Glass Fiber Reinforced Polypropylene Composites Research Articles

Stiffness of bio-based polyamide 11 reinforced with softwood stone ground-wood fibres as an alternative to polypropylene-glass fibre composites

Polyolefin had been successfully reinforced with glass fibres and applied in the industry during the last decades. However there are unsolved processability and recyclability problems due to its fragility. There are also concerns related with the human health. This had promoted the interest towards more environmentally friendly and healthier reinforcements such as natural fibres. In addition, the oil origin of polyolefin increases the interest in researching greener polymer alternatives. This work proposes polyamide 11 (PA11) as a promising alternative to polypropylene or other commodity polyolefin. This paper studies the behaviour of the Young’s modulus of natural fibre reinforced PA11 composites at different fibre contents. The composites were prepared, injection molded and characterized to tensile modulus. Afterwards a micromechanical modelling was performed using two models: Hirsch’s and Tsai-Pagano’s. The results allow proposing natural fibre reinforced PA11 composites as a suitable replacement to glass fibre reinforced polypropylene composites.

Tensile Strength Assessment of Injection-Molded High Yield Sugarcane Bagasse-Reinforced Polypropylene

Sugarcane bagasse was treated to obtain sawdust, in addition to mechanical, thermomechanical, and chemical-thermomechanical pulps. The obtained fibers were used to obtain reinforced polypropylene composites prepared by injection molding. Coupling agent contents ranging from 2 to 10% w/w were added to the composite to obtain the highest tensile strength. All the composites included 30% w/w of reinforcing fibers. The tensile strength of the different sugarcane bagasse fiber composites were tested and discussed. The results were compared with that of other natural fiber- or glass fiber-reinforced polypropylene composites. Pulp-based composites showed higher tensile strength than sawdust-based composites. A micromechanical analysis showed the relationship of some micromechanical properties to the orientation angle, critical length, the intrinsic tensile strength, and the interfacial shear strength. The pulps showed similar intrinsic tensile strengths and were higher than that of sawdust. The properties of the sugarcane bagasse composites compared well with other natural fiber-reinforced composites.

Interfacial charring method to overcome the wicking action in glass fiber-reinforced polypropylene composite

Glass fiber (GF)-reinforced polypropylene composites show high flammability due to wicking actions, which results in accelerated flow of the polymer melt along the GF surface to the flame zone. The conventional bulk charring mode, in which high loading of flame retardants are evenly distributed in the bulk matrix to catalyze the resin into an integrate char-barrier so that the entire composite surface could be covered, is quite inefficient and uneconomic. In this research, an interfacial charring mode differing from the bulk one has been proposed to solve the challenge. The acid-source flame retardants grafted on the GF surface can rapidly carbonize the interfacial resin to form a char layer, which can locally encapsulate the GF during combustion, thus converting the original smooth and polar GF surface to rough and inert carbonates-covered one and preventing the polymer melts from wetting, spreading and flowing on it. In this manner, it effectively eliminated thermodynamic and dynamic factors that cause wicking actions and remarkably improved flame retardance, even at a much lower flame retardant concentration compared with the bulk mode. In addition, without the stress concentration effect caused by the flame retardant particles directly distributed in the bulk resin, the interfacial flame retardant system also showed much better mechanical properties than the bulk one.

Effects of hybrid yarn preparation technique and fiber sizing on the mechanical properties of continuous glass fiber-reinforced polypropylene composites

