Process induced deformations - A study on sandwich test samples

In favor of an optimal utilization of the superior material properties of CFRP structures, the trend points towards more integral and thus geometrically more complicated structures. An understanding of the effect of various phenomena is difficult to develop for complicated geometries, thus investigation of main drivers on simply shaped subcomponents have been used by various researchers in order to differentiate deformation modes. While monolithic parts have gained a lot of attention over the years, little can be found on the deformation behavior of sandwich samples in the literature. In a bigger test campaign experimental deformation data has been generated on various combinations of layups, tooling materials and design concepts for monolithic and sandwich L-shaped test specimen reflecting relevant aerospace setups. The occurrence of the main deformation modes spring-in and warpage are discussed for the different configurations. In a first step the magnitude particularly for the spring-in component is opposed with simple analytical formulae for L-shaped sandwich samples. The findings in terms of spring-in and warpage are discussed and factors of influence are summarized.