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The form of the outer and inner surfaces of hollow spherical parts determines the developments of some particular categories of efforts during the compression tests. The overall purpose of the research presented in this paper was to study the behaviour of the hollow spherical parts under axial compression. The PLA hollow spherical parts were obtained by 3D printing and using distinct values for certain process input factors. The finite element method was used to theoretically investigate the behaviour of the parts and it highlighted the total plastic deformation of the test pieces. To experimentally verify the theoretical considerations, an L9 Taguchi orthogonal design was performed. The empirical mathematical model thus determined highlighted the stronger influence exerted by the printing plate temperature, printing speed, and part wall thickness.

The needs of environmental protection led to the introduction of composites based on the use of plastics reinforced with biodegradable materials or other easily accessible materials. The overall purpose of the research was to experimentally investigate the possibilities of using some accessible reinforcement materials. Textile based on plants fibers and glass fibers were used as reinforcement materials, while the matrix was a polymer type material. An empirical mathematical model was proposed to highlight the effect of the number of glass fiber reinforcements on the tensile strength. The determined mathematical empirical model and graphical representations highlight how the number of glass fiber reinforcements affects the modulus of elasticity of the composite materials.

It is actual now to work out new radiation protecting sheeting on the basis of non-curing polymeric composition which possess self-adhesion properties, are easily mounted and dismantled and provide high tightness and low permeability. Mechanical properties of non-curing composites consisting of ethylene propylene diene monomer (EPDM), industrial oil (IO), alkyl phenol-formaldehyde resin (PF) with addition of barite (52 %) to the total material volume were investigated in this article. The aim of investigation is to find optimal content of the above mentioned components at which it would be possible to get the following properties: composite would be sticky enough (peel strength not less than 4 N/cm); character of a separation would be cohesive (on a material) and thus there would be no migration of softener and satisfactory resistance of fluidity. The results showed that PF addition till 20 % in the system EPDM/PF leads to the increasing of adhesive strength, in this case optimal oil concentration in the system EPDM/PF/IO is in the interval from 45 till 55 %. New self-adhesion lead-free material, exhibited higher X-ray-shielding properties, is also received in the result of investigation.

The paper presents the mechanical behaviour and properties of a new hybrid vegetal based resin. For this, through static loading tests, the main mechanical characteristics were determined: static Young modulus, breaking strength, breaking elongation and transversal Poisson ratio. Samples of the proposed materials were subjected also to free vibration tests, by clamping them at one end and leaving them free at the other. The observation and results from these were used for deduction of the first vibration mode eigenfrequency, the dynamic Young modulus, the loss and damping factors. Some representative SEM images with an electronic microscope were collected and the samples surface roughness was determined. By using the Thermogravimetric analysis (TGA), the mass loss up to 800° C was investigated. Compared to the other resins that have dammar in composition, the proposed dammar based resin from this research has a 15.32 times higher static Young modulus than the oil palm trunk and 8.885 times higher than the oil palm trunk (OPT) with 20% dammar resin.

The first part of the paper presents the specific issues from the injection molding associated with the water content of the hygroscopic plastics (water adsorption, equilibrium moisture level, chemical affinity, hydrolysis) and recommendations regarding the drying of plastics for injection, the drying methods and defects specific to products injected due to the moisture content. The experimental results on the injection of a polyamide (AKULON) and of a thermoplastic polyurethane (DESMOPAN) presented in the second part of the paper are focused on the surface appearance fault `splay` associated with the different values of moisture content for these two materials, verify the value for the admitted moisture content for two hygroscopic materials, polyamide and thermoplastic polyurethane, and ends with conclusions on the residual humidity allowed and opinions on choosing the drying technology and parameters.

In this paper, experimental investigation, modeling and optimization of the drilling of PMMA are performed using the Taguchi Design of Experiments (DOE), analysis of variance (ANOVA) and artificial neural networks (ANN) methods. Drilling experiments were conducted on PMMA to assess the impact of process parameters (drill diameter, spindle speed, and feed rate) on the hole-quality characteristics (surface roughness, circularity error, and cylindricity error). ANOVA was performed to identify the drilling parameters that have a statistically significant influence on the hole-quality characteristics. A predictive model for the hole-quality characteristics was derived using a four-layer ANN with a backpropagation algorithm and a sigmoidal transfer function at the hidden layers. The ANN model was able to accurately predict the hole-quality parameters with the absolute mean relative errors of the testing data in the limits of 3 to 7%. Based on the experimental results and analytical modeling, it was found that drilling of PMMA requires lower spindle speed and high feed rate when the integrity of the drill hole is the main quality criterion.

