Papers by Author: Federica Trovalusci

Abstract: The possibility to produce new components using reclaimed non-woven carbon fabric has been investigated. Being composite waste production increased, different strategies and technologies for recycling are developing to face criticalities and economic aspects related to their disposal. In this scenario, CFRP laminates with recycled carbon fiber and epoxy vinyl ester resin have been fabricated by Resin Infusion under Flexible Tooling (RIFT) and mechanical characterization has been performed to investigate their behavior under tensile, flexural and macro-indentation loads.

Abstract: In this study, an easy and innovative technique for laser welded butt joint characterization is proposed. AISI 304 sheets, 1.25 mm in thickness, were welded in the butt configuration by means of a high power diode laser (HPDL). Different combinations of the process parameters were considered. For each combination, during the process different thermal cycles were induced in the material generating heat affected zones, which were subsequently tested by the double indentation test method. This test was performed on the sheets by means of two co-axial flat indenters, 1 mm in diameter, made of tungsten carbide (WC); the upper indenter penetrates at a constant rate (0.1 mm/min) into the material, whereas the lower indenter acts as a support. On each side of the seam, 10 indentations were performed at fixed positions with different distance from the centre of the seam, to obtain a load map correlated to the mechanical properties. By comparing the maps of the different laser welded joints, a clear effect of the laser scan speed and the power was found. Furthermore, a wake field effect is recognizable, in fact the loads are symmetric as regards the seam, and there is a clear trend in the direction of the laser path. These results confirm the effectiveness of this method, which is also suitable for on-line application because a very small indentation is left on the sheet.

Abstract: In the present study the use of diode laser for stainless steel aesthetic welding is considered. In fact the surface smoothness of the weld bead, attributed to the mode stability of the laser system, suggests its application for aesthetic weld joint. The aims of this work were to: define a process map, based on an aesthetic criterion; mechanically characterize the weld joints (by Vickers micro-hardness and tensile test); analyse the surface of the specimens in terms of roughness. Moreover, gas tungsten-arc (TIG) weld joints were carried out and analogously tested to make a comparison with the diode laser results. Good aesthetic butt joints were obtained with diode laser welding. The same results were found working with constant power speed ratio (i.e. constant fluence). Comparison between TIG and Laser Beam Welding (LBW), showed no significant difference in roughness, while ultimate tensile load was higher for TIG welding. The differences in joint strength depend on the different cross-sectional area and on the extension and microstructure of the base metal, heat-affected zone and melted zone. However, diode laser technology allows to obtain smaller bead size.