دانلود رایگان مقاله مدلسازی رفتار دینامیکی کامپوزیت تقویت شده با الیاف کوتاه

Abstract

This study proposes a constitutive model of viscous behaviour of short-fibre reinforced composites (SFRC) with complex distributions of fibre orientations and for a wide range of strain rates. The model is based on an additive decomposition of the state potential for the computation of composite macroscopic behaviour. Thus, the composite material is seen as the assembly of a matrix medium and several linear elastic fibre media. The division of short fibres into several families means that complex distributions of orientation or random orientation can be easily modelled. The matrix behaviour is strain-rate sensitive, i.e. viscoelastic and/or viscoplastic. Viscoelastic constitutive laws are based on a generalised linear Maxwell model and the modelling of the viscoplasticity is based on an overstress approach. The accuracy of the model is assessed for the case of polypropylene reinforced with short glass fibres. Matrix material parameters are identified from experimental tests carried out at several loading rates. Distributions of fibre orientation are characterised by micro-computed tomography. Comparisons between numerical and experimental responses in different loading directions and under different strain rates demonstrate the efficiency of the model.

5. Conclusions

A strain-rate dependent behaviour model for SFRC is presented here, based on an original approach that aims to be an efficient alternative to more complex procedures of homogenisation. This work presents the extension of this approach to strain rate dependent composite behaviour (i.e. viscoelastic and/or viscoplastic). Complex fibre orientations, including distributed and random orientations can be modelled in a simple way. The implemented constitutive laws are first described in details, begining with coupled viscoelastic–viscoplastic scheme of matrix behaviour. Then constitutive equations of composite bahviour model are detailed. The accuracy of the modelling is assessed for the case of a PP reinforced by 30 wt.% of short-glass fibres by comparison of numerical results with experimental ones. To this end, constitutive parameters involved in the matrix behaviour law are identified based on dynamic mechanical analysis, compression and tensile tests under a wide range of strain rates. Then dealing with the case of injection-moulded PP-short glass fibre composite, a first step is to characterise the actual distribution of fibre orientation using micro-computed tomography. Orientations thus identified were input of the behaviour model according to the ‘‘families of fibres” concept. A comparison of numerical and experimental results obtained for PP material is performed in order to validate the implementation of the matrix behaviour model. Then simulated quasi-static and dynamic tensile tests of PP-GF composite proved the consistency of the implemented model.