This article is devoted to the problem of working out of damping polymer materials which are effective in the wide temperature and frequency range. In the modern world, work is being carried out to create damping polymer composite materials (DPM) from which it is possible to manufacture protective elements and parts of engineering structures of reduced vibration excitability. Existing DPM have a narrow temperature range, within which effective vibration absorption is observed, moreover, most of them go through a vulcanization stage, which increases the cost of the final product, has a harmful effect on environment and allows limited recycling of waste. One of the ways to solve this problem is to replace traditional rubber vibration-absorbing materials with thermo-elastoplasts (TEP). The most promising polymer for TEP is ethylene vinyl acetate (EVA), which has high damping properties, oil resistance and relative incombustibility. In this regard, experimental studies were conducted to establish the patterns of influence of the type and concentration of structure-forming components (plasticizers, fillers, modifiers) on the dynamic mechanical properties of TEP based on EVA in order to develop a new DPM effective in a wide temperature range. The leading method to investigate this problem is a method of dynamic mechanical analysis which allows to get information about changes of mechanical characteristics under mechanical load and controlled temperature and frequency. With the help of detected patterns it was possible to determine type of plasticizer which significantly decreases glass temperature of EVA. The percentage ratio of EVA/plasticizer system is stated, and the type of plasticizer at which the maximum of mechanical losses takes over greater values is accordingly detected. It is revealed, that to work out DPM on EVA basis, which are effective in wide temperature range it is more preferable to add not less than 40 % on volume basis inert fillers, such as talc or mica with addition of 5-10 % of carbon as the hardening additive. The kind of resin improving damping properties and raising rigidity of composites on EVA basis is defined. On the basis of the research, a material was developed which has the following properties: the maximum value of tan δ is at least 0.45 at a temperature of plus 5°C (oscillation frequency 10 Hz); width of the temperature interval within which tan δ is not less than 0.3 from minus 40 to plus 50°С (oscillation frequency 10 Hz); conditional tensile strength of not less than 10 kg/cm2, cold resistance up to minus 50°C.

Carbon fibre reinforced (CFR) laminates were manufactured by prepreg lay-up and deposition of interlaminar carbon nanotubes (CNTs). An easy and innovative manufacturing procedure was used. CNTs were separated in solvent by ultrasonication, and poured on the woven fabric prepreg. Solvent evacuation was performed at low temperature, and dry functionalized prepregs were used for composite lamination. Laminates were cured by compression moulding on a heating plate. Peeling tests, differential scanning calorimetry (DSC), and dynamic mechanical analyses (DMA) were carried out on multiply samples with and without 1 wt% of interlaminar CNTs. Results show that the glass transition temperature of the resin matrix reduces because of the interaction with CNTs. Nevertheless, peeling strength shows 10% increase at room temperature.

Carbon fibre reinforced composites were manufactured by using recycled carbon fibres (CF) and carbon nanotubes (CNT). Dry fabrics were impregnated by hot melting with 1 wt% CNT filled epoxy resin to produce prepregs. Subsequently, composite laminates were manufactured by vacuum bagging and autoclave moulding. Only materials and industrial equipment were used for the laminate production. Laminates with unfilled resin and virgin CFs were also manufactured for comparison. Samples were extracted for physical and mechanical measurements. Dynamic mechanical analyses and bending tests were carried out to evaluate the interaction between CNTs, resin matrix and recycled CFs.

In recent years, the rapid development of electronic equipment led to millions of tons of waste printed circuit boards (WPCB) generated in the entire world rising important concerns regarding its recycling. Besides the metals recovery, intensively studied, the reuse of the nonmetals is especially difficult. In this study, the non-metallic fraction from the waste of printed circuit boards is used as reinforcing filler of a styrene-butadiene block-copolymer. The composites were characterized by mechanical and dynamo-mechanical analysis and thermo-gravimetry. The study aimed the reintroduction into the economic circuit of WPCB as composites suitable for the production of shoe soles injected directly on the footwear faces and as bitumen modifiers for road coverings.