P00003 SPACE VEHICLES USE SANDWICH COMPONENTS FOR ADAPTERS AND PAYLOAD FAIRINGS DUE TO THEIR HIGH BENDING STIFFNESS AND BUCKLING STRENGTHS. HOWEVER, SANDWICH COMPOSITES ARE PRONE TO DAMAGE DUE TO IMPACTS. LOW ENERGY OR BARELY VISIBLE IMPACT DAMAGE CAN LEAD TO SIGNIFICANT LOSS IN LOAD CARRYING CAPACITY. PREDICTING THE EFFECT OF LOW VELOCITY IMPACT DAMAGE ON SANDWICH COMPOSITES ON THEIR RESIDUAL STRENGTH AND LIFE OF A COMPONENT IS CRITICAL TO ASSURE MISSION SUCCESS. TO ASSESS DAMAGE TOLERANCE AND ENSURE SAFETY OF SANDWICH STRUCTURES A NUMBER OF MODEL CALIBRATIONS AND VALIDATION TESTS NEED TO BE PERFORMED. TESTING COSTS LIMIT THE NUMBER OF DESIGN CONFIGURATIONS, LOAD RANGES AND BOUNDARY CONDITIONS THAT CAN BE EXPLORED THEREFORE, THE VALIDITY OF CALIBRATED MODELS IS LIMITED TO SMALL DESIGN REGIONS. WHEN SITUATIONS OR DESIGN REQUIREMENTS FORCE PREDICTING THE RESPONSE OUTSIDE THE CALIBRATED DESIGN RANGE ADDITIONAL TESTS ARE NEEDED. FAILURE IN SANDWICH COMPOSITES INCLUDES DAMAGE TO THE COMPOSITE FACESHEET, DELAMINATION CRACKS AT THE FACESHEET-CORE INTERFACE OR DAMAGE TO THE SANDWICH CORE. POLYMER MATRIX IN COMPOSITES EXHIBIT VISCOELASTIC AND/OR VISCOPLASTIC RESPONSE UNDER IMPACT LOADS. THE DYNAMIC PROGRESSIVE FAILURE OF COMPOSITE UNDER TRANSIENT DYNAMICS LOAD HAS NOT BEEN AS FULLY EXPLORED AND VALIDATED. WE WILL INVESTIGATE MODELING APPROACHES TO PREDICT THE PLY LEVEL TRANSIENT AND INTERFACE DAMAGE RESPONSE IN COMPOSITES UNDER IMPACT LOADS. SANDWICH CORE FAILURE IS DRIVEN BY BUCKLING AND/OR PLASTIC COLLAPSE OF HONEYCOMB CELLS WALLS. ELASTIC RESPONSE OF HONEYCOMB CORES ARE MODELLED WITH EQUIVALENT HOMOGENIZED ORTHOTROPIC MATERIAL MODELS. RECENTLY RESEARCHERS HAVE PROPOSED HOMOGENIZATION TECHNIQUES FOR PLASTIC RESPONSE OF CELLULAR STRUCTURES. WE WILL EXPLORE THE USE OF HOMOGENIZATION MODELS FOR THE VISCOPLASTIC RESPONSE OF SANDWICH CORES UNDER IMPACT TO PREDICT THE STATE OF THE CORE AFTER IMPACT. DELAMINATION OF FACESHEET FROM CORE IS AN IMPORTANT FAILURE MODE IN SANDWICH COMPOSITES. THE INTERFACE FAILURE OF THE FACESHEET CORE IS COMPLEX AND CAN HAPPEN IN DIFFERENT MODES (E.G. COHESIVE FAILURE OF RESIN OR ADHESIVE FAILURE OF CELL WALL OR FACESHEET). IN QUASI STATIC PROGRESSIVE FAILURE ANALYSIS THE INTERFACE FAILURE IS MODELLED IN FINITE ELEMENT ANALYSES USING COHESIVE ZONE MODELS. WE WILL INVESTIGATE COHESIVE ZONE MODELING APPROACHES FOR THE DYNAMIC FRACTURE OF THE SANDWICH FACESHEET AND CORE INTERFACE. MANUFACTURING IMPERFECTIONS SIGNIFICANTLY