Plastic Composites Research Articles

Preparation and properties of bamboo fiber/polylactic acid composite modified with polycarbodiimide

Bamboo fiber (BF) is favored by people for its renewability, low cost, fast growth, low density, high hardness, pollution-free, and easy harvesting. However, when preparing composites by blending and extruding BF and degradable plastic PLA, the significant difference in polarity between the two leads to a significant decrease in mechanical properties, which limits the application of BF in bamboo plastic composites. In order to improve the compatibility between PLA and BF, this study used polymerized carbodiimide (PCD) as a compatibilizer to prepare modified BF/PLA composites and investigate the effect of BF content on the composites. The results showed that the addition of PCD increased the flexural strength, flexural modulus, impact strength, tensile modulus and tensile strength of PCD-BF/PLA compared to BF/PLA composites, with the impact strength increasing the most significantly by 20.91 %. Meanwhile, the tensile strength improved by 15.06 % from 55.1 MPa to 63.4 MPa, and the flexural strength improved by 14.82 % from 80.3 MPa to 92.2 MPa. The experimental investigation of BF content revealed that when the ratio of BF to PLA was 4:6, the impact and flexural strength of the BF composites did not significantly decrease, but the flexural modulus and tensile strength increased, with the flexural modulus increasing the most significantly by 90.53 % compared to PLA, while the cost has been reduced by 13.80 %. The porosity experiment also showed that as the BF content increased, when the ratio of BF to PLA was 4:6, the porosity of the composite material was only 3.98 %, which was not further significantly increased compared to 3.62 %. The prepared high proportion biomass can be used in tableware, and other fields.

Effect of synergistic microalloying on the microstructural optimization of Mo/NiAl alloy with excellent mechanical properties under rapid non-equilibrium solidification

Low room-temperature plasticity and poor high-temperature strength extremely restrain the extensive application of NiAl composites. Herein, our work synergistically optimized the NiAl microstructure via alloying of Mo to relieve imbalance of strength and ductility under rapid non-equilibrium solidification supplemented with the first principle calculation. Remarkably, the addition of Mo significantly refined the microstructure of NiAl–15Mo. Moreover, enhanced by the uniform precipitation Mo phase, the coordinately deformed Mo phase at the grain boundary and the partial Mo solid solution occupied Ni sites, the NiAl–15Mo showed superior strength-ductility. The mechanical properties (σ0.2, σUCS, UT) of NiAl–15Mo composites at room temperature were 944 MPa, 1841 MPa, and 27,068 MPa·%, which were increased by ∼55.3 %, ∼48.7 % and ∼41.0 % compared with the conventional NiAl composites, respectively. In particular, owing to solid-solution Mo atoms restrict the climb of dislocations and the stronger covalent bond orbital hybridization between Ni-3d and Mo-4d, the mechanical properties (σ0.2, σUCS, UT) of NiAl–15Mo at 1000 °C are 212 MPa, 265 MPa and 7922 MPa·%, which has an increase of ∼175.3 %, ∼120.8 % and ∼228.0 %, respectively. This work provides a new perspective to manipulate and coordinate Mo multiple reinforcing ways and achieve the high strength and plasticity of NiAl composites.

Silica nanoparticle-reinforced polyurethane plastic immobilized with strontium aluminate nanofiller: Ultraviolet protection, superhydrophobicity and photoluminescence

A simple strategy was reported toward a possible industrial preparation of smart plastic materials with persistent afterglow, ultraviolet protection, superhydrophobic properties and photochromism. Nanoparticles of rare-earth doped aluminate (NREA) were embedded into a polyurethane plastic composite. A combination of polyurethane (bulk material), silica nanoparticles (nanofiller), and NREA (luminous agent) was prepared. Achieving a uniform distribution of NREA in a polyurethane fluid allows for the manufactured plastic to be colorless. NREA showed diameters between 12 nm and 26 nm. When excited at 365 nm, the produced photoluminescent polyurethane composite demonstrated an emission band at 519 nm. NREA contents more than 1 % were found to exhibit persistent photoluminescence, whereas pigment concentrations less than 1 % were found to exhibit fluorescence emission. The created plastic concrete exhibited photochromism, as shown by the coloration parameters and photoluminescence spectra, which proved a change in color between transparent during daylight, green under ultraviolet rays, and greenish-yellow in darkness. The static contact angle tests demonstrated effective superhydrophobic properties. Significant improvements were detected ultraviolet protection and photostability. The hardness properties, structural compositions, and morphology of the developed polyurethane plastics were also explored.

