EXPERIMENTAL COMPARE OF THE MECHANICAL PROPERTIES OF PULTRUDED GLASS FIBRE REINFORCED PLASTIC BASED ON POLYESTER AND VINYLESTER RESIN

The main purpose of this study is an experimental investigation and comparison of the mechanical properties of pultruded glass fibre reinforced polymer composite based on polyester and vinylester resin. For this purpose, the specimens were cut from the walls of square tube pultruded profile along to the fibres direction. The mechanical properties of the pultruded composite such as ultimate tensile strength and ultimate bending strength, tensile modulus and flexural modulus were obtained. It was observed that using of vinyl ester resin in pultruded composite instead of polyester resin enhanced the ultimate tensile and flexural strength from ~13% to ~24% in dependence of composite specimen’s thickness.

Rotary Friction Welded C45 to 16NiCr6 Steel Rods: Statistical Optimization Coupled to Mechanical and Microstructure Approaches

This work represents the production of dissimilar friction welded joints between C45 carbon steel and nickel-chromium alloy steel 16NiCr6. Central Composite Response Surface (RSM) methodology, optical microscopy, scanning electron microscopy (SEM), backscattered electron diffraction (EBSD) and bending test were performed for this study. Physicochemical characterization was used to reveal the welded joint microstructures. The bending test was done in order to measure the ultimate bending strength (UBS). As a conclusion, regarding the optimization of the parameters, friction time and the rotation speed were the most effective parameters on the joint strength. These parameters revealed that the maximum bending strength of 1406.892 MPa can be obtained at a rotational speed of 2000 rpm, a friction pressure of 24.77 MPa and a friction time of 13 seconds. On the weld samples it was also noted that the particle size decreases significantly as the units of the parameters increase, which led to note that the optimization of these parameters converges towards an average particle size, where were found a good accommodation between hardness and young’s modulus.

Investigation of the Rate of Vacuum-Conductive Drying of Wood-Particle Panels Based on Polyvinyl Alcohol

Wood composites are promising construction and finishing materials that offer the best properties of both wood and polymers. With the industry's need to use low-toxic adhesives in view, one of the ways to ensure the environmental friendliness of composites is the use of polyvinyl alcohol as a binder. In this respect, in order to streamline production, both in terms of reducing energy consumption and improving the quality of the final product, it is vital to choose the drying rate when pressing panels. The paper presents the results of a study of the process of vacuum-conductive drying of eco-friendly polyvinyl alcohol (PVA)-based wood-particle material. It was found that the composite samples with a PVA content of 40% in terms of physical and mechanical parameters (ultimate bending strength and ultimate tensile strength perpendicular to the panel face) fully comply with the established standards. The study provided the values of drying rate depending on 5 factors. The multi-factor regression analysis method was used to derive equations that determine the drying rate of polyvinyl alcohol-based wood-particle panels for two humidity intervals (above and below the cell walls humidification limit), taking into account the properties of different classes of bodies that make up the composite.

Study on Effect of Aerodynamic Sound Hardening for Wear of Coated Carbide Metal Plates

To increase the durability of metal-cutting carbide plates operating during in harsh technological conditions with impact load, an aerodynamic sound hardening method has been developed that can increase a life of carbide tools up to 3.7 times with a small added cost. The wear of plates hardened by the aerodynamic sound method, after 100 min of cutting, is 1.12–1.7 times less than their un-strengthened analogues. A coating on metal carbide plates does not have a prevailing value when a tool is working with impact loads. While working with impact loads viscosity of an internal plate structure occurs the greatest influence on increasing resistance. For metal-cutting carbide plates during interrupted cutting with significant impact loads, a method of aerodynamic sound hardening is more effective than a coating method, not only in terms of tool performance, but also in the cost of completion itself. Empirical dependences of wear on the rear surface of carbide plates hardened by a aerodynamic sound method and plates with PVD coatings have been obtained in the form of approximation by polynomials of the 5th and 2nd degrees, which are convenient to use in a production environment. It has been revealed the higher carbide plate strength in bending leads to less influence of the method of aerodynamic sound hardening on the increase in wear resistance. So, taking into account the fact that for ВК8-base the ultimate bending strength is 1666 MPa, and for T5K10 it is 1421 MPa, wear reduction after hardening by the aerodynamic sound method for ВП3115-plates with ВК base is 11.5 %, while for ВП3225 – plates with ТК-base – 27.1 %.

