Stefano Perilli

Ceramics and defects

The feasibility of square-pulsed thermography nondestructive testing for the detection of defects in one ceramic material sample has been carried out by finite element (FE) analysis. In particular, a ceramic plate containing defects of different diameters, depths, locations, nature, and shapes has been numerically investigated by means of Comsol® Multiphysics computer program, taking into account the results coming from both a MATLAB™ script and the infrared thermography (IRT) technique. Indeed, the FE method simulates through a 3D model the heat transfer process induced into the ceramic material by two halogen lamps that have been applied in order to provoke an optimum thermal stress. Moreover, further defects like cracks arose beneath the surface of the plate due to the shrinkage process, have been discovered, and contrasted using a non-usual segmentation algorithm that when correlated in the time to IRT data simulates the thermo-elastic effect. Following the non-direct procedure proposed, both the depth of each defect and its main dimensions have been retrieved into a satisfactory accuracy.

Optical and Mechanical Excitation Thermography for Impact Response in Basalt-Carbon Hybrid Fiber-Reinforced Composite Laminates

In this paper, optical and mechanical excitation thermography was used to investigate basalt-fiber-reinforced polymer, carbon-fiber-reinforced polymer, and basalt-carbon fiber hybrid specimens subjected to impact loading. Interestingly, two different hybrid structures including sandwich-like and intercalated stacking sequence were used. Pulsed phase thermography, principal component thermography, and partial least-squares thermography (PLST) were used to process the thermographic data. X-ray computed tomography was used for validation. In addition, signal-to-noise ratio analysis was used as a means of quantitatively comparing the thermographic results. Of particular interest, the depth information linked to Loadings in PLST was estimated for the first time. Finally, a reference was provided for taking advantage of different hybrids in view of special industrial applications.

Numerical and experimental analyses for natural and non-natural impacted composites via thermographic inspection, ultrasonic C-scan and terahertz imaging

In this paper, thermographic inspections, ultrasonic C-scan and terahertz imaging were used to detect damages caused by impacts in natural, non-natural and hybrid composites. In particular, different hybrid structures were used. In some samples, numerical simulations were performed to predict the damage. A comparison of the results based on experimental and simulated experiments were afterwards conducted with the aim to explore the inspection capability of each technique.

Eddy current pulsed thermography for ballistic impact evaluation in basalt-carbon hybrid composite panels

In this paper, eddy current pulsed thermography was used to evaluate ballistic impact damages in basalt-carbon hybrid fiber-reinforced polymer composite laminates for the first time, to our knowledge. In particular, different hybrid structures including intercalated stacking and sandwich-like sequences were used. Pulsed phase thermography, wavelet transform, principle component thermography, and partial least-squares thermography were used to process the thermographic data. Ultrasound C-scan testing and X-ray computed tomography were also performed for comparative purposes. Finite element analysis was used for validation. Finally, an analytical and comparative study was conducted based on signal-to-noise ratio analysis.

A multi-technique nondestructive approach for characterizing the state of conservation of ancient bookbindings

The aim of this work is to evaluate the potentiality of a multi-technique nondestructive approach for characterizing the state of conservation of precious bookbindings. In particular, the bookbinding of an ancient book dating back nineteenth century was inspected by infrared thermography, near-infrared reflectography and transmittography, digital speckle photography, holographic interferometry, and proton magnetic resonance relaxometry. Data were processed by different and innovative methodologies, among which, a calibration procedure of the camera for correlation analyses based on specklegrams. The results were compared, showing a promising synergy for the diagnostic purposes, on the basis of the relationship between structure, properties, and uses of the analyzed materials.