CELLULOSE NANOFIBRILS (CNFS) ARE NATURAL MATERIALS WITH EXCEPTIONAL MECHANICAL PROPERTIES THAT CAN BE OBTAINED FROM RENEWABLE PLANT-BASED RESOURCES. CNFS ARE STIFF, STRONG, AND LIGHTWEIGHT, THUS THEY ARE IDEAL FOR USE IN STRUCTURAL MATERIALS. IN PARTICULAR, THERE IS A SIGNIFICANT OPPORTUNITY TO USE CNFS TO REALIZE POLYMER COMPOSITES WITH IMPROVED TOUGHNESS AND RESISTANCE TO FRACTURE. THE OVERALL GOAL OF THIS PROJECT IS TO ESTABLISH AN UNDERSTANDING OF FRACTURE TOUGHNESS ENHANCEMENT IN POLYMER COMPOSITES REINFORCED WITH CNFS. A KEY OUTCOME OF THIS WORK WILL BE PROCESS - STRUCTURE - FRACTURE PROPERTY RELATIONSHIPS FOR CNF-REINFORCED COMPOSITES. THE KNOWLEDGE DEVELOPED IN THIS PROJECT WILL ENABLE A NEW CLASS OF TOUGH CNF-REINFORCED COMPOSITE MATERIALS WITH APPLICATIONS IN AREAS SUCH AS BUILDING MATERIALS, AUTOMOTIVE COMPONENTS, AND CONSUMER PRODUCTS.THE COMPOSITE MATERIALS THAT WILL BE INVESTIGATED ARE AT THE CONVERGENCE OF NANOTECHNOLOGY AND BIO-SOURCED MATERIAL TRENDS. EMERGING NANOCELLULOSE TECHNOLOGIES HAVE THE POTENTIAL TO MOVE BIOMASS MATERIALS INTO HIGH VALUE-ADDED APPLICATIONS AND ENTIRELY NEW MARKETS.