The stresses in a fiber-reinforced plate produced by mechanical interaction between the fiber and the matrix are studied theoretically and experimentally. The plate bent transversely is represented by a fiber-reinforced beam, and the bending stresses caused by external bending moment or differential shrinkage are analyzed. The plate stressed two-dimensionally is represented by an infinite plate in a condition of the plane-stress in which a pair of fibers is embedded, and we analyze the stresses resulted from differential shrinkage or external compressive load regarding the fibers as a non-homogeneous elliptic inclusion.
All the analytical results are compared with photoelastic observations on rectangular epoxy plates reinforced by steel wires. The differential shrinkage is produced by curing the resin in high temperature. The requirements for modelprototype similarity are discussed.

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Analytical studies of the aeroelastic stability of two dimensional flat panels were made for the Mach number range up to one by using the exact linearized aerodynamic forces and adopting GALERKIN method. Flutter instability was predicted for the Mach number range above 0.4 (approx.). However the predicted boundary of static divergence is more critical than that of flutter in the subsonic range. Therefore the possibility of occurence of flutter were examined as a post divergence problem using rather unrealistic rough assumptions to simplify the problem. This examination showed that the tensile axial force which come from the aerodynamic pressure on the diverged panel is strong enough to prevent the panel from going into flutter.
The predicted divergence boundaries agreed reasonably well with the experimental results. As for the post divergence phenomena, including the self-exited oscillation (flutter), the experimentally observed phenomena were much more complicated than analytically predicted ones. Most of the tested panels were free from flutter after they were subjected to divergence, but there were two exceptional cases : a panel started flutter in large amplitude and another panel fluttered in small amplitude keeping its divergence shape as the mean deflection of its oscillation.
It is felt that a nonlinear analysis, which considers the effect of divergence shape of finite panels on the structural and aerodynamic expression, is necessary to explain the experimental results.
The stability boundaries of some simply supported three dimensional panels, of which both surfaces are subjected to the air flow, were tested in order to compare the stabilities of the two dimensional panels.
Some distinct differences of instability types were found between them. And the aspect ratio of three dimensional panel was found to be an important parameter to classify the stability character of the panels.

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