6.2 Hygro-thermal loads

Hygro-thermal loads include the thermal loads $N^ T$, $M^ T$, and the hygroscopic loads $N^ H$, $M^ H$, calculated in Macromechanics, where T is temperature and H is moisture.

An unconstrained homogeneous plate does not develop thermal stresses when subjected to a change in temperature because it can expand freely. On the contrary, a laminate develops thermal stresses because various layers try to expand differently. Since the layers are bonded together, thermal stresses develop. CADEC calculates the set of mechanical loads $N^ T$, $M^ T$, that would produce the same laminate deformations as the change in temperature.

Moisture causes swelling, thus strains, which cannot expand freely because the layers are bonded. CADEC calculates the set of mechanical loads $N^ H$, $M^ H$, that would produce the same laminate deformations as the moisture uptake.

The next three links in Macromechanics are for calculation of stiffness and compliance.