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The anisotropic material behavior of continuous-fiber-reinforced composites that is evident in their mechanical properties should also be considered in their processing. An important step in the processing of thermoplastic unidirectional (UD) fiber-reinforced tapes is consolidation, where a layup consisting of locally welded UD tape layers is firmly bonded. Compression of the molten thermoplastic matrix material during consolidation leads to a squeeze flow, the direction of which is determined by the fibers. This work presents a model that describes the influence of fiber direction on compression and flow behavior, implemented in the computational fluid dynamics (CFD) software tool OpenFOAM®. To validate the simulation results, we performed experiments in a laboratory consolidation unit, capturing the squeeze flow with cameras and then quantifying it by gray-scale analysis. The specimens used were UD polycarbonate tapes (44% carbon fibers by volume) of various sizes and with various fiber directions. The simulation allows prediction of the changes in specimen geometry during consolidation and is a first step towards optimizing the process by avoiding extensive squeeze flow. [ABSTRACT FROM AUTHOR]

The present article focused on the residual strains and deformation of the laminates fabricated by rapid hot press process using prepreg. Strain gauges and laser tracker were utilized to measure the residual strains and deformation of the laminates. By studying the effects of curing time and de-molding temperature on residual strains and deformation of composite laminates, the efficient curing conditions were proposed and good processing quality was ensured. The results indicate that the laminates with low curing degree incline to generate high residual stresses during curing and cooling processes. The effects of cure duration and de-molding temperature on the deformation degree and type of laminates are significant. In order to ensure both curing efficiency and low deformation, the curing time of the resin and de-molding temperature should be designed cautiously. The experimental results suggest that the curing duration longer than 12 min is needed, and the de-molding temperature should be no less than 40°C lower than glass transition temperature of the cured matrix. [ABSTRACT FROM AUTHOR]

Among refractory metals, tantalum has long been the primary material of use in high strain rate applications. Hot pressing (HP) is a technique to produce specimens with high density and homogeneous microstructure. The individual effect of the HP or annealing heat treatment on high strain rate properties of tantalum powder compacts has been investigated, but little attention has been paid to the combined effect of subsequent annealing. In this study, the effect of annealing on the microstructure and mechanical properties of tantalum subjected to hardness and Split Pressure Hopkinson Bar (SHPB) test was investigated. After annealing at 1100°C, the grains are coarsened, thereby hardness and upper yield strength decreased to value 199 VHN and 1833 MPa, respectively. Moreover, an obvious increase in plasticity and toughness is detected at this temperature, indicating subsequent annealing is beneficial to improve the deformation properties of HPed powder compacts; the maximum plasticity of tantalum was 31.74% after annealing. [ABSTRACT FROM AUTHOR]

In this study,in situ50 vol.-% TiCx/2014Al composites with different C/Ti molar ratios (0.6, 0.7, 0.8, 0.9 and 1) were successfully produced by the method of combustion synthesis and hot press consolidation. The microstructure and the mechanical properties of the composites were investigated. Microstructure characterisation of the TiCx/2014Al composites showed relatively uniform distribution of the TiCxparticles with the particle size in the range of 200–900 nm. With the increase of the C/Ti molar ratio, the yield strength (σ0.2) and the ultimate compression strength (σUCS) increased first then decreased, and the fracture strain (εf) increased. Theσ0.2,σUCSand the abrasive wear resistance of the 50 vol.-% TiCx/2014Al composites reached the highest value when the value of the C/Ti molar ratio comes to 0.8. Theσ0.2,σUCSandεfof the 50 vol.-% TiCx/2014Al composites with the C/Ti molar ratio of 0.8 are 1094 MPa, 1454 and 6.13%, respectively. [ABSTRACT FROM PUBLISHER]

The dual phase nanosized (TiB2-Ti5Si3)/TiAl composites were successfully fabricated using in situ method of combustion synthesis and hot press consolidation. The effects of proportions of the in situ dual phase nanoparticles (TiB2 and Ti5Si3) on microstructures and compression properties of the composites were investigated. Compared with the monophase TiB2 and Ti5Si3 particles, dual phase TiB2-Ti5Si3 particles exhibit more obvious grain refinement effect. The grain size of TiAl alloy was refined from ∼66 to ∼12 μm with the the generation of dual phase TiB2-Ti5Si3 particles. Moreover, the TiAl matrix composites reinforced with dual phase nanosized TiB2-Ti5Si3 particles exhibit better comprehensive compression properties. When TiB2:Ti5Si3 = 2:1[Σ(TiB2 + Ti5Si3) = 4 vol.-%], the TiAl matrix composite has a high true fraction strain of 26.1%, a true yield strength of 761 MPa and an ultimate compression strength of 1647 MPa. [ABSTRACT FROM AUTHOR]

