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This paper presents a study focused on sandwich structures as well-known train construction materials that are composed of two thin and rigid face sheets and a thick, low-density core material. For trains, the wheel-rail interface is the main source of noise, and the wheel-rail roughness, especially in the presence of rail corrugation, is the main excitation source transmitted to the interior and area for passengers. The purpose of the study is to optimize the acoustic properties of a composite sandwich panel used for train floors and walls. Sound absorption coefficient (α), noise reduction coefficient (NRC) and Transmission loss (TL) evaluations have been implemented and experimentally validated on a typical sandwich material used for trains. The opportunity to use a different material can be concretely calculated and modified for critical frequency ranges. Sound transmission loss levels of the structural components as the floor and wall of the train body, which are required of producers and customers, were tested in acoustic laboratory and acoustic devices according to ASTM and ISO standards. It is demonstrated that, for honeycomb and cork sandwich panels, acoustic response is not sensitive to cell size. For foam core sandwich panels, it is observed that different compositions with thin layers are effective in the frequency range of 50-1000 Hz. © 2020 Manufacturing Technology., Operational Program Research and Development for Innovations; European Regional Development Fund (ERDF); Centre of Polymer Systems [CZ. 1.05/2.1.00/03.0111]; Ministry of Education, Youth and Sports of the Czech Republic Program NPU I [LO1504]; TBU [IGA/FT/2016/013, IGA/FT/2017/002, IGA/FT/2017/011]; Ministry of Education, Youth and Sports of the Czech Republic [LO1504]; European Regional Development Fund [CZ. 1.05/2.1.00/19.0409]

Presented research paper is focused on the development of carbon fibre wheel. Considering development and construction of wheels for the automotive and motorcycle industry, low weight is one of the most significant factors. In the case of rotating components, the imbalance of the assembly is a problem. This fact affects handling of the vehicle or wheel behavior under the load, for example in the point of turning, acceleration or drive on damaged road. Determination of the most appropriate material composition (sequence) is primarily the main problem of composite material application. Correct design of material composition and also lay-up diagram is determined by material characteristics and strength requirements. A suitable solution is in the application of a group of input material structures creating hybrid composite. Specific combination of various input materials (aluminum ring, 3D printed plastic honeycomb core and carbon fibre composites) guarantees and ensures the fulfilment of the strength requirements which are determined during each particular application. The main aim of presented paper was to design material composition and shape of carbon fibre wheel that were subsequently verified by successful manufacturing process.

A combination of mechanical and chemical treatments was utilized to modify the surface textures of copper and duralumin inserts in order to enhance the adhesion at the metal–polymer interface and provide an adhesive joint with a high loadbearing capacity. Pretreatment of the surfaces with sandblasting was followed by etching with various chemical mixtures. The resulting surface textures were evaluated with a scanning electron microscope (SEM) and an optical confocal microscope. Surface geometry parameters (Sa, Sz, and Sdr) were measured and their relationships to the adhesion joint strength were studied. It was found that the virgin and purely mechanically treated inserts resulted in joints with poor loadbearing capacity, while a hundredfold (duralumin) and ninetyfold (copper) increase in the force to break was observed for some combinations of mechanical and chemical treatments. It was determined that the critical factor is overcoming a certain surface roughness threshold with the mechanical pretreatment to maximize the potential of the mechanical/chemical approach for the particular combination of material and etchant. © 2021 by the authors. Licensee MDPI, Basel, Switzerland., RP/CPS/2020/003; IGA/FT/2021/010, Ministry of Education, Youth and Sports of the Czech Republic DKRVO [RP/CPS/2020/003]; TBU [IGA/FT/2021/010]

Jute fabric is well-known reinforcing material in composite science, however, there is a necessity to treat these fabrics to reduce moisture uptake and improve properties. Nevertheless, every modification increases the cost and reduces the possible applications. Presented research deals with an investigation of possibility to use untreated jute in various fabric weight as a reinforcing material in sandwich structures facings. Untreated jute reinforcements and two types of cork cores were saturated in one step during vacuum infusion creating a lightweight sandwich composite. All samples were mechanically tested in three-point bending test. Experimental results showed the most appropriate material combination and produced sandwich structure are proposed for design applications.

Honeycomb composite structures widely used in aviation are sturdy and light-weight but they may accumulate water from the atmosphere during aircraft operation. The presence of water in honeycomb cells leads to a higher airplane mass and excessive corrosion of aluminum cores, while the frozen water endangers panel integrity. This work describes the use of infrared thermography for detecting water trapped in aviation honeycomb cells.

Presented research paper deals with possibilities of replacement of conventional mold materials by new, unconventional. Traditionally, laminate, wood or gypsum molds (in the case of small production series) are used for the production of composite parts. Furthermore, milled aluminum molds are conventionally used only for mass production. Due to this, thin metal sheet was prepared as an unconventional production mold for manufacturing of motorbike facing part. Vacuum bagging using prepared one side mold was chosen as the most appropriate technology. Normally, two facing sides are not commonly manufactured using this technology. Because of this, possibilities to create two facing sides at areas that are not in contact with mold itself were investigated. Presented results can help manufacturing companies with their production and considerably decrease manufacturing costs due to not necessity to use two side molds.

