Orientation optimization plays an important role in the lay-up design of composite structures.Earlier orientation optimization methods face the main problem of huge number of design variables.Recently,a patch concept is proposed to reduce the number of design variables.However,the traditional stress-based method can not deal with patch orientation optimization of composite structures.In this paper,we propose an extended stress-based method to deal with such problems.The considered problems are to minimize the mean compliance under multiple load cases or to maximize the eigenvalues of a composite structure.Four numerical examples are solved to demonstrate the efficiency of the new method.It is shown that the new method has the ability to deal with constraints on orientation angle,such as symmetric,antisymmetric and discrete orientation angle constraints.The iteration is less time-consuming because no sensitivity analysis is needed and a quick convergence rate can be achieved.
In order to avoid stress concentration,the shape boundary must be properly designed via shape optimization.Traditional shape optimization approach eliminates the stress concentration effect by using free-form curve to present the design boundaries without taking the machinability into consideration.In most numerical control(NC)machines,linear as well as circular interpolations are used to generate the tool path.Non-circular curves,such as nonuniform rotational B-spline(NURBS),need other more advanced interpolation functions to formulate the tool path Forming the circular tool path by approximating the optimal free curve boundary with arcs or biarcs is another option.However,these two approaches are both at a cost of sharp expansion of program code and long machining time consequently.Motivated by the success of recent researches on biarcs,a reliable shape optimization approach is proposed in this work to directly optimize the shape boundaries with biarcs while the efficiency and precision of traditional method are preserved.Finally,the approach is validated by several illustrative examples.
