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Item Effects of liquid disinfectants and ultraviolet-c germicidal irradiation on honeycomb core sandwich panels(American Institute of Aeronautics and Astronautics Inc, AIAA, 2023) Bhasin, Akhil; Ravi, Aswini Kona; Castillo, Luis D.; Maichan, Tanat; Gomez, Luis M.; Olivares, GerardoAs a result of the coronavirus disease 2019 (COVID-19) public health emergency, the airline industry had implemented additional measures to disinfect aircraft interiors. This involved frequent use of disinfectant products on aircraft cabin and seating materials. In this paper, the long-term effects of exposing honeycomb sandwich panels to disinfectant products are presented. The disinfectant methods considered for this study are chemical and ultraviolet-c germicidal irradiation. Five different chemical disinfectants commonly used in the airline industry and three different ultraviolet-c wavelength configurations were selected. Accelerated aging tests with various disinfectant configurations were conducted on honeycomb sandwich specimens and the subsequent effects on mechanical and physical performance are investigated. © 2023, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Item Comparison of wind tunnel vortex survey results with the n-Vortex Model(American Institute of Aeronautics and Astronautics Inc, AIAA, 2023) Kuenn, Aaron D.; Kliment, Linda K.Results of wingtip vortex surveys in the midfield wake of a flat-plate wing with AR=6 and a NACA 0015 wing with AR=5.35 are presented. The majority of the data was collected behind the flat-plate wing at Rec between 1.7 x 105 and 2.6 x 105. Previous comparisons of the experimental data with laminar and turbulent axisymmetric models suggested the trailing vortex had a consistent turbulent structure despite the moderate vortex-circulation Reynolds number. Current comparisons with the turbulent n-family of vortices indicate a high level of turbulence in the vortex. Surveys behind the NACA 0015 wing also suggest a turbulent profile, but indicate a lower level of turbulence despite a higher vortex-circulation Reynolds number. © 2023, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Item Computational methodology to compute unmanned aircraft deflections due to aerodynamiciInteraction with a commercial aircraft(American Institute of Aeronautics and Astronautics Inc, AIAA, 2023) Shah, Harsh; Sathyanarayana, Nidhi; Gomez Valbuena, Luis M.; Olivares, GerardoThis paper describes the study of the possibility of a small Unmanned Aircraft System (UAS)deflecting away from a collision path with a large transport category aircraft due to the influence of only the aerodynamic flow field of the aircraft. The manned aircraft model used in this study is the Common Research Model (CRM) aircraft. The small unmanned aircraft (UA) model used in this study is representative of the DJI Phantom III drone. The authors obtained the UA deflections by performing a series of trajectory analyses in which the small UA is placed on acollision path with the manned aircraft at two different locations on the wing. The first impact location is selected near the mid-span of the wing, and the second near the root of the wing. The aircraft operating conditions are based on a low-altitude holding flight pattern. The trajectory analysis is performed using Computational Fluid Dynamics (CFD) methods coupled with asix-degrees-of-freedom (6-DOF) solver. The authors determined that the vertical deflections are not large enough for the small UA to deflect away from the intended impact location for any of the four impact scenarios described in this paper. The change in orientation of the small UA at the time of impact with the aircraft is observed to be insignificant in three of the four impact scenarios. It is observed that a higher relative speed and a higher CRM aircraft angle of attack results in slightly larger vertical deflections and greater changes in the orientation of the small UA at the time of impact with the aircraft. © 2023, American Institute of Aeronautics and Astronautics Inc, AIAA, All rights reserved.Item 4D X-Ray CT for evaluation of progressive damage growth of composites under fatigue loading(American Institute of Aeronautics and Astronautics Inc, AIAA, 2023) Seneviratne, Waruna P.; Tomblin, John S.Due to the heterogeneous microstructures, fatigue damage growth mechanics of composites are complex and highly dependent on the type of loading mode and load sequencing. Unlike for metals where striation marks can be used for understanding the damage growth rates and mechanics, the final destructive failure mode of composites tends to overshadow damage initiation sites and propagation details. Damage initiation and propagation in composites typically occur from an internal defect/feature or from an area where there is a stress concentration (i.e., fastener hole or impact damage) and are not visible with standard nondestructive inspection (NDI) techniques until they are within the inspection threshold of the equipment or the inspection method, which is also a function of materials, geometry, and location of the defect/feature. Although standard NDI techniques such as ultrasonic testing (UT) and pulse thermography are adequate for detecting such defects, in-depth information related to manufacturing defects (including certain manufacturing features that could potentially be failure initiation or nucleation sites) is required to fully understand the structural capability (i.e., strength and durability) of composites. In addition to high-fidelity post-manufacturing inspections, detailed inspections are required to detect damage initiation and monitor damage propagation through the heterogeneous microstructures of composites. Therefore, a high-fidelity 3D inspection technique such as X-ray computed tomography is required to investigate the damage growth mechanics and interaction of multiple failure modes. Such detailed damage characteristics can then be used for development and validation of high-fidelity progressive damage growth analysis (PDA) techniques and life prediction tools. More importantly, the damage accumulation and growth in composites need to be fully characterized to aid in certification as well as establishing damage tolerance testing and analysis protocols. © 2023, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Item High fidelity digital twin machining tool for quality informed composite drilling(American Institute of Aeronautics and Astronautics Inc, AIAA, 2024) Lua, Jim Y.; Xiao, Jian; Cui, Xiaodong; Saathoff, CalebThis paper presents a high-fidelity digital twin for hole-drilling in composites to provide a physical mapping between drilling parameters, material system, component geometry, and the resulting material removal. Different from a conventional continuum damage modeling approach, a drilling induced shearing failure was included in the intra-ply damage description in addition to the combined matrix and fiber failure modes. Given a spatial and temporal variation of loading condition at a given material point, a micromechanics model was constructed to simulate thermo-mechanical properties of a composite laminate based on its constitutive properties. In order to capture the fiber orientation dependent shear resistance during drilling, a cutting angle dependent shear strength was introduced based on the relative angle between the local material orientation and the cutting direction. A one way thermomechanical coupling was employed to explore the drilling induced temperature distribution in the vicinity of the drilling hole. An extensive experimental study was performed at the coupon level to validate the performance of the drilling simulation tool and examine the failure mechanisms after drilling. The time histories of the thrust force and torque was measured for the direct comparison with the corresponding model predictions. The in-situ temperature measurement during drilling was accomplished using coupons with embedded thermal couples. Post drilling damage evaluation based on X-ray Computed Tomography was performed on selected coupons to examine the delamination distribution near entrance and exit of a drill bit. © 2024 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.