In this study, hybrid yarns were developed by commingling the continuous polypropylene and glass fibers using air jet and direct twist preparation techniques. The non-crimp fabrics were obtained with ± 45 ° fiber orientation from these hybrid yarns. The fabrics were prepared with fiber sizings that are compatible and incompatible with polypropylene matrix to investigate the effect of interfacial adhesion on the properties of the thermoplastic composites. Composite panels were produced from the developed fabrics by hot press compression method and microstructural and mechanical properties of the composites were investigated. It was found that type of the hybrid yarn preparation technique and glass fiber sizing applied on the glass fibers have some important role on the properties of the composites. Composites made of fabrics produced by air jet hybrid yarn preparation technique exhibited better results than those produced by direct twist covering (single or double) hybrid yarn preparation techniques. The highest flexural properties (99.1 MPa flexural strength and 9.55 GPa flexural modulus) were obtained from the composites manufactured from fabric containing compatible sizing, due to better adhesion at the interface of glass fibers and polypropylene matrix. The composite fabricated from fabric with polypropylene compatible sizing also exhibited the highest peel resistance (interlaminar peel strength value of 5.87 N/mm). On the other hand, it was found that hybrid yarn preparation technique and type of the glass fiber sizing have insignificant effect on the impact properties of the glass fiber/polypropylene composites.

Experimental study on strain-rate-dependent behavior and failure modes of long glass fiber-reinforced polypropylene composite

Due to its good mechanical performances and design flexibility, long glass fiber-reinforced polypropylene (hereinafter referred to as LGFRP) composite has been increasingly used in the automotive industry, in which the LGFRP components are likely to sustain different strain rates loading during a crash event. The objectives of this study are to investigate the correlations between the LGFRP and strain rates 10−3 s−1 to 50 s−1, and the corresponding failure modes of LGFRP. Therefore, tensile and compression tests are conducted at different strain rates and the corresponding microstructures of the specimens are investigated with scanning electron microscope. The experimental results show that the failure strain and ultimate strength increase as increasing strain rate. The elastic modulus is sensitive to strain rate in tensile tests, but less sensitive to strain rate in compression tests. The main failure modes of the specimens are the matrix crack and fiber pull-out. The defects such as bubbles, shrinkage cavities, or dry fibers of the specimens play important roles in the initiation and propagation of cracks during the tensile and compression tests.

Structure and Properties of Glass Fiber Reinforced Polypropylene/Liquid Crystal Polymer Blends

A liquid crystal polymer (LCP) was used to improve the physical properties of glass fiber reinforced polypropylene (GFRPP). The LCP was beneficial to improve the mechanical and heat resistant properties of the GFRPP/LCP composite. Compared with the GFRPP with 30% (w%) glass fiber (GF), the yield strength and the impact strength for the GFRPP/LCP composites increased by 62.7% and 18.1%, respectively, with a 6.8°C increase in the Vicat softening temperature for a 5% LCP addition to the GFRPP composites. The crystallinity of the polypropylene (PP) matrix for the GFRPP/LCP composites increased for 5% LCP and then decreased with increasing the LCP content. The γ-phase crystals for the PP matrix occurred in the shear layer of the injection molded GFRPP/LCP samples. The improved adhesion interface between the GF and the PP matrix was beneficial to reinforce and toughen the GFRPP/LCP composites with a small addition of the LCP.

Expanded graphite nanoplatelets as coupling agents in glass fiber reinforced polypropylene composites

The interfacial adhesion between E-glass fibers and various types of nanomodified polypropylene (PP) matrices have been investigated on single-fiber model composites. In particular, an evaluation of the fiber–matrix interfacial shear strength was performed by the fragmentation tests on model composites prepared by using PP matrices containing various amounts (up to 7wt%) of expanded graphite nanoplatelets (xGnP).The presence of xGnP in the polymer matrix resulted in a remarkable increase of the interfacial shear strength values (up to a factor of about 6 for a 7wt% content of xGnP) if compared to neat PP. Moreover, wettability measurements in various liquids evidenced that the work of adhesion of the polymer matrix with respect to glass fiber, was improved by the presence of xGnP.

Optimizing mechanical properties of injection-molded long fiber-reinforced polypropylene

Long glass fiber-reinforced polypropylene composites (LGFPP) are widely used in the industrial field, especially in automotive applications, due to their excellent mechanical properties and low cost. This article focuses on obtaining optimal mechanical properties of LGFPP for different objectives. The primary objective is to minimize the cost of the composite. The other objective is to obtain specific, desired properties of the composite (irrespective of the composite cost). The latter case is useful in designing products where quality of the composite cannot be compromised (while the cost of the composite is secondary). The properties that were optimized include tensile Young’s modulus, flexural Young’s modulus, and notched Izod impact. Surrogate models were obtained and used to predict these properties as functions of corresponding compositions of the composites. Furthermore, optimization framework that employs these models either as constraints or as objective functions was developed with the aim of developing tailored fiber-reinforced polypropylene. All simulations are programmed using MATLAB version 7.10.0 (R2010a).

