Materials Science Forum Vol. 919

Abstract: The spontaneous phase transformation of the unstable phase II to the stable phase I of isotactic polybutene-1 can be affected by several factors (temperature, pressure, mechanical deformation, environments, nucleation agents or presence of –CH₂- groups in polymer chains or in blends). Here we study the effect of the external static electrical field on the iPB-1 structure and phase II →I transformation rate. The phase transition II to I is accelerated by the effect of the static electrical field up to 36%. This effect increases with increasing macromolecular chain length and increasing voltage. The electrical field did not substantially influence the total amount of crystalline phase. The phase transformation of neutral type changed into minus type. This change decreases the transformation rate by blocking the transformation nuclei.

Abstract: This paper deals with natural degradation of PLA (polylactic acid) composites with natural fiber reinforcement in non-simulated conditions. Composite material was made of PLA and 6 different types of biodegradable fibers. Fibers made from pulp, wool, bamboo, soya, flax and hemp. All samples had 20% volume of fibers. Three of each composite sample were placed in compost (aerobic surrounding) for 72 weeks. All samples were examined at the beginning every 2 weeks to observe if the degradation process occurred and all samples were examined at the end of 72 weeks period to observe results of degradation of each composite material.

Abstract: The vacuum infusion process (VIP) is suitable for production of bigger prototypes and low-series production, but their utilization is increasing because their low investment cost, comparability with high-tech technology (pre-preg), possibility to produce sandwich structures in one step and many various advantages.We verify the possibility of VIP to produce various prototypes with increasing degree of flame retarders, specifically aluminium hydroxide (ATH), which fulfil regiments to mechanical and Fire-Smoke-Toxicity (FST) properties according EN 45 545. Mechanical properties we confirmed by testing of bending properties according EN ISO 178 and tensile properties according EN ISO 527-4. FST properties were confirm by flammability test with hot wire according EN ISO 60695-2-11.

Abstract: This article deals with the observation of shape and dimensional accuracy of parts after manufacturing in certain time intervals. The parts was manufactured by additive manufacturing method Fused Deposition Modeling (FDM). The shape and chosen dimension changes due to material shrinkage was observed on materials, namely Polylactic Acid (PLA) and Polyethylene Terephthalate Glycol (PET-G). These materials rank among health-conscious and usable in some medical applications. The parts were measured by using coordinate measuring machine (CMM) in certain time intervals and the shape and chosen dimensions was compared with the reference computer aided designed (CAD) model.

Abstract: The paper is focused on the determination of the course and change of the surface quality parameters obtained by the laser engraving of the material known under commercial name polymethyl methacrylate. The paper aims to find mathematical relations based on regression analysis for amplitudes parameters Ra and Rz. For this purpose, a sample of variable technology parameters will be machined followed by the surface measuring and evaluation using the Talysurf CLI 500 3D Surface Scanner. Thus the data obtained will be subjected to the detailed statistical analysis to check homoscedasticity, the presence of outliers, and multidimensional normality testing.

Abstract: The 3D printing technology used for final production of upper limb prostheses is the topicof this article. It focuses on different 3D printing technologies and testing of different thermoplasticmaterials. As the testing object an index finger of HACKberry open source myoelectric bionic handwas used. This part was 3D printed by using of different printing technologies (FFF/FDM, SLA, SLS,PolyJet), and different materials (PLA, ABS, PC-ABS, Though, etc.), and different strategies (heightof layers). The fingers were mechanically tested to simulate flexion in a tip pinch grip. At the endof this paper results of this research and testing is summarized, and optimal material, technology andstrategies of parts production is highlighted.

Abstract: Graphene has been long considered for application in electronics manufacturing due to its extraordinary electronic, mechanical and thermal properties. This paper focuses on the graphene preparation onto dielectric substrate using transfer-free chemical vapour deposition (CVD) method with an intermediate catalytic metal layer (cobalt, nickel). Graphene layers were formed via segregation mechanism at temperatures in the range of 850 - 1050 °C onto the metal-dielectric boundary. Evaluated Raman spectra, which reveal the number of graphene layers and their defectivity suggested, that thinner metal layer and balanced ratio of H₂:CH₄ yield the best results for both cobalt and nickel layer. Spectra showed low amount of defects and the average number of carbon layers between 2-3, however, single-layer graphene (SLG) samples were also prepared. Scanning electron microscopy images showed that graphene domains on larger scale are not fully continuous.

Abstract: An application of hard engineering materials depends especially on their specific properties, included mechanical properties and their machinability. Technical ceramics belongs to such materials. Nowadays, due to its properties, it is a process of grinding that is applied in machining. Because the technical ceramics has high hardness and brittleness it is important to pay attention to the whole process of machining. In this case of the grinding, there is need to pay attention to the process from disc engagement to grind off the desired layer. The paper deals with an implementation of grinding of ceramic materials in context of determining of elements of cutting forces and the surface roughness evaluation. These are important aspects for determining the suitability of the cutting conditions and the possibility of their use in the production process.

Abstract: The article deals with the topic of 3D printing of pressure vessels and their testing. The main focus of the research was on a 3D model of the pressure vessel, which was originally designed for a student formula racing car project. The described virtual 3D model was designed with regard to 3D printing. The physical model was manufactured using several additive manufacturing technologies. The first technology was FDM using ULTEM 1010 material. The next technology was SLS (Selective Laser Sintering) using polyamide materials (PA3200GF and PA2220). The last technology was SLA (Stereolithography) using a polypropylene material (Durable). Experimental evaluation of the vessels was carried out by a pressure test, which verified the compactness of the 3D printed parts and their possible porosity. At the end of the article, a comparison of each printed model is made in terms of their final price and weight, together with pressure and thermal resistance.

Abstract: 3D printing technology enables the production of functional components in small quantities which can be used as end-use parts. The mechanical properties of the final product define its quality and determine its success or failure in a given application. One at the various additive manufacturing technologies - Fused Deposition Modelling is very often used due to its relatively low cost and the availability of 3D printers and thermoplastic materials. During the process, there are many factors that can affect the mechanical properties of the final product. The temperature of the extrusion nozzle and the layer thickness are two of the basic process parameters. The objective of this work is to investigate the effect of these two processing parameters on the final mechanical properties of the 3D printed samples from acrylonitrile butadiene styrene. Mechanical testing includes the tensile and flexural strength, as well as tensile and flexural modulus.