Reinforced Polypropylene Composites Research Articles

Response of natural fiber reinforced polymer composites when subjected to various environments

The last two decades have witnessed considerable progress in the use of bio-composites. There has been an increase in the global interest in the development of natural fiber reinforced composites. Nowadays, natural fiber reinforced polymer composites are being used in variety of applications, because of the attractive characteristics of being renewable, affordable, recyclable and as well as eco-friendly and biodegradable. Environmental behavior of natural fiber reinforced polymer composites upon exposure to various practical conditions is an important issue before proposing their use in outdoor applications. In the current experimental endeavor, plain-woven natural (hemp, jute, sisal) fabric reinforced polypropylene composites were fabricated using a compression moulding process. Thermal analysis has been utilized to fully understand the mechanical behaviour of developed composites. Effect of environmental aging on tensile and flexural behaviour of the fabricated composites has been investigated by exposing the specimens for 3 months under different conditions (drinking water, alkali solution, petrol-oil, industrial liquid waste and peanut-edible oil). The tensile and flexural properties were tested using computerized UTM machine as per the ASTM standards. The stero-microscope and field-emission scanning electron microscope has also been utilized to analyze the surface morphology of the fractures specimens under tensile loading. The results revealed that, the mechanical properties of polypropylene based composites are significantly influenced on account of the exposure to different environmental conditions.

Strain rate-dependent mechanical behavior of quasi-unidirectional E-glass fabric reinforced polypropylene composites under off-axis tensile loading

To make a better use of quasi-unidirectional fabrics in structural application, the strain rate-dependent tensile behavior of quasi-unidirectional E-glass fabric reinforced polypropylene composites was studied. Monotonic tensile tests were firstly performed on 10°, 20° and 90° off-axis samples of composites. The experimental results show that both mechanical properties and nonlinear stress-strain behavior of composites are dependent of strain rate. A regression function is adopted to describe the variation in overall mechanical properties with the imposed strain rate. A strain rate-dependent coupled damage-plasticity model is built for quasi-unidirectional composites. The damage variables and plastic parameters in the proposed model are determined through cyclic loading-unloading tensile tests and can be represented as a function of the imposed strain rate. In addition, the damage mechanism of composites is observed to evolve with strain rate. Increasing strain rate can hinder the initiation and evolution of damage in composites.

Mechanical characterization, modelling and application design of bamboo-polypropylene composites

This research is focused on characterization, modelling and product designing from bamboo fiber reinforced polypropylene composite. Bamboo fiber of mesh size of − 80/+ 100 (180–225 μm) were blended with polypropylene in a twin screw extrusion system at different weight percentages of bamboo (10, 20, 30, 40, and 50%). In-house synthesized m-TMI-g-PP was used as the coupling agent. Mechanical characterization reveals a continuous increment in tensile strength, flexural strength and elastic modulus with increasing fiber content. At 50% bamboo content, tensile and flexural strengths increased by 36 and 64% respectively and elastic modulus increased by 300% with respect to virgin polypropylene. Scanning electron microscope images of the fractured surface of composite indicated effective wetting of bamboo fiber with polypropylene. Halpin–Tsai model was found to describe the relative modulus of the composites at different fiber content effectively. Macro mechanical approach in which the composite is assumed to be isotropic was used to simulate uniaxial tensile test. The simulation was performed using Hypermesh (a FEM preprocessor) and explicit solver LS-DYNA. The stress–strain behaviour predicted by material model MAT 24 was in close agreement with the experimental results. A portable toilet design is suggested from the developed composite material based on the simulation results.

A recyclability study of bagasse fiber reinforced polypropylene composites

Natural fiber reinforced composites are gaining attention nowadays due to their low cost, biodegradable characteristics, lower density and comparable mechanical properties with synthetic fibers reinforced composites. As the recyclable properties of these composites are still not fully explored and this could be the reason that these are not much used in domestic and other applications to their full potential. In the current experimental investigation, the effects of mechanical recycling on the properties of bagasse fiber reinforced polypropylene composites have been studied. Tensile properties, crystallinity and aspect ratio exhibits an increase, while flexural properties decrease with each recycling step. No significant change in thermal behavior has been detected even after 5 cycles but a slight increase in the hardness has been observed. SEM images confirmed the change in aspect ratio due to crushing of fibers as well as fiber fracture became more dominant after each recycling step.

