Multiscale modelling of thermal conductivity in composite materials for cryogenic structures

A multiscale analysis is performed to estimate overall thermal conductivity in a column-type support post used in particle accelerators to sustain cryomagnets. A non-linear homogenisation of thermal conductivity in a unidirectional composite material including phonon mechanism is firstly proposed by using the two-scale asymptotic expansion method. Next, computed conductivity curves are used for the modelling of heat transfer in a global representative volume element of the braided fabric composite. Thermal tests are conducted to measure conductivity of the material. A good agreement is obtained between estimated and measured values.