A photocurable energetic resin was developed for photopolymerization additive manufacturing. The composition contains 50 wt % RDX, 25 wt % acrylate binder, and 25 wt % energetic plasticizer. The material was characterized in terms of compatibility, printability, mechanical properties and (ballistic) performance. The possibility of printing energetic items of increasing complexity was demonstrated through various print trials. The culmination of the research effort was the firing of a 30 mm gun setup with 3D‐printed propellant.
A new parametrization method for aircraft shapes is presented to enhance shape optimization for aircraft design. This parametrization method was implemented in a tool that creates feasible initial solutions for multidisciplinary design optimization problems. The tool combines all aspects of the aerodynamic design process: parametrization, aerodynamic analysis and optimization. The novel parametrization method presented in this paper makes use of the Class-Shape-Refinement-Transformation (CSRT) method. This method employs a combination of Bernstein polynomials and B-splines to allow for both global and local control of the shape. Additionally, the use of B-splines makes it possible to efficiently handle volume constraints, which are very common in aircraft design. The parametrization method was coupled to two different aerodynamic analysis tools. The commercial panel method code VSAERO was used for the low-speed regime and an inhouse Euler code was used for transonic and supersonic flight conditions. Various different optimization schemes were investigated and compared. A number of test cases were performed. For the first set of test cases, a three-dimensional geometry was optimized for subsonic conditions, using VSAERO and various optimization algorithms. For the second set of test cases, an airfoil was optimized for transonic and supersonic conditions, using the in-house Euler solver and a gradient-based optimizer. From this work it can be concluded that a combination of stochastic and gradient-based optimization algorithms works best together with the CSRT method. Additionally, refining the shape using B-splines proved to be an efficient way of increasing the design freedom, while the design space remained smooth enough to employ gradient-based optimization.
Purpose -An aerodynamic shape optimization algorithm is presented, which includes all aspects of the design process: parameterization, flow computation and optimization. The purpose of this paper is to show that the Class-Shape-Refinement-Transformation method in combination with an Euler/adjoint solver provides an efficient and intuitive way of optimizing aircraft shapes. Design/methodology/approach -The Class-Shape-Transformation method was used to parameterize the aircraft shape and the flow was computed using an in-house Euler code. An adjoint solver implemented into the Euler code was used to compute the required gradients and a trust-region reflective algorithm was employed to perform the actual optimization. Findings -The results of two aerodynamic shape optimization test cases are presented. Both cases used a blended-wing-body reference geometry as their initial input. It was shown that using a two-step approach, a considerable improvement of the lift-to-drag ratio in the order of 20-30 per cent could be achieved. The work presented in this paper proves that the CSRT method is a very intuitive and effective way of parameterizating aircraft shapes. It was also shown that using an adjoint algorithm provides the computational efficiency necessary to perform true three-dimensional shape optimization. Originality/value -The novelty of the algorithm lies in the use of the Class-ShapeRefinement-Transformation method for parameterization and its coupling to the Euler and adjoint codes.
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