M. Durante

The Wear Behaviour of Composite Materials with Epoxy Matrix Filled with Hard Powder

The wear behaviour of composite materials, sliding under dry conditions against smooth steel counterface, has been investigated. The composite materials consisted of glass woven fabric reinforcing three different systems of matrix: epoxy resin, epoxy resin filled with powders of silica and epoxy resin filled with powders of tungsten carbide. The powders were mixed in a volumetric fraction of 6% with the epoxy resin. Three laminates were manufactured by hand lay up technology. The sliding tests have been conducted on the specimens, cut from the three laminates, with a pin on disk apparatus. The results put in evidence different wear behaviours of the composite materials observed at different values of sliding speed and pressure. The presence of different wear mechanisms has been appreciated by SEM-micrographic examinations.

Elevation of tribological properties of alloy Ti – 6% Al – 4% V upon formation of a rutile layer on the surface

The surface morphology, the adhesion of the oxide layer to the substrate, and their effect on the tribological characteristics of rolled sheets from alloy Ti – 6% Al – 4% V are studied at different temperatures and durations of oxidation of the surface. The methods of the study are measuring of microhardness, x-ray diffraction analysis and scanning electron microscopy. The composition of the oxide layer exhibiting good adhesion to titanium, low friction factor and high wear resistance is determined.

A new cost-saving vacuum infusion process for fiber-reinforced composites: Pulsed infusion

A new innovative infusion technology, pulsed infusion, has been developed for the manufacturing of fiber-reinforced thermoset-based composites. Pulsed infusion is a double-bag vacuum infusion process that is based on the use of a proper designed reusable pressure distributor and able to better control the vacuum pressure in pulsed way. Thus, the transverse resin flow through the dry fiber reinforcement is promoted and a better adhesion between the resin and the fibers is achieved. The new process allows to obtain laminates with the same fiber volume fraction and tensile properties of those produced by conventional infusion technologies. An average increase up to 9% for the flexural modulus and up to 24% for flexural strength has been assessed for pulse-manufactured composites compared to traditional vacuum infusion ones. Furthermore, due to a minor consumption of resin and the absence of the distribution net, pulse infusion provides a material cost-saving advantage around 19% and a significant waste reduction.

Silica Treatments: A Fire Retardant Strategy for Hemp Fabric/Epoxy Composites

In this paper, for the first time, inexpensive waterglass solutions are exploited as a new, simple and ecofriendly chemical approach for promoting the formation of a silica-based coating on hemp fabrics, able to act as a thermal shield and to protect the latter from heat sources. Fourier Transform Infrared (FTIR) and solid-state Nuclear Magnetic Resonance (NMR) analysis confirm the formation of –C–O–Si– covalent bonds between the coating and the cellulosic substrate. The proposed waterglass treatment, which is resistant to washing, seems to be very effective for improving the fire behavior of hemp fabric/epoxy composites, also in combination with ammonium polyphosphate. In particular, the exploitation of hemp surface treatment and Ammonium Polyphosphate (APP) addition to epoxy favors a remarkable decrease of the Heat Release Rate (HRR), Total Heat Release (THR), Total Smoke Release (TSR) and Specific Extinction Area (SEA) (respectively by 83%, 35%, 45% and 44%) as compared to untreated hemp/epoxy composites, favoring the formation of a very stable char, as also assessed by Thermogravimetric Analysis (TGA). Because of the low interfacial adhesion between the fabrics and the epoxy matrix, the obtained composites show low strength and stiffness; however, the energy absorbed by the material is higher when using treated hemp. The presence of APP in the epoxy matrix does not affect the mechanical behavior of the composites.

Negative and positive incremental forming: Comparison by geometrical, experimental, and FEM considerations

ABSTRACT This study compares negative incremental forming (NIF) and positive incremental forming (PIF) processes by geometrical considerations, finite element method (FEM) analyses, and experimental evaluations. Conical frusta were manufactured starting from AA5052H19 aluminum alloy sheets using both techniques. The processes were also simulated with LS-DYNA software and a close correlation between the experimental and numerical results was observed. The analysis of forming forces, forming limit diagrams (FLDs), and sheets thinning highlights that the PIF technique allows one to reach higher formability and geometrical accuracy. Finally, the differences in terms of surface quality were also discussed.

