The potential of sandwich structures composed of fibre composite face sheets and a cellular polymer core has been known for years. It has been shown that the efficiency of the traditional manufacturing process which consists of stacking and bonding pre-manufactured layers can be improved by utilizing an expanding matrix in a closed mould, thus creating the sandwich structure within a one-step processs. However, the problem of joining parts that are formed in the said manner by means of load application elements remained.

Therefore, a method has been developed that allows the in-situ integration of topologically optimized lightweight inserts that are tailored to the requirements of integrally manufactured composite sandwich structures. In this lecture we want to show the path of development of said inserts by means of numerical topology optimization supported by 3D-printing. Furthermore, the achieved mechanical characteristics of the resulting joint and the possibilities of integrating inserts into the manufacturing process are presented.