The automotive industry is one of the biggest consumers of polymer composites. Aside from good mechanical properties, polymer composites have low mass, which positively affects the overall vehicle weight reduction and improves energy efficiency. Although polymer composites are used in various vehicle components, this paper focused on the application in vehicle bumper production. Two different composite plates with hybrid fiber layup were made; the first plate with a combination of glass and carbon fibers and the second with carbon and aramid. For comparison, and as a cheaper variant, a third plate was made only with glass fibers. In the first two plates, epoxy resin was used as the matrix, while in the third plate, polyester resin was used. Polyurethane memory foams of different densities (60, 80, 100 kg/m3) and thicknesses (10, 15, 20 mm) were used as impact force energy absorbers. With the factorial design of experiments, it was found that the thickness of the memory foam was the main influence factor. Without the use of memory foam, the hybrid composite, made of glass and carbon fibers, showed the highest energy absorption, while with the use of foam, the highest energy absorption was achieved with the glass fiber composite. Without the memory foam, the impact force measured on the glass/carbon hybrid composite was 9319.11 ± 93.18 N. Minimum impact force to the amount of 5143.19 ± 237.65 N was measured when the glass fiber composite plate was combined with the memory foam. When using memory foam, the impact force was reduced by 30–48%, depending on the type of composite used.
1 December 2020 in Tehnicki vjesnik - Technical Gazette
The composite lighting poles are filament wound GRP tapered tubes with a variable wall thickness across the length. In this study, the effective flexural properties of GRP poles have been determined, experimentally and theoretically. Cantilever bending tests were performed on full-scale GRP tubes and the effective flexural modulus was calculated from the initial slope of the flexural stress-strain curve based on the classical beam theory. The results show that the strain range corresponding to the linear behaviour is the same as under three-point and four-point tests with smaller specimens. Unlike other methods, the proposed method considers the variation of the cross-sectional properties across the pole length. The effective properties of GRP tubes were further determined considering the orthotropic and unsymmetrical layup of the wall segment. A sensitivity analysis was performed at the lamina as well as the laminate level in order to evaluate the influence of material properties of the matrix and the fibres, the amount and orientation of the fibres as well as the layer thickness. Finally, the effective (replacement) flexural modulus of a filament wound tube was determined based on the classical lamination theory and compared to experimentally determined values. It was concluded that the replacement flexural modulus is a matrix dominated property highly influenced by the fibre volume fraction.
The idea of the project was to find a conceptual design of a multi-functional smart orthosis for wrist fixation. The application of additive technologies presents the potential in designing a customised orthosis for every patient individually. By using pre-generated 3d models of various hand shapes it is possible to prepare models for several shapes and sizes of forearms and hands. The conceptual design provides a possible solution for a two-part orthosis bound around the forearm and a modular extension to stabilize the wrist without additional compression. The multi-functionality occurs with the development of a small pre-defined electronic plate located in the bottom part of the orthosis. The temperature and heart rate are constantly monitored and displayed wirelessly on a smartphone. The target group are the patients active in sports or patients with minor injuries. Moreover, the orthosis can be used for body temperature and heart function monitoring during recovery period.