Properties of new cork–polymer composites: Advantages and drawbacks as compared with commercially available fibreboard materials

Cork powder (50 wt.%) was mixed with polypropylene (PP) or polyethylene (PE) by pultrusion aiming to prepare cork-based composites. In a further step, samples were produced by compression moulding using the compounded composites. Bending strength, impact resistance, hardness, dimensional stability, thermal and acoustic properties of the developed cork–polymer composites (CPC) were determined and compared with commercially available products namely medium density fibreboard (MDF) and high density fibreboard (HDF). It was found that the CPC have good dimensional stability, lower water uptake, a better acoustic insulation performance and similar behaviour in terms of hardness and fire resistance when compared with both MDF and HDF. However, the mechanical strength is inferior comparing with both commercial materials based on fibres. It was also observed that addition of cork improved the flexural modulus, impact resistance and hardness on the developed CPC. Thus, the herein described CPC materials showed important characteristics to be considered as good candidates to be applied in the design of flooring and construction systems.     

Rice-husk flour filled polypropylene composites; mechanical and morphological study

To determine the possibility of using lignocellulosic materials as reinforcing fillers in the thermoplastic polymer composite, polypropylene as the matrix and rice-husk flour as the reinforcing filler were used to prepare a particle-reinforced composite in order to determine testing data for the physical, mechanical and morphological properties of the composite according to the filler loading in respect to thermoplastic polymer. In the sample preparation, four levels of filler loading (10, 20, 30 and 40 wt.%) were designed. In the tensile test, six levels of test temperature (−30, 0, 20, 50, 80 and 110 °C) and five levels of crosshead speed (2, 10, 100, 500 and 1500 mm/min) were designed. Tensile strengths of the composites slightly decreased as the filler loading increased. Tensile modulus improved with increasing filler loading. Notched and unnotched Izod impact strengths were lowered by the addition of rice-husk flour. The composite became brittle at higher crosshead speed, and showed plastic deformation with increasing test temperature.     

Water absorption behavior,mechanical and thermal properties of nano TiO2 enhanced glass fiber reinforced polymer composites

Nano TiO₂ particle is one of the promising inorganic nano fillers used in polymer matrix composites to enhance the mechanical properties. However, reliability of this type of nano composites is yet to be ensured in hydrothermal environment. The present work investigates the addition of nano TiO₂ filler on water sorption, residual strength and thermal properties of glass fiber reinforced polymer (GFRP) composites. The results revealed that addition of 0.1 wt% TiO₂ has reduced water diffusion coefficient by 9%, improved residual flexural strength by 19% and residual interlaminar shear strength by 18% among all the nano TiO₂ modified composites. The improvement of mechanical properties in hydrothermal environment creates opportunity and reliability to be used in different engineering applications. Weibull design parameters are evaluated and found a good agreement between Weibull stress-strain curves and experimental one. Fractographic analysis confirmed the various failures and strengthening mechanisms of nano composites in dry and hydrothermal environment.     

Effects of diammonium phosphate on the flammability and mechanical properties of bio-composites

The flammability, thermal stability and mechanical properties of natural fiber-reinforced thermoplastic bio-composites were measured using a horizontal burning test, thermogravimetric analyzer, and universal testing machine, respectively. The composites were fabricated from film resins (Polylactic-acid, PLA and Polypropylene, PP) and natural fibers (coconut filter and jute fiber) by a hot press machine. To improve the flame retardancy of the bio-composites, various diammonium phosphates (DAP) were treated into the fibers. In general, the results indicate that increasing the percentage of DAP used to treat the fibers effectively improves the flame resistant, weight loss rate, and flexural modulus but decreases the flexural and tensile strengths of the bio-composites. Bio-composites with DAP-treated fibers showed a greater flexural modulus than those with untreated fibers, and the flexural modulus was even greater than that of neat polymers (PLA and PP). Also, increasing the percentage of DAP for treatment of the fibers in the composites decreases the temperature required for 5% weight loss and the decomposition rate, but increases the char residual at 500 °C. The best linear burning rate and weight loss rate were observed for fiber treatment with 5% DAP. The compressive and wear properties of these bio-composites were also studied.     