Forces analysis in sheet incremental forming and comparison of experimental and simulation results

Publisher Summary This chapter characterizes innovative techniques, such as hydroforming and incremental forming by the possibility to be easily adapted to realize a small production lot with low tools cost. The chapter discusses grooves in sheets, which have been realized by means of the incremental forming technology. It presents the forces analysis in relation to the tool path and its diameter. FEM simulations are achieved with the purpose to carry out a comparison between the forces values experimentally pointed out and the ones by FEM. FE analysis also allows the individualization of the points where failure conditions take place by simple evaluation of the reach stress values. Therefore, the FE method can be used to determine the tool path in the design phase of the process cycle.

Dimensional analysis in steel rod rolling for different types of grooves

Sequence design for shape-rolling processes consists of roll pass and profile design, i.e., transforming the billet into a final shape. For the prediction of the mean effective strain of the workpiece during rod rolling, an analytical model by Shinokura and Takai was used. They verified the formula by applying it to a variety of rod-rolling geometries (oval-square, oval-round, square diamond, and diamond-diamond). Today, on the other hand, the finite element (FE) techniques allow analysis of rolling processes in such a way as to simplify the work of design engineers. In this study, a round-oval pass and a round-flat oval pass are analyzed for steel rod rolling. In particular, the analysis of the spread, the surface profile, and cross-sectional area of the workpiece were conducted during rolling. Experimental data such as the maximum spread and the radius are compared with the results of the analytical model and FE analysis.

Analysis of Transversal Permeability for Different Types of Glass Fiber Reinforcement

In some of the new processes to produce elements in composite materials, the innovation is due to the fact that the resin flow is perpendicular to the plane of the reinforcement during the impregnation.So a very important parameter is the transversal permeability of the reinforcing materials used in these processes. In fact for a high value of this parameter it is possible to increase the product quality and to reduce the process time.In this work, using Darcys law and a particular permeameter, the transversal permeability of preforms constituted by fabric and mat layers of fiber glass has been valued for different injection pressures. In particular, the permeability of two types of preform, consisting respectively of only mat layers and of only fabric layers, have been determined by tests and calculated by Kozeny–Carman equation. The research has been also focalised on the evaluation of the permeability of preforms constituted by a mix of the two different types of reinforcement. Furthermore an analytical model has been studied to calculate the permeability of preforms consisting of layers of different reinforcement types, starting from the permeability data characterizing the single reinforcement type and determined by the tests or by Kozeny–Carman equation.

Improving of steel superficial properties through thermal sprayed coatings

In many industrial applications it could be useful to cover the mechanical components with harder coatings. For this reason, thermal spray technology is finding widespread use due to the high wear and corrosion resistance of the coatings achieved with these technologies. This paper is focused on the study of two different techniques, high-velocity oxygen fuel and air plasma spray. In particular, two different coatings sprayed on a steel surface were studied. In order to characterise the coatings a whole experimental campaign was carried out. Moreover, both the adhesion to the surface and the wear properties in different conditions were evaluated. In order to evaluate the attitude of these technologies to realise thick coatings were tested coatings with different thickness. The obtained results suggest that both the different coatings typology tested have an optimal internal cohesion, a good adhesion on the substrate and good wear resistance.

Innovative core material produced by infusion process using hemp fibres

This paper investigates the mechanical properties in term of compression, tensile, flexural and shear strength of a new hemp core based on woven fabric. The hemp core is manufactured by means an innovative vacuum infusion process in which the input both of epoxy resin and of air was allowed. In addition, a comparison among this and others more known materials used as core in sandwich structures was carried out. The results showed that the core under investigation has higher mechanical properties, without shear and indentation failure during the tests on the respective sandwich structures.