This work introduces a material modelling approach for explicit finite element simulations of injection moulded short fibre reinforced thermoplastics. The material model considers linear-elastic behaviour and non-linear orthotropic stress-state dependent viscoplastic deformation for arbitrary fibre distributions. Regarding elasticity and the initial yield surface, a micro-mechanical Mori-Tanaka based approach is applied. On the matrix level an isotropic quadratic yield surface is introduced which is transferred into a Tsai-Wu yield surface on the composite level. An analytical expression for non-linear hardening and a simplified consideration of strain rate dependency is presented. The constitutive equations were verified with the experiments of a self-compounded PPGF30 material regarding regarding tension, compression and shear at different orientation distributions.

Autorentext

Dr.-Ing. Felix Dillenberger is a mechanical engineer whose research focusses on the characterisation of the mechanical behaviour of thermoplastic plastics and their modelling in finite element simulations.

Zusammenfassung

A requirement for the safe design of thermoplastic parts is the ability to precisely predict mechanical behaviour by nite 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 bre 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.

Inhalt

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 Denition.- 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.- Verication.- Verication of Linear Elastic Response.- Verication of Plastic Response.- Numerical Verication of the Material Model.- Considerations for Engineering Practice 1857.- Determination of the Elastic Stiffness Matrix.- Determination of the Limit of Linear Deformation.- Determination of Plastic Deformation.- Consideration of Damage and Failure.- Summary and Outlook.