Numerical Modelling of Damage Initiation and Failure of Long Fibre-Reinforced Thermoplastics
Characterising the mechanical properties of long fibre-reinforced thermoplastic (LFT) composites including failure is a challenging task. The macroscopic behaviour is generally associated with parameters like fibre orientation, volume fraction and length.
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Numerical Modelling of Damage Initiation and Failure of Long Fibre-Reinforced Thermoplastics L. Schulenberg, D.-Z. Sun and T. Seelig
Abstract Characterising the mechanical properties of long fibre-reinforced thermoplastic (LFT) composites including failure is a challenging task. The macroscopic behaviour is generally associated with parameters like fibre orientation, volume fraction and length. A thorough understanding of the micromechanical mechanisms gets more and more important for describing macroscopic behaviour. Large aspect ratios (fibre length divided by fibre diameter) make it difficult to create numerical models of the random LFT microstructure since representative volume elements (RVE) that consider the microstructure in a cross section over the entire thickness lead to a large computational effort. Numerical explorations of selectively predetermined fibre constellations can reduce the model size. In addition, complex interface behaviour can be considered. Therefore a numerical study is performed to identify relevant parameters in micromechanical finite element models of a long fibre-reinforced thermoplastic composite. Different unit cell models of discontinuous fibres embedded in a polypropylene matrix are analysed numerically to identify major mechanisms related to damage and failure in relevant loading directions.
6.1
Introduction
Long fibre-reinforced thermoplastics (LFT) are a class of composite materials that have a high priority in industrial applications. The advantages of LFT arise from the combination of short fibre-reinforced thermoplastics and from those of infinitely long fibres that give the material excellent properties, e.g. high strength. Characterising the mechanical properties including failure is a challenging task. The macroscopic behaviour is generally associated with parameters like fibre orientation, fibre density and fibre length. A thorough understanding of the L. Schulenberg (&) D.-Z. Sun Fraunhofer Institute for Mechanics of Materials (IWM), Freiburg, Germany T. Seelig Karlsruhe Institute of Technology (KIT), Institute of Mechanics, Karlsruhe, Germany © Springer International Publishing AG 2017 W. Grellmann and B. Langer (eds.), Deformation and Fracture Behaviour of Polymer Materials, Springer Series in Materials Science 247, DOI 10.1007/978-3-319-41879-7_6
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micromechanical mechanisms gets more and more important for describing macroscopic behaviour. Large aspect ratios (fibre length divided by fibre diameter) of LFTs make it difficult to create numerical models of the microstructure. Representative Volume Elements (RVE) for LFT that consider the microstructure in a cross section over the entire thickness lead to a large computational effort. Numerical explorations of selectively predetermined fibre constellations can reduce the model size. In addition, complex interface behaviour can be considered.
6.2 6.2.1
Problem Formulation Experimental Observation
An injection moulded LFT of polypropylene and 30 wt% glass fibres has been examined. Uniaxial tension tes
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