The “21st Symposium on Composites” covered a wide range of composite-related topics including polymers, metal and ceramic composites, hybrid structures and laminates, coatings, manufacturing technologies, testing and simulation, structural health monitoring, biocomposites and recycling technologies. This conference was organized by “Gemeinschaftsausschuss Verbundwerkstoffe (GAV)” within “Deutsche Gesellschafft für Materialkunde e.V. (DGM)“ in cooperation with the University of Bremen. The attendants from academia and industry presented and discussed their latest research results and developments related to different kinds of modern composites.