Anjali K. M. De Silva

Synthesis, fabrication and mechanical characterization of reinforced epoxy and polypropylene composites for wind turbine blades

Failure of wind turbine blades usually originates from manufacturing defects or in-service defects. In this study, materials selection for manufacturing of wind turbine blades was carried out based on the mechanical and physical results obtained using the Cambridge Engineering Selector program. Thermoplastic and thermosetting composites were synthesized and processed using injection molding and vacuum assisted resin infusion techniques, respectively. Operating conditions (vacuum pressure and temperature) were optimized. The manufactured samples were tested and evaluated using destructive tests. Tensile and fatigue tests were carried out. Polypropylene random discontinuous glass fiber composites were synthesized and processed using mold injection technique. Epoxy-carbon, glass and carbon/Kevlar hybrid fiber composites were manufactured using vacuum assisted resin infusion technique. Surface morphology was characterized using scanning electron microscope analysis. Tensile strength and fatigue resistance were significantly improved by the presence of E-glass fiber (30 wt%) in polypropylene-glass fiber composites. The experimental results were compared with the Cambridge Engineering selector software database. Epoxy-carbon (carbon fiber fraction is 0.61) and carbon/Kevlar hybrid (fibers fraction is 0.6) composites showed superior mechanical properties. Epoxy/carbon composite can withstand stresses up to 1390 MPa at 106 cycles.

New Bending Technologies for the Automobile Manufacturing Industry

This paper is concerned with a relatively new bending technique, known as Free-Bending. Its possibilities to realise geometries with almost arbitrary bending radii, with freely definable bending angles, which can be in several planes make this technique very interesting for an application in the automobile industry, especially in the field of car chassis and space frames. Therefore the paper shows some practical examples of geometries which were investigated with bending tests and examined by means of the finite element method. Furthermore the extended possibilities and the restrictions of this new technology are discussed.

Geometrical shape improvement of steel moulds by robot polishing process for polymer optic replication

ABSTRACT The quality of injection-moulded polymer optic parts depends on the surface finish of the respective mould. In order to improve the surface finish of the mould, it is important to use a tactical material removal, which allows a controlled correction of the mould’s surface geometry. The aim of this work is to use a polishing correction technique to improve and correct the flatness of hardened steel samples in order to reduce the need for manual polishing. A polishing tool function is simulated from the contact between the tool and the hardened steel sample and used to determine the material removal rate per time. A feed profile is calculated, which allows the industrial robot to tactically control the material removal. It is observed that a correction improves the surface’s flatness by up to 70%.

The Application of Thermal Hydroforming in the Automotive Industry

Thermal hydroforming process was developed to overcome the problems of forming aluminium alloy sheets or tubes, which are used extensively in the automotive industry for weight reduction and corrosion resistance. FEA simulation was used to predict the thermal hydroforming process and was verified by experimental analysis. Strains of up to 130% were reached during the experiments, which corresponds to five times higher strains than that present in AlMg alloy at room temperatures. The FEA model can be used to assess the feasibility of new components.

Integration of LS-DYNA in the Process Chain of an Automotive Manufacturer

The introduction and evaluation of the simulation tool LS-DYNA in manufacturing process simulation is the basis for a new view in the virtual development chain. The explicit LS-DYNA forming simulation can map complex processes very exactly. One intention is to achieve more accurate computer models with the transfer of the part properties caused by production for subsequent crash and strength calculations. Using case studies a view of the transferable data is analysed to highlight their effects on the part.