Thermally conductive and electrically insulating polyamide 6 (PA6) matrix quaternary composites were prepared by hot press molding and injection molding, respectively. The quaternary composites were composed of zero-dimensional aluminum oxide particle, one-dimensional silicon carbide whisker, two-dimensional flake graphite, and PA6 resin matrix. Morphology, structure, density, thermal conductivity, volume electrical resistivity, and tensile strength of two types of composites were characterized by scanning electron microscopy, X-ray diffractometer, thermal conductivity tester, high resistance micro-current tester, and tensile tester. The results showed that crystallinity, thermal conductivity, density, and tensile strength of hot press molding samples were superior to those of samples made by injection molding method. This is due to that hot press molding method can provide higher molding pressure and longer annealing time than injection molding. The mechanism could be explained that the performances of the composites were promoted by increasing molding pressure and annealing time. [ABSTRACT FROM AUTHOR]

Nowadays, composite sandwich tubes are extensively utilized in the civil and aerospace industries due to their superior strength-to-weight mechanical properties. Origami-based core offers a large enhancement of the mechanical properties, yet little study research focuses on the effect of various foldcore configurations on the transverse mechanical properties of sandwich tubes, necessitating the design method for applications. This study introduces an innovative approach by incorporating origami into the composite sandwich core to enhance the transverse energy absorption capacity. The quasi-static transverse mechanical properties of carbon fibre-reinforced polymer (CFRP) sandwich tubes with foldcores are studied under three-point bending-like local compression and transverse structural compression. A systematic geometric design framework and numerical modelling technique are provided. By integrating finite element analysis and experiments, the research investigates the effects of various origami foldcore configurations and geometric parameters on transverse energy absorption capacity. The experiment setup is provided by sandwich tubular specimens with a full-diamond configuration as the foldcore. The cylindrical tubes (foldcore) of the sandwich structures were manufactured using four plies [0°]4 of T700 (T300) woven CFRP with the hot press moulding (vacuum bag using female and male moulds) technique respectively. Then, the parametric study and damage mode analysis of eight different foldcore patterns (axial Miura, circumferential Miura, diamond, Kresling, and their curved-creased counterparts) were studied. The results showed the superior energy absorption performance of the sandwich tube with Miura-pattern foldcore over the origami-pattern counterparts, nested tube, and traditional honeycomb sandwich tube with CFRP or aluminium-made cores. Therefore, the structural parameters optimisation of the Miura pattern tube was carried out by the Response Surface method (RSM) and a design strategy for increasing the energy absorption capacity was found. The findings offer guidance for designing high-specific energy absorption tubular structures for future advanced engineering applications. [ABSTRACT FROM AUTHOR]

The glass fiber-reinforced polypropylene/AA2024 hybrid composite (short for Al/Gf/PP laminate) was prepared by hot pressing with anodized 2024-T3 aluminum alloy as the skin and thermoplastic glass fiber-reinforced polypropylene core as a substitute of thermosetting glass fiber-reinforced polymer (based on epoxy) in order to increase the productivity and reduce the production costs during manufacturing procedure. The effect of peel ply (release cloth) and cooling rate on the laminate was investigated elaborately in this work. The orientation of glass fiber is mainly influenced by the peel ply structure, resulting in the resin's overflow during hot press. Moreover, different cooling rates due to various cooling methods significantly affected both the degree of crystallization of the matrix and deformation of the metal skin during the curing process. Finally, a new peel ply structure was adopted to prevent the fiber from spilling during hot press process, while bubbles were allowed to flow out normally along with partial resin. Finally, a novel cooling method to reduce the degree of polypropylene crystallization and control metal deformation was proposed. [ABSTRACT FROM AUTHOR]

Promising carbon fiber-reinforced thermoplastic (CF/polyetherketoneketone (PEKK)) composites were fabricated by the state-of-the-art technology known as "Automated Fiber Placement." The mechanical properties of CF/PEKK were evaluated for four different postprocessing methods: in situ consolidation, annealing, vacuum bag only (VBO), and hot press (HP). The evaluation was performed by narrowing down the relevant processing parameters (temperature and layup speed). Furthermore, the void content and crystallinity of CF/PEKK were measured to determine the effect of these postprocessing processes. The HP process resulted in the best quality with the highest interlaminar shear strength, highest crystallinity degree, and lowest void content. The second most effective method was VBO, and annealing also realized an improvement compared with in situ consolidation. The correlation between the postprocessing method and the void content and crystallinity degree was also discussed. [ABSTRACT FROM AUTHOR]

Fully dense WC-Al2O3 platelet composites with VC additive were fabricated by hot-press sintering. Their mechanical properties and microstructure were examined. The contents of Al2O3 platelet (Al2O3pl) and VC were optimised. The fracture toughness of WC-based composites would be obviously improved with Al2O3pl addition. The defined addition of VC was beneficial for the densification and improved mechanical properties of the WC-based composites. The microstructure of the composites was fine, compact and homogeneous compared with the composites without VC addition. The range of fracture toughness of WC-Al2O3pl composites was 9.3–13.5 MPa m1/2. The flexural strength of the composites varied a little and the maximum was 1289 MPa when the content of Al2O3pl was 5 vol.-%, the content of VC was 0.5wt-%. [ABSTRACT FROM AUTHOR]

