The thermal expansion coefficients (α) of unidirectional reinforced plastics are obtained easily and precisely by the use of explicit algebraic formulae which are functions of thermal and elastic properties of the two constituent materials and of their volume fractions. They are derived by considering uniformly spaced circular anisotropic fibers arranged in a hexagonal array in an elastic matrix. Then the analytical formulae for the thermal expansion coefficients and the residual stresses in filament-wound and laminated composites are given under the assumption of elastic behavior and within the framework of the laminated plate theory. The experiments on carbon fiber/epoxy laminated composite cylinders which are reinforced by helical and circumferential windings show a good agreement with the calculated values. The residual stresses induced during the curing process are found not to be negligible compared with the weak tensile strength normal to fibers. The algebraic formulations for α together with those for elastic moduli and failure criterion proposed by one of the authors seem to be useful for the optimal design of laminated composite structures in a closed form which elucidate the effects of various sorts of constitutive parameters.
The purpose of this paper is to present a detailed study of the forward speed effect to the cushion pressure characteristics of ACV's, from the both theoretical and experimental points of view. The experiments are performed for a two-dimensional rectangular-shaped model in a wind tunnel with a moving ground, and theoretical calculations are carried out by using the momentum theory in the case of the subcritical and supercritical forward speed, The main conclusion are summarized as follows: 1) Experimental results were predicted by the present momentum theory. 2) The cushion pressure in the diffusion region is much less than that in channel flow region. 3) However, even in the channel flow region, the pressure slightly rise up with the downstream. This is caused by the friction-pump effect of the moving ground. 4) The rear ambient pressure affects into the cushion pressure remarkably, that is, as this pressure increase negatively, the cushion pressure is reduced, with the negative increase of the rear ambient pressure.