Ilenia Farina

Recycled nylon fibers as cement mortar reinforcement

We investigate engineering applications of recycled nylon fibers obtained from waste fishing nets, focusing our attention on the use of recycled nylon fibers as tensile reinforcement of cementitious mortars. We begin by characterizing the tensile behavior of both unconditioned and alkali-cured recycled nylon fibers obtained through manual cutting of waste fishing net filaments, with the aim of assessing the resistance of such materials to chemical attacks. Special attention is also given to evaluating the workability of fresh mortar and the possible impacts of contaminants released by waste fishing nets into the environment. Next, we deal with compression and bending tests on cementitious mortars reinforced with recycled nylon fibers, and establish comparisons with the experimental behavior of the unreinforced material and with results given in existing literature. In our analysis of different weight fractions and aspect ratios of the reinforcing fibers, we observe marked increases in the tensile strength (up to +35%) and toughness (up to 13 times greater) of the nylon reinforced mortar, as compared with the unreinforced material. The presented results emphasize the high environmental and mechanical potential of recycled nylon fibers for the reinforcement of sustainable cement mortars.

OPTIMAL DESIGN AND ADDITIVE MANUFACTURING OF NOVEL REINFORCING ELEMENTS FOR COMPOSITE MATERIALS

We experimentally investigate on the use of additive manufacturing technologies for the design and fabrication of innovative reinforcing elements of novel composite materials. We perform short-beam shear tests on cement mortar specimens reinforced with additively manufactured reinforcing fibers made of photopolymers or a titanium alloy. The fracture toughness, shear capacity and first crack strength of the examined materials are estimated based on the provisions of different international standards for construction materials. We also characterize the surface morphology of the examined fibers through microscopy analyses before and after testing. The given results highlight that the microscopic or macroscopic nature of the surface roughness of the analyzed fibers greatly influences the energy absorption capacity of the final materials, while the nature of the fibers’ material (metallic/polymeric) is of central importance in terms of strength properties. The present study represents a first step in the direction of designing reinforcing elements with hierarchical structure to form fabrics, fibers and coatings of groundbreaking reinforcements for next generation composites, profiting from the rapid prototyping capabilities of additive manufacturing technologies at different scales. Fabbrocino, I. Farina, A. Amendola, L Feo, F.Fraternali

ON THE FORCED VIBRATION TEST BY VIBRODYNE

Abstract. In civil engineering, Experimental Modal Analysis (EMA) dynamic tests are powerful aids to the seismic design of new structures, and useful tools for the structural identification of existing structures. EMA tests require to accurately evaluate the harmonic forcing function that is applied to the structure under testing, in order to correctly apply “model updating” procedures. The present work experimentally investigates on the nature of the forcing function applied by a vibrodyne, and its influence on the results of simulations on the dynamics of a single degree of freedom system . By using wireless accelerometers attached to a vibrodyne, we were able to measure the applied accelerations in the time domain, and the applied forcing function under different frequencies. Such an identification procedure was applied both in presence of 3+3 keyed masses, and in presence of 5+5 keyed masses, considering different angular speeds. In both cases, the forcing function applied by the vibrodyne was accurately determined as a function of time. We found out that the actual forcing function is slightly different from the theoretical sinusoidal profile, featuring marked oscillations.The work is completed by the analysis of the dynamic response a simple degree of freedom system under the action of smooth and oscillating sinusoidal forcing functions. A comparison between the results of the analyzed systems highlights marked mismatches in terms of predicted displacements, velocities, and accelerations. We therefore conclude that an accurate knowledge of the applied forcing function in EMA tests is essential in order to correctly identify the properties of the tested structures.

Investigations for Thermal and Electrical Conductivity of ABS-Graphene Blended Prototypes

The thermoplastic materials such as acrylonitrile-butadiene-styrene (ABS) and Nylon have large applications in three-dimensional printing of functional/non-functional prototypes. Usually these polymer-based prototypes are lacking in thermal and electrical conductivity. Graphene (Gr) has attracted impressive enthusiasm in the recent past due to its natural mechanical, thermal, and electrical properties. This paper presents the step by step procedure (as a case study) for development of an in-house ABS-Gr blended composite feedstock filament for fused deposition modelling (FDM) applications. The feedstock filament has been prepared by two different methods (mechanical and chemical mixing). For mechanical mixing, a twin screw extrusion (TSE) process has been used, and for chemical mixing, the composite of Gr in an ABS matrix has been set by chemical dissolution, followed by mechanical blending through TSE. Finally, the electrical and thermal conductivity of functional prototypes prepared from composite feedstock filaments have been optimized.

Binders alternative to Portland cement and waste management for sustainable construction—part 1:

This review presents “a state of the art” report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1—the present paper—focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Experimental Investigations for Development of Hybrid Feed Stock Filament of Fused Deposition Modeling

In this article a detailed study for controlling the process parameters of twin screw extruder (TSE) has been highlighted for in-house preparation of reinforced nylon-TiO 2 hybrid feed stock filament (HFSF) of fused deposition modeling (FDM). This case study has been performed on recycled nylon-TiO 2 (70–30 wt%) blend. The experimental study has been reported for field engineers, to understand the influence of TSE process parameters on mechanical and metallurgical properties of nylon-TiO 2 HFSF for printing of functional prototypes by FDM.