COMPUTATIONAL DESIGN OF CARBON NANOTUBE NETWORK MATERIALS AND POLYMER MATRIX NANOCOMPOSITESCARBON NANOTUBE (CNT) BASED COMPOSITES CONSTITUTE A BROAD CLASS OF MULTIFUNCTIONAL HIERARCHICAL MATERIALS DERIVING THEIR PROPERTIES FROM THE INTIMATE CONNECTIONS BETWEEN THE ATOMIC STRUCTURE OF INDIVIDUAL CNTS ARRANGEMENT OF CNTS INTO MESOSCOPIC STRUCTURAL ELEMENTS SUCH AS CNT BUNDLES AND BRANCHING STRUCTURES STRUCTURAL ORGANIZATION OF THE MESOSCOPIC ELEMENTS INTO COMPLEX NETWORKS AND IN THE CASE OF POLYMER MATRIX COMPOSITES DISTRIBUTION OF CNTS IN THE MATRIX AND THE CHARACTERISTICS OF CNT-MATRIX INTERACTIONS. THE UNIQUE COMBINATION OF STRUCTURAL MECHANICAL AND TRANSPORT PROPERTIES OF CNT MATERIALS MAKES THEM ATTRACTIVE CANDIDATES FOR DESIGNING LIGHTWEIGHT MULTIFUNCTIONAL MATERIALS. THE HIERARCHICAL MULTISCALE ORGANIZATION OF THE CNT MATERIALS WIDE DIVERSITY OF MATERIAL STRUCTURES AND VARIABILITY OF PHYSICAL PROPERTIES PRESENT A CHALLENGE FOR THEORETICAL EVALUATION OF THE STRUCTURE-PROPERTIES RELATIONSHIPS AND DEFINE THE CRITICAL ROLE THE COMPUTATIONAL MODELING CAN PLAY IN DESIGNING THE ADVANCED CNT MATERIALS. THE MAIN GOAL OF THE PROPOSED RESEARCH PROGRAM IS TO DEVELOP A ROBUST MESOSCOPIC COMPUTATIONAL MODEL CAPABLE OF REVEALING THE STRUCTURE-PROPERTIES RELATIONSHIPS IN CNT NETWORK MATERIALS AND POLYMER MATRIX NANOCOMPOSITES. THE ABILITY OF THE MESOSCOPIC MODEL TO BRIDGE THE GAP BETWEEN THE BEHAVIOR AND PROPERTIES OF THE INDIVIDUAL COMPONENTS OF NANOCOMPOSITES (NANOTUBES POLYMER MATRIX AND CNT-MATRIX INTERFACES) AND THE EFFECTIVE MACROSCOPIC PROPERTIES DEFINED BY THE COLLECTIVE BEHAVIOR OF MULTIPLE NANOTUBES AND THEIR INTERACTION WITH EACH OTHER AND WITH THE MATRIX WILL BE FULLY UTILIZED IN A SYSTEMATIC ANALYSIS OF THE STRUCTURAL MECHANICAL AND THERMAL TRANSPORT PROPERTIES OF THE CNT MATERIALS. THE SPECIFIC OBJECTIVES OF THE PROPOSED RESEARCH PROGRAM ARE(1)TO DEVELOP BASED ON THE PRIOR WORK BY THE PI AND CO-I AN ADVANCED STATE-OF-THE-ART MESOSCOPIC COMPUTATIONAL MODEL CAPABLE OF REALISTIC REPRESENTATION OF THE COLLECTIVE DYNAMICS AND STRUCTURAL REARRANGEMENTS IN SYSTEMS CONSISTING OF UP TO TENS OF THOUSANDS CNTS;(2)TO IMPROVE THE FLEXIBILITY OF THE MODEL BY ENABLING SIMULATIONS OF FLATTENED CNTS (NANORIBBONS) AND ADDING COARSE-GRAINED DESCRIPTIONS OF CROSSLINKS AND CHEMICAL FUNCTIONALIZATION OF CNTS;(3)TO FURTHER ADVANCE THE MODEL BY INCORPORATING AN ORIGINAL HEAT BATH APPROACH ACCOUNTING FOR DIFFERENT CHANNELS OF THE MECHANICAL ENERGY DISSIPATION;(4)TO DESIGN AND IMPLEMENT INNOVATIVE APPROACHES FOR COMPUTATIONALLY-EFFICIENT MESOSCOPIC DESCRIPTION OF POLYMER MATRIX AND CNTMATRIX INTERACTIONS;(5)TO APPLY THE MODEL FOR A SYSTEMATIC COMPUTATIONAL ANALYSIS OF THE STRUCTURAL SELF-ORGANIZATION IN VARIOUS CNT MATERIALS (AEROGELS FILMS FORESTS AND FIBERS)AND TO BUILD MAPS OF STABILITY OF THE CNT STRUCTURES IN A BROAD RANGE OF MATERIAL PARAMETERS (MATERIAL DENSITY CNT TYPE AND LENGTH DENSITY OF CROSS-LINKS);(6)TO ESTABLISH THROUGH ADVANCED MULTISCALE MODELING THE KEY MICROSTRUCTURAL FEATURES AND ELEMENTARY PROCESSES THAT CONTROL THE MECHANICAL BEHAVIOR AND ENERGY DISSIPATION IN CNT MATERIALS UNDER CONDITIONS OF QUASI-STATIC AND DYNAMIC LOADING;(7)TO INVESTIGATE THE EFFECTS OF DISPERSION AND ALIGNMENT OF CNTS AS WELL AS INTER-TUBE AND CNT-MATRIX CROSS-LINKS ON THE LOAD TRANSFER AND MECHANICAL PROPERTIES OF POLYMER MATRIX CNT NANOCOMPOSITES;(8)TO REVEAL THE EFFECT OF THE MECHANICAL DEFORMATION ON THE THERMAL TRANSPORT PROPERTIES OF CNT MATERIALS. THE EMERGENCE OF A FLEXIBLE AND COMPUTATIONALLY EFFICIENT MESOSCOPIC MODEL FOR SIMULATION OF CNT-BASED MATERIALS WILL FACILITATE THE DEVELOPMENT OF MULTIFUNCTIONAL LOW-DENSITY MATERIALS WITH MECHANICAL AND TRANSPORT PROPERTIES TAILORED FOR AEROSPACE APPLICATIONS AND WILL MAKE A BROAD IMPACT IN THE GENERAL AREA OF COMPUTATIONAL DESIGN OF NANOFIBROUS COMPOSITE MATERIALS.