About the prediction of the stress-strain-behaviour of short-fibre reincorced polymers by the using the finite-element-method
Two models based on the finite element method (FEM) are developed. These allow the prediction of the nonlinear stress strain and the failure behaviour of short fibre reinforced polymer composites (SFRCs) with a high degree of fibre orientation. Length, diameter and volume content of the fibres as well as the material properties of fibres and matrix may be chosen freely. It is further possible to model a material layer between fibres and matrix (interphase, interlayer) of arbitrary thickness and material properties. Such interphases are of interest since in many SFRCs they automatically develop during the manufacturing process or may be deliberately applied in order to improve composite properties.
Thus a tool is provided to optimise the spectrum of SFRP properties. One special interest of practical nature is the maximisation of composite toughness through the optimisation of stiffness and thickness of a deliberately applied interphase. The models automatically show the influence on other important composite properties such as stiffness and failure strain.
Three dimensional (3D) model:
Basis of this model is a close to reality positioning of fibres and the fact, that no stresses are transferred across the fibre ends. This model enables the calculation of the non linear stress strain behaviour of the composite. Another use of the model lies in the deeper insight it provides into microscopic stress distributions.
Two dimensional (2D) model:
The basis of this model is the geometry of the 3D-model reduced to one of rotational symmetry. Thereby, several non trivial constraint equations are introduced. The reduced dimensionality of this FE model allows a more accurate stress determination which is a prerequisite for the developed microscopic failure description: Based on the G concept an overall failure model was developed.
In order to compare the predictions of both models with real SFRCs, experiments were conducted, respectively results were taken from literature.
One result of practical interest is this: The energy needed to fracture a highly orientated SFRC is increased when an interphase is applied having a modulus less than that of the matrix.Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Finite-Element-Method, FEM, Short fibre reinforced, Thermoplastic, Polymer, Composite, Simulation, Failure, Stress-Strain-Curve, Force-Elongation-Curve, Fibre-length, Fibre-orientation, Stiffness, Failure,Toughness, Interlay
Institute / chair: Fachbereich Maschinenwesen der Universität Kaiserslautern
Technical consultant for expert services: Prof. Dr.-Ing. K. Friedrich (Betreuer), Prof. Dr.-Ing. M. Maier
Publication year: 1992
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de
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