Finite element contact, stress and strain analysis of a composite fibre-matrix micro system subjected to ball indentation

Károly Váradi, Zoltán Néder, Klaus Friedrich, Joachim Flöck

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The presented FE contact technique is applied to the problem of a steel ball indented into a composite material consisting of unidirectional continuous carbon fibres in a polyetheretherketone matrix. Indentation was carried out with fibre orientations either normal (N) or parallel (P) to the contact surface at fiber volume fraction 44%. The FE contact stress analysis of a fibre/matrix micro structure has some strong limitations. If FE micro models are used, only a very small (for example 0.1×0.1×0.1 mm) 3D segment can be modelled while the number of degrees of freedom (DOF) is immediately in the range of 100.000. If anisotropic numerical models are used, there are no size limitations but the results can not describe the stress and strain states of a real fibre/matrix micro structure. The FE contact analysis involves both an anisotropic (homogeneous) macro and (inhomogeneous) micro contact analysis, following an approximate displacement coupling technique. This technique considers only the displacements along the coupled surfaces. The coupled solution provides a more realistic elastic deformation, stress and strain results of the composite micro system in the vicinity of the contact area, and at the same time the effect of the macro system is also incorporated. The FE contact results show the location and the distribution of the subsurface stresses and strains. For N fibre orientation there is a high shear stress region below the surface, from where the fibre/matrix interfacial failure initiates before propagation to the surface. These results are in good agreement with experimental results published in the open literature. In case of P fibre orientation the matrix is subjected to local plastic deformation while the characteristic deformation of the fibre is bending.

Original languageEnglish
Pages (from-to)23-32
Number of pages10
JournalAmerican Society of Mechanical Engineers, Design Engineering Division (Publication) DE
Publication statusPublished - Dec 1 1997


ASJC Scopus subject areas

  • Control and Systems Engineering
  • Engineering(all)

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