Solid State Phenomena Vol. 320

Abstract: In this study, effect of wood flour addition on warm/cool feeling of green composite using wood flour and poly(lactic acid) was investigated for comfortability of interior product. Additive amounts of wood flour were 10 – 40 wt.%. Measurement of initial maximum values of heat flux of green composite using wood flour was conducted under constant temperature and humidity chamber. Surface of green composite using wood flour was observed by Scanning Electron Microscope (SEM). Following conclusions were obtained. The initial maximum value of heat flux of green composite decreased with an increase of wood flour additive amount until 20 wt.%. But, initial maximum value of heat flux of green composite at more than wood flour additive amount 30 wt.% almost did not change. From SEM observation, the appearance void area on surface of green composite at wood flour additive amount 20 wt.% was larger than that of green composite at wood flour additive amount 10 wt.%. Therefore, initial maximum value of heat flux of green composite was mainly affected because of increase of void area and wood flour until wood flour additive amount 20 wt.%.

Abstract: This study investigated the optimal use of industrial hemp fibers for polylactide (PLA) biocomposite and linear low density polyethylene (LLDPE) composite reinforcement. In these samples both low-grade fiber, waste and high-quality hemp fiber are used. To optimize the use of hemp fiber in both the biocomposite and the fossil-based polymer matrix composite, the first phase of the technology envisages the use of high-quality hemp fibers in the production of the PLA biocomposite. This process also produces a by-product (hemp waste). Further, in the second stage, the technology envisages the use of hemp waste in the production of LLDPE (semi-fossil) composite. PLA and hemp fiber biocomposites have high mechanical properties, which allow reducing the amount of materials in the product. Also, low-grade fiber composites show remarkable mechanical properties. The advantage of extracting hemp fibers is that it is possible to use all parts of the plant at the same time for the production of different products – hemp seeds, their shells, hemp shives, thus maximizing the value added of this resource, that conforms to the concept of sustainable development and circular economy principles. Also, it improves the ecological assessment (Life Cycle Assessment) of the product and reduces the environmental impact. Annually renewable hemp fiber resource has the potential to create new products and develop the renewable material industry in EU. Considering the Europe Green Deal guidelines [1], it is important for the manufacturer to provide a sustainable, economically justified and environmentally friendly material (switch to recyclable materials till 2021, switch to recycled, reusable or alternative materials till 2025).

Abstract: The goal of this work was to investigate effect of heating time during welding on mechanical properties of High Performance Polyamide thermoplastic composite material PPAGF40. Studies showed that welded joints with shorter heating time from 6.1 s to 6.7 s had a higher amount of pores and burn mark defects compared to the welded joints with longer heating time. Cross-section analysis of welded samples revealed tendency, that samples with higher heating time from 7.4 s to 11.5 s possessed more homogenous weld seam and higher resistance to burst pressure, respectively from 5.1 bar to 7.5 bar, while the resistance to pressure values of shortest heating time range, respectively are varying from 3.3 bar to 3.9 bar. The weld seam defects like pores and burn marks weakened the welded joint. 470 W of laser power energy input influenced fast melt-down of a cover and a housing, which caused material partial evaporation and later on formation of pores inside weld seam. By using lower 450 W of laser power and scanning speed of 1900 – 1700 mm/s, we can observe more homogenous weld seam. The cross-section of the samples were examined by using optical microscope. Mechanical resistance to pressure was performed in order to evaluate the performance of welded joints of different heating time of PPAGF40.

Abstract: Friction stir welding (FSW) is employed primarily for metals characterized by poor weldability at fusion welding: aluminium, magnesium, titanium and copper alloys as well as stainless steels. The focus of the study was on the feasibility of application of WC-based hardmetal 85WC-Co and TiC-based cermet 80TiC-NiMo as potential tool materials for FSW of copper. The single-pass welding trials of Cu sheets were performed using a vertical milling machine. For better understanding of interactions between the tool and workpiece at welding temperature EDS line scans across the interfaces tool-workpiece after welding as well as after diffusion tests were performed. It was concluded that both tested ceramic-metal composites did not failure during multiple plunges and during the total transverse welding distance of 10 m. Also, significant tool wear was not observed after such a welding distance. The possibility of producing visually defect-free welds using tools from WC- and TiC- based ceramic-metal composites was proved and also mutual diffusion of elements across the interface tool-workpiece was discussed.