Here, composite based on quartz fibre-reinforced fluoro-polyimide was fabricated using a hot press process, which was reported having well thermal and dielectric properties. The polyimide exhibited extremely high glass transition temperature (Tg) up to 471°C, and 5% weight loss temperature (T5) about 560°C both in nitrogen and air. Also, optimisation of processing parameters of composite was investigated. Moreover, the quartz fibre/polyimide composite possessed excellent high-temperature mechanical properties due to the high Tg. Importantly, the composite exhibited excellent dielectric performance. Especially, the dielectric constant values had remained basically unchanged of 3.43–3.46 at 400°C in the frequency range of 7–18 GHz, indicative of a remarkable wave-transmitting property. Besides, the transmission efficiency of the composite was up to 83% in the frequency range of 7 –18 GHz. This study can serve as a basis for rapid evaluation of the high heat resistance and waving-transmitting property polyimide composite in various application environments. [ABSTRACT FROM AUTHOR]

Based on the problem of shape-preserving property of complex geometry shape preform, a kind of new fabric with thermal bonding layers was designed in our work. From the apparent view, it can be seen that the carbon cloth was attached with a layer of thermal bonding layer structure. The two adjacent carbon fabrics can be bonded together by the thermal bonding layers through hot press actions. Because of the particular characteristics, this type of fabrics can help to achieve the overall integrity of complex geometry shape preform. This kind of particular fabric with thermal bonding layers was prepared by 3D weaving process using carbon fiber and thermoplastic nylon fiber. To evaluate the effect of thermal bonding layers on shape-preserving property of fabric, the fabrics were prepared with five different contents of thermoplastic nylon fiber. And the pure carbon cloth without thermoplastic nylon fiber was also prepared as control group. The shape-preserving property of fabric was evaluated by single-wing springback test and fabric peeling test in the 0° and 90° direction. The experimental results show that the effect on shape-preserving property of fabric enhanced with the increase of contents of thermoplastic nylon fiber, and the shape-preserving property of fabric was more significant in 0° direction compared with 90° direction. [ABSTRACT FROM AUTHOR]

The effect of Thermo-Hydro-Mechanical densification on selected properties of western hemlock was investigated. The drive was to explore the possibility of using hemlock as a replacement for expensive hardwoods for flooring applications. Kiln-dried boards at about 12% moisture content were subjected to densification in a hot press. As a special treatment, half of the samples were surface-sprayed with water before densification and three pressing times (5, 10, and 15 min), as well as temperature levels (120°C, 160°C, and 200°C) were used. Sample density, hardness, colour change, and abrasion resistance were evaluated after densification. Data analysis revealed that the temperature level, densification time, and type of pre-treatment were statistically significant factors. Compared to controls, densification significantly improved density, hardness, and abrasion resistance by 197%, 386%, and 437%, respectively. As a possible desired aesthetic feature, this process darkened hemlock by about 200%. [ABSTRACT FROM AUTHOR]

In this work, the effects of the coating composition and the welding parameters on the heat generation and nugget formation during resistance spot welding of the hot press forming steels have been evaluated. Two types of coated steels were used, termed as Al-Si and Zn coating. Al-Si coated steel showed rapid nugget growth toward the electrode direction, which is the probable reason of the higher heat conduction from the electrode-sheet surface toward the bulk material. In Zn coated steel, heat was generated and localised at the faying interface and uniformly propagated to the steel substrate. High speed camera images showed that the presence of oxide at faying interface provides inhomogeneous current flow and violent heat generation in the Zn coated steel. [ABSTRACT FROM AUTHOR]

The objective of the present work was to determine the suitability of a new iron-based Mn–Cu–Sn matrix alloy for the manufacture of diamond-impregnated tool components. A number of specimens were consolidated by the hot press route from ball-milled powders. Density, microstructural features, phase composition, bending properties and hardness were evaluated. The results revealed excellent mechanical properties, includingσ0.2 > 850 MPa in 3-point bending and HK0.5 > 300. A commercial Co-WC reference matrix alloy was also produced for comparison purposes. Diamond-impregnated specimens with different matrices were tested for wear rate on abrasive sandstone using a test rig specially designed to simulate tool application conditions. The tests that involved 3- and 2-body abrasion ranked the alloys in different orders. Statistical analysis showed that the wear rate of diamond-impregnated composites was mainly affected by diamond concentration, but statistically significant contribution of the matrix resistance to 3-body abrasion was also found. [ABSTRACT FROM PUBLISHER]

Effects of TiB2/TiCx ratios on compression properties and abrasive wear resistance of 50 vol.-% (TiB2–TiCx)/Al–Cu composites fabricated via the combustion synthesis (CS) method assisted with hot press from the Al–Ti–B4C system were studied. With decrease in the TiB2/TiCx ratio from 3:1 to 1:3, the shape of TiB2 changed from platelike to clubbed while the size of TiCx particles increased, which directly led to different mechanical properties. The 50 vol.-% (TiB2–TiCx)/Al–Cu composite with the TiB2/TiCx ratio of 2:1 exhibited good compression strength without sacrificing the fracture strain, while the composite possessed the highest abrasive wear resistance when the TiB2/TiCx ratio was 3:1. The appropriate TiB2/TiCx ratio was recommended to be 2:1 in this research. [ABSTRACT FROM AUTHOR]

