Conference Agenda

The present work aims at studying voids detection in bonded metal/composite or concrete/composite assemblies using numerical simulations of Acousto-Ultrasonic (AU). The assemblies are made of a steel or concrete substrate and a unidirectional composite laminate bonded with an epoxy adhesive. This study allows assessing experimentally and numerically the sensitivity of AU technique to voids within the joint. Three-dimensional FE models are developed to simulate the influence of voids and sensor location on the recorded signal. Both the relative location of the sensor with respect to the defect epicentre and the kind of receiver sensor are thus fundamental for defect detection. The proposed model enables determining the parameters affected by the size of the defect (such as e.g., amplitude and frequency centroid) and an analysis based on the relevant parameters increases the probability of detection of voids.

Extrusion-based 3D concrete printing is one of the most popular additive manufacturing techniques in the construction industry, where layer-by-layer structures form. For the 3DCP, most of the researchers use cement mortars of different configurations to the almost total exclusion of aggregates. Although the rheology of cement mortars may make them more amenable to 3D printing, the absence of coarse aggregate fraction in this material makes it more susceptible to the baleful effects of time-dependent phenomena like creep and shrinkage while at the same time, compromising elastic properties of the material and increasing the cement consumption. Incorporating coarse aggregates in 3D printable concrete is one of the ways for the construction industry to achieve sustainability and overcome these problems. This study examines the flexural performance of printed beams through acoustic emission (AE) monitoring to record real-time damage progression during loading. Tue specimens under examination include coarse aggregate-based printed beams in comparison with mortar-based printed beams in different orientations with respect to the printing direction. Tue analysis focuses on the evaluation of various AE parameters such as rise time, count, duration and amplitude. Tue study indicates that the inclusion of coarse aggregates reduces the anisotropic behaviour of printed specimens to some extent. Further, the study found that the AE signals can be effectively used to identify the initiation and propagation of cracks in the printed specimens.

Concrete is a quasi-brittle material characterized by limited tensile strength and toughness, making it prone to cracking under different loading conditions. Its fracture behavior is heavily influenced by factors such as aggregate size and type, water-cement ratio, curing practices, and the incorporation of fibers. This research investigates the impact of polypropylene fibers on concrete’s fracture performance using Acoustic Emission (AE) monitoring. The study aims to correlate AE parameters—such as event counts, amplitude, and energy—with various fracture stages, providing insights into the initiation, growth, and merging of microcracks leading to large-scale failure. The distribution of AE events is used to quantify the relative brittleness of the specimen. The nature of cracks, i.e. tensile or frictional can also be determined through the average frequency of AE. The b-value analysis of AE events can give further details on the crack growth rate in a specimen. Geometrically similar concrete specimens with varying amounts of polypropylene fibers were subjected to controlled static loading, while AE sensors continuously tracked crack development. The study captures key characteristics of the Fracture Process Zone (FPZ), such as its size, development rate, and the transition from stable to unstable crack growth. The results demonstrate that polypropylene fibers effectively enhance concrete’s fracture toughness, as confirmed by AE analysis. The findings provide crucial insights into the behavior of the FPZ, which can aid in optimizing concrete designs and improving the durability and performance of concrete structures, especially in applications where crack control and damage monitoring are essential.