The evolution of morphology, crystallization and static and dynamic mechanical properties of long glass-fibre–reinforced polypropylene composites under thermo-oxidative ageing

In this work, the static and dynamic mechanical properties, crystallization behaviours, and morphology of long glass-fibre–reinforced polypropylene (PP) composites with thermo-oxidative ageing time from 0 day to 50 days at 120°C were investigated and discussed. The static mechanical properties showed a global decrease in tensile, bending and impact strengths with increasing ageing time. From the results obtained by scanning electronic microscopic observations, interface debonding clearly occurred between the glass fibre and PP matrix in the aged samples. The crystallinity ( Xc) of the composites was analyzed by differential scanning calorimetry; annealing process played the leading role in the early period of ageing, while as ageing progressed, the degradation of PP matrix dominated the ageing process and Xc decreased. The dynamic mechanical analysis results indicated that the storage modulus and glass transition temperature of the composites also decreased with prolonging ageing time. Then, the apparent activation energy ( E) of glass transition was calculated by the Arrhenius equation with different scanning frequencies. A higher value of E was obtained for the samples in the later ageing period, which means a higher energy barrier for glass transition.

Impact Resistance of Bamboo Fabric Reinforced Polypropylene Composites and Their Hybrids

Bamboo in woven fabric form embedded in the polymer results in easier material handling during production and reduction in the manufacturing cost of the composites. In the current study, the effect of hybridization of bamboo fabric with glass fibres on the impact properties of the composites made from them has been studied. The composites were fabricated using a compression moulding method. Bamboo fibres were in the form of twill-weave fabric. Impact tests were conducted using an instrumented drop weight impact test system. It can be seen that the peak load and energy absorbed increase with the increase in the applied impact energy. For the BPP composites, the applied energy of the impact was increased until penetration was occurred at 55 J. While for the BGPP hybrid composites, they were penetrated at the applied energy of only 35 J. However, The hybrid composites exhibit a greater peak load resistance than the BPP composites. The crack damage in the composites was also reduced with the presence of fabric reinforcement. These preliminary results indicate that bamboo fabric is truly a new contender for developing excellent and balanced properties of composites such as for the interior components.

Temperature-dependent response of quasi-unidirectional E-glass fabric reinforced polypropylene composites under off-axis tensile loading

Abstract The temperature-dependent off-axis tensile behavior of quasi-unidirectional E-glass fabric reinforced polypropylene composites has been investigated both experimentally and constitutively in this paper. The nonlinearity in composites under off-axis loading is shown to be a combination of damage and plasticity regardless of temperature. A nonlinear constitutive model is established to predict the temperature-dependent nonlinear stress-strain curves of composites, in which the accumulation of plastic strain and evolution of damage in composites are described by the plasticity and damage theories, respectively. A full suite of temperature-dependent plastic and damage parameters in the model are determined through cyclic loading-unloading tests.

The thermal and thermomechanical behaviors of Spartium junceum flour reinforced polypropylene composites: effects of treatment and flour content

The effects of Spartium junceum (SJ) flour content, treatment time on the thermal and thermomechanical properties of polypropylene/Spartium junceum flour (PP/SJ) composites were studied. In order to improve the interfacial adhesion between the PP matrix and the SJ flour, SJ flour was treated with NaOH (2 wt%) for 8, 24 and 48 h at ambient temperature, respectively, and treated by vinyltrimethoxysilane (VTMS) (5 wt%). The results of thermogravimetric analysis (TGA) of SJ flour shows that the treatment improves the thermal stability of SJ flour. DSC analysis measurements illustrates that the addition of SJ flour increase the degree of crystallinity X c, which indicate that the SJ flour plays a significant role in heterogeneous nucleating of PP matrix. The chemical treatments significantly affect the storage modulus of composite, where E′ increases for composites with treated flour in comparison to the untreated ones.