Sisal fibers (SFs) were pretreated by heat treatment (HT). The SFs were mixed with a biodegradable material, polylactide (PLA), and the composites were prepared by hot press molding. The effects of the HT temperature and time on the mechanical properties of the composites were investigated, and the HT mechanism was studied by scanning electron microscopy and infrared, x-ray photoelectron, and nuclear magnetic resonance spectroscopies. The results show that an appropriate HT can remove strongly hydrophilic materials such as hemicelluloses from the fibers, and thus decrease their hydrophilicity, thereby improving the retting between the fibers and the matrix. This improves fiber–matrix interfacial adhesion, which can improve the mechanical properties of the composites. The HT also influences the fiber strength to some extent and affects the mechanical properties of composites. [ABSTRACT FROM PUBLISHER]

This work fabricated CoMoNiTa3 medium-entropy alloys using the vacuum hot pressing process of powder metallurgy technology. Micron-grade cobalt (6.3 μm), molybdenum (13.2 μm), nickel (2.4 μm) and tantalum powders (25.0 μm) were combined using ball milling. The experiments utilised various hot pressing temperatures (1000, 1050, 1100, and 1150 °C) and hot pressing pressures (20, 35, and 50 MPa) to identify the optimal parameters for CoMoNiTa3 alloys, while simultaneously investigating the differences in microstructures. The experimental results reveal that the optimal hot pressing parameters of this alloy were 1100 °C at 50 MPa for 1 h. The sintering density was enhanced to 9.65 ± 0.01 g cm−3, while the hardness, transverse rupture strength, and flexural modulus reached 85.5 ± 0.1 HRA, 1370.3 ± 90.1 MPa and 168.6 ± 12.7 GPa, respectively. Moreover, the electrical conductivity was 6.53 ± 0.13 × 104 S cm−1. Furthermore, the electron probe microanalyser, electron backscatter diffraction, and transmission electron microscopy results confirmed the face-centred cubic solid solution, Ni3Ta, and μ phases of the CoMoNiTa3 structure, and no preferred grain orientation was found. [ABSTRACT FROM AUTHOR]

An analytical densification model describing the final stages of hot pressing and sintering has been developed and found to be consistent with empirical findings. The behaviour of composite powders for the matrices of diamond tools has been studied under hot pressing conditions. Differential scanning calorimetry was used to determine the heat capacity at constant pressure Cp of pure Co, 663Cu, and composite iron- and cobalt based powders (also containing WC, Ni and 663Cu). The relationship between Cp and composite densification has been analysed, and it has been found that optimised rare earth additions to the iron based composite powders can produce Cp characteristics close or equivalent to that of pure Co powders. This modified composite powder has been used to hot press diamond drill and saw bits that show good properties. Employing a densification regime guided by the dynamic model has been found radically to improve stability in service (bend strength, hardness, impact, ductility and porosity). [ABSTRACT FROM AUTHOR]

This article presents a research into the development of novel Hybrid Laminates (HLs) prepared with the use of hot-pressing method. Two types of HLs are fabricated through the composite coating with different fiber amounts (40 and 50% wt.) of only one surface of 7075-O Al alloy substrate. Effects of the fiber contents of the thermoplastic composite in the hybrid structures are investigated with regards to the tensile and flexural properties. The influence of bending load applied from different surfaces on flexural responses is also evaluated. The tensile test results indicate that the increased fiber ratio slightly affects the failure load of composite layer in the HLs. On the other hand, the flexural strength decreases with the increasing fiber amount in the HLs whether the three-point bending is performed on the Al surface or the composite layer. Scanning electron microscopy (SEM) is used to study the fracture surfaces after the mechanical characterization. From the SEM observations, it has been realized that fiber/matrix debonding is the key failure mechanism during the tensile tests. The failure mode of both HLs is delamination in the PP composite at the tensile side when the bending applied from the Al layer. [ABSTRACT FROM AUTHOR]

