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Structural Design Process for High-Cycle Fatigue Performance of Composite Materials


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Advanced Materials The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Develop, execute, and validate methodologies to efficiently establish high-confidence design allowable for high-cycle fatigue performance of composite materials and structures. DESCRIPTION: The United States (US) maritime Navy uses laminated fiber-reinforced composite materials in a variety of submarine external non-pressure hull applications, including sonar bow domes, an assortment of composite hydrodynamic fairings, acoustic windows, access panels, grates, and cover plates. Maximum cyclic load requirements for these types of applications typically range from 10^6 to 10^7 cycles. Fatigue is usually accounted for implicitly during the structural design process by defining factors of safety for stress analyses that are known to provide the required fatigue life for the material system of interest. This design approach has been confirmed in select instances by testing a representative full-scale part to demonstrate adequate residual strength after applying a complete lifetime of cyclic loads. There is increasing US maritime Navy interest in using composite materials in high-cycle applications that will require sustaining a much larger number of load cycles (perhaps on the order of 10^9) over the life of the structure. Composites are attractive for these applications for weight reduction, corrosion resistance and associated through-life cost savings, design flexibility, and potential fabrication cost and schedule benefits relative to metallic designs. However, for high-cycle applications, fatigue becomes a dominant driver of the structural design. This larger load cycle requirement introduces significant challenges that are currently outside the Navy community experience accumulated from prior maritime Navy composites applications. Testing without interruption at an assumed 5-Hz cycle rate, it takes well in excess of 6 years to exercise 10^9 load cycles for a single test. Under those circumstances, it is difficult to provide timely and cost-effective material and/or structural testing support for design activities. These issues can be mitigated via the identification, development, and demonstration of efficient test methods to reduce the time required to apply the full lifetime of load cycles, and/or establishment of technically justified methods for obtaining necessary test results with cycle counts reduced to manageable levels, in support of the generation of high confidence material design allowable. Some methods have been developed in support of more efficient evaluation of high-cycle fatigue performance of composites using non-traditional test techniques. A large majority of these methods rely on some form of accelerated test rate, or frequency, to expedite the process typically required of executing coupon-level experiments comprised of high cycle counts using standard servo-hydraulic equipment. While this is commonly accepted practice for characterizing high-cycle fatigue performance of metallic materials, there are several challenges associated with such methods as they pertain to composite material high-cycle fatigue characterization. Such challenges include a) overheating of the test specimen, b) introduction of viscoelastic effects resulting in artificial response, c) wear of the test equipment, and d) lack of suitable instrumentation technologies for accurately measuring specimen response. Other non-traditional test methods developed for evaluating high-cycle fatigue performance of composites rely on flexural test configurations to leverage small, stiff specimen geometries that provide an opportunity to evaluate both tensile (bottom surface) and compressive (top surface) response. However, such methods often result in maximum stress/strain states at the point of load application (for the cases of 3-and-4-point bending) and, as a result, typically produce limited relevant data from a given test. The efficient test methods and approaches the Navy seeks should be applicable to a range of non-metallic materials (e.g., Glass Fiber Reinforced Polymer [GFRP] and Carbon Fiber Reinforced Polymer [CFRP]), reinforcement architectures (e.g., unidirectional, woven), processing techniques (e.g., autoclave-cured, out-of-autoclave oven vacuum bag cured, infused), and fatigue test stress ratios (i.e., R=-1, 0.1, 1). In addition, the resulting methods and approaches should be capable of developing, with high confidence, material design allowable pertinent to typical composite failure modes, including but not limited to the following: in-plane tension, in-plane compression, interlaminar shear, and bolt bearing. Such methods and approaches will permit the development and validation of a) design criteria, b) efficient and robust material selection processes, c) efficient static, fatigue, and environmental characterization in support of structural design, and d) efficient static, fatigue, and environmental testing for structural verification. Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. Owned and Operated with no Foreign Influence as defined by DOD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence Security Agency (DCSA), formerly the Defense Security Service (DSS). The selected contractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances, in order to perform on advanced phases of this contract as set forth by DSS and NAVSEA in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material IAW DoD 5220.22-M during the advance phases of this contract. All DoD Information Systems (IS) and Platform Information Technology (PIT) systems will be categorized in accordance with Committee on National Security Systems Instruction (CNSSI) 1253, implemented using a corresponding set of security controls from National Institute of Standards and Technology (NIST) Special Publication (SP) 800-53, and evaluated using assessment procedures from NIST SP 800-53A and DoD-specific (KS) (Information Assurance Technical Authority (IATA) Standards and Tools). The Contractor shall support the Assessment and Authorization (A&A) of the system. The Contractor shall support the government’s efforts to obtain an Authorization to Operate (ATO) in accordance with DoDI 8500.01 Cybersecurity, DoDI 8510.01 Risk Management Framework (RMF) for DoD Information Technology (IT), NIST SP 800-53, NAVSEA 9400.2-M (October 2016), and business rules set by the NAVSEA Echelon II and the Functional Authorizing Official (FAO). The Contractor shall design the tool to their proposed RMF Security Controls necessary to obtain A&A. The Contractor shall provide technical support and design material for RMF assessment and authorization in accordance with NAVSEA Instruction 9400.2-M by delivering OQE and documentation to support assessment and authorization package development. Contractor Information Systems Security Requirements. The Contractor shall implement the security requirements set forth in the clause entitled DFARS 252.204-7012, “Safeguarding Covered Defense Information and Cyber Incident Reporting,” and National Institute of Standards and Technology (NIST) Special Publication 800-171. PHASE I: Define, develop, and demonstrate an experimental approach to efficiently evaluate the high-cycle (> 10^8 cycles) fatigue performance of non-metallic materials using novel coupon specimen geometries and/or test methods. Results of the proposed experimental approach shall be compared to currently available relevant fatigue data and/or limited experimental fatigue data generated under the proposed effort using traditional experimental techniques to substantiate the approach. The feasibility of the specimen and/or test method design should be supported by analysis and/or simulation. The Phase I Option, if exercised, will include documentation of performance demonstration and conceptual specification of proposed improvement and/or refinement to the resulting approach to be further developed in Phase II. PHASE II: Refine, demonstrate, validate, and deliver the experimental approach developed in Phase I by conducting a suite of experiments on multiple material systems targeting a range of composite failure modes exercised under high-cycle fatigue loading. Demonstration of the proposed approach shall include testing on both CFRP and GFRP materials. Validation of experimental results generated using the proposed approach shall be established via comparison with relevant currently available material fatigue databases (where applicable) and/or verification testing using traditional experimental methods. Work with NAVSEA to identify relevant cycle counts and stress ratios of interest in support of experimental testing. It is probable that the work under this effort will be classified under Phase II (see Description section for details). PHASE III DUAL USE APPLICATIONS: Assist the Navy in transitioning the technology to Navy use and propose and define an article(s) to be fabricated and subjected to a representative lifetime cyclic load spectrum in order to validate the proposed experimental methodology for developing fatigue design allowable. Work with NAVSEA to identify a representative cyclic profile in support of defining an applicable load spectrum comprised of relevant load magnitudes, cycle counts, and stress ratios in support of experimental verification testing. Efficient experimental methods developed under this effort are not relegated to US maritime Navy use and are applicable to the commercial (and non-Defense US Government sectors) use of composites in high-cycle fatigue applications (> 10^8 cycles), such as wind energy. While current wind energy design methodologies facilitate general robustness and lack a general need for significant design margin (relative to manned US Navy platforms), the opportunity to leverage developments in experimental testing to promote efficient characterization of high-cycle fatigue performance certainly offers the opportunity to reduce maintenance costs and associated down-time, improving operational efficiency and overall power output. Any industry that leverages the use of composites for fatigue-critical applications comprised of moderate to high load cycles would benefit from this technology. REFERENCES: 1. Alam, P., Mamalis, D., Robert, C., Floreani, C., and Bradaigh, C. M. O. “The Fatigue of Carbon Fibre Reinforced Plastics – A Review.” Composites Part B, Vol. 166, pp. 555-579, February 2019. 2. Chona, R. “A Review of Research on Aeronautical Fatigue in the United States.” Presented at The Meeting of the International Committee on Aeronautical Fatigue and Structural Integrity: Krakow, Poland. June 2019. 3. Makeev, A., Seon, G., Nikishkov, Y., Nguyen, D., Mathews, P., and Robeson, M. “Analysis Methods for Improving Confidence in Material Qualification for Laminated Composites.” Journal of the American Helicopter Society, Vol. 64, pp. 1-13, January 2019. 4. Mandall, J. F., Samborsky, D. D., and Miller, D. A. “Analysis of SNL/MSU/DOE Fatigue Database Trends for Wind Turbine Blade Materials, 2010-2015.” SAND2016-1441, Sandia National Laboratories. February 2016. 5. Horst, P., Adam, T. J., Lewandrowski, M., Begemann, B., and Nolte, F. “Very High Cycle Fatigue – Testing Methods.” IOP Conference Series – Materials Science and Engineering, 388, 2018. KEYWORDS: High-Cycle Fatigue; Composite Materials and Structures; Design Allowable; Glass Fiber Reinforced Polymer; Carbon Fiber Reinforced Polymer; Non-Metallic Materials
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