Modelling of size-dependent plasticity in polymer-based composites based on nano- and macroscale experimental results

A number of experimental evidences indicate that the local response of polymer matrices near fibres is inadequately represented by classical continuum models relying on the bulk polymer behaviour. This results from size-dependency associated to large plastic strain gradients, complex interphase behaviour and/or changes of polymer structure. Classical multiscale models require artificial tuning of the properties to provide realistic macroscale predictions. We demonstrate that an unprecedented modelling approach based on a micromorphic theory is able to capture such size effects in long-fibre composites. The model is identified via nano digital image correlation strain fields and validated by predicting the strengthening found in transverse compression of UD composites, not captured by classical models. Micro-shear bands are properly regularised by the model, thus correctly handling the size-dependent plasticity and softening effects. The improved prediction of the strain localisation pattern in the matrix opens avenues to more accurately model interfacial failure and damage processes.

Numerical simulation of mechanical properties of composite high-pressure vessel for space application

Abstract A composite high-pressure vessel reinforced with T1000 carbon fiber and featuring an ultra-thin titanium lining for space applications is examined. Using the laminated plate theory for composite materials and the elastic-plastic theory for isotropic materials, a three-dimensional finite element model is developed. The pressure test results confirm the correctness of the finite element model. Under various internal pressure circumstances, the displacement and strain distribution of the metal liner and the laminated composite are compared and analyzed. It is shown that the composite vessel primarily deforms along the axial direction when the internal pressure is greater than the working pressure of the vessel. Only elastic deformation is present in the composite layer, but both plastic and elastic deformation are present in the ultra-thin titanium liner.

Study on flexural property of glass fiber-reinforced polymer reinforced wood–plastic composite panels

ABSTRACT Fiber-reinforced polymers (FRPs) and wood–plastic composites (WPCs) have broad application prospects with the advantages of recyclability, lightweight, and corrosion resistance. However, WPCs cannot be used for bearing structures because of their poor mechanical properties. In order to improve the mechanical properties of WPCs, this study proposed a glass fiber-reinforced polymer (GFRP) to reinforce the tensile zone of WPCs. The failure mode, ultimate bearing capacity, and deformation of the panels were studied by four-point bending tests and finite-element simulations. The results showed that the failure modes of the panels were a mainly flexural failure, flexural shear failure, and interface debonding, and the optimal thickness of GFRP improved the ultimate bearing capacity of the WPC panel by 205% and the deflection by 55%. Finite-element simulations of WPC reinforced with GFRP were carried out, and the densities of WPC and the angles of glass fiber layup were considered. The results showed that the higher the density of WPC, the better the strengthening effect of the structure, and the fiber layup angles had less effect.

Evaluation of Cutting Parameters on Heat-Affected Zone in Wood Plastic Composites by Pulsed Fiber Laser

Biodegradable and environmentally friendly composite materials such as wood plastic composites (WPCs) have gained attention in industrial applications due to environmental concerns and global sustainability goals. However, owing to their unique structures and properties, cutting on WPCs can be challenging. Continuous wave (CW) mode laser may result in heat build-up and easily warp the WPCs during laser cutting. Therefore, minimizing these defects and determining the cutting parameters that influence the heat-affected zone (HAZ) by pulsed mode laser is essential. In this present work, 1 mm thickness of WPC 30 wt.% of wood fiber (WF) filled with recycled high-density polyethylene (rHDPE) has been experimentally cut by single-mode pulsed fiber laser to evaluate the minimum laser energy required to cut the WPC and the influence of cutting parameters on the HAZ. The HAZ was measured using a digital microscope, and the statistical significance of the cutting parameters to HAZ was determined by analysis of variance (ANOVA). The results confirmed that a minimum linear energy of more than 9 J/mm is required to cut the WPC. It has been found that the cutting speed is the major influence on the HAZ, followed by pulse width. Adequate interaction time by cutting speed and duration of the single-laser pulse also significantly affects the cutting process. The higher gas pressure could minimize the HAZ at the surrounding cutting region of the WPCs. Understanding the influence of these parameters could minimize the thermal effect of HAZ and improve the laser cut quality.

