Papers by Keyword: Composite Design

Abstract: The objective of this study focuses on developing empirical prediction models using response regression analysis and fuzzy-logic. These models latter can be used to predict surface roughness according to technological variables. The values of surface roughness produced by these models are compared with experimental results. Experimental investigation has been carried out by using scientific composite factorial design on precision lathe machine with tungsten carbide inserts. Surface roughness measured at end of each experimental trial (three times), to get the effect of machining conditions and tool geometry on the surface finish values. Research showed that soft computing fuzzy logic model developed produces smaller error and has satisfactory results as compared to response regression model during machining.

Abstract: Nowadays, carbon fiber reinforced plastics (CFRP) are present in a variety of applications. However, it is still possible to maximize the potential of CFRP by creating multi-material designs of CFRP and metal. The key to success for multi-material designs is the joining technology. In this work a metal/carbon fiber connection module was develop. Carbon fibers (CF) were integrated with stainless steel by using a powder metallurgy approach. After this, the created connection module was integrated in a fiber layup, which was infiltrated with epoxy resin by a Resin Transfer Molding (RTM) process. Leveraging from this technology, a M6 thread-forming screw was chosen and added in the sintered body. The screw press out test indicated that the strength between the screw and the sintered body was above 11 kN, which can be still enhanced for future by thread optimization. Microscopic cut images and computer tomography (CT) were used to characterize the CF in the sintered steel body and to examine the border area between the two materials.

Abstract: The Development of Fiber Reinforced Plastics (FRP) offers a great opportunity for applications in automobile industry, aeronautics and consumer goods to achieve light weight structures. However, the connection technology between FRP and mainly metallic based structures is the key to use the full potential of the FRP. Out of this motivation recent developments address this aspect.Using the powder metallurgical approach to generate a metal/ FRP connection module by spark plasma sintering a great variety is possible by integration of different metal and/ or fiber components. In this work aluminum and stainless steel was chosen for the upper and lower metallic side. The fibers integrated into the metal were glass, basalt and carbon fiber in one layer, two layer and mixed layer configuration. To connect the sintered module to greater CF weaves an infiltration process with a room temperature curing resin was used in a modified vacuum infusion (MVI) setup. In not optimized configuration the shear test after infiltration indicated an initial value for module shear strength above 20 MPa which can be enhanced in future developments by optimized armor between the upper and lower metal side and the number of integrated fiber layers of the connection module. A model is predicted to calculate the module shear strength in sintered state by multiplication of the armor area with the shear strength of the armor material. First experiments additionally show the possibility to weld the connection module directly to metallic structures.

Abstract: A mixture of structural functions can be accomplished using different reinforcements in epoxy-nickel matrix composites. In the frame of the common research project, mechanical and physical properties of the epoxy resin-nickel matrix composites containing extremely fin aluminum and fine waste elastomer powders were studied. A comprehensive study is given with different static and dynamic aspects as a function of composition, frequency and temperature. Two types of waste elastomeric powders were used for the reinforcement: Styrene-Butadyene Rubber SBR and Ethylene Vinyl Acetate (EVA). All of the composites were fabricated by mixing during 4h and then put in an ultrasonic dispersion for 1h. After that, a detail analyses has been carried out by means of Dynamic Mechanical Thermal Analysis (DMTA), microindentation and wear - scratch test. Dielectric properties (Permittivity (ε′)) and dielectric loss angle tangent (tan delta) were investigated using a Dielectric Thermal Analyzer (Rheometric Scientific) at three different frequencies (1 kHz, 10 kHz, 100 kHz) from room temperature up to 280°C. Wear of surface resistance measurement has been carried out by scratch test with a normal of 2.06N load with the frequency of 10Hz in two different number of cycles; 50000 and 100000. After the test, damaged zone were measured by 3D optical roughness meter to characterize damage occurred after the scratch test.

Abstract: The goal of the present work was to investigate the effects of several cement preparation parameters on setting and hardening reaction mechanisms and hydroxyapatite (HA) cement properties. A central composite experimental design (CCD) was conducted by choosing particle size, solid to liquid ratio, pH, seed concentration and buffer concentration as design parameters along with compressive strength and setting time being the responses. Tetracalcium phosphate (TTCP) powders were prepared by heat treatment of calcium and phosphate source mixtures in the 1200-1400°C temperature range followed by quenching to room temperature in a dessicator. The second phase used in the formulations (brushite) was prepared by aqueous chemical methods. A series of HA pastes/cements were prepared by changing the above mentioned design parameters. Cements were characterized by a standardized setting time test, mechanical testing machine, SEM and XRD. HA cements with the desired properties can be formulated by using CCD in which the responses were expressed by a second order polynomial equation of the parameters. Compressive strengths for the majority of HA cements were determined to be in the 100-160 MPa range which is significantly higher than those reported in the literature.

Abstract: Glass fiber reinforced polymer (GFRP) is a common composite material used for wind turbine blades because of its good strength to weight ratio. This paper describes the design process of GFRP material for a low wind speed (LWS) turbine blade. The wind turbine analyzed in this study is a 3-blades horizontal axis wind turbine (HAWT) with NACA 4415 airfoil and rotor diameter of 5 m. Parameters for the blade are thickness of skin and spar, lamination angle, and stacking sequence of the laminae. The design approach uses Carpet Plot Method based on Tsai-Hill failure criteria. Materials analyzed in this study are unidirectional E-glass fiber/epoxy composite and plain weave woven roving WR200 E-glass fiber/epoxy composite. There are 15 material configurations analyzed using a finite element software. The result shows top five of the composites configuration consisting of minimum 3 plies of 0°/90 direction fiber for the skin and ±45° direction fiber for the spar. The optimum configuration is [(0/90)]3 for the skin and (±45) for the spar both using plain weave woven roving WR200 E-glass fiber/epoxy composite. This configuration has margin of safety of 1.42 based on maximum principal stress and maximum deflection of 346 mm which is 0.14 of the total blade length. The predicted overall weight of the blade is 1.52 kg.

Abstract: The field of application of composites is ever-growing because of their unrivalled combinations of functional and structural properties. Such associations seem the more improvable as there are at once manifold possibilities to modify the architecture of composites, their route of elaboration, an ever-increasing scientific potency for both experimental investigations and modelling, and always more demanding materials performances in projects. This presentation wants to illustrate all these aspects by the example of metal matrix composites (MMCs) mostly elaborated by severe plastic deformation. Emphasis is given to results dealing with the effects of composite design and conditions of metalworking on the success of the fabrication process that depends on the uniformity of deformation and/or on the quality of the interfaces. At last, the consequences of all these data, and the need of complementary work, for the continuous improvement of the properties MMCs are delineated.