玻璃纤维增强光固化树脂基齿科生物复合材料的半互穿网络结构界面的形成及力学性能

采用不同浓度的聚甲基丙烯酸甲酯(PMMA)丙酮溶液对玻璃纤维进行表面处理,并对不同处理条件下的玻璃纤维表面化学组成、PMMA的吸附量及齿科树脂基复合材料的力学和界面性能进行了分析和测试。结果表明,经过表面处理,玻璃纤维表面吸附上PMMA,且吸附量随PMMA溶液浓度的增大而增大。控制玻纤表面吸附的PMMA质量分数在1%左右,可以设计其与齿科树脂形成半互穿网络结构的良好界面。与未处理的玻纤复合材料相比,用质量分数为5%的PMMA溶液处理的玻纤/光固化树脂基复合材料的弯曲强度提高29.6%,弯曲模量提高30%,可以作为一种齿科修复用的新型生物复合材料应用。     

Microstructure, mechanical properties and aging behavior of Mg–5Li–3Al–2Zn–xAg

Mg–5Li–3Al–2Zn–xAg (x = 0, 0.1, 0.3, 0.6, 1.2) alloys were prepared by medium-frequency induction furnace under the ambient of pure argon. The effect of Ag addition on the microstructure, tensile properties, and aging behavior was investigated. Results show that the addition of Ag can restrain the decomposition from MgAlLi₂ to AlLi. With the addition of Ag, the over-aging point is retarded and the over-aging phenomenon is avoided in Mg–5Li–3Al–2Zn–1.2Ag. The solid solution of Ag in matrix phases and the restraining of the decomposition from MgAlLi₂ to AlLi are two aspects that strengthen the alloys.     

Fabrication and mechanical properties of steel–steel composites

Metal matrix composites based on a low carbon steel matrix reinforced with high carbon steel wires have been fabricated by a combined cold and hot rolling process. Both continuously and discontinuously aligned composites have been produced. A subsequent heat treatment allowed the formation of martenisitc, bainitic or pearlitic wires in a ferrite predominantly matrix. The optimum wire microstructure giving a composite with high strength and reasonable ductility was found to be bainitic — martensitic wires were found to contain microcracks that gave poor composite strengths and ductilities. The discontinuous wire composites produced similar strengths to the continuous composites only when they were deformed to give a wire aspect ratio greater than 20. The strengths of both types of composites showed a good fit to the rule of mixtures as the volume fraction of fibers was increased.     

Thermal stability and mechanical properties of nanostructured Ti–24Nb–4Zr–7.9Sn alloy

Thermal stability of the nanostructured grains of cold-rolled Ti–24Nb–4Zr–7.9Sn alloy and corresponding variations in mechanical properties were investigated. The activation energy for grain growth was found distinct below and above the ( + β)/β transus of 950 K, with values of 47 and 206 kJ/mol, respectively. Due to the pinning effect of the precipitates at β grain boundaries, grains sizes can be maintained at less than 100 nm during prolonged annealing at temperatures up to 773 K, and are less than 1 μm for annealing temperature up to 923 K and time up to 2 h. Annealing above the β transus resulted in coarse grains with sizes of tens of micrometers in less than 2 h. Tensile and hardness tests showed rapid strengthening with the increase of annealing time below 773 K, which was attributed to both the rapid formation of nano-sized precipitates and the slow growth rate of β grains. By adjusting the grain size of the cold-rolled material the high strength/low Young's modulus match desirable for implant applications can be improved over the hot-rolled bars with coarse grains.     