Combustion characteristics of refuse-derived fuel pellets having varying plastic compositions.

The plastic fraction of refuse-derived fuel (RDF) pellets influences fuel's physico-chemical, and mechanical properties, which in turn might affect the combustion behavior of RDF. In the present study, the combustion behavior of different plastic fraction-simulated RDF pellets is reported. The simulated pellets were prepared based on the Indian commercial RDF composition. Initially, the plastic content varied from the existing fraction in Indian commercial RDF, i.e., 35% (RDF-1), to a lower plastic content of 5% (RDF-2). Physico-chemical characterization showed that a higher plastic fraction in RDF-1 reduces its pellet density by 25% as compared to RDF-2. The changes in RDF physico-chemical properties due to plastic variation are reflected in the RDF conversion process. Single-particle and packed-bed studies concluded that the lower density for higher plastic RDF-1 leads to lower conversion times (36%), and higher flame front speed (11%), which are desirable conditions for faster conversion. However, packed-bed studies also showed limitations regarding the utilization of high plastic RDF as RDF-1 has a narrow range of operating air mass flux due to the early advent of convective cooling of the bed. Finally, considering the constraints associated with the utilization of high plastic fraction (~ 35%) RDF and to maximize the effective utilization of plastic in RDF, a workable plastic fraction of 15% in RDF was proposed and tested for its combustion properties. RDF with 15% plastic showed faster conversion, higher flame front speed, and a wider range of operating air mass flux before the advent of convective cooling of the bed.

Thermal-oxidative stability of PVC compositions modified with a bromine-containing plasticizer-flame retardant

The possibility of creating polymer compositions based on polyvinyl chloride plasticized with a bromine-containing flameretarding plasticizer has been investigated. Their thermostability at introduction of plasticizer with different bromine content was evaluated. The optimal concentrations of bromine in the flame-retarding plasticizer to increase the thermal stability of the polymer composition have been established. It is noted that increasing the concentration of bromine in the flame-retarding plasticizer increases the rate of elimination of hydrogen bromide and slows down the thermal destruction of the polymer matrix. It is shown that during thermo-oxidative degradation of plasticized PVC composite, hydrogen bromide is first eliminated from flame-retarding plasticizer, which accelerates the process of polyene formation and additional cross-linking of polymer macromolecules. An increase in the tensile strength of plasticized compositions at the introduction of optimal dosages of flame-retarding plasticizer was observed.

Chip morphology’s effect on properties of PLA-based bamboo–plastic composites produced using hot-pressing

This study explored the effect of raw material morphology on the properties of bamboo–plastic composites produced using hot-pressing. To provide a reference for reducing the production cost and improve the product properties of the composites, polylactic acid (PLA)-based bamboo–plastic composites were prepared using bamboo chips with a shaved morphology (BS) and fiber morphology (BF) and PLA as the matrix material, via hot-pressing. The properties of the bamboo–plastic composites formed with BS and BF chips were studied and compared with those of composites with conventional granular morphology (BM) and powder morphology (BP). The results showed that when the content of the bamboo chips was at 50% (the same below), the mechanical properties of the BF/PLA composites were remarkably better than those of the other PLA-based composites. However, the BF/PLA composites showed a high degree of hydrophilicity, with a water contact angle of 70.0° and a water absorption of 10.8% at 288 h. More holes could be seen in the BF/PLA composites using a scanning electron microscope. Among the four types of PLA-based composites, better melt fluidity was found only in the BF/PLA composites, and the melting index was 65.3 g/min.