The mechanical properties of open-hole tensile (OHT) specimens made of 3D-printed continuous carbon-fiber-reinforced thermoplastics (CFRTPs) were investigated. The stacking sequence of the OHT specimens were [0/90]2s, and the as-printed specimens possessed higher porosity (15.19%) than conventional fiber reinforced composites. The OHT tests demonstrated that the tensile modulus and fracture strength of the as-printed specimens exhibited 36.7 ± 0.3 GPa and 226.0 ± 9.0 MPa, respectively. To evaluate the effects of voids on the OHT properties, the 3D-printed CFRTPs were hot-pressed, where fiber orientation and porosity (3.41 ± 0.10%) were improved. Additionally, the tensile modulus was increased to 45.1 ± 0.8 GPa, which is 23% higher than the as-printed specimens, even though the fracture strength were comparable or lower than that of as-printed specimens. To validate such OHT properties, a numerical multiscale model was introduced, with a microscale periodic unit cell (PUC) analysis for determining the effective tensile moduli and mesoscale extended finite element method (XFEM) analysis for OHT properties. In the PUC analysis, we considered a two-scale numerical model including a fiber-resin scale with fiber orientation for effective tensile moduli of a CFRTP filament, and filament-void scale for those of a CFRTP laminate. The porosity and fiber orientation were measured by X-ray computed tomography and digital microscopy observations, and the porosity for the 0° specimen were 14.86%. By substituting the effective tensile moduli of the filament-void scale and those of the fiber-resin scale into the XFEM, respectively, the stress-strain responses of the computational OHT models were found to be in good agreement with those of the experimental results of as-printed and hot-pressed CFRTP, respectively. Both the OHT models showed that the Weibull criterion was satisfied without significant delamination at the failure strain, corresponding to the brittle failure mode due to fiber breakage, which agreed reasonably well with the experimental observations. [ABSTRACT FROM AUTHOR]

The experimental study of single point incremental forming (SPIF) of a thermoplastic matrix composite (TMC) was presented in this research. The TMC's matrix was built of polyamide (PA) 6.6, and the reinforcement was 30 wt percent short glass fiber (GF). The TMC was manufactured by hot pressing PA/30 wt percent GF granules to a thickness of 1.5 mm. The impact of SPIF process variables such as forming temperature (60°C–120°C), spindle speed (500 rpm–3000 rpm), wall angle (30°–60°), and step size (0.5 mm–1.5 mm) on forming depth and shrinkage owing to cooling were investigated. The findings revealed that the wall angle is the most effective parameter on TMC forming depth and shrinkage. Furthermore, TMC showed a significant percentage of shrinkage when it is cooled (up to 83.6% of shrinkage). [ABSTRACT FROM AUTHOR]

The use and disposal of traditional fiber-reinforced polymer composites is an important environmental challenge as one of the factors contributing to worsening climate change. The primary objective of this research is to synthesize thermoplastic starch (TPS) from edible banana skins which can potentially be used as a matrix to produce bio-composite films. For the synthesis of TPS, the preparation of banana peels was performed followed by plasticization to obtain the banana peels TPS. For bio-composite film fabrication, the TPS was mixed with short false banana fibers (FBF) (10-30% by weight of the film) with an electronic blender to form a uniform dispersion of the fibers in the TPS. The FBF/TPS blend was applied uniformly on the surface of the rectangular metal mold. The autoclave method has been adopted for curing and molding the bio-composite film. Then, it was hot pressed varying the temperature and pressure from 131-141 OC to 3-6 MPa, respectively, to obtain the final cured film. The specimen was then solidified or hardened at ambient temperature. Finally, optimization of process parameters, fiber content, and their interaction effects on the tear strength, tensile strength, and bending modulus of the bio composite films were conducted using response surface methodology. The results indicate that both the effects of one factor and the interaction of factors have a significant effect on the mechanical properties of composite films. The optimum processing parameters for TPS production are a temperature of 50 OC and a drying time of 24 h. The optimal result indicates that, at 30% fiber loading, the optimum processing temperature and pressure are 135.14°C and 4.33 MPa, respectively, resulting in a composite film with good mechanical properties. [ABSTRACT FROM AUTHOR]

In this study, copper powders with dendritic morphology were produced by the electrolysis method, and then silver coating was applied to these powders by an electroless coating method. The bulk samples were fabricated by hot pressing method using different ratios of copper and silver-plated copper powders. The results showed that the electroless silver coating layer provided a strong bond at the particle boundaries of the samples, significantly improving the physical and mechanical properties of the materials. Accordingly, the hardness, tensile strength, electrical and thermal conductivity values of the samples produced from silver-plated dendritic copper particles were determined to be approximately 98 HB, 185 MPa, 102 IACS% and 402 W mK−1, respectively. In addition, the oxidation resistance of the sample produced from completely silver-coated copper powders is 4 times higher than that of pure copper. [ABSTRACT FROM AUTHOR]

Seven groups of different layering angles of Graphene oxide/Carbon fiber (GO-CF) hybrid reinforced shape memory composites are prepared by vacuum infiltration hot pressing system. The layering angles are respectively [0°]4, [±15°]s, [±30°]s, [±45°]s, [±60°]s, [±75°]s, and [90°]4. The shape fixation ratio, shape recovery ratio, and shape recovery driving force of GO-CF hybrid reinforced shape memory composites are investigated. The composite with the layering angle of [0°]4 has the minimum shape fixation ratio of 90.9%, the maximum shape recovery ratio of 97.6%, and the maximum recovery force of 2.83 N. Compared to [0°]4, the composite with the layering angle of [90°]4 has the 9.13% higher shape fixation ratio, but it has 16.1% lower shape recovery ratio and 59.4% lower recovery force. The microstructure of the composites is characterized and the microstructure of seven groups of composites is satisfactory. Therefore, the matrix within each group of composites has a similar effect on the shape memory properties of the composites. With the layering angle increased, the fiber resilience in the axial direction (X-direction) and the accumulated internal stress gradually decrease. With the layering angle increased, the shape fixation ratio and recovery time of GO-CF hybrid reinforced shape memory composites increase, while the shape recovery ratio, recovery force, and recovery rate decrease. [ABSTRACT FROM AUTHOR]