AFFECT THE STRENGTH AND FAILURE RESPONSE OF COMPOSITES. CONCURRENTLY WITH INCREASING ACCURACY OF THE FAILURE PHYSICS IN ANALYSIS MODELS ONE MUST ALSO INCLUDE MANUFACTURING INDUCED IMPERFECTIONS TO INCREASE MODEL FIDELITY. WE WILL INVESTIGATE EFFECT OF MANUFACTURING IMPERFECTIONS AT MACRO- AND MICROSCALE ON THE IMPACT RESPONSE OF COMPOSITES. MOST IMPACT TESTS AND SIMULATIONS ON SANDWICH PANELS HAVE INVESTIGATED IMPACTS ON FLAT SANDWICH PANELS IN AN UNLOADED STATE. TO UNDERSTAND IMPACTS THAT CAN OCCUR IN A LOADED STATE (E.G VEHICLE ON LAUNCH PAD OR AT LIFT-OFF) WE WILL INVESTIGATE EFFECT OF INPLANE LOADS, CURVATURES AND THERMAL STRESSES ON THE IMPACT DAMAGE RESPONSE OF SANDWICH PANELS. MODELS USED TO PREDICT IMPACT DAMAGE IN SANDWICH COMPOSITES ARE OFTEN VERY DETAILED AND CANNOT BE USED IN ANALYSIS OF LARGE STRUCTURAL COMPONENTS TO ASSESS THE DAMAGE GROWTH UNDER SERVICE LOADS OR CYCLIC LOADS. WE WILL INVESTIGATE DIFFERENT MODELING APPROACHES FOR REPRESENTING THE IMPACT DAMAGE IN STRUCTURAL SCALE MODELS TO ASSESS THE REDUCTION OF STATIC STRENGTH, BUCKLING MARGINS AND LIFE OF THE COMPONENT UNDER REPEATED LOADS. WE WILL PERFORM A COMPREHENSIVE ASSESSMENT OF APPROACHES FOR PREDICTING EFFECT OF IMPACT DAMAGE. THE UNDERSTANDING OF THE OPTIONS AND KNOWLEDGE OF ACCURACY AND EFFICIENCY OF DIFFERENT MODELS WILL BE USED TO PROPOSE EFFICIENT MULTIFIDELITY MODELING APPROACHES THAT CAN PROVIDE THE BEST ACCURACY FOR A GIVEN COMPUTATIONAL RESOURCE BUDGET Funding Only Action $14.5k 8/25/21 Not listed SPACE VEHICLES USE SANDWICH COMPONENTS FOR ADAPTERS AND PAYLOAD FAIRINGS DUE TO THEIR HIGH BENDING STIFFNESS AND BUCKLING STRENGTHS. HOWEVER SANDWICH COMPOSITES ARE PRONE TO DAMAGE DUE TO IMPACTS. LOW ENERGY OR BARELY VISIBLE IMPACT DAMAGE CAN LEAD TO SIGNIFICANT LOSS IN LOAD CARRYING CAPACITY. PREDICTING THE EFFECT OF LOW VELOCITY IMPACT DAMAGE ON SANDWICH COMPOSITES ON THEIR RESIDUAL STRENGTH AND LIFE OF A COMPONENT IS CRITICAL TO ASSURE MISSION SUCCESS. TO ASSESS DAMAGE TOLERANCE AND ENSURE SAFETY OF SANDWICH STRUCTURES A NUMBER OF MODEL CALIBRATIONS AND VALIDATION TESTS NEED TO BE PERFORMED. TESTING COSTS LIMIT THE NUMBER OF DESIGN CONFIGURATIONS LOAD RANGES AND BOUNDARY CONDITIONS THAT CAN BE EXPLORED THEREFORE THE VALIDITY OF CALIBRATED MODELS IS LIMITED TO SMALL DESIGN REGIONS. WHEN SITUATIONS OR DESIGN REQUIREMENTS FORCE PREDICTING THE RESPONSE OUTSIDE THE CALIBRATED DESIGN RANGE ADDITIONAL TESTS ARE NEEDED. FAILURE IN SANDWICH COMPOSITES INCLUDES