MATERIAUXCOMPOSITES A RENFORT FIBREUX
Micro-indentation:quantitative analysis of the interface's behaviour




     The fiber/matrix interface plays an essential part in the mechanical behaviour, fatigue life and durability of fiber-reinforced composite materials.

A research team at Ecole Centrale de Lyon has developed a micro-indentation test whichallows the mechanical characterisation of such an interface within realcomposite systems: the cross-section of a glass fibre (diameter 2r,Young modulus E=73000 MPa) within a polished polymer matrix compositeis indented using a Vickers indenter. The resulting interfacial stressconcentration close to the indenter induces a progressive fibre/matrixdebonding. The information related to the interfacial behaviour are includedwithin the indentation curve giving the applied load P as a functionof the indenter's displacement ut.

A shear-lag model has been developed in order to quantitatively analyse those indentation curves, giving:

- a parameter, n, which characterises the fibre environment around the tested fiber: This parameter is sensitive to the local fiberpacking and it's regularity. It is estimated from the experimental initialstiffness, k, of the system  (n=(k/rE)½).

- the interfacial debonding stress td

- the debonding length h at the interface versus the appliedload
  the length H over which sliding may happen during theindentation unloading

We propose here an applet whichsimulates the micro-indentation test according to the shear-lag model.The user hasto select a fibre of diameter 2r with a characteristicinterface debonding stress td and the stiffness k of thesystem.
By appliying a cycle of load P (by clicking on the scrollbaryouwill get incrementations of 0.1N until a threshold of 1N), one canvisualize the load/displacement curve and the associated values of h and H during the loading/unloading cycle.

This work is based upon the following publication:

Quantitativeanalysis of the micro-indentation behaviour of fibre reinforced composites:development and validation of an analytical model
Mondher Zidi (a,b), Luc Carpentier (b),Antoine Chateauminois (c), François Sidoroff(b)
Composites Science and Technology 60 (2000) 429-437
(a) Laboratoire de Mécanique des Solides, EcoleNationale d'Ingénieurs de Monastir, Tunisie
(b) Laboratoire de Tribologie et Dynamique des Systèmes (LTDS), UMR CNRS 5513, Ecole Centrale de Lyon, France
(c) Laboratoire d'Ingénierie et Fonctionnalisation des Systèmes (IFoS), UMRCNRS 5621, Ecole Centrale de Lyon, France

See other available interactive documents in those pages :

- Analytical models of stress transfert in fiber reinforced composites: theapplet

- Numerical computations of stress transfert in a fibre/matrix interface: theapplet

- Lectures notes :stress transfert models for fiber reinforced composites (in french)

versionfrançaise


Authors : Marie-Hélène Levé et AntoineChateauminois  - Ecole Centrale de Lyon - June 2000