ZrSi2 was fabricated via reactive hot-pressing technique for 45 min at 1250°C and 1350°C, respectively. The hot-pressed sample exhibited Vickers hardness of 10.93 ± 0.32 GPa and indentation fracture toughness of 3.16 ± 0.54 MPa.m1/2. Thermal conductivity (RT-2.99 W (m.K)−1) and diffusivity (RT–18.2 mm2 s−1) of the sample decreased with increasing temperature due to phonon scattering. Oxidation studies were carried out for the hot-pressed samples from 1000°C to 1200°C for 5, 48 and 100 h in air. The oxidation test results showed that ZrSi2 followed selective oxidation with Si diffusing into the oxide layers at high temperatures. At 1200°C, the surface of ZrSi2 oxidised completely to form a high-temperature stable phase, zircon (ZrSiO4). The autoclave test at 250°C and 250 bar shown negligible mass gain (∼0.022 g) which suggests the usage of ZrSi2 for nuclear fuel cladding applications. [ABSTRACT FROM AUTHOR]

This study fabricated Ni–35Mo–15Cr alloys by the vacuum hot pressing technique. The experiments utilised various hot pressing temperatures (1050°C, 1100°C, 1150°C, and 1200°C) and pressures (20, 35, and 50 MPa) to determine the optimal parameters for Ni–35Mo–15Cr alloys. The experimental result showed that the optimal hot pressing parameters of this alloy were 1150°C at 35 MPa for 1 h. Among them, the sintering density reached 8.92 g·cm−3, and the hardness and TRS increased to 77.1 HRA and 1218.2 MPa, respectively; while, the electrical conductivity was 7.08 × 103 S cm−1 and the polarisation resistance was 294.65 Ω·cm2. Furthermore, the TEM observation identified the HCP structures of the Mo2C that precipitated in the Ni–35Mo–15Cr alloys, and the [02 2 ¯ 1] and [01 1 ¯ 2] crystal axis of Mo2C can be found. Overall, the properties of Ni–35Mo–15Cr alloys were effectively improved through the hot pressing process. [ABSTRACT FROM AUTHOR]

Different approaches to take advantage of powder metallurgy in the manufacturing of diamond-impregnated components were studied. Three different powders were used as starting materials; two pre-alloyed powders, based on Fe–Cu and Fe–Cu–Sn systems, and one pre-mixed Fe-based powder. Different manufacturing routes as a strategy to obtain tailored mechanical properties were studied, with the influence of alloying elements such as graphite, iron phosphide and Mn–Ni–B master alloy to reinforce the iron-based powders. Both uncoated and coated commercial synthetic diamonds were introduced in the systems to analyse the surface reactions that depend on both metallic matrix and processing parameters. Hardness values from 88 to 105 HRB were obtained with a wide range of transverse rupture strength values from 1250 to 1640 MPa. An appropriate combination of metallic matrix, alloying elements and processing parameters makes the materials analysed here suitable powders for the manufacturing of diamond-impregnated tools. [ABSTRACT FROM AUTHOR]

In this study, the compositions 4TaC-1HfC and 1TaC-1HfC ceramics were prepared via hot pressing 5 vol.-% La2O3-doped TaC-HfC powder mixtures in temperature range of 1700–2000°C. The effect of sintering temperature on the densification of the two compositions was assessed. Highly dense TaC-HfC ceramics were obtained after hot pressing at sintering temperature of 1750°C or greater, depending on the composition. The elastic properties, electrical conductivity, hardness, fracture toughness and flexural strength of the resulting highly dense ceramics were evaluated. The results show that the elastic properties, hardness and fracture toughness were insensitive to the composition, but the electrical conductivity and room temperature strength. On the other hand, the strength of the two compositions substantially degraded as the temperature increased from room temperature to 1000°C and the degradation depended on the composition. Subsequently, the strength gradually decreased with further increasing temperature up to 1400°C, but this decrease was insensitive to the composition. [ABSTRACT FROM AUTHOR]

In situ TiB2 and TiC reinforced copper matrix composites with tailored heterogeneous structure were fabricated via high-energy ball milling of Cu, TiH2 and B4C powders followed by hot pressing. The microstructures of both ball-milled powders and hot-pressed composites were compared. Although the dislocation density of Cu matrix was changed after hot pressing, the mode of distribution of ceramic phases in the Cu matrix was noted to transmit from the ball-milled powders to hot-pressed composites in case of the TiH2 particles synthesised by the in situ reactions. The structural inheritance between the ball-milled powders and hot-pressed composites could be used to control microstructural features and thus to tune properties. The hot-pressed TiB2–TiC/Cu composites with tailored heterogeneous structure exhibited better performance than those of homogeneous counterparts. [ABSTRACT FROM AUTHOR]

