EFFECT OF FIBER-MATRIX INTERPHASE ON WAVE-PROPAGATION ALONG, AND SCATTERING FROM, MULTILAYERED FIBERS IN COMPOSITES - TRANSFER-MATRIX APPROACH

This paper reports an analysis of the effect of the fibre-matrix interphase on ultrasonic wave interaction with multilayered fibres in a solid matrix. A transfer method is developed, which significantly simplifies the theoretical treatment of wave interaction with multilayered fibres, Two phenomena are investigated, one the dispersion of waves propagating in the composite along fibres, the other the scattering of waves incident normally to the fibres. To facilitate the derivation of solutions for waves in a multilayered cylindrical system, a transfer matrix is obtained for each cylindrical layer to relate the stresses and displacements on the inner and outer boundaries of the layer. Therefore, a total transfer matrix, which relates the elastic field in the surrounding matrix to that in the fibre core, is obtained as a product of individual transfer matrices for each intermediate layer. Based on this approach the wave dispersion and scattering for a single multilayered fibre are found. The results are extended to a unidirectional composite to analyse the dispersion along the fibres and the attenuation and dispersion perpendicular to the fibres. The effect of the fibre-matrix interphase is studied with numerical examples of coated multiphase SiC fibres embedded in a titanium matrix. The results show that the transverse moduli of the interphase have much stronger effects on wave propagation than the interphase axial moduli. Experimental data on wave dispersion and attenuation in a unidirectional SiC/Ti composite also show good agreements with the theory.