Collection of selected, peer reviewed papers from the 20th Symposium on Composites, July 1-3, 2015, Vienna, Austria. The 137 papers are grouped as follows: Chapter 1: Polymer Matrix Composites; Chapter 2: Metal Matrix Composites and Interpenetrating Materials; Chapter 3: Ceramic Matrix Composites; Chapter 4: Hybrid Structures, Laminates; Chapter 5: Structural Health Monitoring; Chapter 6: Coatings; Chapter 7: Modelling, Simulation; Chapter 8: Manufacturing Technology, Components/Products/Applications; Chapter 9: Testing and Characterization; Chapter 10: Cemented carbides, Cermets, Wear and Abrasion Materials; Chapter 11: Bio-Composites; Chapter 12: Recycling & Sustainability, Building Materials