Integrative development of fibre-reinforced polymer parts

Abstract

In this work, the development process of an injection moulded, short fibre reinforced polymer part is presented by means of a case study, which deals with the development of a "pocket wheel" used for lifting applications with high loads. A pocket wheel is made for use as an idler pulley or driving wheel for a round link steel chain, functioning by tight fit. So as to reach a high load carrying capability, the design of the pocket wheel goes to the limit concerning surface pressure and wall thickness. In order to fulfil the requirements concerning stiffness and strength, it is necessary to use fibre-reinforced polymers (FRP's). But the enhancement of stiffness and strength appears only in the direction of the fibres; perpendicular to the fibres the strength and stiffness are much weaker. In addition, the part becomes more brittle and less ductile. Also weak areas of the component, such as weld lines, become more critical. Hence it becomes more difficult to predict warpage and shrinkage because the FRP parts behave anisotropic, dependent on fibre orientation. Thus fibre orientation has to be taken into consideration. The aim of this work is to analyse the whole development process, to show the main problems and to find solutions as to how these problems can be solved using currently available tools and methods. As a result, recommendations for the development of highly loaded, fibre-reinforced polymer parts should be compiled. In this work, currently available simulation methods for fibre-reinforced parts like Injection Moulding Simulation, Process Structure Linking, Finite Element Method (FEM) stress calculation and Multi-Scale Modelling are used and discussed. The new "Integrative Development" process is described from the conception phase at the beginning, via Computer Aided Design (CAD) modelling, Finite Element Method (FEM) calculation and optimisation, filling study and the mould design to the mechanical testing of prototypes at the end. The quality, mechanical properties and rheological properties are determined by mechanical testing, Computer Tomography (CT), Light Microscopy, Differential Scanning Calorimetry (DSC), Thermo Gravimetrical Analysis (TGA) and Ash Content Investigation.