between the wet and the dry strengths are used to illustrate the effect of the fiber -matrix interfacial bond. A new parameter, Δθ, is introduced to describe the effect of structure on the fiber -matrix interface. The effect of water at the fiber -matrix interface is further demonstrated through the determination of dielectric constant and dissipation factor of the composite before and after water immersion. The rule of mixtures was found to apply to dry electrical properties of composites.     

Mechanical and morphological properties of carbon fiber reinforced–modified epoxy composites

Epoxy, prepared through aminomethyl 3,5,5‐trimethylcyclohexylamine hardening of diglycidylether of bisphenol‐A (DGEBA) prepolymer, toughened with polycarbonate (PC) in different proportions, and reinforced with carbon fiber, was investigated by differential scanning calorimetry, tensile and interlaminar shear strength testing, and scanning electron microscopy (SEM). A single glass transition temperature was found in all compositions of the epoxy/PC blend system. The tensile properties of the blend were found to be better than that of the pure epoxy matrix. They increased with PC content up to 10%, beyond which they decreased. The influence of carbon fiber orientation on the mechanical properties of the composites was studied, where the fiber content was kept constant at 68 wt %. Composites with 45° fiber orientation were found to have very weak mechanical properties, and the mechanical properties of the blend matrix composites were found to be better than those of the pure epoxy matrix composites. The fracture and surface morphologies of the composite samples were characterized by SEM. Good bonding was observed between the fiber and matrix for the blend matrix composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3529–3536, 2006     

Polyester composites of short pineapple fiber and glass fiber: Tensile and impact properties

The tensile and impact performance of intimately mixed (IM) hybrid composites based on glass fiber (GF) and pineapple leaf fiber (PALF) was investigated. The composite was fabricated at constant volume fraction of fiber 0.3 V_f (fiber 0.3 and matrix 0.7). Keeping the volume fraction of matrix a constant (0.7 V_f), we have varied the PALF/GF ratio from 0 to 1. Incorporation of 0.1 volume fraction of GF increases the tensile strength of the hybrid composite by about 28%. The tensile strength showed a further increase when the volume fraction is changed to 0.7 and 0.9 V_f of GF. Intimately mixed hybrid composites exhibited higher impact strength than the individual fiber composites; the composite of PALF/GF ratio 70:30 showed maximum impact strength of 1203 J/m. A positive hybrid effect is observed for impact properties. Scanning electron micrographs of the fractured surfaces were examined to understand the fiber‐matrix adhesion. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

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     

Adaptive Adjustment of Injection Molding Process for Mechanical Characteristics Using the Taguchi Method and Response Surface Methodology

This study is analyzed variations of mechanical characteristics that depend on the injection molding techniques during the blending of short glass fiber (SGF) and polytetrafluoroethylene (PTFE) reinforced polycarbonate (PC) composites. Planning of experiment is based on a Taguchi orthogonal array table, and applied signal-to-noise ratios to determine an optimal setting. Simultaneously, applying response surface methodology (RSM) analysis, a mathematical predictive model of the tensile strength and flexural strength properties of mechanical characteristics were developed in terms of the injection molding process parameters. In addition, analysis of variance (ANOVA) also was applied to identify the effect of process parameters of SGF and PTFE reinforced PC composites for the tensile strength and flexural strength. Additional runs were conducted in order to validate the optimal setting and compare the performance of Taguchi method and RSM approach.     

Investigation of unsaturated polyester composites reinforced by aspen high‐yield pulp fibers

Aspen chemithermomechanical pulp fiber‐reinforced unsaturated polyester (UPE) composites were fabricated using premade paper handsheets. The effects of handsheet wet‐pressing pressure, grammage, and subsequent fabrication methods on the composite properties were evaluated. The composites obtained using the optimum process parameters had tensile moduli and tensile strengths comparable with those of traditional glass fiber‐reinforced UPE composites. The pressed composites had very consistent tensile moduli that were well fitted by the Halpin–Tsai and Tsai–Pagano models. The classical Kelly‐Tyson and Bowyer‐Bader models significantly underestimated the composite tensile strengths and the potential reasons for this discrepancy are discussed. POLYM. COMPOS., 2012. © 2011 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.     