Abstract: This study investigated the impact of various reactive diluents on viscosity of uncured mixture at 50 °C over a 12-week period. This criterion is important to predict the shelf life of uncured composition. Studied mono-functional acrylate monomers were: hydroxypropyl methacrylate (HPMA), hydroxyethyl methacrylate (HEMA), tetrahydrofurfuryl acrylate (THFA), isobornyl methacrylate (IBOMA), isobornyl acrylate (IBOA), 2-(2-Ethoxyethoxy)ethyl acrylate (EOEOEA), acryloyl morpholine (ACMO), glacial methacrylic acid (GMAA) and phosphate acrylate monomer (PAM); and various solvents: isopropanol(IP) ethyl acetate (EA), butyl acetate (BA). There was found the difference of effect on the systems viscosity in time between the mono-functional monomers and solvents. HPMA and IPA showed the most stable viscosity values in time.

Abstract: Nowadays, the growing attention has focused on the sandwich-structured composites (panels), especially on those, which are environmentally friendly. The sandwich panel is a special type of the composites made of at least three layers: a core and a skin-layer bonded to each side. The aim of this paper is to investigate the possibility of using of perforated metallic materials for producing sandwich panels for the different application in the civil engineering. By using the perforated metallic materials in combination with different core materials or by using the perforated metallic material as the core material the wide range of products for the construction, damping or isolation purposes could be manufactured. In the paper the example of using of perforated metallic sheet materials for manufacturing the sandwich panels is proposed. Both, the simulation and experimental studies (mechanical testing) were carried out in order to assess the load-bearing capacity of sandwich panels and to prove the applicability of the proposed sandwich panels for construction structures. For the analysis of the achieved structures the finite element analysis (FEA) software was used. The simulation results are well-coincided with the results of the experimental studies. Thus, new types of the sandwich panels and the manufacturing technology thereof are shown its reliability and could be recommended for application in the different branches, in particular for producing lightweight ceiling panels with filler from heat insulating materials.

Abstract: For an effectiveness improvement of conventional pultrusion processes, new optimization methodology is developed by using the design of experiments and response surface technique. An application of this methodology with two objective functions describing the minimum electrical energy spent for a curing and maximum pull speed is successfully demonstrated for the pultrusion process producing thin-walled-rectangular profile.

Abstract: Niobium slag as a waste product from metallurgical production of metallic niobium, containing calcium aluminates mainly, is valuable raw materials for different new products in the building materials industry. Disintegrator milling technology for pretreatment of Nb-slag was used, consisting of following steps: a) precrushing of slag, b) separative milling for extraction of metallic Nb. The yield of metallic Nb with a purity of 90 – 95 % was about 1.0 %; mineral ballast consists mainly (about 98 %) from calcium aluminates. The potential application areas of fine fraction (less 0.3 mm) of calcium aluminates were studied a) as a component in concrete and ceramics and b) as the main component of heat conductive material. The technology, mechanical and thermal properties (strength, thermal conductivity and expansion) of materials were studied. As reference material analogous CPA commercial thermal plates (Cebud, Poland) were studied. In the result of studies of mechanical and thermal properties of calcium aluminate based materials, it was demonstrated that the application of them as heat conductive material is more prospective.

Abstract: Reactive sintering of cemented carbides involves mechanical and thermal activation of precursor elemental powders, followed by in-situ synthesis of tungsten carbide. This approach promotes formation of ultrafine microstructure favored in many cemented carbide applications. Our study focuses on the effect of mechanical activation (high-energy milling) on the properties of powder and following thermal activation (sintering) on the microstructure characteristics and phase composition. Reactive sintering proved effective – an ultrafine grained microstructure of cemented carbides with Co and Fe binders was achieved. Formation of tungsten carbide grains was complete at low temperature during reactive spark plasma sintering, resulting in textured microstructure with anisotropic grain formation and growth.

Abstract: Because of low calcination temperature, magnesia binders are attributed as low-CO₂ emission materials that can benefit the environment by reducing the energy consumption of building sector. Portland cement in different areas of construction can be replaced by magnesia binder which do not require autoclave treatment for hardening, it has low thermal conductivity and high strength properties. Magnesium-based materials are characterized by decorativeness and ecological compatibility.The experimental part of this research is based on the preparation of magnesia binders by adding raw materials and calcinated products and caustic magnesia. The aim of this study was to obtain low-CO₂ emission and eco-friendly material using local dolomite waste materials, comparing physical, mechanical, thermal properties of magnesium binders.