DAMAGE TO THE COMPOSITE FACESHEET DELAMINATION CRACKS AT THE FACESHEET-CORE INTERFACE OR DAMAGE TO THE SANDWICH CORE. POLYMER MATRIX IN COMPOSITES EXHIBIT VISCOELASTIC AND/OR VISCOPLASTIC RESPONSE UNDER IMPACT LOADS. THE DYNAMIC PROGRESSIVE FAILURE OF COMPOSITE UNDER TRANSIENT DYNAMICS LOAD HAS NOT BEEN AS FULLY EXPLORED AND VALIDATED. WE WILL INVESTIGATE MODELING APPROACHES TO PREDICT THE PLY LEVEL TRANSIENT AND INTERFACE DAMAGE RESPONSE IN COMPOSITES UNDER IMPACT LOADS. SANDWICH CORE FAILURE IS DRIVEN BY BUCKLING AND/OR PLASTIC COLLAPSE OF HONEYCOMB CELLS WALLS. ELASTIC RESPONSE OF HONEYCOMB CORES ARE MODELLED WITH EQUIVALENT HOMOGENIZED ORTHOTROPIC MATERIAL MODELS. RECENTLY RESEARCHERS HAVE PROPOSED HOMOGENIZATION TECHNIQUES FOR PLASTIC RESPONSE OF CELLULAR STRUCTURES. WE WILL EXPLORE THE USE OF HOMOGENIZATION MODELS FOR THE VISCOPLASTIC RESPONSE OF SANDWICH CORES UNDER IMPACT TO PREDICT THE STATE OF THE CORE AFTER IMPACT. DELAMINATION OF FACESHEET FROM CORE IS AN IMPORTANT FAILURE MODE IN SANDWICH COMPOSITES. THE INTERFACE FAILURE OF THE FACESHEET CORE IS COMPLEX AND CAN HAPPEN IN DIFFERENT MODES (E.G. COHESIVE FAILURE OF RESIN OR ADHESIVE FAILURE OF CELL WALL OR FACESHEET). IN QUASI STATIC PROGRESSIVE FAILURE ANALYSIS THE INTERFACE FAILURE IS MODELLED IN FINITE ELEMENT ANALYSES USING COHESIVE ZONE MODELS. WE WILL INVESTIGATE COHESIVE ZONE MODELING APPROACHES FOR THE DYNAMIC FRACTURE OF THE SANDWICH FACESHEET AND CORE INTERFACE. MANUFACTURING IMPERFECTIONS SIGNIFICANTLY AFFECT THE STRENGTH AND FAILURE RESPONSE OF COMPOSITES. CONCURRENTLY WITH INCREASING ACCURACY OF THE FAILURE PHYSICS IN ANALYSIS MODELS ONE MUST ALSO INCLUDE MANUFACTURING INDUCED IMPERFECTIONS TO INCREASE MODEL FIDELITY. WE WILL INVESTIGATE EFFECT OF MANUFACTURING IMPERFECTIONS AT MACRO- AND MICROSCALE ON THE IMPACT RESPONSE OF COMPOSITES. MOST IMPACT TESTS AND SIMULATIONS ON SANDWICH PANELS HAVE INVESTIGATED IMPACTS ON FLAT SANDWICH PANELS IN AN UNLOADED STATE. TO UNDERSTAND IMPACTS THAT CAN OCCUR IN A LOADED STATE (E.G VEHICLE ON LAUNCH PAD OR AT LIFT-OFF) WE WILL INVESTIGATE EFFECT OF INPLANE LOADS CURVATURES AND THERMAL STRESSES ON THE IMPACT DAMAGE RESPONSE OF SANDWICH PANELS. MODELS USED TO PREDICT IMPACT DAMAGE IN SANDWICH COMPOSITES ARE OFTEN VERY DETAILED AND CANNOT BE USED IN ANALYSIS OF LARGE STRUCTURAL COMPONENTS TO ASSESS THE DAMAGE GROWTH UNDER SERVICE LOADS OR CYCLIC LOADS. WE WILL INVESTIGATE DIFFERENT MODELING APPROACHES FOR REPRESENTING THE IMPACT