Nanosilica as dry bonding system component and as reinforcement in short nylon‐6 fiber/natural rubber composite

Nanoscale silica was synthesized by acid hydrolysis of sodium silicate using dilute hydrochloric acid under controlled conditions. The synthesized silica was characterized by SEM, BET adsorption, and XRD. The particle size of silica was calculated to be 13 nm from the XRD results and the surface area was found to be 295 m²/g by BET method. This synthesized nanosilica was used in place of conventional silica in HRH (hexamethylenetetramine, resorcinol and silica) bonding system for natural rubber/Nylon‐6 short fiber composite. Nanosilica was also used as reinforcing filler in natural rubber/Nylon‐6 short fiber hybrid composite. Mechanical, thermal, and dynamic mechanical properties of the composites were evaluated. The introduction of the nanosilica in hybrid composites improved the tensile strength, modulus, and tear strength through improved interaction with the matrix which is facilitated by the higher surface area. Abrasion loss and hardness were also better for the nanosilica composites. Resilience and compression set were adversely affected. The hybrid composites showed anisotropy in mechanical properties. Peak rate of thermal decomposition decreased and temperature of initiation of thermal degradation increased with silica content, indicating improved thermal stability of the hybrid composites. The storage modulus and loss modulus showed two‐stage dependence on frequency at higher fiber loading. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Strength of short fiber reinforced polymers: Effect of fiber length distribution

In this study, the prediction of mechanical strength of short fiber reinforced plastics (SFRPs) is made possible by obtaining a Fiber Length Distribution (FLD) efficiency factor, η_FLD, from the formerly known twofold discrete strengthening equation of Kelly–Tyson. The unified parameter η_FLD is developed involving both the effects of fiber breakage and resulting distribution, fiber volume fraction and fiber and interface properties, so that they can be incorporated into modified rule of mixtures (MROM). This procedure helps to clarify the experimentally observed loss in strengthening rate with increasing fiber fraction. By adapting a few experimentally determined distributions to a Weibull type function, the analytical solutions described in this study establish the exploration of the strength of SFRPs in the entire fiber content range or can reveal the interfacial bond strength. After investigating the effects of fiber and interface parameters on strengthening efficiency, it is found that common fiber‐matrix combinations possessing intermediate critical fiber lengths show a significant decrease in strengthening efficiency with increasing fiber content at low fiber loadings. On the contrary, higher and lower critical fiber lengths yield less significant losses. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Design and fabrication of long‐carbon‐fiber‐reinforced polyamide‐6/nickel powder composites for electromagnetic interference shielding and high mechanical performance

The long‐carbon‐fiber‐reinforced polyamide‐6/nickel powder composites were designed as electromagnetic interference (EMI) shielding materials and then were prepared through the joint processing of melt blending and thermoplastic pultrusion. The obtained composites show high conductivity and permittivity as well as a high dielectric loss with co‐addition of carbon fiber and nickel powders, which makes the resulting composites a higher level of shielding effectiveness due to the combination of conductive and magnetic fillers. The composites are capable of shielding mainly through absorption rather than reflection. On the other hand, the composites achieved significant improvements in tensile, flexural, and impact strength due to the superiority of the long‐carbon‐fiber‐reinforced technique. The residual fiber length in the injection‐molded specimens is greatly superior to the critical one predicted by the Kelly–Tyson model. This takes full advantage of the strength of the reinforcing fiber itself, thus leading to a promising reinforcement effect. The enhancement of impact toughness is due to the energy dissipation by fiber fracture as a result of long fiber effect. The morphologic investigation indicated that the fiber fracture and fiber pullout concurred on the impact and tensile fracture surfaces, and the former preceded the latter. Highlighted with both good EMI shielding properties and excellent mechanical performance, the composites designed by this work exhibit potential applications for the automotive, electronic, aerospace, and military industries. POLYM. COMPOS., 37:2705–2718, 2016. © 2015 Society of Plastics Engineers