Session: 05-06-01: Lightweight Sandwich Composites and Layered Structures

Paper Number: 111362

111362 - Lightweight Design With Topology Optimization for Additive Manufacturing of Aircraft Components 

The additive manufacturing (AM) becomes more and more popular in the aerospace industry. It provides the powerful tool to realize the complex part geometries which are impossible to produce via traditional subtractive manufacturing. Also, AM can reduce time and cost for maintenance and overhaul of the aircraft parts by making best use of on-site manufacturing and customized production.
Topology optimization (TO) is, in principle, to determine the optimal distribution of material in design space and its results generally show very complicated geometries. Thus, it has been used mostly at the concept design stage because manufacturing restrictions from conventional machining prevented direct producing of the TO results. But recent advance in AM technologies makes it possible to utilize TO solutions almost as near net shape, and this attracts a lot of research interest on combining TO with AM.
This paper deals with lightweight design of an aircraft part using TO with the goal for fabricating the part through AM. A landing gear torque link is selected as a case study. In landing gear, one end of the torque link is attached to the cylinder and the other end is attached to the lower piston. So it prevents the relative rotation and keeps the wheel aligned. Torque link can be a good candidate for additive manufactured part with TO because it is not a primary structural parts and has a rather simple load path.
First, the existing part is re-designed for additional weight reduction with TO. In the optimization, the averaged compliance is selected as objective function and volume fraction and other structural responses are considered as constraints. The application of lattice structure is also studied for further optimization. The intermediate density elements after conventional TO process are replaced with lattice structures, which consist of beams interconnecting the nodes of those elements, and then lattice member dimensions are optimized in the subsequent phase. The results from the above processes need to be adjusted considering manufacturability related factors such as minimum lattice beam size and support structure requirements. Also, very thin members or small holes are edited and irregular outer lines and interfaces are smoothed without loss of structural performance.
It is important to have reliable material characteristics of AM part to verify the analysis model and the optimized results. For this, the tensile test of additively manufactured coupons is performed to investigate basic mechanical properties. The specimens are manufactured using a titanium alloy Ti6AlV with DMLS (Direct Metal Laser Sintering) system for this study. And the different build orientations, heat treatment conditions and post processes are considered to figure out the effects of those factors on material properties. The protyping results show that the weight of existing part can be effectively reduced using the synergy between TO with AM.

Presenting Author: Tae-Uk Kim Korea Aerospace Research Institute

Presenting Author Biography: I received Ph.D. degree in computational mechanics from Seoul National University, 2000. I have been working at Korea Aerospace Research Institute for over 20 years, and my research interests are in structural optimization, aircraft structural analysis and testing, and dynamic modeling and simulation of landing gear systems.

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