Predicting the stress relaxation behavior of glass-fiber reinforced polypropylene composites

It is well established that the addition of short elastic fibers slows the relaxation process in composites, but this phenomenon is not well-understood. Our recent study explained changes in the stress relaxation constant by accounting for the time-dependent interfacial shear stress transfer at the fiber-matrix interface. An analytical model was developed and was successfully compared to finite-element experiments. This approach represents a significant departure from the previously published literature, where the effect of fibers on viscoelasticity was typically attributed to changes in the covalent bonds at the fiber-matrix interface. In the present study, the stress relaxation behavior of glass fiber-reinforced polypropylene composites was experimentally measured and compared to analytical model predictions. Further, the effect of additional covalent bonding at the fiber-matrix interface was studied experimentally by introducing an interfacial coupling agent. Good agreement was obtained between the experimental data and the analytical model and it was concluded that most of the stress relaxation behavior of a composite can be predicted using a model that only accounts for the time-dependent matrix modulus and a time-dependent shear stress transfer efficiency.

Fabrication, Mechanical Characterization and Interfacial Properties of Okra Fiber Reinforced Polypropylene Composites

In this study, an attempt has been taken to manufacture okra fiber (OF) composites with varying the fiber content ranging from 25-65% on total weight of the composites and polypropylene (PP) was preferred as matrix material. To fabricate the composites untreated and mercerized fibers were selected. A systematic study was done to observe the mechanical behaviors of the composites such as tensile, impact and bending properties. It was found that treated (mercerized) fiber composites exhibited improved mechanical properties than that of untreated fiber composites. Maximum tensile strength (TS) and bending strength (BS) was examined 38.5 MPa and 72.5 MPa respectively, whereas the highest tensile modulus (TM) and bending modulus (BM) was observed 675 MPa and 5.4 GPa respectively. The optimum impact strength (IS) and hardness value was found to be 22.87 KJ/m2 and 97 (Shore-A) for mercerized fiber composites containing 45% fiber. The composite samples were exposed to different intensities of γ radiation (2.5 kGy–10.0 kGy) and found significant improvement in the mechanical properties up to 5.0 kGy dose. Water absorption, degradation properties due to heat and soil medium of the composites were also performed. The interfacial property was examined by Microscopic Projector and Scanning Electron Microscope (SEM) and found that the interfacial bonding between matrix material and fiber was enhanced due to the treatment of fibers which authenticate the found mechanical characteristics of the composites.

TENSILE PROPERTIES OF SURFACE TREATED COIR FIBRE REINFORCED POLYETHYLENE

The need to pursue an environmentally safer future has prompted the researchers to look beyond the inorganic fibre-based composites and engage in putting more thought into the utilization of natural fibre-based polymer composites. Although inorganic fibres, such as glass and carbon have a lot of advantages but we can owe its declining use in recent years to high initial cost, non-biodegradability, non-renewability, high energy consumption in manufacturing process and adverse environmental impacts. Natural fibres however more than compensate for their poor compatibility with the matrix, inherent high moisture absorption rate with their positive attributes like low cost, low density, non-abrasivity, good thermal properties, enhanced energy recovery and bio degradability. This work is aimed at investigating the effect of alkali treatment and fibre load on the tensile properties and hardness properties of coir fibre reinforced polypropylene composites. Polypropylene (PP) was used as the matrix resin and coir fibre (CF) as the reinforcing agent. The brown coconut fibres were pulled out and extracted manually from the coconut husks. To ensure proper interaction between fibre and matrix material, the outermost wax layer of the coir was removed by soaking the coir in hot water. The coir fibres are then prepared for treatment with NaOH solution to improve its surface properties and provide better adhesion with the matrix after the removal of lignin and pectin from the surface of the fibre. The tensile properties indicated that both the strength and modulus increased with increasing fibre content. However, in this investigation, the maximum fibre content is 20%. It could have been more than this but we encountered processing problem. Alkaline treated samples had higher tensile properties than untreated samples. The hardness of the material is not significantly affected by the surface treatment.