Fracture behavior and mechanical properties of Mg–4Y–2Nd–1Gd–0.4Zr (wt.%) alloy at room temperature

The microstructure, mechanical properties and fracture behavior of gravity die cast Mg–4Y–2Nd–1Gd–0.4Zr (wt.%) (WNG421) alloy are studied at room temperature in different thermal conditions, including as-cast, solution-treated and different aging-treated (both isothermal and two-step aging) conditions. The results indicate that WNG421 alloy shows different behaviors of crack initiation and propagation in different thermal conditions during tensile test at room temperature. After pre-aged at 200 °C for 5 h, the hardness of WNG421 alloy first reduces and then increases when secondary aged at 250 °C (two-step aging). The peak hardness and corresponding tensile strength of the two-step aged alloy both increases compared with those in 250 °C isothermal peak-aged condition. Tensile strength of WNG421 alloy at room temperature in low temperature (200 °C) isothermal peak-aged condition is much higher than that in high temperature (250 °C) isothermal peak-aged condition.     

Investigation of the mechanical properties of the Ni–P–CNTs coated copper composite materials: Experiments and modeling

Recent studies on the mechanical properties of nickel–phosphorous–carbon nanotubes (Ni–P–CNTs) coated copper composite materials have shown surprising results. Their Young’s modulus and tensile strength cannot reach the theoretical values, even falling below those of copper, and the Young’s modulus decreases with the increment of CNT concentrations. Materials used in those studies were prepared through electroless composite plating process, with the Ni–P–CNTs composite electrolessly deposited on the copper substrate. In the present study, however, it is shown that the Young’s modulus and the tensile strength do increase significantly with the increment of the CNT concentrations without activating the CNTs. A composite method of Voigt model and a random distributed discontinuous fiber model is applied to obtain the equivalent Young’s modulus of the composite, which agrees very well with the experimental data.     

Effect of the long periodic stacking structure and W-phase on the microstructures and mechanical properties of the Mg–8Gd–xZn–0.4Zr alloys

Microstructures and mechanical properties of the Mg–8Gd–xZn–0.4Zr (x = 0, 1 and 3 wt.%) alloys, in the as-cast condition and the as-extruded condition, have been investigated. The results show that both the 14H long periodic stacking structure and the W-phase coexist together in the cast Zn-containing alloys. The volume fraction of the W-phase increases with increasing the addition of Zn. This phase is the crack source of the fracture. The 6H long periodic stacking structure is observed in the extruded Zn-containing alloys. The Mg–8Gd–1Zn–0.4Zr alloy exhibits the highest elongation, and the value of its elongation is 130% at 300 °C due to the refined microstructure. The W-phase plays an important role in improving the mechanical properties via pinning the movement of the grains at elevated temperature.     

Effect of heat treatment on the microstructure and mechanical properties of the spray-deposited Al–10.8Zn–2.8Mg–1.9Cu alloy

In this study, effect of various aging tempers (T6, T73 and RRA treatment) on the microstructure and mechanical properties of the spray-deposited Al–10.8Zn–2.8Mg–1.9Cu alloy was studied using high-resolution electron microscopy, selected area diffraction, and tensile tests. The results indicate that the two types of GP zones, GPI and GPII, are major precipitates for the alloy under T6 condition. No clear precipitation free zone was observed, and the grain boundary precipitates were continuous. Under two-step aging condition, the GP zones and η′ are major precipitates for the alloy, the discontinuous grain boundary precipitates are favorable to SCC resistance in over-aged condition, which reduces its strength 58 MPa (about 7%) compared to the peak-aged condition. After retrogression and re-aging treatment, the grain boundary precipitates are discontinuous, which is closed to that resulting from T73 temper. RRA treatment decreased ultimate tensile strength 25 MPa (about 3%) in values compared with the alloy at T6 condition.     

Structural and mechanical properties of titanium oxide thin films for biomedical application