Effect of temperature on the uniaxial tensile properties of wood plastic composites: Experimental investigation and numerical analysis

Seven groups of uniaxial tensile experiments on wood plastic composites with a High Density Polyethylene (HDPE) matrix at different temperatures were completed in this paper. The test temperatures ranged from -60 °C to 60 °C, with a temperature difference of 20 °C for each group. All samples exhibited tensile brittle fracture. The test results showed that the tensile strength of the specimens decreased continuously with increasing temperature. Taking 0 °C as the reference temperature, the ultimate strength of the sample at -60 °C was 1.63 times that at 0 °C. When the temperature was 60 °C, this value was 0.41. Then, it can be calculated that the ratio of the strength of the sample at -60 °C to that at 60 °C was approximately 3.93, and the corresponding ratio of the elastic modulus was approximately 4.52. This shows that the mechanical properties of WPC are sensitive to changes in temperature. The variation coefficient of the average strength and elastic modulus of WPC for different specimens at different temperatures was less than 0.17, showing good stability due to the small dispersion of mechanical properties among different samples at any specific temperature.

Estimation of the earlywood and latewood ratio with different particle size of dry and wet milled Japanese cedar wood flour by using hyperspectral imaging

Mechanical properties of wood–plastic composites are influenced by a particle size and surface morphology of wood flour. Generally various sizes of wood flour are produced from single solid wood even if the single process is used. If the different particle size of wood flour is produced from different wood tissue such as earlywood (EW) and latewood (LW), not only particle size but also density and chemical composition of wood flour might influence the mechanical property of final products. This study aims to investigate the relationship between particle size and their origin; EW and LW. EW and LW were separately milled to produce the EW and LW flour by dry and wet milling. Hyperspectral images ranging 400–1000 nm for each wood flour were used as training data. Discriminant model of EW and LW flour developed by PLS-DA showed over 0.77 of accuracy. Then the EW and LW were dry and wet milled together and screened by three different sieve openings to obtain different particle size wood flour. Discriminant model was applied for the hyperspectral images of each size of wood flour to estimate the EW and LW ratio. The result showed that increasing sieve opening resulted in the increasing ratio of LW for dry milled wood flours. The results suggest that the EW was easily pulverized than LW.

Valorization of Cork and High-Density Polyethylene and Polypropylene Wastes in Cork–Plastic Composites: Their Morphology, Mechanical Performance, and Fire Properties

Valorization of Cork and High-Density Polyethylene and Polypropylene Wastes in Cork–Plastic Composites: Their Morphology, Mechanical Performance, and Fire Properties

Programmable Retention Characteristics in MoS2-Based Atomristors for Neuromorphic and Reservoir Computing Systems.

In this study, we investigate the coexistence of short- and long-term memory effects owing to the programmable retention characteristics of a two-dimensional Au/MoS2/Au atomristor device and determine the impact of these effects on synaptic properties. This device is constructed using bilayer MoS2 in a crossbar structure. The presence of both short- and long-term memory characteristics is proposed by using a filament model within the bilayer transition-metal dichalcogenide. Short- and long-term properties are validated based on programmable multilevel retention tests. Moreover, we confirm various synaptic characteristics of the device, demonstrating its potential use as a synaptic device in a neuromorphic system. Excitatory postsynaptic current, paired-pulse facilitation, spike-rate-dependent plasticity, and spike-number-dependent plasticity synaptic applications are implemented by operating the device at a low-conductance level. Furthermore, long-term potentiation and depression exhibit symmetrical properties at high-conductance levels. Synaptic learning and forgetting characteristics are emulated using programmable retention properties and composite synaptic plasticity. The learning process of artificial neural networks is used to achieve high pattern recognition accuracy, thereby demonstrating the suitability of the use of the device in a neuromorphic system. Finally, the device is used as a physical reservoir with time-dependent inputs to realize reservoir computing by using short-term memory properties. Our study reveals that the proposed device can be applied in artificial intelligence-based computing applications by utilizing its programmable retention properties.