In this work the mechanical performance of various sandwich constructions with respect to core material were experimentally evaluated. Sandwich structures were made of glass prepreg and three types of plastic core using vacuum bagging, technology traditionally used for production of parts for transport industry. The aim of this study is to analyze the impact of the core material type and its thickness on bending behavior at different environmental temperatures. Moreover, the effect of core layers compared to one layer core of same thickness was determined. Conducted research provided useful information of bending behavior and showed specific failure modes of individual sandwich constructions.

This paper presents an experimental investigation of mechanical and impact properties of carbon and Kevlar-glass composites prepared from pre-impregnated materials. Namely, flexural performance in three-point bending at different temperatures is evaluated. Moreover, Charpy impact test and low-velocity impact test are also conducted for classification of impact properties and character of rupture. These all properties are important for material design of sport bike rims and many sport and other applications.

In the present work, mechanical properties and bending stiffness of composite structures with ribs are studied. The aim of this work was making ribbed composite structures in one step, where the ribs are inserted between glass reinforcement of composite system. In practice, the ribs on the composite structure (final products) are glued, but where there is a lower strength (according to the type of surface, the surface treatment, suitable bonding technology, the type of glue) and the adhesives are relatively expensive. The production of samples was used technology of vacuum infusion under flexible foil.

In the present work, mechanical properties of prepreg carbon composites are studied. Five types of composite samples with different number of layers and prepreg material corresponding to material composition used for carbon rims are manufactured by compression molding. Prepared composites are tested and compared with respect to flexural strength and modulus. Furthermore, impact performance using Charpy impact test is also evaluated.

This research paper deals with an experimental investigation of mechanical properties of prepared composite panels. Flexural behavior in three-point bending test is measured. Composites are prepared in order to satisfy requirements for transport industry. Totally, three material compositions are tested with different multiaxial reinforcing fabric and polyester resin. All samples are produced by low-pressure vacuum infusion mainly used for large-scale composite parts. Furthermore, fire resistance of prepared laminates is tested and appropriate classification into corresponding categories is also done. Experimental results proved suitability of prepared glass fiber composites for application in transport industry.

This research paper deals with an investigation of the mechanical properties of sandwich structures consisting of High Pressure Laminate facing layers (HPL) and various types of cores that are produced by vacuum bagging technology. These materials are connected with different adhesive layers and quality of connection to individual materials is evaluated. Moreover, prepared sandwich structures are tested in three-point bend. Based on the results, suitable combinations of individual materials are proposed for sandwich structures with regard to the quality of the adhesive bonding.

The paper provides experimental results from tensile and flexural tests of HPL composites. Mechanical properties of HPL laminates from four worldwide producers (Fundermax, Polyrey, Abet and Rexin) are compared. Composites are compared due to their stiffness and strength, both tensile and flexural. The exterior environment effect on mechanical behaviour of composites in service load conditions are presented too.

This research paper deals with an investigation of the influence of honeycomb core compression on the mechanical properties of sandwich structures. These structures consist of prepreg facing layers and two different material types of honeycomb and are produced by modified compression molding called Crush-Core technology. Produced structures are mechanically tested in three-point bending test and subjected to low-velocity impact and Charpy impact test.

Sandwich construction is a composite material structure combining low weight, high strength and good dynamic properties. Typically a sandwich composite consists of three main parts: two thin, stiff and strong facing layers separated by a thick, light and weaker inner core. The faces are adhesively bonded to the core to obtain a load transfer between the components. By this way the properties of each separate component is utilized to the structural advantage of the whole assembly leading to a very high stiffness-to-weight and high bending strength-to-weight ratio. As a result sandwich components achieve the same structural performance as conventional materials with less weight. The material characterization described in the paper is aimed at the structural design of the end cub for a high speed train made of composite sandwich materials. A sandwich structure was considered, made of glass fibber polyester face sheets with a polymeric foam core. Initially, the material properties and the rate sensitivity of the skin and core materials were investigated through a series of static and quasi-static tests. Static and dynamic impact tests were then run on the sandwich structure. For all materials tested, no significant strain-rate effects were observed over the range of test conditions investigated in the study. Results show that the structural response of the sandwich depends primarily on the strength properties of the foam core material. Sandwich peel test is intended for determining the comparative peel resistance of adhesive bonds between facing and cores of sandwich constructions tested under specified test conditions. One method, the climbing drum peel method, is most applicable when the peeled facings are relatively thin, but it can not be applicable in tested composite structures. Peel resistance was tested by modified experimental setup.

