Application of martensitic SMA alloys as passive dampers of GFRP laminated composites

This paper describes the application of SMA (Shape Memory Alloy) materials to enhance the passive damping of GFRP (Glass Fiber Reinforced Plastic) laminated composite. The SMA has been embedded as reinforcement in the GFRP laminated composite and a SMA/GFRP hybrid composite has been obtained. Two SMA alloys have been studied as reinforcement and characterized by thermo-mechanical tests. The architecture of the hybrid composite has been numerically optimized in order to enhance the structural damping of the host GFRP laminated, without significant changes of the specific weight and of the flexural stiffness. The design and the resultant high damping material are interesting and will be useful in general for applications related to passive damping. The application to a new designed lateral horn of railway collector of the Italian high speed trains is discussed

Application of martensitic SMA alloys as passive dampers of GFRP laminated composites

This paper describes the application of SMA (Shape Memory Alloy) materials to enhance thepassive damping of GFRP (Glass Fiber Reinforced Plastic) laminated composite. The SMA has been embeddedas reinforcement in the GFRP laminated composite and a SMA/GFRP hybrid composite has been obtained.Two SMA alloys have been studied as reinforcement and characterized by thermo-mechanical tests. Thearchitecture of the hybrid composite has been numerically optimized in order to enhance the structural dampingof the host GFRP laminated, without significant changes of the specific weight and of the flexural stiffness. Thedesign and the resultant high damping material are interesting and will be useful in general for applicationsrelated to passive damping. The application to a new designed lateral horn of railway collector of the Italianhigh speed trains is discussed

Zeeman splitting of excited boron states in p-Ge

The photothermal spectrum of shallow acceptors in p-Ge has been investigated at various magnetic field strengths up to 5.6 T at a temperature of 7.5 K by FIR-Fourier-spectroscopy. From the observed Zeeman splittings of the excited states of the boron acceptor the coefficients of the linear and quadratic field dependence have been evaluated andg-factors of theD-,C- and theG-transitions have been determined based on a standard group theoretical approach

Properties of aluminium alloys produced by Selective Laser Melting

Analysis of peculiar properties offered by Al alloys produced according to additive manufacturing techniques, specifically by Selective Laser Melting (SLM), is carried out. Two alloys are considered, derived by casting (AlSi10Mg) and by wrought (ENAW 2618) applications. The SLM processed samples are investigated considering their microstructural and mechanical properties after SLM and compared to cast and wrought counterparts. A strong microstructural refinement induced by SLM processing is observed for both alloys, resulting in excellent hardness properties. Investigation on integrity of samples revealed that smallsize microvoids and unmelted regions could be present in SLM parts

Composito in fibra di vetro con inserti di CuZnAl a memoria di forma per applicazioni ad alto smorzamento

In questo lavoro è proposta la realizzazione e caratterizzazione di un materiale composito, in cui la leggerezza della struttura in fibra di vetro viene combinata alla capacità di smorzamento di inserti in lega a memoria di forma (SMA) a base rame, per la riduzione delle vibrazioni in sistemi meccanici. Gli inserti in SMA sono costituiti da due sottili lamine di CuZnAl, tagliate mediante tecnologia laser secondo una geometria ottimizzata per migliorare l’adesione tra l’elemento metallico e la fibra di vetro. Lo studio proposto valuta dapprima l’effetto della lavorazione laser sulla trasformazione martensitica e sulle proprietà di smorzamento del materiale SMA e successivamente propone misure di smorzamento di vibrazioni flessionali sul composito realizzato, e su campioni analoghi privi dell’elemento SMA. Dall’analisi di queste ultime prove è possibile concludere che l’introduzione della lega a memoria di forma consente di migliorare le capacità di smorzamento del materiale composito, per l’utilizzo in sistemi meccanici

Simulated and Experimental Damping Properties of a SMA/Fiber Glass Laminated Composite

In this article, an advanced laminated composite is developed, combining the high damping properties of shape memory alloy (SMA) with mechanical properties and light weight of a glass-fiber reinforced polymer. The composite is formed by stacking a glass-fiber reinforced epoxy core between two thin patterned strips of SMA alloy, and two further layers of fiber-glass reinforced epoxy. The bars of the laminated composite were assembled and cured in autoclave. The patterning was designed to enhance the interface adhesion between matrix and SMA inserts and optimally exploit the damping capacity of the SMA thin ribbons. The patterned ribbons of the SMA alloy were cut by means of a pulsed fiber laser source. Damping properties at different amplitudes on full scale samples were investigated at room temperature with a universal testing machine through dynamic tension tests, while temperature dependence was investigated by dynamic mechanical analyses (DMA) on smaller samples. Experimental results were used in conjunction with FEM analysis to optimize the geometry of the inserts. Experimental decay tests on the laminated composite have been carried out to identify the adimensional damping value related to their first flexural mode