LIGHTHILL's two-dimensional inviscid-fiow model (1973) for the WEIS-FOGH mechanism is investigated. For the 'fling' (or opening) stage, the lift and the moment acting on the wing are calculated from the LIGHTHILL solution. The effect of the angular acceleration due to wing rotation is also accounted for. For the separating stage, a doubly-connected region of the flow-fleld is analyzed by transforming it into a circular ring. The circulation around the wing is determined by assuming that KUTTA's condition is satisfied at the trailing edge, and the unsteady lift, drag, and moment are also calculated. It is found that the circulation can be made constant by taking the acceleration of the wing motion properly.
This paper deals with a numerical method for calculating the Clβ of rectangular flat wings. The computational system is based on a discrete vortex method in order to take account of separated flow at the side edges. Two kinds of wings, one has sharp side edges and the other has conventional blunt ones, are used to examine the effect of side edge thickness on the flowfield around the edges and on the Clβ. Comparison of the results of this method and experiment indicate good agreement of the Clβ for a moderate range of CL. The wings having sharp side edges show a substantial decrease in the Clβ.
Three analytical models for the investigation of the stiffness and nonlinear behavior of woven fabric composites are presented in this paper. The "mosaic model" is effective in rough prediction of the elastic properties of fabric composites. The "fiber undulation model" takes into account fiber continuity and crimp in fabrics and has been employed for modelling the "knee behavior" of plain weave composites. The "bridging model" is developed to simulate the load transfer among the interlaced regions in satin weave composites. Material nonlinearity of undulated fill thread is also considered to describe macroscopic nonlinear behavior of fabric composites. The theoretical predictions by the bridging model coincide very well with experimental results of satin composites. The bridging effect plays an important role in linear and nonlinear behavior of satin composites.
The optimum stacking sequence of lamination of graphite-epoxy cylindrical shells is analytically studied under the condition to get the highest compressive buckling load. The shells are composed of three types of layers of whichfiber directions are 0° (axial layer), 90° (circumferential layer) and ±α° (helical layer)with respect to the generatrix of the cylinder. The buckling load is evaluated with the coefficient f=σcr·(R/t). For the optimum constitution of the orthotropic cylinder corresponding to the case where the laminates are composed of many numbers of layers and regarded as homogeneous in the thickness direction, it is disclosed that the maximum value of f, i.e. f0max, is 34. 1GPa for Vf=65%, at first. The values of f of the 2-, 3-, 4-, 6- and 8-layer cylinders are calculated for all combinations of the stacking sequences of each number of layers in the use of an energy method. In the case of 2-layer one the value of f for the optimum lamination is only about 47% of f0max. However, the maximum value of f of the 6-layer one is very close to f0max.