DAMAGE IN STRUCTURAL SCALE MODELS TO ASSESS THE REDUCTION OF STATIC STRENGTH BUCKLING MARGINS AND LIFE OF THE COMPONENT UNDER REPEATED LOADS. WE WILL PERFORM A COMPREHENSIVE ASSESSMENT OF APPROACHES FOR PREDICTING EFFECT OF IMPACT DAMAGE. THE UNDERSTANDING OF THE OPTIONS AND KNOWLEDGE OF ACCURACY AND EFFICIENCY OF DIFFERENT MODELS WILL BE USED TO PROPOSE EFFICIENT MULTIFIDELITY MODELING APPROACHES THAT CAN PROVIDE THE BEST ACCURACY FOR A GIVEN COMPUTATIONAL RESOURCE BUDGET $14.5k 8/25/21 Not listed SPACE VEHICLES USE SANDWICH COMPONENTS FOR ADAPTERS AND PAYLOAD FAIRINGS DUE TO THEIR HIGH BENDING STIFFNESS AND BUCKLING STRENGTHS. HOWEVER SANDWICH COMPOSITES ARE PRONE TO DAMAGE DUE TO IMPACTS. LOW ENERGY OR BARELY VISIBLE IMPACT DAMAGE CAN LEAD TO SIGNIFICANT LOSS IN LOAD CARRYING CAPACITY. PREDICTING THE EFFECT OF LOW VELOCITY IMPACT DAMAGE ON SANDWICH COMPOSITES ON THEIR RESIDUAL STRENGTH AND LIFE OF A COMPONENT IS CRITICAL TO ASSURE MISSION SUCCESS. TO ASSESS DAMAGE TOLERANCE AND ENSURE SAFETY OF SANDWICH STRUCTURES A NUMBER OF MODEL CALIBRATIONS AND VALIDATION TESTS NEED TO BE PERFORMED. TESTING COSTS LIMIT THE NUMBER OF DESIGN CONFIGURATIONS LOAD RANGES AND BOUNDARY CONDITIONS THAT CAN BE EXPLORED THEREFORE THE VALIDITY OF CALIBRATED MODELS IS LIMITED TO SMALL DESIGN REGIONS. WHEN SITUATIONS OR DESIGN REQUIREMENTS FORCE PREDICTING THE RESPONSE OUTSIDE THE CALIBRATED DESIGN RANGE ADDITIONAL TESTS ARE NEEDED. FAILURE IN SANDWICH COMPOSITES INCLUDES DAMAGE TO THE COMPOSITE FACESHEET DELAMINATION CRACKS AT THE FACESHEET-CORE INTERFACE OR DAMAGE TO THE SANDWICH CORE. POLYMER MATRIX IN COMPOSITES EXHIBIT VISCOELASTIC AND/OR VISCOPLASTIC RESPONSE UNDER IMPACT LOADS. THE DYNAMIC PROGRESSIVE FAILURE OF COMPOSITE UNDER TRANSIENT DYNAMICS LOAD HAS NOT BEEN AS FULLY EXPLORED AND VALIDATED. WE WILL INVESTIGATE MODELING APPROACHES TO PREDICT THE PLY LEVEL TRANSIENT AND INTERFACE DAMAGE RESPONSE IN COMPOSITES UNDER IMPACT LOADS. SANDWICH CORE FAILURE IS DRIVEN BY BUCKLING AND/OR PLASTIC COLLAPSE OF HONEYCOMB CELLS WALLS. ELASTIC RESPONSE OF HONEYCOMB CORES ARE MODELLED WITH EQUIVALENT HOMOGENIZED ORTHOTROPIC MATERIAL MODELS. RECENTLY RESEARCHERS HAVE PROPOSED HOMOGENIZATION TECHNIQUES FOR PLASTIC RESPONSE OF CELLULAR STRUCTURES. WE WILL EXPLORE THE USE OF HOMOGENIZATION MODELS FOR THE VISCOPLASTIC RESPONSE OF SANDWICH CORES UNDER IMPACT TO PREDICT THE STATE OF THE CORE AFTER IMPACT. DELAMINATION OF FACESHEET FROM CORE IS AN IMPORTANT FAILURE MODE IN