Potsdam, NY, Dec. 13, 2022 (GLOBE NEWSWIRE) -- Dr. Craig Merrett and Dr. Marcias Martinez of the Department of Mechanical and Aerospace Engineering recently won a $1.43M equipment grant from the Office of Naval Research. The grant will enable the acquisition of advanced material testing equipment for polymers, composites, and metals. The equipment will extend the testing capabilities within the Center for Advanced Material Processing (CAMP), the Holistic Structural Integrity (HolSIP) Laboratory, and the Aero-Servo-Thermo-Visco-Elasticity Laboratory (ASTVEL). Researchers and graduate students will be able to test materials from -40 ⁰C to 1200 ⁰C, and for a range of moisture levels.
This enhanced range of testing environments will further existing research on the fundamental behavior of polymers, composites and metals; and enable applied research improving structures and materials in the aerospace and maritime industries. Metals at high temperatures, polymers, and composites exhibit energy dissipation and a memory effect that are not well understood but lead to observed creep and stress relaxation in components manufactured from these materials. The creep and stress relaxation cause dimensional issues for high-precision assemblies, or contribute to incorrect estimates for the service life of a component. These behaviors are core elements of the field of viscoelasticity.
Linear viscoelasticity was first introduced in the 1950s, and nonlinear viscoelasticity was developed in the 1970s; however, much of the field requires redevelopment following a mathematical proof published in 2009 that demonstrated that some of the earlier assumptions were incorrect. To formulate a new approach to viscoelasticity requires more detailed experiments involving meticulous control of temperature and moisture. Dr. Merrett and his graduate students have pursued this redevelopment leveraging existing testing equipment in CAMP, and custom-built test frames to collect the necessary data across multiple polymers. In collaboration with Dr. Martinez, existing computational models implemented in ANSYS and ABAQUS have been assessed and their errors quantified relative to exact, analytical solutions. The equipment provided by the DURIP funding is a substantial upgrade in testing capabilities over the existing equipment and will provide high-quality data and more training opportunities for graduate students on viscoelasticity.
The practical applications of a new approach to viscoelasticity will first appear in aerospace and naval applications. The use of polymer composite materials has increased substantially in both fields over the last 20 years. Polymer composites promise high strength and stiffness for much less weight compared to conventional metal structures; however, the accuracy of current predictions of composite structures is limited by the existing understanding of viscoelasticity. The new approach enabled by the DURIP grant will improve the strength and stiffness predictions for components such as single-shear lap joints and double-shear lap joints. These joints are common in aircraft wings and fuselages, and naval hulls. They also appear in the support structures for satellites carrying telescopes for Earth observation. Further, the approach will support endeavors pursued by the HolSIP Laboratory for structural integrity and health monitoring of structures, and by ASTVEL in fluid-structure interactions of aircraft wings.
The DURIP grant will enable CAMP, HolSIP Laboratory, and ASTVEL to launch research in associated areas that involve viscoelasticity. A key area of interest is hypersonic vehicle design as these high-speed vehicles encounter high temperatures during flight. The aerodynamics of these vehicles are thoroughly studied; however, the structural implications of the high temperatures are less well-known. The high-temperature testing capabilities of the DURIP grant will allow testing of composites and metals up to 1200 ⁰C and the exploration of viscoelasticity under this temperature regime. The viscoelastic response of the structure under these conditions may lead to insight into the vehicle’s structural design. A second area of interest is developing advanced models for skin. These models will lead to improved medical devices that involve needles and skin insertion. An example is insulin delivery pumps that insert a needle into the patient’s tissue to provide a consistent delivery of insulin for up to 72 hours.
