Rotary braiding is a cost effective method to manufacture near net shaped preforms that generally have a closed section and may have an arbitrary shape if braiding is performed over a shaped mandrel. The reinforcement architecture can be varied by the number and spacing of active bobbins, and by the speeds used to 'take-up' the braid and move the circumferential bobbins. Analytical methods are available that can reliably predict yarn paths and the final braid meso-structure for simple regular sections, and further analytical methods have been proposed to estimate composite braid elastic mechanical properties. A full simulation chain using the explicit Finite Element (FE) technique is presented for composite braid manufacture and mechanical stiffness prediction of the final composite. First simulation of the braiding process provides detailed information on yarns paths and braid meso-structure, from which Representative Volume Elements (RVE) of the braid may be constructed for analysis of stiffness properties. The techniques are general and can be applied to any braid geometry. A specific problem of meshing the yarn structure and interspersed resin volumes is overcome using conventional solid elements for the yarns and Smooth Particle Hydrodynamics for the resin, with link element to join the two constituents. Details of the background theory, braid simulation methods, meso-model analysis and validation again analytical and test measurements are presented.
Für das Umfangsplanfräsen werden heute Werkzeuggrundkörper aus Aluminium eingesetzt, die jedoch aufgrund der großen Durchmesser eine hohe Masse aufweisen. Neben der Werkzeugbeanspruchung infolge von Fliehkraftbelastung haben die Werkzeugmasse und Steifigkeit einen wesentlichen Einfluss auf die dynamischen Eigenschaften der Werkzeuge, die Produktivität des Bearbeitungsprozesses sowie auf die erzeugte Oberflächenqualität des Holzproduktes. Dieser Beitrag beschreibt die Entwicklung sehr leichter und steifer Werkzeuge aus kohlenstofffaserverstärktem Kunststoff (CFK). Damit wird eine nachhaltige Drehzahlsteigerung und eine verbesserte Oberflächenqualität ermöglicht.
Today, tools made of aluminum are used for face milling, but they have a high mass due to their large diameters. In addition to the tool stress due to centrifugal force loading, tool mass and stiffness have a relevant significant influence on the dynamic properties of the tools as well as on the produced surface quality of the wood product. The development of very light and stiff tools with the aid of high-performance carbon fibers made of carbon fiber-reinforced plastic (CFRP) should enable an increase in speed and improved surface quality to be achieved.
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