Soňa Rusnáková

Manufacturing and Mechanical Characterization of Bio-Based Laminates and Sandwich Structures

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.

Artificial Neural Network Modelling of Glass Laminate Sample Shape Influence on the ESPI Modes

The present work is devoted to the applications of artificial neural networks (ANN) for material design prediction. We have investigated the dependence of the generated mode frequency as a function of a sample thickness and a sample shape of glass laminate samples by electronic speckle interferometry (ESPI). The obtained experimental results for differently shaped (thickness, canting and rounding) glass laminate samples are compared with those of ANN. The coincidence of both experimental and simulated results is very good.

The Limits of Vacuum Infusion Technology during the Production of Filled Polymer Composite Systems

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.

Optimization of the Material of External Fixator with FEM Simulation

Patients and surgeons with tibia fracture using external fixator are worried about a higher weight of metal fixator´s construction and therefore also poor manipulation ability with this tool [1]. During the last few years the bone tissue engineering has improved significantly and along with that also material development has increased [2,3]. Therefore patients requirements can be achieved by optimizing the material composition of this product. The main objective of this research is a weight reduction by material and design changes of the external fixator. Another aim is the evaluation of the final model. The model of innovative fixator was created and also computed in software CATIA V5-6 using finite element method simulation. Appropriate forces were applied and the simulation was performed. Results of FEM simulation indicate that the final weight of complete product declined significantly after application of carbon-fiber composite. Test results also suggest that the rigidity and the stability of complete fixator are safe. Hence this research describes that application of carbon fiber composite into the external fixator design is an important improvement of the external fixator.

Preparation and Dynamic Mechanical Analysis of Glass or carbon Fiber/Polymer Composites

Nowadays, glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) composites are broadly used so it is essential their properties to be explored in depth. In this study, GFRPs and CFRPs were produced by vacuum bag oven method and their viscoelastic behaviour at elevated temperatures was investigated. In particular, by Dynamic Mechanical Analysis experiments properties such as storage modulus, loss modulus, tanδ and glass transition temperature were determined. The results showed that, apart from a very small increment in the low temperatures in some of the compounds, as the temperature increases the storage modulus of the composites decrease while the composite containing unidirectional glass fibers in longitudinal direction and 34% percentage of matrix achieved the higher storage and loss modulus. Furthermore, as the unidirectional fibers change direction from transverse to longitudinal the GFRPs exhibit much higher storage and loss modulus.

Detecting Water in Composite Sandwich Panels by Using Infrared Thermography

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.

On Flexural Stiffness of Polymer Sandwich Walls

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.

Analysis of Mechanical and Impact Properties of Prepreg Composites under Elevated Temperature

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.

An Experimental Analysis of Bending Behavior of Sandwich Constructions for Transport Industry

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.

Experimental Characterization of Multiaxial Glass Laminates for Front End Cab

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.