Search results for "Ultima"
showing 10 items of 396 documents
Determination of lifetime probabilities of carbon fibre composite plates and pressure vessels for hydrogen storage
2011
International audience; It is shown that an analogy can be made between the failure of unidirectional carbon fibre reinforced epoxy plates and filament wound carbon fibre composite pressure vessels and that their strengths and failure probabilities can be determined. Fibres in filament wound composite structures are placed on geodesic paths around the mandrel, which becomes the liner; so that when the structure is pressurised the fibres are only subjected to tensile forces, as in a unidirectional composite. Multiscale modelling reveals that composite failure is controlled by fibre breakage and that clustering of fibre breaks determines ultimate reliability of the structure. Time dependent r…
Friction Stir Welding of Magnesium Alloys under Different Process Parameters
2010
Experimental and numerical investigations have been performed in order to study the effect of welding parameters on properties of FSW-ed AZ31 magnesium alloy sheets. The results, presented in terms of tensile strength and numerical field variables distributions, allow to understand the behaviour of such material when FSW-ed using different rotational and welding speeds for a given tool geometry.
Prediction of crack onset strain in composite laminates at mixed mode cracking
2009
Failure process of continuous fiber reinforced composite laminates in tension usually starts with appearance of intralaminar cracks. In composite laminates with complex lay-ups and/or under combined loading, intralaminar cracks may develop in plies with different reinforcement directions. A necessary part of mixed mode cracking models is the criterion of failure. For propagation-controlled fracture it is usually formulated in terms of energy release rates and their critical values of the particular composite material. Intralaminar fracture toughness of unidirectionally reinforced glass/epoxy composite was experimentally determined at several mode I and mode II ratios. It is found that the c…
Analogy between the effects of a mechanical and chemical perturbation on the conductivity of passive films
2002
Abstract In order to study the passivity breakdown of a type 316L stainless steel, the electrochemical impedance and surface stresses were measured under straining conditions. The Mott–Schottky analysis, performed at high frequency, appears as very useful method to study, below the apparent yield strength, the effects of a mechanical stress on the capacitance values. The results obtained in sodium chloride media indicate that the semiconducting properties of passive films formed in a tensile stress field reflect a higher vacancies concentration than those formed in a stress-free state, suggesting that the passive film conductivity is increased. It was also shown that the Mott–Schottky plots…
Molecular-dynamics study of mechanical properties of copper
1998
Mechanical properties of copper have been studied using effective-medium theory and Molecular-Dynamics simulations. At room temperature we calculate the tensile moduli of systems that are elongated along different crystal orientations. These moduli are in very good agreement with the experimental values, the difference being less than 6%. The elastic constants obtained from simulations were also in good agreement with experiments. In addition, the point of maximum stress is found to be of the same order of magnitude as the experimental value. Also crack propagation in systems with periodic boundaries has been studied and micro-voids are seen to generate near the crack tip. Crack propagation…
Lessons Learned on the Tensile and Bond Behavior of Fabric Reinforced Cementitious Matrix (FRCM) Composites
2020
Fabric Reinforced Cementitious Matrix (FRCM) composites represent an effective, compatible and cost-efficient solution for strengthening and retrofitting existing structures. A strong research effort was done to investigate the tensile and bond properties of these materials, as well as the overall behaviour of strengthened members. A Round Robin Test was organized by Rilem TC 250-CSM on 28 FRCM composites comprising basalt, carbon, glass, PBO, aramid and steel textiles, embedded in either cement, lime or geopolymer mortars, to collect an experimental dataset and define test protocols. This paper collects the outcomes of this study to highlight fundamental properties of FRCM and to investiga…
Constitutive Numerical Model of FRCM Strips Under Traction
2020
In this paper, the tensile behavior of Fiber Reinforced Cementitious Matrix (FRCM) strips is investigated through Finite Element (FE) models. The most adopted numerical modeling approaches for the simulation of the fiber-matrix interface law are described. Among them, the cohesive model is then used for the generation of FE models which are able to simulate the response under traction of FRCM strips tested in laboratory whose results are available in the technical literature. Tests on basalt, PBO and carbon coated FRCM specimens are taken into account also considering different mechanical ratios of the textile reinforcement. The comparison between FE results and experimental data allows val…
Preparation and characterization of continuous fly ash derived glass fibers with improved tensile strength
2018
Abstract The coal-based energy production in China generates more than 600 million tons of coal fly ash (CFA) each year, which drives us searching for new methods for recycling CFA. In this work, continuous glass fibers with a range of CFA (25–45%) were successfully prepared without showing any sign of fiber crystallization. The measured fiber tensile strength was found to increase with CFA proportionally. The fiber derived from 45% CFA exhibited the best tensile strength (higher than the E glass fiber prepared/tested under the same conditions) and good chemical stability (98% mass retention in the acid corrosion test). Our study shows a feasibility of making continuous CFA derived glass fi…
Experimental analysis and micromechanical models of high performance renewable agave reinforced biocomposites
2017
Abstract The present work deals with the experimental study of high performance biocomposites reinforced with optimized agave fibers, as well as the successive implementation of reliable micromechanical models that can be used at the design stage. In detail, systematical experimental analyses performed on biocomposites with epoxy or PLA matrix, have permitted to highlight that for short fibers biocomposites the reinforcing leads to a significant improvement of the matrix stiffness, whereas the particular damage mechanism based essentially on the matrix failure with consequent tensile failure of the fibers aligned with the applied load, does not allow to obtain an actual reinforcing of the m…
Lignocellulosic fillers and graphene nanoplatelets as hybrid reinforcement for polylactic acid: Effect on mechanical properties and degradability
2020
Abstract This work investigates the effect of adding relatively low amounts of graphene nanoplatelets (GNP) to a biocomposite based on polylactic acid (PLA) and a lignocellulosic filler achieved by grinding Posidonia Oceanica leaves (Posidonia flour, PF). The ternary composites were prepared by melt extrusion and characterized from a morphological and mechanical point of view. Furthermore, hydrolytic degradation tests were performed under acidic, neutral and alkaline environment up to 900 h. Density measurements enabled to assess the degree of intraphase, i.e. the capability of polymer macromolecules to enter the voids of PF and a modified Halpin-Tsai model was presented and used to fit exp…