Suitability of paulownia wood from Malaysia for furniture application

Imported wood resources, especially yellow poplar and Chinese poplar, are increasingly evident in the Malaysian furniture sector due to declining supply of domestic wood materials. In order to reverse this trend, paulownia, a fast-growing forest plantation tree species, is emerging as an alternative wood material source. This study evaluated the mechanical strength, including fatigue life, machining, adhesive bond, screw withdrawal, and finishing properties of paulownia against the imported wood of yellow poplar and Chinese poplar. The results revealed that paulownia has better properties than Chinese poplar, but it is inferior to yellow poplar due to its lower density. In terms of fatigue strength, all the wood species performed comparably equal, with the allowable design stress set at 40% of the wood species’ respective ultimate bending strength. Against these findings, paulownia is a promising alternative wood resource for furniture manufacturing in Malaysia, and it could possibly replace the imported yellow poplar and Chinese poplar. Nevertheless, the successful application of paulownia for furniture manufacturing will depend on its supply volume and economics in the future.

The Influence of Heat Treatment on the Quality of Vehicle Component Parts Made of Rigid Polyurethane Foam

The paper provides the results of the investigation in the influence of heat treatment on the quality of vehicle component parts made of rigid polyurethane integral foam. The temperature of heat treatment was based on the exo-peak of the first heat cycle in DSC curve, and was equal to 135 °С. At that temperature, the samples were treated for 2-8 hours, and, as a result, they experienced an abnormal exo-effect in the glass transition region, which was indicative of thermal relaxation. The paper shows that the additional heat treatment stage for parts made of rigid polyurethane integral foam results in an increase in molecular mass of polymer, due to a smaller quantity of end groups, and, thus, in an increase in glass transition temperature from 169 °С to 176 °С. An increase in heat treatment time to 6 hours at 135 °С leads to a higher ultimate bending strength, which reaches its maximum, while further heat treatment (up to 8 hours) lowers this value. Therefore, with a higher degree of cross-linking the fracture toughness increases and passes its maximum, after that it starts to decrease, and the material becomes brittle.

An experimental investigation for the temperature effect on the bending properties of multiaxial warp-knitted composite

An experimental study of bending properties of composites reinforced with triaxial and quadaxial warp-knitted glass fabrics was carried out in the 0°, 45°, and 90° directions at −30°C, 0°C, 20°C, and 40°C, respectively. The relationships between the stress–strain curves, bending strength, bending modulus, and temperature were obtained. The failure mechanisms at different temperatures were also analyzed based on the fracture morphologies and scanning electron microscope (SEM) images. The results indicated that the bending properties decrease slightly with the increase in temperature from −30°C to 20°C and decrease dramatically from 20°C to 40°C. The ultimate bending strength of triaxial and quadaxial warp-knitted composites decreases approximately 31.34% and 34.29%, respectively. In particular, the relationships between bending strength and temperature were also obtained by nonlinear fitting with the experimental data, which could be used to predict the bending behavior at different temperatures.

EXPERIMENTAL INVESTIGATION OF THE STRUCTURE, ELASTIC, AND STRENGTH CHARACTERISTICS OF POROUS CORUNDUM CERAMICS

This paper aims to investigate the internal structure and to evaluate the elastic and strength characteristics of the corundum ceramic samples sintered at different temperatures. The average value of porosity of the sintered samples at the temperatures of 1400, 1500, and 1600 °C is 33, 26, and 17%, respectively. Mechanical tests of the ceramic samples are performed using the threepoint bending method. The ultimate bending strength varies from 135 to 265 MPa in the studied sintering temperature range. The elastic moduli of the sintered samples are found to be in the range of 58 – 113 GPa. An analysis of the ceramic samples’ microstructure is performed using a scanning electron microscope. The dependence of the porosity, pore size, and grain size on the sintering temperature is indicated. The values of strength and elastic modulus of the samples increase nonlinearly with rising sintering temperature in the experiment. Statistical behavior of mechanical properties of the ceramic samples is described using the Weibull analysis. The strength data for the sintering temperatures of 1500 and 1600 °C are well described by the Weibull distribution, and the strength values for a sintering temperature of 1400 °C are described with a significant scatter.

Experimental analysis and research on flexural properties of reinforced concrete composite beams

In order to further study the flexural properties of reinforced concrete beams after composite reinforcement, three composite beams and one cast-in-situ beam were tested under static load focusing on the bearing capacity, the law of crack development and the change of deflection. Test results demonstrate the yield strength, ultimate bending strength, and deflection of the composite beams are similar to those of the cast-in-situ beam, which confirms that the reinforced concrete composite beams can be used for reinforcement purposes in engineering projects.