Titanium oxide thin films were deposited by radiofrequency reactive sputtering in Ar-O₂ atmosphere on silicon (100) wafers and titanium alloy plates (Ti-6Al-4V). Thin films structural characterization was carried out by grazing incidence X-ray diffraction, atomic force microscopy, scanning and transmission electron microscopies. Chemical composition was checked by X-ray wavelength dispersive spectroscopy. Mechanical assessment was achieved by nano-indentation and nano-scratch measurements. The films deposited on silicon substrates are over-stoechiometric in oxygen, with an oxygen to titanium ratio of about 2.2. The growth of anatase and rutile phases was promoted by ranging the total and oxygen partial pressures between 0.17-1.47 Pa and 35-85%. The growth rate of films, determined by grazing incidence X-ray reflectivity, was ranging from 35 to 55 nm/h. The rutile single-phased films possess a hardness of about 2.5 times higher and a lower friction coefficient than the anatase films. The films which contain anatase possess a high surface root-mean-square roughness and a reduced elastic modulus of around 120 GPa close to reduced elastic moduli of hydroxyapatite bioceramic and titanium alloy. So the anatase film could be the best candidate as a titanium oxide intermediate layer between hydroxyapatite and titanium alloy in the field of biomedical implants.     

Structure and mechanical properties of extruded Mg–Gd based alloy sheet

The Mg–8Gd–2Y–1Nd–0.3Zn–0.6Zr (wt.%) alloy sheet was prepared by hot extrusion technique, and the structure and mechanical properties of the extruded alloy were investigated. The results show that the alloy in different states is mainly composed of α-Mg solid solution and secondary phases of Mg₅RE and Mg₂₄RE₅ (RE = Gd, Y and Nd). At aging temperatures from 200 °C to 300 °C the alloy exhibits obvious age-hardening response. Great improvement of mechanical properties is observed in the peak-aged state alloy (aged at 200 °C for 60 h), the ultimate tensile strength (σ_b), tensile yield strength (σ_0.2) and elongation () are 376 MPa, 270 MPa and 14.2% at room temperature (RT), and 206 MPa, 153 MPa and 25.4% at 300 °C, respectively, the alloy exhibits high thermal stability.     

Manufacture, microstructure and mechanical properties of Mo–W–N nanostructured hard films

Mo_1−xW_xN_y (x = 0–0.67) hard films were fabricated on wafers of silicon and high speed steel by dc magnetron sputtering technique. The effect of tungsten concentration on the phase composition, microstructure, surface morphology, hardness, adhesion, and corrosion resistance of the films was studied by X-ray diffraction, scanning electron microscopy, nano-indentation, and scratch test. It was found that if the W concentration (x) in the film is in the range of 0–0.52, the films exhibit fcc (Mo,W)N_y single phase where larger W atoms substituted Mo atoms in fcc MoN_y. At higher x values (x > 0.52) the films exhibit a two-phase structure consisting of fcc (Mo,W)N_y and pure bcc tungsten phase. The hardness of the Mo_1−xW_xN_y films increases at first with increasing x, and then decreases after passing a maximum. The maximum hardness of 47 GPa is obtained at x = 0.37 corresponding to an adhesion strength of 60 N. The Mo–W–N coated high speed steel has a lower corrosion current density and higher corrosion potential than the bare high speed steel substrates.     

Thermoplastic polymer impregnation of cellulose nanofibre networks: Morphology,mechanical and optical properties

Biobased nanocomposite sheets of cellulose nanofibres (CNF) and cellulose acetate butyrate (CAB) were prepared using resin impregnation. Porous nanofibre networks together with a low viscosity thermoplastic resin were the key elements in the processing. SEM images of the network before the impregnation showed high porosity and after the impregnation indicated impregnated fibre network. A significant improvement in the visible light transmittance was observed for the nanocomposite compared to the nanofibre network, which is explained on the filling of the pores with a transparent matrix. The tensile tests showed an increase of 364% and 145% for stiffness and strength respectively for nanocomposites with 60 wt.% CNF when compared to CAB. Dynamic mechanical properties showed a good interaction between the CAB and cellulose nanofibres. These results show that CAB impregnated cellulose nanofibre networks are promising biocomposite that could be used in applications where transparency and good mechanical properties are of interest.     

