THIS GRANT IS A CONTINUATION OF N000141410278 Materials Concept Development

Task 1: Literature ReviewARL Penn State will perform a comprehensive open literature review of work being performed on underwater acoustic materials. The review will focus on materials which are effective in the frequency ranges of interest and will be used to identify individuals and organizations in the country with expertise in relevant materials development. The results of this task will be used to identify performers for task 2 below.Task 2: Materials DevelopmentBased on the overall system requirements, ARL Penn State will explore innovative materials and combinations of materials which provide the necessary characteristics for a variety of applications. The required characteristics for the applications include; high density, specified modulus and energy absorption, and low modulus materials. It is envisioned that within the coating system design Task there will be materials design activities focused on high density materials, transition materials, and soft materials. The characteristics required for the various materials system components will be provided by the requirements definition team. Materials will be characterized for performance using both standard ASTM and application-unique test methods. Modulus, density compressibility will be measured. Appropriate methods for characterization of viscoelastic material behavior in the temperature and frequency space of interest will be selected and applied. Promising materials will be assessed for durability in the environment, e.g., hydrolytic stability, creep, aging. In addition, promising materials will be assessed for scalability and compositional and process robustness for anticipated application in the shipyard environment.Task 3: Materials Adhesions and Integration TechnologiesARL Penn State will examine adhesion behavior of promising materials emerging from Task 2 with the standard surface preparation processes used with current coating systems. Adhesion testing of promising candidates will be performed using standard test methods. Modifications to existing surface preparation materials and procedures will be examined as required. In addition, we will study innovative surface preparation approaches as well as assess the state-of-the-art in inspection technologies which can be used to characterize adhesion behavior. Adhesion durability will be assessed using conventional test methods. Lastly, we will assess the compatibility of the components developed in Task 2 and will develop system-level processes for incorporation of these components into advanced materials solutions.Task 4: Acoustic Performance ModelingARL Penn State will perform acoustic modeling of sample material concepts and predict performance for multiple incidence angles. The results will be compared to experimental results to assess the performance of the modeling tools. This work will leverage the existing work sponsored by ONR Code 33 in high performance computing for structural acoustic computations.Task 5: Requirements Definition and Project Integration/CoordinationThe focus of this task will be participation as part of the project's requirements definition team as well as coordination of the materials development efforts. The requirements definition team will work with NSWC-Carderock to provide material requirements to the performers in Task 2. This task will provide oversight of the material development efforts in Task 2 and involves providing feedback to ONR Code 33 on the progress of the material efforts. Additionally, under this task, performers will interact with the other teams, e.g. the testing teams.