On the anisotropic plastic behaviour of short fibre reinforced thermoplastics and its description by phenomenological material modelling

A requirement for the safe design of thermoplastic parts is the ability to precisely predict mechanical behaviour by finite element simulations. Typical examples include the engineering of relevant components in automotive applications. For this purpose adequate material models are essential. In this context, the present work introduces a material modelling approach for short fibre reinforced thermoplastics (SFRTPs). SFRTP parts are processed cost-effectively by injection moulding and show a varying degree of anisotropy due to the locally inhomogeneous fibre distributions that arise during the moulding process. The presented material model considers linear-elastic behaviour and non-linear orthotropic stress-state dependent viscoplastic deformation for arbitrary fibre distributions. The constitutive equations are verified with the experiments of a PPGF30 material regarding different stress-states and orientations.

Glossaries. - Motivation and Outline. - Injection Moulded Short Fibre Reinforced Thermoplastics. - Polymeric Matrix Materials. - Reinforcement Fibres. - Composite Properties. - Injection Moulding. - Determination of Fibre Distributions. - State of the Art of SFRP Material Modelling. - Mechanical Basics. - Kinematics. - Stress. - Linear Elasticity. - Yield Condition and Plastic Potential. - Limit Criteria. - Damage. - Rate Dependency. - Material Characterisation. - Choice of Material. - Coordinate System De nition. - Experimental Set-up. - Experimental Results. - Discussion of Temperature Effects. - Material Modelling. - Overview. - Modelling of Linear Elasticity. - Modelling of Plastic Behaviour. - Modelling of Damage and Failure. - Numerical Implementation. - Veri cation. - Veri cation of Linear Elastic Response. - Veri cation of Plastic Response. - Numerical Veri cation of the Material Model. - Considerations for Engineering Practice 1857. - Determination of the Elastic Stiffness Matrix. - Determination ofthe Limit of Linear Deformation. - Determination of Plastic Deformation. - Consideration of Damage and Failure. - Summary and Outlook.