Experimental Determination of the Mechanical Behavior of Glass Fiber Reinforced Polypropylene Composites

Thermoplastic composites have been widely used in structural and engineering applications, due to their high specific strength and stiffness, high strain to failure, better impact strength, shorter processing cycle time, infinite shelf life, and recyclability. This paper discusses the influence of the forming pressure and coupler concentration on the mechanical behavior of glass fiber reinforced polypropylene composite laminates. The Design of Experiments’ (DOE) full factorial approach was adopted for conducting the composite laminate fabrication experiments. The thermoplastic composite laminates were fabricated in a hot compression molding machine, using the film stacking technique. This is an innovative approach to develop thermoplastic composite laminates, using the available low cost raw materials, instead of high end prepreg materials. As per the ASTM standard, the tensile and flexural tests were carried out, in order to evaluate the influence of the parameters on the mechanical behavior of the composite laminates. The Tensile and flexural strengths of the thermoplastic composite laminates were the responses measured to identify the most influencing parameter. The experimental results show that the increase in forming pressure and coupler concentration initially increases both the mechanical properties, and then decreases the properties of the composite laminates. Compared to the coupler concentration, the forming pressure greatly improves both the tensile and flexural properties. Using the Scanning Electron Microscope (SEM), a morphological analysis was carried out to observe the bonding between the matrix and reinforcement.

Impact properties of glass-fiber/polypropylene composites: The influence of fiber loading, specimen geometry and test temperature

Glass fiber reinforced polypropylene composites were compounded with a twin-screw extruder and injection molded. Fiber length distribution study showed that more fiber degradation occurred during processing of the composites with higher fiber loading. Dynamic mechanical analysis carried out showed that magnitudes of storage and loss modulus of composites are improves with the presence of the glass fiber in the system. The incorporation of fibers into the composites has slightly shifted the glass transition temperature to lower values. On the other hand, the presence of the glass fiber reduces the magnitude of tan δ at α-transition dramatically due to the strengthening effect by the fibers. From impact test, it was found that increment in glass fiber loading leads to an increase in peak load, critical strain energy release rate and critical stress intensity factor indicating the improvement in the material toughness. However, there was no significant change observed in fracture energy. With respect to increasing in specimen geometry, despite an improvement in peak load and fracture energy of the impact specimen, the critical strain energy release rate and critical stress intensity factor values were decreased. On the other hand, increase in test temperature resulted in reduction of peak load and critical stress intensity factor due to increment in material ductility, whereby fracture energy and critical strain energy release rate improved.

Flame Retardancy and Mechanical Properties of Brominated Flame Retardant for Long Glass Fiber Reinforced Polypropylene Composites

The effects of brominated flame retardant which composed of decabromodiphenyl ethane (DBDPE) and antimonous oxide (AO) on long glass fiber reinforced polypropylene (LGFPP) were investigated by means of limiting oxygen index (LOI), vertical burning (UL-94), thermogravimetry analysis (TGA), and mechanical properties. With the increase of DBDPE-AO content, the LOI values of DBDPE-AO/LGFPP composites increased from 21 to 27.6, and when the content of DBDPE-AO was 16wt%, the composites passed the V-0 rating in UL-94 testing. The experimental results showed that the brominated flame retardant improved flame retardancy of LGFPP, which was proved by the TGA testing. Whats more, the mechanical properties of composites even improved compared with pure LGFPP.