This paper deals with the flexural stiffness of sandwich structures based on fiberglass and polymeric foams. The influence of geometrical and material parameters on the resulting effective flexural stiffness of the sandwich structure is being studied experimentally, analytically and using FEM models. The effective elasticity module of the sandwich-structured element is being studied and it’s theoretical and model dependencies on the stiffness of the foam core are being investigated. These dependencies are then compared with experimentally observed values. This study shows it is necessary to pay special attention to the issue of flexural stiffness of walls when designing sandwich shell products in order to prevent possible failures in the practical applications of these types of structures. © 2016 Trans Tech Publications, Switzerland.

Composite materials used in the transport industry and also in other sectors must have a certain degree of flame resistance. For this purpose, commonly used flame retardants are based on halogen compounds in the liquid state or aluminum hydroxide in the solid state. Solid flame retardants have a negative effect on the processing and mechanical properties. Low viscosity and rapid wettability of fibers are very important, especially in an resin transfer molding (RTM) process. Therefore, a new advanced matrix system based on phosphorus flame retardants was developed. The flame resistance and mechanical properties of the composite materials produced from the new resin system were tested. Furthermore, the processing parameters and tests are described in the article., Ministry of Industry and Trade of the Czech Republic [FR-T13/433]; TBU in Zlin [IGA/FT/2015/001]

This research paper deals with an investigation of the flexural properties measured in a three-point bending test depending on the type and number of the E-glass prepreg layers applied to the facing sides of the resulting sandwich structure used for floor panels in the transport industry. The values of the low-cycle fatigue were measured according to the values of the flexural strength obtained from the static test. Cycling was performed at (70, 60 and 50) % values of the ultimate flexural load. Moreover, a decrease in the flexural strength and stiffness depending on the number of cycles was also studied. For the production of samples, one type of aluminum honeycomb core and various phenolic prepregs with different numbers of layers were used. These samples were produced with two, in practice commonly used methods - compression molding and vacuum bagging. The measured results show that the production technology has a certain influence on the mechanical behavior in bending and the fatigue life of sandwich structures. The experimental results proved that the type of prepreg (defined by the reinforcing fabric and the amount of resin) and the number of layers also affect the properties of these structures. All the obtained results provide useful information for designing the sandwich structures for the transport industry., TBU in Zlin [IGA/FT/2015/001]; Operational Program Research and Development for Innovations; ERDF; national budget of the Czech Republic, within the framework of project Centre of Polymer Systems [CZ.1.05/2.1.00/03.0111]

This essay aims to describe technology and mold design for production of hollow composite parts like carbon rims or sport rackets. Tested materials correspond to those used for composites in sport applications. Production technology called inflatable bladder molding (IBM) is describe with respect to used material, molds and process parameters. Furthermore, prototype mold for verification of flexible bladder, inner pressure and curing conditions is constructed and tested. Construction design of manufacturing mold together with description of technological steps is proposed.

Sandwich composites are well known for many years and its place among the construction materials have they deserved mainly due to very good mechanical properties related to their weight. These materials have been a subject for many researches, but very few of them were focused on the behavior of curved constructions in bend with respect to their specific shape (curvature). With increasing number of new materials and resulting possible material combinations, it is necessary to characterize performance of new prepared structures and also evaluate the effect of a shape on the behavior of sandwich constructions with regard to their material composition. Presented paper deals with an investigation of flat and curved beams of sandwich structures, which correspond by their material composition to those, used in transport industry. Specifically, the influence of curvature size on a change of bending properties of structures with specific material composition compared to flat constructions is evaluated. This influence is also investigated in terms of specimen clamping and type of bending test. Obtained results showed that properties of sandwich structures are dependent not only on size of curvature, bud also on core thickness. Moreover, these results can help designers, constructers or technologists with design, dimensioning or production of these materials for specific applications.

In the production of polymer parts, great emphasis is placed on the quality of polymer product in terms of dimensional accuracy and optimally surface quality. Achievement of high surface quality of injection molded products correlate to the high surface quality of core or cavity in injection molds. This surface is copied during injection of polymer material. The kind of polymer material and its rheological properties can strongly influence this surface copying. Production of cores and cavities takes in the manufacturing process a considerable part of time, where some finishing technologies are more economically and time consuming than other processes. Thus, it is necessary to choose an appropriate finishing operations considering cost of injection mold, which is reflected in future price of polymer product. This paper experimentally examines the influence of the surface quality of mold cavities and rheological properties of polymer on the surface quality of injection molded product.

This article is focused on influence of finishing operations on the surface quality of polymer products. Finishing operations are the necessary part in the production of injection mold cavities. Surface quality of cavities is reflected to quality of future polymer products. Therefore, it is very important to use appropriate finishing operations and its technological conditions from the aesthetic point of view. However, it is not always necessary to use time consuming and most expensive finishing operations, because the polymeric products are not able to achieve similar surface quality as cavities. The different surface quality of injection molded parts can be also expected using various supramolecular structure of polymer (amorphous, semicrystalline). Supramolecular structure of polymer determines the future properties of product as well as the distribution of the individual macromolecules in the polymer chain. Divergent distribution may result to achievement of different surface quality of injection molded parts. This research is focused on finding an influence of supramolecular structure of chosen polymer on the surface quality of polymer product.