This paper presents a set-based approach to use functional models for platform concept development to identify feasible modules at early design stages. The concepts are defined using functional requirements, design solutions and their interconnections. These models are then encapsulated into functional modules through clustering of Design Structure Matrixes (DSM). A metric is introduced to quantify the ability to modularize a certain concept, which may be used to assess and eliminate inferior concepts. The approach is illustrated using a case study from the aerospace industry. The result shows that modules can be identified by clustering of the functional structure. This has an integral effect on early division of work, possibility to design reuse, etc. The ability to modularize a specific concept The case study also shows that, despite of the traditionally integrated character of the product studied, it is possible to identify functional modules for reuse in a platform.