Owing to the strong covalent B-N bonding and layered structure, complete sintering of h-BN ceramics is quite difficult to attain without using high-pressure and high-temperature processes. In this paper, a commercial pure h-BN powder was sintered by hot pressing (uniaxial – HP and isostatic – HIP) and spark plasma sintering (SPS) aiming at studying the anisometry among microstructures and their influence in the density and in the dielectric properties of this material. The results are compared to a commercial h-BN product in terms of densification, microstructure and dielectrical properties. Samples sintered by hot pressing processes presented microstructures with random alignment of the grains while the samples sintered by SPS showed an aligned microstructure with grains oriented perpendicular to the pressing direction. A higher dielectric constant was observed for the HIP sintered sample and the results of this sample show similar behaviour to the commercial h-BN ceramic component. [ABSTRACT FROM AUTHOR]

The possibility of producing binderless panels made of milled coconut husk, a largely available by-product of the coconut oil industry, has been shown in previous researches. Long pressing times and a high risk of blisters have however hindered the industrial implementation of the process. In this study, a more energy-efficient manufacturing process, involving a tailored degassing step, was developed on a laboratory scale and then validated at an industrial size (2 × 1 m2). To achieve mechanical properties close to the European and Japanese standards for fibreboards and to avoid the delamination of the boards, final densities between 900 and 1000 kg m−3 had to be targeted. Similarly, a successful board production was only possible if the moisture content of the husk was between 10 and 25%. The need for a suitable mat-forming technology to avoid the risk of warping of the panel was highlighted. [ABSTRACT FROM AUTHOR]

WC–α-Al2O3composites, with the rare earth oxides (Y2O3or CeO2) as sintering additives, were fabricated by mechanical alloying and hot pressing sintering. The microstructure and mechanical properties of WC–Al2O3with and without oxides were investigated. The appearance of rare oxides increased the density of sintered bulk materials and suppressed the decarburisation due to the decrease of surface activation energy in sintering process. The hardness and fracture toughness of the samples first increased and then decreased, indicating that an appropriate addition of Y2O3or CeO2could strengthen the properties of samples. Microstructure observation results revealed that the grain growth of WC was significantly retarded, and the homogeneity of Al2O3particulate dispersion was improved with the addition of Y2O3and CeO2. [ABSTRACT FROM AUTHOR]

In this study, two different compositions of submicrometre copper and chromium powders were mixed and the Cr50Cu50 alloys were fabricated via the powder metallurgy technique. The research imposed various hot pressing pressures, while the temperature was maintained at 1050°C for 1 h, respectively. The experimental results showed that the Saint Venant's effect obviously appeared in 1050°C, 48 MPa, 1 h hot pressing Cr50Cu50 alloys, which led to differences in the surface and internal hardness of the specimens. As a result, the optimal parameters of hot pressing of Cr50Cu50 alloys were 1050°C, 36 MPa for 1 h possessing the highest transverse rupture strength value (921.69 MPa). Moreover, the surface hardness increased to HV0.2221.78 (HRB 95.4), the relative density reached 97.15% and apparent porosity decreased to 0.10%, respectively. Furthermore, the resistivity decreased to 5.28 × 10−6 Ω cm, and ICAS was enhanced to 32.65% after the optimal procedure. [ABSTRACT FROM PUBLISHER]

ZrB2-SiC composites were prepared by hot pressing with different sources of SiC to study the effect of SiC with different morphology on densification, microstructure, phase composition and mechanical properties like hardness, fracture toughness and tribological properties (namely, scratch resistance, wear parameters) and thermal behaviour of the composites. Three different ZrB2-SiC composites, i.e. ZrB2-SiCP (polycarbosilane derived SiC), ZrB2-SiCC (SiC from CUMI, India) and ZrB2-SiCH (SiC from H. C. Starck, Germany), were studied. It is found that ZrB2-SiCC composite shows highest hardness (19·13 GPa) and fracture toughness (5·30 MPa m1/2 at 1 kgf load) in comparison with other composites. Interconnected network, better contiguity between grains of ZrB2-SiC composites and impurity content in starting powders can play significant roles for achieving high mechanical, tribological and thermal properties of the composites. Coefficient of friction and wear parameters of all ZrB2-SiC composites are very low, and thermal conductivity of ZrB2-SiC composites varied from 52·71 to 65·53 W (m K)−1 (ZrB2-SiCP), 54·30 to 71·55 W (m K)−1 (ZrB2-SiCC) and 64·25 to 88·02 W (m K)−1 (ZrB2-SiCH), respectively and also calculate the interfacial resistance of all the composites. [ABSTRACT FROM AUTHOR]

