Theoretical and computer modelling of debonding mechanisms in fibrous micro- and nano-composites

Debonding is one of common failure mechanisms in fibre-reinforced composite materials (Broutman and Krock [1] ). Both shear forces acting along or perpendicularly to the fibres and tensile forces acting perpendicularly to the fibres can contribute to the breakdown of interfacial adhesion between the fibres and the matrix. In this paper, deformation due to plane harmonic waves propagating along the fibres and polarised perpendicular direction is considered. To describe the behaviour of the material, a second-order continuum theory, namely the theory of two-component elastic mixtures (Guz, Rushchitsky [2-4] ), is used. Analytical solution to the problem is derived and then used to study wave propagation phenomena in fibre reinforced composite materials with epoxy matrix. Four types of fibres are considered: Thornel-300 carbon fibres; carbon whiskers; zigzag carbon nanotubes; chiral carbon nanotubes. Of particular interest is the case when two waves are propagating in the material in-phase or in anti-phase, with the amplitudes strongly dependent on the frequency. Theoretical analysis and numerical results indicate that in unidirectional fibre-reinforced micro- and nanocomposites, the second mode of the transverse wave, propagating along the fibres and polarised perpendicularly to the fibre direction, can be critical to the strength of the material at high frequencies. This mode generates anti-phase vibrations in the composite constituents and forces that could cause interfacial debonding. This phenomenon can be classified as a new mechanism of debonding in fibre-reinforced composite materials.