SANDWICH COMPOSITES. THE INTERFACE FAILURE OF THE FACESHEET CORE IS COMPLEX AND CAN HAPPEN IN DIFFERENT MODES (E.G. COHESIVE FAILURE OF RESIN OR ADHESIVE FAILURE OF CELL WALL OR FACESHEET). IN QUASI STATIC PROGRESSIVE FAILURE ANALYSIS THE INTERFACE FAILURE IS MODELLED IN FINITE ELEMENT ANALYSES USING COHESIVE ZONE MODELS. WE WILL INVESTIGATE COHESIVE ZONE MODELING APPROACHES FOR THE DYNAMIC FRACTURE OF THE SANDWICH FACESHEET AND CORE INTERFACE. MANUFACTURING IMPERFECTIONS SIGNIFICANTLY AFFECT THE STRENGTH AND FAILURE RESPONSE OF COMPOSITES. CONCURRENTLY WITH INCREASING ACCURACY OF THE FAILURE PHYSICS IN ANALYSIS MODELS ONE MUST ALSO INCLUDE MANUFACTURING INDUCED IMPERFECTIONS TO INCREASE MODEL FIDELITY. WE WILL INVESTIGATE EFFECT OF MANUFACTURING IMPERFECTIONS AT MACRO- AND MICROSCALE ON THE IMPACT RESPONSE OF COMPOSITES. MOST IMPACT TESTS AND SIMULATIONS ON SANDWICH PANELS HAVE INVESTIGATED IMPACTS ON FLAT SANDWICH PANELS IN AN UNLOADED STATE. TO UNDERSTAND IMPACTS THAT CAN OCCUR IN A LOADED STATE (E.G VEHICLE ON LAUNCH PAD OR AT LIFT-OFF) WE WILL INVESTIGATE EFFECT OF INPLANE LOADS CURVATURES AND THERMAL STRESSES ON THE IMPACT DAMAGE RESPONSE OF SANDWICH PANELS. MODELS USED TO PREDICT IMPACT DAMAGE IN SANDWICH COMPOSITES ARE OFTEN VERY DETAILED AND CANNOT BE USED IN ANALYSIS OF LARGE STRUCTURAL COMPONENTS TO ASSESS THE DAMAGE GROWTH UNDER SERVICE LOADS OR CYCLIC LOADS. WE WILL INVESTIGATE DIFFERENT MODELING APPROACHES FOR REPRESENTING THE IMPACT DAMAGE IN STRUCTURAL SCALE MODELS TO ASSESS THE REDUCTION OF STATIC STRENGTH BUCKLING MARGINS AND LIFE OF THE COMPONENT UNDER REPEATED LOADS. WE WILL PERFORM A COMPREHENSIVE ASSESSMENT OF APPROACHES FOR PREDICTING EFFECT OF IMPACT DAMAGE. THE UNDERSTANDING OF THE OPTIONS AND KNOWLEDGE OF ACCURACY AND EFFICIENCY OF DIFFERENT MODELS WILL BE USED TO PROPOSE EFFICIENT MULTIFIDELITY MODELING APPROACHES THAT CAN PROVIDE THE BEST ACCURACY FOR A GIVEN COMPUTATIONAL RESOURCE BUDGET $0 6/23/21 P00002 SPACE VEHICLES USE SANDWICH COMPONENTS FOR ADAPTERS AND PAYLOAD FAIRINGS DUE TO THEIR HIGH BENDING STIFFNESS AND BUCKLING STRENGTHS. HOWEVER, SANDWICH COMPOSITES ARE PRONE TO DAMAGE DUE TO IMPACTS. LOW ENERGY OR BARELY VISIBLE IMPACT DAMAGE CAN LEAD TO SIGNIFICANT LOSS IN LOAD CARRYING CAPACITY. PREDICTING THE EFFECT OF LOW VELOCITY IMPACT DAMAGE ON SANDWICH COMPOSITES ON THEIR RESIDUAL STRENGTH AND LIFE OF A COMPONENT IS CRITICAL TO ASSURE MISSION SUCCESS. TO ASSESS DAMAGE TOLERANCE AND ENSURE SAFETY OF