  The future ATLAS ITk strip tracker will consist of 17,000 silicon strip
detector modules mounted on support structures called cores. Cores are
assembled from a number of components, among others carbon fibre facings,
honeycomb structure and carbon foam surrounding titanium tubes used for
cooling, using a two-component epoxy (Hysol 9396) loaded with boron nitride for
good thermal conductivity. The adhesive constitutes about 20 % of a core's
weight. During operation, the detector is cooled down to -40 $^\circ$C using
bi-phase carbon dioxide and flushed with dry gas to prevent condensation. The
effect of this temperature change has been simulated to study the impact of
Coefficient of Thermal Expansion (CTE) mismatches between different materials
and investigate resulting deformations and misalignment. In addition to the
shrinking of an adhesive during cooling, which can be estimated well using its
known CTE, flushing the detector volume with dry gas removes the moisture
contained in the adhesive, leading to an additional shrinking. In order to
estimate the impact of shrinking during drying, the Coefficient of Moisture
Expansion (CME) of Hysol samples with different contents of boron nitride as
well as their overall moisture absorption were measured and their extent
compared to the contraction associated with cooling.