Investigation on Fabrication of Glass Fiber Reinforced Polypropylene by Recycled FRTP and their Properties

In this paper, glass fiber reinforced polypropylene composites have been successfully fabricated via double screw extrusion by using mechanical crushed leftover materials as the raw materials with maleic anhydride grafted polypropylene (PP-g-MAH) and γ-ammonia propyl-triethoxy silane (KH-550) as the compatilizer and coupling agent, respectively. The influences of the contents of PP-g-MAH and KH-550 on the micro-structures and crystallization as well as mechanical properties of the fabricated composites have been systematically investigated. The results showed that: the recycled raw materials were homogenously dispersed in the polymer matrix without obvious agglomerations; with adding the recycled raw materials and compatilizer, the crystallization behaviors of PP did not changed dramatically while their thermal stabilities were greatly improved; the tensile strength of the product increased by 14% while notched impact strength increased by 21% as the contents of PP-g-MAH and KH-550 were 10phr and 1phr, respectively.

Processing, characterization, and wear analysis of short glass fiber-reinforced polypropylene composites filled with blast furnace slag

Blast furnace slag (BFS) is a major solid waste in iron industries that results from the fusion of fluxing stone with coke and the siliceous and aluminous residues remaining after the reduction and separation of iron from the ore. Using this BFS in different proportions (0, 10, 20, and 30 wt%) in thermoplastic polypropylene matrix base, hybrid composites are prepared with and without 20 wt% short glass fiber reinforcement, by injection-molding route. The composites are characterized in regard to their physical and mechanical properties and their dry sliding wear characteristics are studied experimentally. For this, a standard pin on-disk test set-up and Taguchi’s orthogonal arrays are used. Taguchi’s experimental design method eliminates the need for repeated experiments and thus saves time, materials, and cost. It identifies the significant control factors predominantly influencing the wear rate. From the experimental findings, optimal combinations of control factors are obtained for minimum wear rate and on that basis, predictive correlations are proposed. The morphology of worn surfaces is then examined by scanning electron microscopy and possible wear mechanisms are discussed. Furthermore, a model based on artificial neural networks (ANN) for the prediction of sliding wear properties of these thermoplastic polymer composites is implemented. The ANN prediction profiles for the characteristic wear properties exhibit very good agreement with the measured results demonstrating that a well-trained network has been created. The simulated results explaining the effect of significant process variables on the wear rate indicate that the trained neural network possesses enough generalization capability of predicting wear rate even beyond the experimental range.

Characterisation of the friction and wear behaviour of textile reinforced polymer composites in contact with diamond-like carbon layers

The tribological behaviour of composites, particularly in contact with steel, is to be estimated as relatively weak. As a promising improvement, the application of modern coatings is considered. In this context, the results of frictional and wear investigations of carbon fibre reinforced epoxy and polyethersulfone as well as glass fibre reinforced polypropylene composites in contact with coated and uncoated steel 100Cr6 are presented. The coating consists of diamond-like carbon (ta-C) layer. A remarkable outcome of the study is the substantial decrease of the specific wear rate of the investigated material pairings by the application of carbon coated metal. The tribological system, which is responsible for the excellent tribological characteristics, is determined by predominantly sliding wear and suppressed abrasive wear.

Analysis of the Creep Behavior of Polypropylene and Glass Fiber Reinforced Polypropylene Composites

In this paper tensile and creep tests were performed on polypropylene (PP) and its glass fiber reinforced composites. The tensile tests were carried out on 6 different glass fiber content reinforced PP composites (0, 5, 10, 20, 30 and 40%) while the creep tests were performed on the unreinforced and 30% and 40% fiber reinforced ones of industrial importance. 50 N/s constant force rate was used until the specimen failed (tensile test) or the preset load level was reached (creep test). The applied load levels for the creep experiments were determined as given ratios of the average breaking force. The tensile breaking strain and tensile strength versus fiber content relationship were analyzed and described by empirical formulas based on the correction and averaging procedure developed.

Creep failure strain estimation of glass fibre/polypropylene composites based on short-term tests and Weibull characterisation

In order to study the short- and long-term creep behaviours of injection moulded, unreinforced and glass fibre reinforced polypropylene composites, tensile and creep measurements were carried out and analysed. Based on the linear viscoelastic behaviour and variable transformations as well as Weibull-based distribution characterisation, estimations for the tensile strength parameters and creep failure strain were determined and fitted to the measurements. These mathematical estimations and the relationships between the material model czonstants and the fibre content, determined by fitting, give a possibility for designers’ calculations at arbitrary creep load levels and fibre contents.