SANDWICH STRUCTURES A NUMBER OF MODEL CALIBRATIONS AND VALIDATION TESTS NEED TO BE PERFORMED. TESTING COSTS LIMIT THE NUMBER OF DESIGN CONFIGURATIONS, LOAD RANGES AND BOUNDARY CONDITIONS THAT CAN BE EXPLORED THEREFORE, THE VALIDITY OF CALIBRATED MODELS IS LIMITED TO SMALL DESIGN REGIONS. WHEN SITUATIONS OR DESIGN REQUIREMENTS FORCE PREDICTING THE RESPONSE OUTSIDE THE CALIBRATED DESIGN RANGE ADDITIONAL TESTS ARE NEEDED. FAILURE IN SANDWICH COMPOSITES INCLUDES DAMAGE TO THE COMPOSITE FACESHEET, DELAMINATION CRACKS AT THE FACESHEET-CORE INTERFACE OR DAMAGE TO THE SANDWICH CORE. POLYMER MATRIX IN COMPOSITES EXHIBIT VISCOELASTIC AND/OR VISCOPLASTIC RESPONSE UNDER IMPACT LOADS. THE DYNAMIC PROGRESSIVE FAILURE OF COMPOSITE UNDER TRANSIENT DYNAMICS LOAD HAS NOT BEEN AS FULLY EXPLORED AND VALIDATED. WE WILL INVESTIGATE MODELING APPROACHES TO PREDICT THE PLY LEVEL TRANSIENT AND INTERFACE DAMAGE RESPONSE IN COMPOSITES UNDER IMPACT LOADS. SANDWICH CORE FAILURE IS DRIVEN BY BUCKLING AND/OR PLASTIC COLLAPSE OF HONEYCOMB CELLS WALLS. ELASTIC RESPONSE OF HONEYCOMB CORES ARE MODELLED WITH EQUIVALENT HOMOGENIZED ORTHOTROPIC MATERIAL MODELS. RECENTLY RESEARCHERS HAVE PROPOSED HOMOGENIZATION TECHNIQUES FOR PLASTIC RESPONSE OF CELLULAR STRUCTURES. WE WILL EXPLORE THE USE OF HOMOGENIZATION MODELS FOR THE VISCOPLASTIC RESPONSE OF SANDWICH CORES UNDER IMPACT TO PREDICT THE STATE OF THE CORE AFTER IMPACT. DELAMINATION OF FACESHEET FROM CORE IS AN IMPORTANT FAILURE MODE IN SANDWICH COMPOSITES. THE INTERFACE FAILURE OF THE FACESHEET CORE IS COMPLEX AND CAN HAPPEN IN DIFFERENT MODES (E.G. COHESIVE FAILURE OF RESIN OR ADHESIVE FAILURE OF CELL WALL OR FACESHEET). IN QUASI STATIC PROGRESSIVE FAILURE ANALYSIS THE INTERFACE FAILURE IS MODELLED IN FINITE ELEMENT ANALYSES USING COHESIVE ZONE MODELS. WE WILL INVESTIGATE COHESIVE ZONE MODELING APPROACHES FOR THE DYNAMIC FRACTURE OF THE SANDWICH FACESHEET AND CORE INTERFACE. MANUFACTURING IMPERFECTIONS SIGNIFICANTLY AFFECT THE STRENGTH AND FAILURE RESPONSE OF COMPOSITES. CONCURRENTLY WITH INCREASING ACCURACY OF THE FAILURE PHYSICS IN ANALYSIS MODELS ONE MUST ALSO INCLUDE MANUFACTURING INDUCED IMPERFECTIONS TO INCREASE MODEL FIDELITY. WE WILL INVESTIGATE EFFECT OF MANUFACTURING IMPERFECTIONS AT MACRO- AND MICROSCALE ON THE IMPACT RESPONSE OF COMPOSITES. MOST IMPACT TESTS AND SIMULATIONS ON SANDWICH PANELS HAVE INVESTIGATED IMPACTS ON FLAT SANDWICH PANELS IN AN UNLOADED STATE. TO UNDERSTAND IMPACTS THAT CAN OCCUR IN A LOADED