Abstract: Light alloys are a very interesting challenge in order to have light components with high mechanical features. One of these is the 7075 aluminum alloy, which is commonly employed in aeronautic, automotive and maritime fields.On the other hand, the application of a PVD (Physical Vapor Deposition) coating can improve the hardness of the surface and the tribological properties of the component.The effectiveness of these coatings on the fatigue behavior of the sublayer material is not already clear. For this reason, bending tests on uncoated and coated specimens in air were performed in order to evaluate the S-N diagrams
Abstract: In this study, interfacial shear strength of resin particles added carbon fiber/maleic acid anhydride grafted polypropylene under water temperature was investigated. Water temperature range was from room temperature to 80 oC. The maximum immersion time was 24 hours. Micro debonding tests of non and resin particles added composites were conducted. Fracture surface of resin particles added composite were observed by Scanning Electron Microscope (SEM). As a result, interfacial shear strengths of non particles added composite monotonously decreased with an increase of water temperature. Interfacial shear strength of resin particles added composite was higher than that of non resin particles added composite under all water temperatures except for 50 oC. From SEM observation, large resin particles on surface of carbon fiber after water immersion at 50 oC were found. And, many matrices and large resin particles on surface of carbon fiber after water immersion at 80 oC were found. Therefore, interfacial shear strength of composite was improved because resin particle addition prevented water penetration into the interface between fiber and matrix under water immersion less than 50 oC. And, interfacial shear strength of composite was probably improved by anchor effect of resin particle under water immersion at 80 oC.
Abstract: In this paper, three kinds of different fiber reinforced vinyl composite plates are prepared by VARI technique, the mechanical parameters and failure modes of these panels under different strain rates are experimentally studied. The results show that loading velocity has a great influence on the tensile modulus of elasticity and strength as well as failure mode of the plates. At the same time, UMAT functional element program is used to write the failure criterion by ABAQUS finite element software, then the damage mode of composite fiber and matrix under tensile load are studied.
Abstract: This study deals with the influence of thickness of copper foil on its tensile property. Tensile tests were carried out on copper foils with various thickness ranging from 5 μm to 2 mm in air. Then, the tests on copper foil with the thickness of 20 μm and copper sheet with the thickness of 2 mm were also conducted in a scanning electron microscope, and their deformation was examined during testing using an electron backscattered diffraction method. The influences of thickness of copper foil on its deformation, tensile strength, and fracture morphology were investigated. As a result, the tensile properties of copper foil depend on its thickness, and the tensile strength decreased when the foil thickness was thinner than the grain diameter.
Abstract: This paper deals with a new fabrication technique of carbon fiber-reinforced thermoplastic (CFRTP) honeycomb cores and all-CFRTP honeycomb sandwich panels. The CFRTP core was made of plane woven carbon fiber-reinforced polypropylene prepreg sheets. The stacked CFRTP prepreg sheets were periodically hot-pressed at the node locations, and then expanded to form an all-CFRP honeycomb core. The resultant CFRTP honeycomb cores were glued with the same polypropylene-based plain-woven CFRTP skin plates. The mechanical performance of the all-CFRTP honeycomb sandwich panels was evaluated by flexural tests. The experimental results showed the effectiveness of proposed all-CFRTP sandwich panels.
Abstract: Modified 9Cr-1Mo steel is a heat-resistant steel developed for a steam generator in a FBR (Fast Breeder Reactor) and it has been applied to various thermal power plants. Recently, it was found that the fatigue limits did not appear up to 108 cycles at temperatures higher than 500oC. The reason for the decrease of the fatigue life was attributed to the change of the initially designed microstructure of the alloy. The initially dispersed fine lath martensitic texture disappeared at temperatures higher than 500°C, when the magnitude of the applied stress exceeded a certain critical value. In order to explicate the dominant factors of the change quantitatively, the change of the microstructure and the strength of the alloy were continuously observed by applying an intermittent fatigue and creep tests at elevated temperatures and EBSD analysis. It was found that there was a critical stress which caused the microstructure change at each test temperature higher than 500°C, and the activation energy of the change was determined as a function of temperature and the applied tensile stress. The dominant factor of the micro structure change was the stress-induced acceleration of the atomic diffusion of the component element of the alloy.
Abstract: The adhesively bonded joints behaviour under cyclic loading is not yet well understood due to its inherent complexity. Numerical approaches appear, therefore, as the easiest way to simulate such mechanical behaviour. In this work, double strap bonded joints with Carbon Fibres Reinforced Polymers (CFRP) and aluminium are numerically simulated and subjected to a cyclic loading history. In the numerical simulation, the Distinct Element Method (DEM) is used and it is assumed cohesive bi-linear bond-slip models with local damage of the interface. The evaluation of the bonded joints under cyclic loading is made by comparing the results with those simulated with a monotonic loading.
Abstract: Based on a few experimental results available in the literature, this work presents a simple analytical approach that allows the study of the long-term behaviour of CFRP-to-concrete interfaces under an initial sustaining load. Only the elastic regime is studied, which means that the interfacial maximum bond stress and maximum slip are never exceeded. Therefore, the maximum initial load to be sustained by the joints is limited by its corresponding elastic value. The analytical results provided by the proposed model are compared with some experimental results found in the literature. The results showed strain redistribution throughout the bonded length over the time.
Abstract: The influence of the notch geometry on the stress intensity factor at the front of the emanating cracks is well known for the opening loading mode. The critical length of the crack corresponding to a vanishing of the influence of the notch stress concentration can be approximately expressed by the formula aI,c = 0.5ρ(d/ρ)1/3, where d and ρ are the depth and radius of the notch, respectively. The aim of the paper was to find out if this formula could be, at least nearly, applicable also to the case of shear mode loading. The related numerical calculations for mode II and III loading were performed using the ANSYS code for various combinations of notch depths and crack lengths in a cylindrical specimen with a circumferential U-notch. The results revealed that, for mode II loading, the critical length was much higher than that predicted by the formula for mode I loading. On the other hand, the critical lengths for mode I and mode III were found to be nearly equal.