Significant reduction of compressive buckling and postbuckling properties of composite cross-ply laminate owing to multiple delaminations is studied experimentally and analytically. Through-width multiple delaminations with equal length are considered. In the analysis, Timoshenko type beam theory is adopted. An analytical method is formulated on the basis of the Rayleigh-Ritz approximation technique, where the deflection and rotation of the crosssection are developed with the use of global mode functions and local mode functions which are not zero only on the delaminated portion. In order to conduct the eigen-value problem, closed delamination is assumed. The agreement of the analytical results with the experimental ones is excellent. The degradation of the compressive properties of crossply laminate due to the multiple delaminations is more serious than the homogeneous materials such as woven-cloth laminate. The simple method of the estimation of energy release rate is proposed, which is consistent with the experimental results. The delamination instability point can be estimated with the value.
Effect of wing planforms on the induced drag is studied by using Boundary Element Method. It is shown that the sweeping back of the wing tip of elliptical wings can reduce the induced drag. This reduction results from the increase of spanwise velocity component around the tip leading edge through the local increase of sweepback angles. The wake non-planarity is shown to have little influence on the evaluation of induced drags. The minimum induced drag planforms are computed by using the Non-Linear Programming technique combined with some constraints on the wing tip maximum lift.
The shape of scramjet-engine utilized for a space vehicle may be unsymmetrical in general. Supersonic flows generated in such asymmetric nozzle are very unstable due to pseudo-shock waves. To analyze the effects of the nozzle contour on the flow, three kinds of nozzle configuration were examined experimentally. The interaction of supersonic expansion flows in the nozzle with the boundary layer developed on a nozzle wall was investigated by applying a Mach-Zehnder interferometer. This used an Argon-Ion laser with an electro-magnetic shutter (AOM and EOM) as the light source. The frequency of the pseudo-shocks was not affected by the flow velocity at the nozzle entrance but was affected by the nozzle configuration. It is possible to measure the density distribution in supersonic un-steady flow fields quantitatively by using the present optical system.
This is the second report of the paper which discusses the physical meaning between flight test data and analyses, by studying the equation error method. As the more inclusive concept in the equation error method, the “in-flight wind tunnel test” concept is introduced. Under this concept, two methods can be thought out in addition to the equation error method, which respectively correspond to the output error method and the maximum likelihood method. Furthermore, it is represented that the equation error method has the built-in weighting function, which makes smaller the roles of the explanatory variables having noises as these noises increase. And the modified use of the multiregression analysis, in the case that the noise variances in the explanatory variables are known, is represented.