Jiří Bobek

Impact Testing of H13 Tool Steel Processed with Use of Selective Laser Melting Technology

This paper deals with experimental determination of toughness, hardness and impact properties of AISI H13 (DIN 1.2344) tool steel which was manufactured using Selective Laser Melting (SLM) technology. The H13 is a chromium-based tool steel which is primarily used for hot working applications such as pressure casting moulds for automotive industry. Evaluation of toughness and impact properties are vital for reliable use of SLM-processed material, especially in the case of highly loaded structures. Mechanical tests were carried out on printed specimens, subjected to thermal treatment and proper data were evaluated. For better understanding of differences between conventionally produced and SLM-processed material, same mechanical tests were done even for hot-rolled H13 tool steel. SLM-printed material shows more brittle behaviour than conventionally made material. This is most probably caused by combination of H13 thermal properties and fast melting and solidification due to SLM processing.

Use of Composite Materials for FDM 3D Print Technology

This article deals with specific polymer composites modified for the Fused Deposition Modelling (FDM) which is a 3D print technology. These two phase systems involve thermoplastic matrix filled with natural fibres. The crucial demand of this progressive technology is put on the accuracy of the semi-product formed into the filament shape. To reach the smooth production of 3D prototypes the filament should have a constant diameter. In the article, individual steps of the polymer composite pelletization and following pre-processing and processing activities are described. Among these steps the extrusion of the filaments belongs and subsequent print test on “RepRap” device accompanied by optimization of building parameters. Tensile specimens were chosen for print with regard to maps mechanical properties of this newly developed material which was the final stage of this work. Tensile test curves were then compared with those graphs which can be found for the material produced by conventional technologies such as injection moulding.

New Silane and MAPP Coupling Agents as Natural Composites Production Systems Improvement

Still more and more applications using synthetic polymers find new material alternative in materials based on synthetic polymer filled with nature fibers mainly plant fibers. Not only in common applications but also in technical applications is possible to use nature fiber composites. But some additional modifications are necessary to perform to gain properties possible to use in technical applications. Mainly increasing adhesion between matrix and fibers is the most common intent of these additional operations. This paper deals with maleic anhydride based coupling agent and silane coupling agent effect in the polypropylene matrix and jute fiber composite and its mechanical properties. By using of silane coupling agents was achieved mechanical properties which are possible to compare with composites with glass fibers mechanical properties mainly in case of the flexural and tensile modulus and mainly was gained significant increasing of composite production system stability.

Computer Analysis of Polyolefins Produced with Injection Molding Process Using Physical Blowing Agents

The complexity of todays plastic parts as well as the costs, quality makes it necessary to recognize potential errors early, already in the development phase of parts and moulds. Therefore, computer analysis became requisite part of any preprocessing phases. Due to the continuous effort decrease product weight and price many new techniques were developed recently. One relatively new end very effective technique is production of light construction products with using foaming agents. The main aim of this paper is therefore focuses on verification of computer analysis of Microcellular injection moulding process using physical blowing agents for the most used group of polymers which are polyolefins.

Influence of Different Coupling Agent Type on Processibility and Applicability of Polymer Composites

The contribution deals with the processibility and applicability of polymer composite systems based on polypropylene matrix. The composites were filled with vegetable fibres (particularly the cotton fibres, coir fibres, hemp fibres and jute fibres) and the interface between the polymeric matrix and the natural fibres was modified using two types of coupling agents (the organosilane coupling agent and maleic anhydride grafted polypropylene). For evaluation of the final impact of all three phases presence on the processibility of the polymer composite the melt flow behaviour was analyzed (MFI analysis according to ISO 1133) for the filler concentration of 10, 20 and 30 wt. %. This study involves also the natural fibre surface profile analyses (based on SEM observation) and the applicability of created composite materials was determined using the heat deflection temperature (HDT analysis according to ISO 75).