Strength-Plasticity Relationship and Intragranular Nanophase Distribution of Hybrid (GNS + SiCnp)/Al Composites Based on Heat Treatment.

The distribution of reinforcements and interfacial bonding state with the metal matrix are crucial factors in achieving excellent comprehensive mechanical properties for aluminum (Al) matrix composites. Normally, after heat treatment, graphene nanosheets (GNSs)/Al composites experience a significant loss of strength. Here, better performance of GNS/Al was explored with a hybrid strategy by introducing 0.9 vol.% silicon carbide nanoparticles (SiCnp) into the composite. Pre-ball milling of Al powders and 0.9 vol.% SiCnp gained Al flakes that provided a large dispersion area for 3.0 vol.% GNS during the shift speed ball milling process, leading to uniformly dispersed GNS for both as-sintered and as-extruded (0.9 vol.% SiCnp + 3.0 vol.% GNS)/Al. High-temperature heat treatment at 600 °C for 60 min was performed on the as-extruded composite, giving rise to intragranular distribution of SiCnp due to recrystallization and grain growth of the Al matrix. Meanwhile, nanoscale Al4C3, which can act as an additional reinforcing nanoparticle, was generated because of an appropriate interfacial reaction between GNS and Al. The intragranular distribution of both nanoparticles improves the Al matrix continuity of composites and plays a key role in ensuring the plasticity of composites. As a result, the work hardening ability of the heat-treated hybrid (0.9 vol.% SiCnp + 3.0 vol.% GNS)/Al composite was well improved, and the tensile elongation increased by 42.7% with little loss of the strength. The present work provides a new strategy in achieving coordination on strength-plasticity of Al matrix composites.

Behavior of rock bolt plates made of engineering fiber composites: Experimental investigations, 3D surface characterization and numerical models

Bearing plates made from plastic composites can be used as an alternative to their steel counterparts in rock bolt or soil nail applications. To achieve this goal, an existing recycled high-density polyethylene bearing plate was investigated and later modified to improve its engineering properties. Laboratory studies were conducted to determine the failure load of the existing and modified plates, and a numerical model was developed for complementary analysis. The results of both efforts clearly showed that the existing bearing plate was not adequate in terms of strength and creep properties, as it quickly yielded with large displacements at relatively low loads. In order to enhance the strength of the plate, both geometric and material modifications are made by our research group to obtain a more efficient plate. Numerical models were used to determine the frame layout, and a series of analyses were performed to evaluate the effects of frame thickness, number and arrangement. Once the design was optimized and finalized, a mold was created to match the new geometry for manufacturing new plates through injection molding. A test setup was also established in the laboratory and numerous compression tests were performed on the manufactured new plates. The measured load-displacement behavior of plates made of polyethylene and polyamide with a variety of additives were discussed separately. It was determined that the new plastic plates reinforced with polyamide through various additives have the potential to reach a strength up to 200–240 kN, which is at least two times higher than the existing one, with distinct economic advantages.

Influence of Fibre Orientation on the Slotting Quality of CFRP Composites Using the Multi-Tooth Mill.

Carbon fibre-reinforced plastic (CFRP) composites, prized for their exceptional properties, often encounter surface quality issues during slotting due to their inherent heterogeneity. This paper tackles CFRP slotting challenges by employing multi-tooth mills in experiments with various fibre orientations and tool feed rates. In-plane scratching tests are performed under linearly varying loads; then, slotting experiments are conducted at different parameters. The scratching test results indicate that the fibre orientation and cutting angles have significant influences on forces and fracture process. The slotting experiments demonstrate that cutting forces and surface roughness Sa of the bottom slotting surface are notably affected by the fibre orientation, with disparities between up-milling and down-milling sides. Reorganising Sa data by local fibre cutting angle θ highlights consistent Sa variations between up-milling and down-milling sides for 0° ≤ θ ≤ 90°, with lower Sa on the up-milling side. However, for 90° < θ ≤ 150°, Sa variations diverge, with lower Sa on the down-milling side. Unexpectedly, Sa on the down-milling side decreases with increasing θ in this range. Additionally, the tool feed rate exerts a more pronounced influence on Sa on the up-milling side.