STATE (E.G VEHICLE ON LAUNCH PAD OR AT LIFT-OFF) WE WILL INVESTIGATE EFFECT OF INPLANE LOADS, CURVATURES AND THERMAL STRESSES ON THE IMPACT DAMAGE RESPONSE OF SANDWICH PANELS. MODELS USED TO PREDICT IMPACT DAMAGE IN SANDWICH COMPOSITES ARE OFTEN VERY DETAILED AND CANNOT BE USED IN ANALYSIS OF LARGE STRUCTURAL COMPONENTS TO ASSESS THE DAMAGE GROWTH UNDER SERVICE LOADS OR CYCLIC LOADS. WE WILL INVESTIGATE DIFFERENT MODELING APPROACHES FOR REPRESENTING THE IMPACT DAMAGE IN STRUCTURAL SCALE MODELS TO ASSESS THE REDUCTION OF STATIC STRENGTH, BUCKLING MARGINS AND LIFE OF THE COMPONENT UNDER REPEATED LOADS. WE WILL PERFORM A COMPREHENSIVE ASSESSMENT OF APPROACHES FOR PREDICTING EFFECT OF IMPACT DAMAGE. THE UNDERSTANDING OF THE OPTIONS AND KNOWLEDGE OF ACCURACY AND EFFICIENCY OF DIFFERENT MODELS WILL BE USED TO PROPOSE EFFICIENT MULTIFIDELITY MODELING APPROACHES THAT CAN PROVIDE THE BEST ACCURACY FOR A GIVEN COMPUTATIONAL RESOURCE BUDGET Other Administrative Action $0 6/23/21 P00001 SPACE VEHICLES USE SANDWICH COMPONENTS FOR ADAPTERS AND PAYLOAD FAIRINGS DUE TO THEIR HIGH BENDING STIFFNESS AND BUCKLING STRENGTHS. HOWEVER, SANDWICH COMPOSITES ARE PRONE TO DAMAGE DUE TO IMPACTS. LOW ENERGY OR BARELY VISIBLE IMPACT DAMAGE CAN LEAD TO SIGNIFICANT LOSS IN LOAD CARRYING CAPACITY. PREDICTING THE EFFECT OF LOW VELOCITY IMPACT DAMAGE ON SANDWICH COMPOSITES ON THEIR RESIDUAL STRENGTH AND LIFE OF A COMPONENT IS CRITICAL TO ASSURE MISSION SUCCESS. TO ASSESS DAMAGE TOLERANCE AND ENSURE SAFETY OF SANDWICH STRUCTURES A NUMBER OF MODEL CALIBRATIONS AND VALIDATION TESTS NEED TO BE PERFORMED. TESTING COSTS LIMIT THE NUMBER OF DESIGN CONFIGURATIONS, LOAD RANGES AND BOUNDARY CONDITIONS THAT CAN BE EXPLORED THEREFORE, THE VALIDITY OF CALIBRATED MODELS IS LIMITED TO SMALL DESIGN REGIONS. WHEN SITUATIONS OR DESIGN REQUIREMENTS FORCE PREDICTING THE RESPONSE OUTSIDE THE CALIBRATED DESIGN RANGE ADDITIONAL TESTS ARE NEEDED. FAILURE IN SANDWICH COMPOSITES INCLUDES DAMAGE TO THE COMPOSITE FACESHEET, DELAMINATION CRACKS AT THE FACESHEET-CORE INTERFACE OR DAMAGE TO THE SANDWICH CORE. POLYMER MATRIX IN COMPOSITES EXHIBIT VISCOELASTIC AND/OR VISCOPLASTIC RESPONSE UNDER IMPACT LOADS. THE DYNAMIC PROGRESSIVE FAILURE OF COMPOSITE UNDER TRANSIENT DYNAMICS LOAD HAS NOT BEEN AS FULLY EXPLORED AND VALIDATED. WE WILL INVESTIGATE MODELING APPROACHES TO PREDICT THE PLY LEVEL TRANSIENT AND INTERFACE DAMAGE RESPONSE IN COMPOSITES UNDER IMPACT LOADS. SANDWICH CORE FAILURE IS DRIVEN BY BUCKLING