Methodology for Predicting and Testing the Onset of Matrix Damage in Fiber Reinforced Composites under High Cycle Fatigue Loading - MSC P4776

The Department of the Navy (DON) has issued a broad agency announcement as part of the Small Business Innovative Research (SBIR) program soliciting proposals to develop methods for better understanding high cycle fatigue in composites. Typical fatigues relies on testing either a single component to multiple design times or testing a large amount of smaller coupons and sub elements toĀ a single design life.Ā Both these solutions take a significant amount of time to complete and for designs with long design life (greater than 109 cycles), these solutions can decades to complete.Ā In order to fully utilize the benefits of composites, quicker methods for understanding high cycle fatigue response must be developed.ĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀĀ ĀĀ Ā MSC has previously developed and validated tools to evaluate damage in composites under repetitive loading events.Ā However, validation has not been completed for fatigue at cycles of these orders of magnitude.Ā During this effort, MSC will develop and demonstrate a method to complete fatigue tests to 109 cycles while maximizing the load rate and thus minimizing the total test time.Ā The R. R. More Rotating Beam Test has been the standard solution for high cycle fatigue in metals.Ā With an equivalent of completing one cycle of loading with one rotation of the beam, cycling can be driven with a motor at speeds upwards of 10,000 RPM, resulting in 600,000 cycles per hour.Ā MSC will leverage the pedigree of the R. R. More Rotating Beam Test to devise a similar approach for the use of composite materials.Ā During these high speed loadings, MSC will determine methods to observe changes in stiffness of the specimen, which are result of internal matrix damage within the composite.Ā One such methods is the use of embedded fiber optic strain sensors.Ā These sensors will be embedded into the laminate and be able to monitor stiffness in real time during the testing.Ā During the Phase I effort, MSC will complete low cycle and high load fatigue testing and determine the initiation of damage within the specimen.Ā This data will be used validate and verify the tool set, where in future efforts these approaches can be conducted for longer high cycle fatigue testing.