1,720,992 research outputs found
Effect of chemical etching on adhesively bonded aluminum AA6082
No full textThe efforts of new automotive industry are mainly directed towards the substitution of aluminum for steel in the body structure because the aluminum structures are lighter than traditional steel ones and meet the requirements, in terms of both vehicle design and manufacture. However, this substitution is not so automatic, but it is important to study the material properties and the structure design, focusing the attention on the methods of joining. Welding, typical technique to joint steel parts, is particularly difficult when applied on aluminum ones and then, in many cases, the adhesive bonding is preferred. To optimise the joint performances it is necessary to pre-treat the metal surface, not only to remove contaminants, but also to provide the intimate contact needed for the adhesive to successfully bond with the adherent surface. The mere cleaning of aluminum surfaces is not suitable for their bonding due to the oxide layer that naturally occurs on exposure to air so we need to apply a more effective treatment (mechanical or chemical etching) to increase the adhesion capability of the substrates. In this work different adhesive joint configurations (single lap) between aluminum substrates are studied. Two different resins are employed to evaluate the influence of the adhesive on the joint performances. Moreover the aluminum sheets are treated with a chemical etching with two different procedure
Sandwich compositi per tavole da windsurf,proprietà a confronto / Sandwich composite for windsurf boards,properties compared
No full textExperimental and numerical evaluation of sandwich composite structures
No full textThe main problem working with sandwich composite structures is their intrinsic anisotropy and non-homogeneity that does not allow their correct modelling. Nowadays the available data on mechanical properties of complex structures, necessary to allow a correct and reliable design, are not sufficient. The aim of the present work is to extend the knowledge of mechanical properties both on single components and on complete structures, focusing on the effects induced by different kind of skin arrangements (Kevlar, glass and carbon fibres). Compressive, shear and flexural tests were performed for a complete static mechanical characterisation of the sandwich structure both on each single component and on the complex structures in order to acquire important comparison parameters. The mechanical results of each component were used as input data in order to implement the FEM analysis by the commercial ANSYS code. A simplified model is proposed to simulate the compressive and flexural tests of a glass fibre sandwich structure. In addition their mechanical behaviour has been compared with experimental data by the aforesaid static tests of complex sandwich structures
Comparisons of processing and strength properties of two adhesive systems for composite joints
No full textIn the present study rheological, static and impact tests are carried out on two adhesive resins usually employed in marine applications; then single lap joint tests are conducted on composites joints evidencing the effect of the curing time of both resins on the mechanical properties of the joint.
The applicability and workability conditions of the adhesive resins are determined evaluating the curing evolution by a preliminary rheological analysis; then the relation of curing properties with the mechanical performances of the resins themselves and with ones of the composite joints is estimated. Static flexural and Izod impact tests are performed on the resins at increasing time after the specimen production (curing time); also the resistance properties of adhesives joints are studied as well the stabilisation of the mechanical properties after long times. Moreover a relationship between the different failure mechanisms, observed for both resins joints, and the curing reaction is observed.
A numerical model of the single lap joint test is developed: a simple and versatile numerical analysis (FEA with software ANSYS) is carried out in elastic regime. Such model should be suitable for designing and/or verifying the mechanical performances of composites joints, evaluating the shear, axial and peel stress trends on the joint overlap length
Geometry and stacking sequence effect on composite spinnaker pole’s stiffness: experimental and numerical analysis
No full textComposite materials are widely employed in sailing sports, a possible application is for the mast pole or other sail poles. In the paper the attention is focused on the spinnaker poles mechanical performances; in particular the focus is on axial and ring compressive properties of three different carbon fibre/epoxy resin spinnaker poles, to investigate both the diameter and stacking sequence effect on the mechanical performance of the structure. Starting from the stacking sequence used in the production of a particular spinnaker pole, the effect of a lamina at 0- in the middle of wall thickness is investigated with the purpose to obtain a more stiff structure. Moreover to test the proposed stacking sequence on different size products, a prototype with lower diameter is realized. To properly evaluate axial and ring stiffness, axial compression test and ring stiffness one are performed. Then a numerical model is developed to support the design of the finished product: A simple and versatile numerical analysis (FEA with software ANSYS), by simulating ring stiffness and pull-direction compression tests, is carried out in elastic regime.
Such model should be suitable for designing and/or verifying the mechanical performance of pole structures, even though differing from those above described, for materials, geometry and stacking sequence
Ottimizzazione delle prestazioni di tangoni in composito in fibra di carbonio/Better performance for carbon fibre composite spinnaker poles
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