RT&L FOCUS AREA(S): General Warfighting Requirements TECHNOLOGY AREA(S): Air Platforms; Materials / Processes; Weapons OBJECTIVE: Develop a data-driven computational framework to enable prediction of material aging for designing a new/replacement composite component or its repair, assessing airworthiness of such a component during its lifetime and for assessing life extension. DESCRIPTION: A building block approach is typically used in the design of composite material systems and their qualification and certification (Q&C). Knowledge gained by employing analytical models, along with tests at the coupon level, is employed in developing the next level design of structural elements. Similarly, the knowledge gained at the structural elements through computational models and testing enable the development of subcomponents and components [Ref 1]. Composite structures are typically designed to operate at much lower stress levels than their maximum strength and most of the loads are below fatigue threshold. However, history has shown widespread damage to occur towards the end of the designed life. This could very well be due to degradations in the metallic structures with which the composite parts interface in an aging aircraft. It could also be due to the accumulations of in-service overloads, such as flying over the rated G limits or impact loads caused by severe landings, both resulting in flaws that grow with further usage. These reveal the uncertainties and shortcomings of the current design and Q&C's approach in meeting the damage tolerance design requirements, as included in the Joint Services Specification Guide, JSSG2006 [Ref 2]. A novel, computationally efficient framework is sought to accurately assess the structural integrity of individual airframe subjected to realistic flight usage and operating environments [Refs 3, 4, 5]. It should be capable of integrating various aircraft data ranging from flight state parameter history, available Structural Health Monitoring (SHM) sensors (e.g., strain gages, acoustic and/or fiber optic sensors) to airframe configuration, and maintenance and repairs [Refs 5, 6]. The framework should account for, but not be limited to,: (a) realistic flight history data of flight conditions; (b) the gaps in the data; (c) mission specific loading and environmental variability; and, (d) identifying potential multiphysics trade-offs to enable accelerated testing. Some of the composite material systems of Navy's interest are glass fiber reinforced plastic and graphite-epoxy resin systems such as IM7/ 8552, AS4/3501-6, AS4/ IM977-3, and IM7/977-3. PHASE I: Explore the feasibility of developing a framework for data-driven multiphysics algorithms for predicting the damage tolerance requirements of JSSG2006 for composites, as described above. Include the methodology for testing in-service loading and environmental conditions [Refs 9,10] for validation of the algorithms. Further, include the mechanism for filling gaps in the data for prediction of the airworthiness of composite components. The Phase I effort will include prototype plans to be developed under Phase II. PHASE II: Develop the framework and demonstrate it for the platform chosen by the Navy by utilizing realistic flight history data for predicting damage tolerance of the component with specific issues identified by the Navy. Validate the multiphysics-based algorithms using appropriate tests simulating the in-service loading environment and for different blocks in the building block approach. PHASE III DUAL USE APPLICATIONS: Apply the framework to the Navy selected platforms by integrating it with the data available from Structural Health Monitoring sensors, if any, and databases providing aircraft history of maintenance, repairs, and structural upgrades. Commercial passenger and cargo airlines could potentially benefit from this technology. REFERENCES: MIL-HDBK-17-1F, Composite Materials Handbook: Vol. I. Polymer Matrix Composites Guidelines for Characterization of Structural Materials . U.S. Department of Defense, June 17, 2002. http://everyspec.com/MIL-HDBK/MIL-HDBK-0001-0099/MIL_HDBK_17_1F_237/ Department of Defense Joint Service Specification Guide: Aircraft Structures (JSSG-2006). U.S. Department of Defense, October 30, 1998.. http://everyspec.com/USAF/USAF-General/JSSG-2006_10206/ Cortial, J.; Farhat, C.; Guibas, L.J. and Rajashekhar, M. Compressed sensing and time-parallel reduced-order modeling for structural health monitoring using a DDDAS. Computational science 7th international conference, Beijing, China, May 27-30, 2007, Proceedings, Part I ICCS 2007: Lecture notes in computer science, Vol. 4487, pp. 1171-1179. https://doi.org/10.1007/978-3-540-72584-8_153 Amsallem, D.; Farhat, C. and Lieu, T. Aeroelastic analysis of F-16 and F-18/A configurations using adapted CFD-based reduced-order models [Paper presentation]. 48th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, Honolulu, HI, United States, April 23-26, 2007. https://doi.org/10.2514/6.2007-2364 Michopoulos J.; Tsompanopoulou P.; Houstis E.; Farhat C.; Lesoinne M.; Rice J. and Joshi A. On a data-driven environment for multiphysics applications. Future generation computer systems, 21(6), June 2005, pp. 953 968. https://doi.org/10.1016/j.future.2003.12.023 Molent, L. and Aktepe, B. Review of fatigue monitoring of agile military aircraft. Fatigue and Fracture of Engineering Materials & Structures, 23(9), September 2005, pp. 767-785. https://doi.org/10.1046/j.1460-2695.2000.00330.x Michopoulos, J.; Hermanson, J. and Iliopoulos, A. Advances on the constitutive characterization of composites via multiaxial robotic testing and design optimization. Advances in computers and information in engineering research, Vol. 1, 2014, pp. 73 95. ASME. https://doi.org/10.1115/1.860328_ch4 Seneviratne, W.; Tomblin, J. and Kittur, M. Durability and residual strength of adhesively-bonded composite joints: The case of F/A-18 A D wing root stepped-lap joint. Woodhead Publishing, Fatigue and Fracture of Adhesively-Bonded Composite Joints, 2015, pp. 289-320. https://doi.org/10.1016/B978-0-85709-806-1.00010-0 MIL-HDBK-530-1, Department Of Defense Handbook: Aircraft Uage and Service Loads Statistics, Volume 1, Criteria and Methodology, 01 July 2019. Nickerson, W.; Amiri, M. and Iyyer, N. "Building environmental history for Naval aircraft." Corrosion Reviews 37, No. 5, 2019, pp. 367-375
