In this work, the problem of non-destructive testing on composite components with complex shapes for civil constructions and transport infrastructures is analyzed. In such applications at the state of the art main challenges are related with the inspection of thick sandwiches with low density cores (below 80 kg/m³) and curved panels. After a review of suitable non-destructive testing techniques, an original set-up for low frequency (100 kHz) ultrasonic inspection is proposed, which combines different solutions in through-transmission mode. The set-up is based on a hybrid configuration coupling a contact emitting probe with a non-contact air-coupled receiver. The use of a contact probe in emission is necessary to have enough energy to analyze thick components with low density core. The contact between probe and surface is made small (spot of 1 mm) and smooth using a spherical cap to increase lateral resolution at low frequency and to allow scan on irregular surfaces sometimes present in curved parts. To improve understanding this cap has been tested here also with a single probe in pulse echo mode. The non-contact probe in reception allows a better inspection flexibility on curved and thick components, where pulse echo is not feasible at all. The system is mainly developed for inspection after production in an industrialized production process, where through-transmission testing is possible. The analysis of results on two different samples (one thick sandwich with low density 40 kg/m³, 50 mm thick PUR core and one curved laminate panel) shows that the proposed methods can efficiently inspect construction composites of complex shape with satisfactory signal-to-noise ratio (usually SNR > 15 dB) and lateral resolution (2–3 mm).

This paper aims to evaluate the effect of carbon-based conductive recycled additions, i.e., recycled carbon fibres (RCF) and gasification char (GCH), on the mechanical, electrical, and durability properties of concretes. The obtained results show that the compressive strength of concrete is not affected by conductive additions, whereas electrical impedance, measured according to Wenner’s method, is significantly reduced (6%, 30% and 74% with RCF, GCH, and their combination, respectively) to the advantage of self-sensing properties. As durability is concerned, conductive additions slightly increase capillary water absorption, whereas they decrease chloride ingress through diffusion and do not significantly modify carbonation resistance.

This paper details the comprehensive activities conducted in a laboratory setting to assess the structural health monitoring (SHM) of prefabricated building envelopes. Integrating sensors into building components like curtain wall facades poses challenges but offers opportunities for monitoring structural health, requiring compliance with regulatory standards. The research investigates the possibility of defining a kit of conventional and multi-parameter sensors integrated within the building envelope to monitor its behavior during the performance test conducted. The kit of sensors also includes Fiber Optic Sensors for effectively monitoring building envelope behavior and structural integrity. In this context, the European project InComEss (H2020-GA862597) aims to define a stand-alone solution for SHM using Piezoelectric Energy Harvesting Systems (PE-EHS) for façade monitoring through FBG/FOS system. After analyzing the main façade structural stress, a series of FBGs, accelerometers, and force washers were integrated within a 1:1 scale façade prototype and tested in a laboratory following the test sequence parameters required by the curtain wall standard EN 13830. The data collected were analyzed with the aim of monitoring the façade behavior before and after the tests. The results show that the façade’s performance passed the assessing test criteria without reporting any damages. In addition, the outcomes demonstrated the effectiveness of the defined kit of multi-parameter sensors for the building envelope’s SHM.

This paper deals with the development of a measurement procedure to characterize anomalies, i.e. voids and defects, in four composite material (CM) samples. For this aim, four CM samples, each of them characterized by specific manufacturing techniques, have been analyzed. The first one (CM1) has Teflon defects, the second one (CM2) has undergone a low-degree manufacturing process and thus judged too porous at quality control, the third one (CM3) has passed the interlaminar shear strength (ILSS) test and so is expected to have a low-level of anomalies, unlike the fourth one (CM4), which has failed at ILSS test. An industrial X-ray computed tomography (CT) has been used to scan the CM samples and a specific image processing technique has been developed to measure the number and dimension of anomalies within them. The calculated amount of anomalies seems to be within the acceptable range identified in literature, always below 5%, showing the goodness of manufacturing process, and furthermore a threshold level of 0.09 mm has been statistically calculated to discriminate between voids and the other kinds of defects.

Speckle shearography is often used in the aerospace industry to detect defects in composite materials because it allows noncontact, full field, and fast measurements. However, despite this advantage, this nondestructive technique is still not widely established, due to its limitations in performing defect quantitative estimations. The main issue lies in the extrapolation of phase profile boundaries, which represent defect edges. In this paper, this was achieved by studying the multimodal distribution of a characteristic parameter, called structural intensity, which is the probability of finding a denser population of local maxima of wavelet coefficients at a given position and adding an adaptive threshold selection in the structural intensity distribution. Once the damage boundaries were detected, the defect dimensions were computed by subtracting the local shearing amount, which was defined by a circle detection code, from each coordinate in both Cartesian directions. The paper shows an improvement to the algorithms able to detect defect area and perform morphological estimation previously developed by the authors and an in-depth study of the parameters involved in these algorithms. This resulted in both a high accuracy (0.04%) revealed by the calibration process on a PVC test panel and a close morphological agreement with the ultrasound reconstruction of unknown defects in composite materials. Thanks to this improvement, shearography becomes a quantitative inspection technique that takes few minutes compared to ultrasound inspection of the same area, which may require up to an entire day.