Abstract Ti3AlC2 is successfully synthesised by in situ hot pressing process from 2TiC/xAl/Ti (x = 1, 1·2) raw powders. The phases and microstructure of the samples are identified by X-ray diffraction and scanning electron microscopy. It is found that aluminium content influences on the generating content of Ti3AlC2 significantly. High purity Ti3AlC2 can be obtained from a compacted cylinder composed of TiC-Ti-1·2Al at 1350°C for 2 h, and the purity of Ti3AlC2 is nearly 96·9 wt-%. The corresponding density and compressive strength are 3·93 g·cm-3 and 377·34 MPa respectively. Ti3AlC2 grain exhibits typical plate-like structure. When aluminium melts, a mass of Al atoms diffuse to Ti grain rapidly, and Ti-Al intermetallic compounds generate. Then, Ti-Al intermetallic compounds react with TiC to form Ti3AlC2 directly. Using TiC powders as the raw materials provides Ti6C octahedra directly. At elevated temperature, a part of aluminium will evaporate and lose. This will result in that every two layers of Ti6C octahedra are linked by aluminium planes directly and Ti3AlC2 can be formed. [ABSTRACT FROM AUTHOR]

Recycled high-modulus Kevlar fibers were blended with Nylon 6 staple fibers and biocomponent low-Tm/high-Tm polyester fibers to form high-modulus puncture-resistance nonwoven fabrics via opening, mixing, carding, lapping, needle-punching, as well as hot-pressing processes. In this paper, biocomponent low-Tm/high-Tm polyester fiber content, needle-punching density, and hot-pressing temperature were changed to evaluate the tensile strength, bursting strength and static puncture resistance of resulting nonwoven fabrics as related to aforementioned three parameters based on response surface methodology. The result shows that the tensile strength is highly related to needle-punching density and hot-pressing temperature; but the bursting strength and static puncture resistance are significantly involved with the aforementioned three parameters. The tensile strength, bursting strength, and static puncture resistance all present increasing and then decreasing trend with increase of its respective concerning parameters. Moreover, the static puncture resistance strength has linear dependence on bursting strength. [ABSTRACT FROM AUTHOR]

In the present work, alumina and diopside were introduced in hydroxyapatite matrix, and hydroxyapatite/Al2O3/diopside ceramic composites with good mechanical properties were fabricated by uniaxial hot pressing. The behaviours of hydroxyapatite/Al2O3/diopside ceramic composites in simulated body fluid were studied by SEM, Fourier transform infrared spectroscopy and electron probe microanalyser. Scanning electron microscopy images showed an obvious mineral layer formed on the soaked composite surface, which indicated that the introduction of Al2O3 and diopside in hydroxyapatite matrix could not only improve the strength and toughness of the composites but also maintain its ability to precipitate an apatite layer. [ABSTRACT FROM AUTHOR]

In situTi2AlC/TiAl composite was first fabricated by reactive hot-pressing technique at low temperature of 1150°C for 2 h using Ti3AlC2and Ti–Al alloy powders. The composite with fine-grained structure consisted of TiAl, Ti3Al and Ti2AlC phases. The Vickers hardness, flexural strength and fracture toughness of the Ti2AlC/TiAl composite reached 5.2 GPa, 937.7 MPa and 7.7 MPa m1/2, respectively. The action mechanism for the composite was mainly attributed to the grain refinement, the uniform distribution of the dispersed Ti2AlC particles, transgranular cracking, crack deflection, crack bridging and pull-out of Ti2AlC. [ABSTRACT FROM PUBLISHER]

Based on some assumptions, this study derives an equation that estimates the theoretical molding thickness hc of knitted fabric reinforced thermoplastic composites (KFRTC). This is required for controlling the actual molding thickness of KFRTC that are produced by hot pressing knitted preforms made from reinforcing fiber/matrix fiber commingled yarns. The relationship between the optimum actual molding thickness h that can result in composites with higher tensile strength and lower void content and the theoretical molding thickness hc are also determined experimentally in this study. It is found that the composites produced can have higher tensile property and lower void content when h and hc satisfy h = khc (0.85 ≤ k ≤ 0.95). This estimation of h contributes to manufacturing KFRTC. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) is a consolidation technique that can combine high heating and cooling rates with a uniaxial applied pressure resulting in short processing time. SPS has been successful in producing ceramics with novel microstructures, which are often reported to have been produced at temperatures lower than would be possible using conventional densification techniques. This has led many authors to infer the presence of additional densification mechanisms intrinsic to the SPS process. The present study considers the relationship between temperature measured in SPS and that experienced by the sample. A simple analytical model enables calculation of the equilibrium temperature distribution in a cylinder of known thermal conductivity and emissivity with constant heat generation per unit volume. Application of this model to the die assembly used in SPS allows estimation of the equilibrium sample temperature. Optimised processing conditions were identified for a fully dense submicrometre grain size alumina, and a SiN–40 vol.-%TiB2 composite. Both materials can only be processed to full density with optimised microstructures in a narrow temperature window. Using the analytical model, the temperature seen by the sample was calculated, and compared with the temperature required using conventional processing techniques. Observed microstructures were consistent with those obtained using conventional processing techniques when processed at the calculated temperatures, suggesting that when SPS is applied to ceramics, additional densification mechanisms intrinsic to the SPS process are not required to explain the observed microstructures. The dynamics of the temperature distribution and problems associated with producing large samples using SPS are also considered. [ABSTRACT FROM AUTHOR]