Rockfall is a phenomenon which, when uncontrolled, may cause extensive material damage and personal injury. One of the structures used to avoid accidents caused by debris flows or rockfalls is flexible barriers. The energy dissipating devices which absorb the energy generated by rock impact and reduce the mechanical stresses in the rest of the elements of the structure are an essential part of these kinds of structures. This document proposes an overview of the performance of energy dissipating devices, as well as of the role that they fulfil in the barrier. Furthermore, a compilation and a description of the dissipating elements found in the literature are proposed. Additionally, an analysis has been performed of the aspects taken into account in the design, such as experimental (quasi-static and dynamic) tests observing the variation of the behaviour curve depending on the test speed and numerical simulations by means of several finite element software packages.

In this paper a fracture assessment in additive manufactured acrylonitrile butadiene styrene (ABS) fracture specimens containing U-notches is performed. We performed 33 fracture tests and 9 tensile tests, combining five different notch radii (0 mm, 0.25 mm, 0.50 mm, 1 mm and 2 mm) and three different raster orientations: 0/90, 30/−60 and 45/−45. The theory of critical distances (TCD) was then used in the analysis of fracture test results, obtaining additional validation of this theoretical framework. Different versions of TCD provided suitable results contrasting with the experimental tests performed. Moreover, the fracture mechanisms were evaluated using scanning electron microscopy in order to establish relationships with the behaviour observed. It was demonstrated that 3D-printed ABS material presents a clear notch effect, and also that the TCD, through both the point method and the line method, captured the physics of the notch effect in 3D-printed ABS. Finally, it was observed that the change in the fracture mechanisms when introducing a finite notch radius was limited to a narrow band behind the original defect, which appeared in cracked specimens but not in notched specimens.

This study investigates the influence of the addition of glass powder, nozzle size, and infill density on the mechanical properties of 3D-printed polylactic acid (PLA) pieces. To do so, a factorial design of experiments was accomplished. The specimens were tested under tensile and bending conditions. Regression equations were extracted from the maximal strength, strain at maximal strength and modulus, and an analysis of the significance of the terms was carried out. All the factors influence the output variables, independently and in combination. As for the environmental impact, a cradle-to-gate life cycle analysis (LCA) of the printing material with different glass powder additions, including the manufacturing process and transportation of the raw materials, was performed. Additionally, a cost assessment of each alternative was calculated for each case. Since the concurrence of mechanical, environmental, and cost performance is needed to enter a new product in the industry, a multicriteria decision-making analysis was performed to select the best combination. The criteria considered were the material and printing costs and the environmental impact, all normalized with maximal strength. Two different alternatives were found to be the best solution depending on the strength selected. Both of them were printed using a 1.2-mm nozzle with 100% infill and different glass percentages.