Micromechanical and dynamic mechanical analyses for characterizing improved interfacial strength of maleic anhydride compatibilized basalt fiber/polypropylene composites

For fiber reinforced polymer composites, it is important to obtain a good interfacial bonding between the fibers and the polymer matrix to enhance the physical properties of the composites. In particular, the mechanical and thermal properties of the composites differ depending on the interfacial bonding strength, lengths, and orientations of the fibers. We investigate the microstructural anisotropy of the basalt fiber reinforced polypropylene composites and evaluate their mechanical properties, such as elastic modulus and ultimate tensile strength in order to understand the relationship between the local anisotropy and the mechanical strength of the composites. Dynamic mechanical and thermal analyses are performed to characterize the grafting effect of maleic anhydride polypropylene on the basalt fibers. The grafting effect enhances the bonding strength between the basalt fibers and matrix and the thermomechanical properties of the composites. The elastic modulus and ultimate tensile strength of the composites with the grafting effect show enhancement compared to the composites without the grafting effect. The predictions of the elastic modulus by the Mori–Tanaka model and the ultimate tensile strength by the rule of mixture model are in good agreement with the experimental results.

Macro and micro-mechanics behavior of stifness in alkaline treated hemp core fibres polypropylene-based composites

Abstract Traditionally, glass fibre has been used as plastic reinforcement whenever mechanical properties of a matrix, like stiffness, do not meet the specifications. However, current tendencies try to replace glass fibres by more sustainable fibres to obtain eco-friendlier products. Natural fibres show comparatively good physical and mechanical properties and, unlike glass fibres, come from renewable resources and are recyclable and sustainable. In this work, hemp straw discarded from hemp manufacturing was used as reinforcement in polypropylene composites. One drawback associated to hemp straw is its high lignin content that reduces its reinforcing potential. Therefore, a soft alkaline treatment was employed to adjust the lignin contents. In this work, the evolution of the Young's modulus with the NaOH treatment is assessed and discussed. Intrinsic Young's moduli of hemp straw fibres at different alkaline conditions were determined by Hirsch model. Finally, Tsai-Pagano and Halpin-Tsai equations allowed the prediction of the theoretical Young's modulus of the composites. The results showed the competitiveness of a by-product reinforced composite in front of commodity materials.

Tensile and Flexural Performance of Polypropylene Based Oil Palm Fibre Reinforced Metal Laminates

In this research, the effects of fibre composition on the tensile and flexural performance of Oil Palm Fibre Metal Laminates have been experimentally investigated. OPFMLs are constituted of aluminium 6061 and oil palm empty fruit bunch fibre reinforced polypropylene composite. OPFMLs with four different fibre weight compositions (10%, 20%, 30% and 40%) were manufactured in 2/1 configuration. OPFMLs and their respective composite layers were prepared through hot press moulding compression technique using hot press machine. The mechanical properties of OPFMLs were characterised by tensile and flexural tests in accordance with ASTM D3039 and ASTM D790 respectively. Results showed that tensile and flexural performances of OPFMLs depend on fibre composition in the composite layer. It was found that increase in fibre composition increased the tensile strength but decreased the flexural strength. OPFMLs with 40 wt% showed the highest tensile strength of 65.99MPa whereas OPFMLs with 30 wt% showed the highest flexural strength of 152.45MPa. The optical microscopic images showed damage mechanisms in OPFMLs for different fibre weight composition, which includes delamination and debonding.

Multiscale tribo-mechanical analysis of natural fiber composites for manufacturing applications

Abstract This paper aims to investigate the tribo-mechanical behavior of natural fiber reinforced plastic (NFRP) composites with specific consideration of the multiscale complex structure of natural fibers. Understanding the multiscale tribo-mechanical performances of these eco-friendly materials can lead to a better design of their manufacturing processes. Nanoindentation and nanoscratching experiments are conducted on flax fibers reinforced polypropylene composites using a triboindenter at a specific contact scale generated by the tip indenter radius (100 nm). Results confirm the significant effect of the geometric contact scale on the flax fibers stiffness. Moreover, flax fibers friction shows a multiscale behavior where the mechanisms of nano-friction are vastly different from those of micro-friction, which is related to the physical phenomena arisen at each scale.

