Topology Optimisation applied to WAAM for a mold of composites parts

What is topology optimization? What does it aim at?

In engineering applications, we aim for optimized structures such that the usage of materials can be minimized without affecting the structures’ functionalities. Topology optimization (TO) is a structural framework for finding optimum material distributions in a predefined design domain to achieve various design goals. In other words, topology optimization helps us to decide where material can be left out, because it is not really needed there to support the structure; According to the late French engineer Robert Le Ricolas (1894-1977), “the art of structure is where to put the holes”. In the same spirit, we can consider topology optimization as the art to put the holes in structures.

Why using TO during the Grade2XL project?

In the Grade2XL project, we would like to exploit the advancements of the so-called Wire-Arc Additive Manufacturing (WAAM) technique to design and manufacture engineering structures more efficiently and more sustainably. Especially, the WAAM technique can produce parts made of multiple materials. Thus, it creates more room for engineers to design innovative and high-performing structures. The natural question that arises is how we can deposit different materials optimally within a predefined design domain such that the resultant structure can achieve a certain design goal. This question can be addressed by using topology optimization. Moreover, topology optimization typically results in quite organic shapes that are very difficult to produce with conventional machining procedures, but WAAM offers much more flexibility to print complex and organic shapes.

What is the use-case you have been working on within the Grade2XL project ? Which problem were you requested to solve?

Within the Grade2XL project, we have worked closely with colleagues from GKN Aerospace, M2i, TU Delft, and RAMLAB. We aim to create an optimum design for a large-scale mold at GKN Aerospace to produce composite parts (see picture below).

The mold would be manufactured with the Invar alloy using the WAAM technique. In service, the mold is subjected to both mechanical and thermal loadings that are induced during the manufacturing of the composite part inside the mold, thus the optimum mold is on one hand minimum in mass, but is on the other hand strong enough to withstand the thermo-mechanical loadings such that the molded composite parts have accurate dimensions.

At Ghent University, we have developed in-house software to perform topology optimization for thermoelastic structures. Our software can couple with any commercial finite element code so that we can utilize the finite element software to solve large-scale coupled thermal-mechanical problems efficiently. Moreover, we have also integrated different modern optimizers in our software thus users can choose the most efficient optimizer for their applications. As preliminary work, we have performed topology optimization for a small-scale production mold for composites. The target of the optimization problem is to reduce the deflection of the mold, denoted as U3 in figure 1, and at the same time satisfy a mass constraint. A design solution was found with less deflection and a lower weight.

Can the work you carried out in Grade2XL be applied to other technical fields and/or industries? Which other use-case for example?

Topology optimization using multiple materials for thermo-mechanical problems has a wide range of applications, for example, thermal protection systems in an aircraft or battery pack design. Therefore, we believe that our work developed in Grade2XL can leverage the usage of additive manufacturing techniques in a lot of high-end applications.

Dr. Tien Dung DINH ( is postdoctoral researcher in the Mechanics of Materials and Structures research group at Ghent University, Belgium (UGent-MMS). This group, under supervision of Prof. Wim VAN PAEPEGEM (, counts about 30 researchers and focuses on experimental mechanics, numerical modelling and nondestructive testing of composites and additive manufactured materials. For additive manufactured materials, there is a wide expertise on (multi-axial) fatigue testing, topology optimization, multi-scale modelling, FEM simulation for industrial and biomedical applications, and quality control of complex shaped parts.