Carbon and glass hierarchical fibers: Influence of carbon nanotubes on tensile, flexural and impact properties of short fiber reinforced composites

Dense carbon nanotubes (CNTs) were grown uniformly on the surface of carbon fibers and glass fibers to create hierarchical fibers by use of floating catalyst chemical vapor deposition. Morphologies of the CNTs were investigated using scanning electronic microscope (SEM) and transmission electron microscope (TEM). Larger diameter dimension and distinct growing mechanism of nanotubes on glass fiber were revealed. Short carbon and glass fiber reinforced polypropylene composites were fabricated using the hierarchical fibers and compared with composites made using neat fibers. Tensile, flexural and impact properties of the composites were measured, which showed evident enhancement in all mechanical properties compared to neat short fiber composites. SEM micrographs of composite fracture surface demonstrated improved adhesion between CNT-coated fiber and the matrix. The enhanced mechanical properties of short fiber composites was attributed to the synergistic effects of CNTs in improving fiber–matrix interfacial properties as well as the CNTs acting as supplemental reinforcement in short fiber-composites.

Ultrasonic Welding of Glass Fiber Reinforced Polypropylene

Glass fiber reinforced polypropylene composites were joined by ultrasonic welding, employing various weld conditions. Single-lap shear testing was used to evaluate the effect of weld time and weld pressure on the weld performance. The weld strength increased with increasing weld time and weld pressure until a plateau or maximum strength was reached. The required weld time to obtain a complete weld became shorter when the weld pressure was increased. As lower weld pressure was applied, a complete weld could not be obtained unless relatively longer weld times were employed. A welding map, showing conditions of weld time and weld pressure to get a good weld, was obtained.

NaBF 4 as a hygrothermal durability enhancer for glass fibre reinforced polypropylene composites

The long term performance of composite materials is highly desired for their expanding application range. Tuning the interphase properties has been proven to be a practical way to enhance the performance of composites. In this study, short glass fibre (GF) reinforced polypropylenes (PPs) with improved hygrothermal durability were obtained by incorporating NaBF 4 into the sizing and thus the interphases of GF/PP composites. Detailed investigations were performed on the surface properties of sized GFs and the mechanical properties of virgin and aged composites. It was found that the retention in both ultimate tensile strength and Charpy impact toughness of aged composites monotonically increased with increasing NaBF 4 content. The improvement in hygrothermal durability was related to the enhanced fibre/matrix adhesion strength induced by the presence of NaBF 4 as indentified by fracture surface analysis using field-emission scanning electron microscopy and single fibre pull-out test.

Shear induced fiber orientation, fiber breakage and matrix molecular orientation in long glass fiber reinforced polypropylene composites

Long fiber reinforcement is well known to offer thermoplastic materials with high performances. But little work has been done to systematically investigate the effect of shear on the structures and properties of long glass fiber reinforced thermoplastics. The purpose of this work is to investigate the effect of shear on fiber orientation, fiber breakage and matrix molecular orientation in long glass fiber reinforced polypropylene composites, and to construct the structure–property relations. A so-called dynamic packing injection molding (DPIM) technique, which imposed oscillatory shear (10 s −1) on the gradually cooled melt during the packing solidification stage, was used to prepare the dynamic samples, and optical microscope (OM), scanning electron microscope (SEM), micro-Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to characterize the samples. The results show that despite the well-published enhanced fiber and matrix orientation, shear will cause a remarkable fiber breakage. Combined effect of fiber breakage and orientation on the mechanical properties of the composites was qualitatively investigated and tensile properties of the dynamic samples, the conventional injection molded samples and the short glass fiber reinforced samples were compared. It is demonstrated that shear will induce more severe fiber breakage in long glass fiber reinforced polypropylene than in short glass fiber reinforced polypropylene, and that compromising the decreased strength caused by the severe fiber breakage is very difficult.