Preparation and characterization of graphene oxide and it application as a reinforcement in polypropylene composites

In this article, graphene oxide (GO) is modified using Phosphorous acid via the strong –P = O in the study reported in the paper. And the chemical structure was characterized by Fourier Transform infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction. And polypropylene (PP) composites are prepared by melt compounding method, and functionalized graphene oxide (FGO) is in situ thermally reduced during the processing. The thermal stability, mechanical and flame properties, and morphology for the char layer of composite materials were separately investigated using TG (Thermogravimetric analysis), tensile and charpy impact tests and SEM (scanning electron microscope). The results of SEM and TEM indicate that FGO nanosheets are homogeneously dispersed in polymer matrix with intercalation and exfoliation microstructure. The FGO/PP nanocomposite exhibits higher thermal stability and flame retardant property than those of the GO counterpart and pure PP. During the thermal decomposition, The –P = O introduced to improve the flame effect and the yield of the carbon residue was increase. The heat release rate and the escape of volatile degradation products are reduced in the FGO‐based nanocomposites. POLYM. COMPOS., 40:723–729, 2019. © 2018 Society of Plastics Engineers

Effects of thermal‐oxidative aging on the flammability, thermal degradation kinetics and mechanical properties of DBDPE flame retardant long glass fiber reinforced polypropylene composites

Long glass fiber reinforced polypropylene composites containing 2,2′,3,3′,4,4′,5,5′,6,6′‐decabromobibenzy flame retardants (LGF/DBDPE/PP) are prepared by melt blending method. The flame‐retardant properties of the composites with various thermal‐oxidative exposure time (0–50 days) at 140°C were investigated by the limiting oxygen index (LOI) and UL‐94 vertical burning test. The LOI values vary slightly with increasing the aging time, while the UL‐94 level maintains a constant V‐0 rating. The results demonstrate that the flammability of LGF/DBDPE/PP composites can remain at a relatively stable level in long time thermal‐oxidative aging process, which can be attributed to the excellent efficiency of DBDPE fire retardant and the impacts of thermal‐oxidative aging on the thermal stability of the composites turned out to be small. The thermal degradation kinetics of the unaged and aged LGF/DBDPE/PP composites are investigated by the Flynn‐Wall‐Ozawa and Kissinger methods. The obtained activation energy values can further provide objective evidence for revealing the regularities about the flammability of the LGF/DBDPE/PP composites during the thermal‐oxidative aging process. However, the crystallinity and mechanical properties of LGF/DBDPE/PP composites show a slow downtrend after thermal‐oxidative aging. POLYM. COMPOS., 39:E1733–E1741, 2018. © 2018 Society of Plastics Engineers

GF/PPプレス射出ハイブリッド成形品の機械的特性評価

GF/PPプレス射出ハイブリッド成形品の機械的特性評価

Effect of Fiber Loading on the Dynamic Mechanical Properties of Jute Fiber Reinforced Polypropylene Composites

Jute fiber (woven fabric, 1 × 1 plain weave) reinforced polypropylene matrix composites were prepared by compression molding with various fiber loading such as 30%, 40%, 46%, 50%, 55% by weight. The mechanical properties such as tensile strength (TS), bending strength (BS), tensile modulus (TM), bending modulus (BM) and impact strength (IS) of the composite were assessed and analyzed. The highest value of TS, BS, TM, BM and IS were 68.1 MPa, 94.1 MPa, 2936 MPa, 4831 MPa and 14.5 kJ/m2 respectively with 50% fiber loading by weight. It was found that the mechanical properties of the composites were increased with the increase in jute fiber content up to 50% by weight; however, further increase in fiber loading the value decreased. On the basis of fiber content, 50% fiber reinforced composites had the optimum set of mechanical properties. Initially the water absorption rate was higher and then it became slower and static with time. Chemical ageing test with various chemical media such as H2O2, NaOH, HCl and NaCl were performed up to 168 hours. After first 24 hours the composite samples showed gradual weight gain (%) and then the weight gain was become slow and steady in the chemical solution.

Study on strain-rate-dependent behaviour and constitutive model of long glass fibre reinforced polypropylene composite

Accurate material model under different strain rates (˙ε) is important for numerical simulations in vehicle design and crashworthiness assessment. Therefore, the objectives of this study are to develop the constitutive model of long glass fibre reinforced polypropylene composite (hereinafter referred to as 'LGFRP') which related to strain rate range of 10-3/s-50/s. Tensile and compression tests are conducted at different strain rates. 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. According to the experimental results, a novel constitutive model proposed by the authors is used to represent stress-strain relationship related to strain rate of the LGFRP. The analysis results show that the novel constitutive model agrees well with the experimental results.