Effect of Zr on the microstructure, mechanical properties and corrosion resistance of Mg–10Gd–3Y magnesium alloy

The influence of Zr on the microstructure, mechanical properties and corrosion resistance of Mg–10Gd–3Y (wt.%) magnesium alloy was investigated. The grain size of alloys decreased with Zr content from 0% to 0.93% (wt.%). The addition of Zr greatly improved the ultimate tensile strength (UTS) and the elongation (EL), while slightly improved the tensile yield strength (TYS). The UTS and the EL of the alloy containing 0.93% Zr increased by 125.8 MPa and 6.96% compared with base alloy, respectively. The corrosion resistances were found to decrease with Zr content from 0% to 0.42% and then increase from 0.42% to 0.93%. The differences in the sizes and distributions of the Zr-rich particles have significant effects on the corrosion behaviors. The alloy with 0.42% Zr addition revealed the optimum combination of mechanical properties and corrosion resistance.     

PHBV nanocomposites based on organomodified montmorillonite and halloysite: The effect of clay type on the morphology and thermal and mechanical properties

The aim of this study was to evaluate the effect of the addition of two types of nanoparticles, organomodified montmorillonite Cloisite® 30B (C-30B), and a tubular like clay, halloysite (HNT), on the morphology and thermal and mechanical properties of poly(hydroxybutyrate-co-hydroxyvalerate) – PHBV nanocomposites. TEM and WAXD results showed a combination of a few tactoids and a partially exfoliated structure for PHBV/C-30B nanocomposites and a good dispersion of HNT in the PHBV matrix. DSC analysis indicated a lower nucleation density with the addition of nanoparticles. Furthermore, the presence of C-30B led to the formation of double melting peaks, related to different crystalline phases. However, a higher melting temperature was obtained for PHBV/HNT nanocomposites. A general increase in the Young’s modulus was observed. However, for PHBV/C-30B nanocomposites, this enhancement was at the expense of the strain at break and impact strength, probably due to the degradation of the polymer during processing.     

Mechanical and thermal properties of AlN–BN–SiC ceramics

Mechanical and thermal properties were characterized for two AlN:BN:SiC composite ceramics produced from BN with different particle sizes. The ceramics were hot pressed at temperatures from 1950 to 2100 °C to 97% relative density. For both materials, the matrix (90:10 vol% SiC:AlN) had a grain size of 0.4 μm, and the BN grains (10 vol%) were crystallographically aligned. Microhardness values were between 20 and 22 GPa, while fracture toughness values were between 2.5 and 3.1 MPa m^1/2. Other properties were found to be dependent on testing direction. Elastic moduli were between 260 and 300 GPa and strengths were 630 MPa for small particle BN additions. Thermal conductivity was calculated to be between 25 and 37 W/m K at room temperature and 17 and 25 W/m K at 900 °C. The low values compared to traditional SiC ceramics were attributed to AlN–SiC solid solution formation and sub-micron matrix grain sizes.     

A comparison of the mechanical characteristics of kenaf and lyocell fibre reinforced poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) composites

Cellulose fibre-reinforced poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) composites have become increasingly interesting with regard to their biodegradability and mechanical characteristics. The use of different matrices leads to variable composite characteristics. This study provides a comparison of the mechanical characteristics of compression-moulded 30 mass% lyocell and 40 mass% kenaf fibre-reinforced PLA and PHB. The results of the tensile tests showed that 30 mass% lyocell/PLA composites reached the highest tensile and bending strength with 89 and 148 N/mm², respectively. The highest Young’s modulus was also measured for 30 mass% lyocell/PLA with 9.3 GPa, and the highest flexural modulus was measured for 40 mass% kenaf/PHB with 7.1 GPa. By far, the best impact strength was determined for lyocell/PHB with 70 kJ/m², followed by lyocell/PLA with 52 kJ/m². The investigation of the Shore D hardness resulted in a higher value for the PLA matrix with 81.5. PHB achieved a hardness of 67.5. By adding fibres as reinforcement, the Shore D hardness increased up to 83.6 for lyocell/PLA and 73.1 for kenaf/PHB. Density measurements showed lower densities for the composites with higher fibre loads (kenaf/PLA and kenaf/PHB) in comparison to the theoretical density. This speaks for a higher proportion of air inclusion in the composites which could negatively affect the mechanical composite characteristics.