1,721,051 research outputs found
Mechanical characterization of Carbon Fiber Reinforced Plastics specimens for aerospace applications
No full textEffetti Della Corrosione Sulle Proprietà Meccaniche Di Sinterizzati In Acciaio Inossidabile
No full textQuesto lavoro si propone di analizzare gli effetti di un ambiente corrosivo su campioni in acciaio inossidabile 316L sinterizzato. In particolare, si è analizzata la relazione esistente tra resistenza alla corrosione e peso, densità e proprietà meccaniche a trazione. Sono stati studiati tre gruppi di acciaio inossidabile 316L sinterizzato, diversi tra loro per potenza laser e per velocità di scansione. Per ogni gruppo sono stati preparati 9 provini e su tutti sono state eseguite misure sia di peso che di densità. Un provino per ogni gruppo è stato testato a trazione senza aver subito alcun trattamento corrosivo, i restanti 8 esemplari di ogni gruppo sono stati sottoposti ad atmosfera con soluzione salina neutra (NSS) per valutare la resistenza alla corrosione del materiale oggetto di studio. Sono stati definiti quattro diversi periodi di esposizione selezionati tra quelli previsti nella normativa di riferimento. Alla fine di ogni periodo di esposizione, due provini per gruppo sono stati rimossi dalla camera di corrosione e analizzati al fine di studiare e registrare tutte le modifiche subiteThis paper aims to analyze the effects of a corrosive atmosphere on sintered stainless steel (316L) samples. In particular, the relationship between resistance to corrosion and weight, density and tensile mechanical properties were investigated. Three groups of sintered stainless steel (316L) were studied, each of them characterized by laser power and scanning speed. For each group 9 specimens were prepared. For all of them, measurements of both weight and density were performed. One specimen for each group was tested, as received, for tensile mechanical test; the remaining 8 specimens of each group were subjected to a neutral salt spray (NSS) to evaluate the corrosion resistance of the studied material. Four different exposure periods were selected from the standard. At the end of each exposure period, two specimens per group were removed from the corrosion chamber and analyzed in order to study and record all the changes that were made
Mechanical Comparison Of New Composite Materials For Aerospace Applications
Full text linkComposite materials are becoming the most useful material for aircraft structures. Their main advantage is connected to the possibility of deeply reducing weight and costs by maintaining high performances in terms of strength and security. The second major advantage in using this them depends on the possibility they could be proper designed to guarantee services they are made to. Many ways to combine them lead to the necessity of planning experimental tests in order to evaluate the real both elastic and plastic mechanical properties and to compare their variability as function of the fiber type, matrix type and manufacturing technology involved for realizing them. In this paper, a comparison between two innovative Carbon Fiber Reinforced Plastic materials was done. They differ, one from each other, for the matrix type (PEEK and BENZOXAZINE) and for the manufacturing process used to assemble the matrix with the reinforcement (Compression Molding and Resin Transfer Molding). On the other hand, the resin percentage weight content of both materials is maintained constant for all the tests: it is 42% for PEEK matrix and 64% for BENZOXAZINE matrix. The aim of the work is to critically analyze the results in order to get useful information for choosing the best one intended for designing and making the back section of fuselage of a regional aircraft. The component will consist of a front portion with structural aims (zoom phase) and a back part able to withstand to elevated temperatures
Analisi Delle Forme D’onda Associate Ad Emissioni Acustiche In Provini In CFRP Sottoposti A Test Di Delaminazione Modo I
No full textAcoustic Emission Analysis On CFRP Laminates Subjected To Open Hole Testing
No full textCarbon Fiber Reinforced Plastic materials (CFRP) are widely used for aeronautical and aerospace applications since they offer high specific mechanical properties. However, their damaged behavior is quite concerning and, if these damages are not visible on the surface their use could become deeply dangerous if not properly monitored. It is therefore essential to detect, evaluate and analyze the several types of propagation of damage caused by static, cyclic and environmental effects. Acoustic Emission technique (AE) is an innovative practice that is providing good results in detecting and identifying CFRP damages. In this paper, the AE technique was applied to CFRP specimens subjected to open hole testing
Superficial Stress Reduction By Laser Annealing: Preliminary Study