Short term creep properties of WPC at different temperatures—An experimental and numerical investigation at different stress levels

AbstractUsing a two‐step molding process, wood plastic composite (WPC) were prepared under temperatures ranging from 160 to 180°C. Uniaxial compression tests of WPC were conducted at temperatures of −20°C, 0°C, 20°C, and 40°C, determining stress levels of 30%, 45%, and 60% based on the test results. Subsequently, 24‐hour compression creep tests were performed for WPC under 12 different conditions. The Findley power law model was employed to fit the experimental results, indicating that creep deformation increased with both stress level and environmental temperature. Notably, specimens at 0°C failed after sustaining a load for 13.6 hours at 60% stress, while those at 20°C failed after only 0.72 hours under the same conditions. Overall, the Findley model effectively predicted the creep behavior of WPC under all temperature conditions and stress levels.Highlights The influence of temperature variation on the strength of WPC. Short term creep of WPC under different stress levels. Creep of WPC at different temperatures. Prediction of creep performance under different operating conditions.

Enhancing Building Energy Efficiency: Leaf Transpiration Inspired Construction of Lignin-Based Wood Plastic Composites for Building Energy Conservation

Incorporating phase change materials (PCMs) into buildings represents a strategic method for reducing reliance on air conditioning systems and decreasing energy usage consequently. Inspired by leaf veins providing channels for transpiration, lignin porous carbon (LPC) was synthesized by chemical activation, showing a vein pore structure. The capillary network system of the LPC provided more channel to adsorb PCM through surface tension and capillary force, achieving an impressive loading capacity of LPC for polyethylene glycol (PEG) (75%), which demonstrated exceptional heat storage capability (133.21 J/g). The lignin-derived wood-plastic composite (L-WPC) was further prepared. With the gradual increase of LPC/PEG, the latent heat of L-WPC increased gradually. The ΔHm, ΔHc and energy storage efficiency of L-WPC-50 (incorporated 50 wt% LPC/PEG-75) reached 39.99 J/g, 42.65 J/g and 90.26%, respectively. The vein pore structure of LPC also provided a thermal conductivity link for L-WPC. L-WPC-50 demonstrated an increased thermal conductivity (0.66 W/(m·K)) and a reduced thermal diffusion coefficient (0.24 mm2/s), optimizing the effectiveness of the phase transition. Additionally, L-WPC-50 displayed satisfactory mechanical properties and dimensional stability, with tensile strength, bending modulus and water absorption thickness swelling rate measuring 14.40 MPa, 1043.72 MPa, and 1.61% respectively. It introduced a feasible approach for utilizing biomass in enhancing building energy efficiency, marking a significant stride towards reducing building energy consumption and advocating sustainable energy practices.

Effects of structural parameters on radial crashworthiness of 3D braided hybrid tubes with Janus structure

Hybrid fiber reinforced plastic (HFRP) composites have been widely used in various fields, but delamination is a fatal damage mode in laminated hybrid tubes. In the current paper, carbon fibers/Kevlar fibers hybrid tubes with Janus structure were fabricated by three-dimensional (3D) tubular braiding technique. The radial crushing performances of 3D braided Janus hybrid tubes were analyzed while hybrid layer ratio and yarn type were both considered. With the increase of hybrid layer ratio from 1:3 to 2:2 to 3:1, the specific energy absorption (SEA) increased 149 % and 21.39 % for specimens with carbon fibers placed on the skin region, and that decreased 12.46 % and 10.66 % for samples with Kevlar fibers arranged on the skin region. Furthermore, samples with Kevlar fibers arranged on the skin region presented excellent radial crashworthiness. The current work could be helpful for the design, fabrication and application of HFRP tubes.