The 2-D deformation of bleached plain weave cotton ready-to-wear clothing was measured during adsorption and desorption cycles. A digital X-ray imaging system was coupled with a climatic chamber to control temperature and relative humidity. An image of each sample was recorded for several equilibrium states. The strain along warp (epsilon(cc)) and weft (epsilon(ww)) directions and the shear deformation (epsilon(wc)) were evaluated by image correlation process. The dimensional variations are explained by geometrical consideration of the structure at microscopic (fibers scale) and macroscopic levels (yarns scale). Indeed, the reaction between water vapor molecules and material enlightens two steps. At first, the swelling fibers fill the micropores inside the yarns. Then, the yarns swell and push on their neighbors to fill up the macropores and cause the macroscopic swelling of the overall structure. During the desorption phase, the fibers shrink to create a free space inside the plain weave structure that will be relaxed to find its initial state. The isotropy between the two main directions is explained by the weave symmetry and the similar yarn properties. The shear deformation is related to the cohesion by twist between cotton fibers. This work is more specifically focused on the ironing process (T = 200 degrees C + steam). The ironing generates flattened yarns and increases their friction, which amplifies the deformation during the first adsorption cycle. However, this effect is cancelled at the end of the first adsorption/desorption cycle with no memory effect of the ironing process.