No full textMost of the manufacturing processes introduce a locked-in stress state in the material that can have strong effect on the lifetime of the component. The presence of residual stress must be conveniently taken into account during the design process and minimized when possible. Thermal processing of the component is also possible in order to relax residual stress. If a proper thermal cycle is designed for the specific material it can be possible to reduce and even eliminate the state of stress. In this paper we explored an alternative approach to obtain stress relaxation based upon the focusing on the surface of an Al 5068 aluminium alloy of a high power diode laser (HPDL) source. In this way it is possible to obtain a localized effect of stress relaxation limited to the neighbourhood of the area irradiated by the laser beam. Final results, however, depend upon several factors, such as the adopted wavelength, the reflectivity of the material at that specific wavelength, the power of the HPDL source, the mode distribution and the duration of the irradiation. In this work temperature field distributions are calculated for the case of interaction with a point source, a Gaussian source and a double-Gaussian source. For these two, in particular, the influence of the HPDL power was studied. Results obtained by the double-Gaussian distribution analysis were used to set the proper experimental parameter for the experimental study. Finally, repeated annealing cycles were performed and the sample and the obtained stress reduction was evaluated by X-Ray diffraction
The influence of stitching and unconventional fibres orientation on the tensile properties of CFRP laminates
No full textIn the typical structures of carbon-fibre-reinforced plastics (CFRP), multiple layers are stacked together with a particular sequence in order to give specific mechanical characteristics. Layers are organized with different angles, different sequences and different technological processes to obtain innovative materials. This paper introduces a new parameter, able to improve mechanical properties of composites. It analyses an unconventional fibres orientation combined with the through-the-thickness stitching on the in-plane mechanical properties of CFRP. Conventional carbon fibres orientation is generally referred to a Cartesian coordinate system, in which fibres are arranging in bundles along different angle orientations respect to the zero lamina. In this paper a polar coordinate system of continue carbon tow is introduced to create specimens as well as complex geometry components in an easy way. Five different configurations are studied: two are classified as traditional composites (unstitched and Cartesian orientation of woven carbon cloth), three are defined as innovative composites (stitched laminates and continue carbon tow organized in polar or Cartesian system). The application of this technique aims to introduce some advantages in the material's manufacturing process and if compared with the conventional strategy seems to be very promising since it appears to be very efficient in stopping delamination phenomenon
Mechanical characterization of carbon fiber reinforced plastics specimens for aerospace applications
Full text linkThe use of new Composites Fibers Reinforced Plastics materials for structural applications in aerospace industry is fast increasing in the last years. Ensuring high performances requires a deep knowledge of the mechanical behavior of the composite components subjected to different workloads. Components are subjected to strict environmental conditions that are typical of flight settings, as cold temperature and/or elevated temperature close to engines. In the typical assembly of composites, multiple layers are stacked together with a given sequence. Layers could be organized with different angles, different sequences and different technological process for providing specific mechanical properties that need to be studied. The possibility to introduce new parameters, able to improve mechanical properties of composites is also investigated. It refers to an unconventional fibers orientation combined with the through-the-thickness stitching on the in-plane mechanical properties of composites. Conventional carbon fibers orientation is generally referred to a Cartesian coordinate system, in which fibers are arranging in bundles along different angle orientations respect to the zero lamina. The opportunity to use a polar coordinate system of continues carbon tow is introduced to create specimens as well as complex geometry components easily. The application of this technique aims to introduce some advantages in the material's manufacturing process and if compared with the conventional strategy seems to be very promising since it appears to be very efficient in stopping delamination phenomenon. POLYM. COMPOS., 00:000–000, 2018. © 2018 Society of Plastics Engineer
Special Issue: Nondestructive Evaluation of Material Surfaces: Theory, Techniques, and Applications
No full textDue to the fast-growing industrial world, the demand for characterization tools and techniques has increased equally [...
L’approccio decisionale nella complessità: dal problem solving al problem scouting
No full textLe problematiche decisionali del management richiedono tempi sempre più stretti in spazi sempre più ampi. Obiettivo del capitolo è argomentare perché, nella complessità contestuale che genera discontinuità, piuttosto che l’attitudine al problem solving, di tipo adattivo, sia di maggior utilità per il management la capacità di problem scouting, ovvero d’immaginazione e creazione del problema, e come il metodo filosofico di ragionamento può supportare il processo decisionale
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