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 inter phase on ultrasonic wave interaction with multilayered fibres in a sol id matrix. A transfer method is developed, which significantly simplif ies the theoretical treatment of wave interaction with multilayered fi bres, Two phenomena are investigated, one the dispersion of waves prop agating in the composite along fibres, the other the scattering of wav es incident normally to the fibres. To facilitate the derivation of so lutions for waves in a multilayered cylindrical system, a transfer mat rix is obtained for each cylindrical layer to relate the stresses and displacements on the inner and outer boundaries of the layer. Therefor e, a total transfer matrix, which relates the elastic field in the sur rounding matrix to that in the fibre core, is obtained as a product of individual transfer matrices for each intermediate layer. Based on th is approach the wave dispersion and scattering for a single multilayer ed fibre are found. The results are extended to a unidirectional compo site to analyse the dispersion along the fibres and the attenuation an d dispersion perpendicular to the fibres. The effect of the fibre-matr ix interphase is studied with numerical examples of coated multiphase SiC fibres embedded in a titanium matrix. The results show that the tr ansverse moduli of the interphase have much stronger effects on wave p ropagation 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.