Utilizing of inner porous structure in injection moulds for application of special cooling method

The article is focused on impact evaluation of controlled inner structure of production tools and new cooling method on regulation of thermal processes for injection moulding technology. The mould inserts with porous structure were cooled by means of liquid CO2 which is very progressive cooling method and enables very fast and intensive heat transfer among the plastic product, the production tool and cooling medium. The inserts were created using rapid prototype technology (DLSM) and they had a bi-component structure consisting of thin compact surface layer and defined porous inner structure of open cell character where liquid CO2 was flowing through. This analyse includes the evaluation of cooling efficiency for different inner structures and different time profiles for dosing of liquid CO2 into the porous structure. The thermal processes were monitored using thermocouples and IR thermal analyse of product surface and experimental device. Intensive heat removal influenced also the final structure and the shape and dimensional accuracy of the moulded parts that were made of semi-crystalline polymer. The range of final impacts of using intensive cooling method on the plastic parts was defined by DSC and dimensional analyses.

Mechanical Properties of Metal-Plastic Composite with Internal Fractal Shape Reinforcing Structure

This paper deals with mechanical properties research of innovative polymer multiphase metal and polymer composite materials consisting of matrix and isotropic or anisotropic oriented deterministic fractal shapes made by 3D printing. By creating of reinforcing internal structure consisting of deterministic fractal connected shapes is possible to gain unlimited mechanical properties directing. These fractal shapes - placed in multiphase system matrix – are significantly influencing whole material system mechanical properties mainly in case of stress on the limit of strength, proportional elongation on the limit of strength or tensile/ flexural modulus. Fractal shapes are also possible to properly locate, orient or shape modify according to potential material using with goal to gain maximal efficiency of fractal shapes occurrence. Producing of this multiphase system is realized by the help of 3D printing technology. Internal fractal shape structure is 3D printed from aluminium. This feature is in the next step over injected by polymer. So is possible to create any fractal shapes placed in polymer matrix which are by another technology unmanufacturable. Mechanical properties analyse is performed with respect to fractal shape type, fractal dimension, and fractal shape orientation.

Impact of Innovative Cooling System on Mechanical Properties of Moulded Parts

This article deals with the impact evaluation of utilization of innovative cooling system exploiting liquid carbon dioxide injected into injection mould. Process of heat transfer from the polymeric melt and final part solidification has a direct impact on creation of morphology structure of semi-crystalline thermoplastic materials and their ultimate mechanical properties. Usually the heat processes in the production tools are controlled by tempering channels where heat transfer medium circulates (oil, water tec.). This conventional way of cooling has some limitations that cause an uneven distribution of temperature fields on the part surface. Spot cooling system is one of unconventional cooling ways that increase the uniformity of temperature fields distribution on the part surface. This system utilizes the cooling potential of liquid CO2. For the purpose of this study the special shaped insert was designed that was modified both for conventional cooling and for spot cooling system. Flexural modulus very responsively reflects the changes of morphology structure formed by different cooling progressions of the plastic melt and was chosen as an evaluating criterion.

Adhesion Additive Influence on Polyamide Nanopolymer Composite Properties

In recent years there are efforts to use polymer nanofibers and their properties in polymer composites. The aim of such efforts is to develop composites with nanofibers fillers which would be able into a great extend to take advantage of any unique properties of polymer nanofibers. Such area of research belongs into the research project whose part is also to incorporate nanofibers and nanoparticles into composite with thermoplastic matrix. The important part of research represents also finding the suitable additives to ensure sufficient adhesion between filler and polymer matrix which is crucial for the final composite properties.

Two Component Parts Hardness Optimization Regarding Production Systems

This paper deals with optimization of mechanical properties mainly hardness and stiffness of flexible part of two component injection molded part regarding production systems. Optimization is performed on two material combinations: Thermoplastic - thermoplastic elastomere and thermoplastic - silicone. Polymers used for two component part are suitable for medical applications.