Modeling for Suppression of Moisture/Temperature Induced Dimensional Changes in Unbalanced Fibrous Composite Structures with Perfect Bonding

Abstract

Suppression of dimensional change induced by moisture and temperature changes is studied for perfectly bonded, unbalanced, parallel fibrous structures composed of at least one hygroscopic component, taking into account various parameters such as initial moisture content and temperature at the time of assembly, width or height ratio of the two components. molecular orientation, and bonding length. The results show that two factors play major roles in moisture/temperature induced dimensional (curvature) change: longitudinal fiber swelling/shortening and material softening/stiffening. Whether the effects of the two factors are additive or compete against each other depends on the initial moisture content and temperature at the time of structural assem bly. When the structure subsequently absorbs moisture, the resulting maximum cur vature decreases as initial moisture regain and initial temperature increase, whereas the opposite is true when the structure desorbs moisture. A higher orientation factor of the hygroscopic component results in a higher maximum curvature. The induced curvature of an unbalanced structure goes through a maximum when the width ratio or height ratio of the two components changes.