Master of Science in Mechanical Engineering (MSME)
A shape memory polymer (SMP) is a polymeric material that exhibits shape memory behavior. It can be “programmed” to take on a desired shape and “recovered” to revert back to its original shape. This ability to remember multiple shapes and switch between them with the application of a stimulus from an outside source is very desirable in certain applications. By dispersing glass microspheres in a SMP matrix, a syntactic foam is created that retains much of the shape memory capabilities but has higher strength and lower density than the pure SMP. These characteristics make this material a good candidate for use in a sealant for expansion joints on bridges. In order to be used in this situation, the SMP based syntactic foam must be tested under a complex loading scenario which is the first of its kind. A new testing procedure is developed along with a new test sample design. In one direction, the SMP based foam is programmed in tension at 79 degrees C. Then, in the transverse direction it is programmed in compression at room temperature. Finally, it is reheated to 79 degrees C for free recovery. Shape recovery has a broader meaning as it pertains to the two-stage biaxial thermomechanical cycle but comparison of results shows that room temperature compressive programming negatively affected the shape recovery values in that direction. The free direction had the second best shape recovery, leaving the tensile direction with the highest shape recovery values ranging from 77% to 88%. For full understanding and representation of the thermomechanical cycle, it must be plotted using stress-strain-temperature and stress-strain-time. These plots are created for a range of tensile and compressive programming strains.
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King, Abraham Michael, "Two-stage biaxial thermomechanical cycle of shape memory polymer based syntactic foam" (2011). LSU Master's Theses. 1915.