AND/OR PLASTIC COLLAPSE OF HONEYCOMB CELLS WALLS. ELASTIC RESPONSE OF HONEYCOMB CORES ARE MODELLED WITH EQUIVALENT HOMOGENIZED ORTHOTROPIC MATERIAL MODELS. RECENTLY RESEARCHERS HAVE PROPOSED HOMOGENIZATION TECHNIQUES FOR PLASTIC RESPONSE OF CELLULAR STRUCTURES. WE WILL EXPLORE THE USE OF HOMOGENIZATION MODELS FOR THE VISCOPLASTIC RESPONSE OF SANDWICH CORES UNDER IMPACT TO PREDICT THE STATE OF THE CORE AFTER IMPACT. DELAMINATION OF FACESHEET FROM CORE IS AN IMPORTANT FAILURE MODE IN SANDWICH COMPOSITES. THE INTERFACE FAILURE OF THE FACESHEET CORE IS COMPLEX AND CAN HAPPEN IN DIFFERENT MODES (E.G. COHESIVE FAILURE OF RESIN OR ADHESIVE FAILURE OF CELL WALL OR FACESHEET). IN QUASI STATIC PROGRESSIVE FAILURE ANALYSIS THE INTERFACE FAILURE IS MODELLED IN FINITE ELEMENT ANALYSES USING COHESIVE ZONE MODELS. WE WILL INVESTIGATE COHESIVE ZONE MODELING APPROACHES FOR THE DYNAMIC FRACTURE OF THE SANDWICH FACESHEET AND CORE INTERFACE. MANUFACTURING IMPERFECTIONS SIGNIFICANTLY AFFECT THE STRENGTH AND FAILURE RESPONSE OF COMPOSITES. CONCURRENTLY WITH INCREASING ACCURACY OF THE FAILURE PHYSICS IN ANALYSIS MODELS ONE MUST ALSO INCLUDE MANUFACTURING INDUCED IMPERFECTIONS TO INCREASE MODEL FIDELITY. WE WILL INVESTIGATE EFFECT OF MANUFACTURING IMPERFECTIONS AT MACRO- AND MICROSCALE ON THE IMPACT RESPONSE OF COMPOSITES. MOST IMPACT TESTS AND SIMULATIONS ON SANDWICH PANELS HAVE INVESTIGATED IMPACTS ON FLAT SANDWICH PANELS IN AN UNLOADED STATE. TO UNDERSTAND IMPACTS THAT CAN OCCUR IN A LOADED STATE (E.G VEHICLE ON LAUNCH PAD OR AT LIFT-OFF) WE WILL INVESTIGATE EFFECT OF INPLANE LOADS, CURVATURES AND THERMAL STRESSES ON THE IMPACT DAMAGE RESPONSE OF SANDWICH PANELS. MODELS USED TO PREDICT IMPACT DAMAGE IN SANDWICH COMPOSITES ARE OFTEN VERY DETAILED AND CANNOT BE USED IN ANALYSIS OF LARGE STRUCTURAL COMPONENTS TO ASSESS THE DAMAGE GROWTH UNDER SERVICE LOADS OR CYCLIC LOADS. WE WILL INVESTIGATE DIFFERENT MODELING APPROACHES FOR REPRESENTING THE IMPACT DAMAGE IN STRUCTURAL SCALE MODELS TO ASSESS THE REDUCTION OF STATIC STRENGTH, BUCKLING MARGINS AND LIFE OF THE COMPONENT UNDER REPEATED LOADS. WE WILL PERFORM A COMPREHENSIVE ASSESSMENT OF APPROACHES FOR PREDICTING EFFECT OF IMPACT DAMAGE. THE UNDERSTANDING OF THE OPTIONS AND KNOWLEDGE OF ACCURACY AND EFFICIENCY OF DIFFERENT MODELS WILL BE USED TO PROPOSE EFFICIENT MULTIFIDELITY MODELING APPROACHES THAT CAN PROVIDE THE BEST ACCURACY FOR A GIVEN COMPUTATIONAL RESOURCE BUDGET Other Administrative Action $0 11/18/19