Progressive Damage and Failure Analysis of Bonded Composite Joints at High Energy Dynamic Impacts

Both wing and fuselage structures utilize bonded composite joints for structural efficiency in modern commercial and military aircraft. To ensure compliance with certification requirements mechanical fasteners are typically used as a failsafe mechanism for appropriate strength in the event of complete stiffener disbond. However, the use of fasteners decreases the structural efficiency of the structure by adding weight. This establishes the requirement to better exploit the efficiency of bonded structures and fully understand the failure behavior of adhesively bonded composite structures, particularly when subjected to elevated loading rates due to high energy dynamic impacts (HEDI). For this reason, the NASA Advanced Composite Consortium (ACC) HEDI team developed an experimentation and numerical modeling program for high rate loading of composite joints. In the present work, the response of adhesively bonded composite joints subjected to elevated loading rates is studied numerically and validated against experimental results. Due to dynamic considerations of experiments, the idea of wedge insert was extended to use with Split Hopkinson Pressure Bar (SHPB) testing techniques. Mode-I and Mode-II test configurations were simulated to evaluate the capability of two continuum damage material (CDM) models in LS-DYNA, namely MAT162 and MAT261. Three different levels of fidelity were considered to investigate the level of detail required to numerically predict the failure behavior and the results from high fidelity analysis are presented

Effect of Disinfectants on Aircraft Cabin Interior Materials

Due to the coronavirus 2019 (COVID-19) public health emergency, the airline industry implemented meticulous and frequent interior disinfection procedures. This excessive use of disinfectants raised concerns on its potential negative impact on materials performance. This research focuses on evaluating the performance of aircraft cabin materials when conditioned with liquid chemical disinfectants in a controlled manner. In collaboration with the SAE Aircraft Seat Committee and SAE S-9 Cabin Safety Provisions Committee, the researchers identified five different types of materials commonly used in the aircraft cabin. Additionally, five liquid disinfectants commonly used at the time of this research were selected. All materials were evaluated for changes in flammability performance and physical properties such as weight, color, and texture. Change in mechanical properties were also evaluated for the selected materials

Effects of Ultraviolet-C Germicidal Irradiation on Aircraft Cabin Interior Materials

As a result of the coronavirus disease 2019 (COVID-19) public health emergency, aircraft owners and operators may find it necessary to increase the frequency with which they disinfect aircraft interiors. The disinfectant procedures included conventional chemical liquid disinfectants and Ultraviolet-C (UV-C) germicidal irradiation. In the first two phases of this project, we evaluated the effects of liquid chemical disinfectants on materials used in aircraft seats and other interior applications. In the third phase of this project, long-term exposure to UV-C irradiation on various aircraft cabin interior materials has been investigated. In this study, eight different materials typically used in aircraft interiors, including seats, were considered. Three UV-C irradiation configurations with peak emissions at 222 nm, 253.4 nm, and 280 nm were selected. The test materials were subjected to accelerated UV-C aging tests at multiple cumulative dosage configurations, representing a single daily exposure over a time period of one, four, and eight years. Post the UV-C exposure, the materials were evaluated for change in weight, color, flammability performance, and mechanical properties