Patrizio Capoluongo

A magnetic field sensor based on the integration of a fiber Bragg grating (FBG) with a magnetic shape memory alloy (MSMA) is demonstrated. MSMA is a new kind of material able to show extremely large strains in response to a magnetic field. Moreover, differently from classical shape memory alloys, which are actuated by temperature, MSMAs normally show quite fast responses. In this brief, the basic features of the proposed device are illustrated, and field range and sensitivity of the device are… Visualizza altro

A magnetic field sensor based on the integration of a fiber Bragg grating (FBG) with a magnetic shape memory alloy (MSMA) is demonstrated. MSMA is a new kind of material able to show extremely large strains in response to a magnetic field. Moreover, differently from classical shape memory alloys, which are actuated by temperature, MSMAs normally show quite fast responses. In this brief, the basic features of the proposed device are illustrated, and field range and sensitivity of the device are also discussed. Moreover, comparison with Terfenol-based FBG sensor performances is reported showing results with a sensitivity (DeltalambdaB/lambdaB)/(DeltaH/Hm) of 1.81middot10-4, where lambdaB is the Bragg wavelength and Hm the mean magnetic field in the considered range Meno dettagli

A critical issue in practical structural health monitoring is related to the capability of proper sensing systems integrated within the host structures to detect, identify, and localize damage generation. To this aim, many techniques have been proposed involving dynamic measurements such as modal analysis, acoustic emission, and ultrasonics. This paper relies on the use of embedded fiber Bragg grating sensors for performing an experimental modal analysis on a wing of an aircraft model. Time… Visualizza altro

A critical issue in practical structural health monitoring is related to the capability of proper sensing systems integrated within the host structures to detect, identify, and localize damage generation. To this aim, many techniques have been proposed involving dynamic measurements such as modal analysis, acoustic emission, and ultrasonics. This paper relies on the use of embedded fiber Bragg grating sensors for performing an experimental modal analysis on a wing of an aircraft model. Time domain response of the embedded fiber-optic sensors induced by hammer impacts were acquired and transformed into the frequency domain. Using a classical technique based on the frequency transfer function, the first displacement and strain mode shapes of the wing have been retrieved in terms of natural frequencies and amplitudes. Experimental results confirm the excellent performances of this class of sensing devices to determine the modal behavior within complex structures compared with conventional accelerometer-based detection systems Meno dettagli

A partially embedded chirped fiber-Bragg grating (FBG) has been used to monitor the strain build up during nonisothermal curing of a model thermoset resin. The particular feature of the spectrum of a linearly chirped and strongly apodized FBG to encode position along the sensor has been used to simultaneously measure temperature and strain during the cure cycle of an epoxy-based polymer. In particular, the embedded part of the grating allows the monitoring of temperature and processing strain… Visualizza altro

A partially embedded chirped fiber-Bragg grating (FBG) has been used to monitor the strain build up during nonisothermal curing of a model thermoset resin. The particular feature of the spectrum of a linearly chirped and strongly apodized FBG to encode position along the sensor has been used to simultaneously measure temperature and strain during the cure cycle of an epoxy-based polymer. In particular, the embedded part of the grating allows the monitoring of temperature and processing strain while the rest of the sensor is sensible to temperature variation only. A new self-temperature referenced sensor system has been successfully tested in an operative condition where usually thermomechanical loading are simultaneously active. The onset and progression of gelification, as well as the residual processing strain, have been experimentally measured Meno dettagli

Cooling down from the equilibrium state at different rates reveals the dynamic behavior of glass forming materials. In particular, the dependence of the glass transition region on the cooling rate, q is commonly agreed to contain information regarding the activation energy of the relaxation time, τ. In this work experimental and theoretical aspects of such a relationship have been highlighted. Experimentally, the glass transition zone of amorphous polystyrene films has been investigated over… Visualizza altro

Cooling down from the equilibrium state at different rates reveals the dynamic behavior of glass forming materials. In particular, the dependence of the glass transition region on the cooling rate, q is commonly agreed to contain information regarding the activation energy of the relaxation time, τ. In this work experimental and theoretical aspects of such a relationship have been highlighted. Experimentally, the glass transition zone of amorphous polystyrene films has been investigated over two decades of cooling rate (0.5–50 K/min) by using refractive index measurements. The shift of the glass transition temperature and the broadening of the transition zone at increased cooling rate have been characterized. Theoretically, the cooling experiments have been simulated within the integral formulation of the Kovacs–Aklonis–Hutchinson–Ramos (KAHR) model using the Vogel temperature dependence for the relaxation time. The Frenkel–Kobeko–Reiner equation, τq = constant, provided the needed relationship between the experiments and the theory, enabling the evaluation of the relevant parameter of the kinetic model, i.e. the Vogel activation energy and the zero configurational entropy temperature, from the shift of the glass transition temperature with cooling rate Meno dettagli