MODELING FOR SUPPRESSION OF MOISTURE TEMPERATURE INDUCED DIMENSIONAL CHANGES IN UNBALANCED FIBROUS COMPOSITE STRUCTURES WITH PERFECT BONDING/

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 tempe rature at the time of assembly, width or height ratio of the two compo nents, molecular orientation, and bonding length. The results show tha t two factors play major roles in moisture/temperature induced dimensi onal (curvature) change: longitudinal fiber swelling/shortening and ma terial softening/stiffening. Whether the effects of the two factors ar e additive or compete against each other depends on the initial moistu re content and temperature at the time of structural assembly. When th e structure subsequently absorbs moisture, the resulting maximum curva ture decreases as initial moisture regain and initial temperature incr ease, 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 str ucture goes through a maximum when the width ratio or height ratio of the two components changes.