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Bio-Mimetic Self-Healing Composite Sandwich for Impact Tolerant NextGen Aerospace Structures (Self-Healing Structures)

LA

Louisiana State University/Southern University/NASA DRC, Aeronautics Research Mission Directorate

Dr. Guoqiang Li, Science PI, Louisiana State University

Sarah Cox, NASA Technical Monitor, Kennedy Space Center, STMD

Mr. Ukeamezhim Ayaugbokor, a M.S. student at Southern University Mechanical Engineering and participant of this project, is preparing his DSC test of a SMP in LSU Composite Materials and Structures Lab.

In the last year of the project, several advancements have been made, including (1) A multi-mechanism phenomenological model is developed within the finite deformation framework for capturing the thermomechanical behavior of shape memory polymers (SMPs) both during programming and in service. Particularly, the damage mechanisms in SMPs, including mechanical damage and functional damage, are studied within the continuum damage mechanics framework. Statistical mechanics is incorporated to describe the initiation and saturation of these damage mechanisms. The main advantage of the model, compared to the existing counterparts, is its simplicity by minimizing the need for curve fitting, and capability in simulating the non-linear stress-strain behavior of SMPs with various morphologies. (2) A new healing-on-demand composite made of fishing-line artificial muscle, thermoset matrix, and thermoplastic healing agent, was fabricated and tested. The artificial muscles

www.nasa.gov/epscor/stimuli

were arranged in either unidirectional or orthogrid pattern. Repeated fracture/healing cycles by low velocity impact and/ or three-point bending of beam specimens were conducted. It is found that artificial muscles can achieve a healing efficiency as high as 100% with a volume fraction as low as 3.5%. It is also found that the muscles behave similarly to SMP fibers in terms of closing wide-opened cracks, but are stronger and stiffer, respond faster with larger actuation force, and cost less. (3) A computationally efficient phenomenological constitutive model is developed for polymeric muscles made of fishing-lines or sewing threads. Two types of molecular chains are considered in micro-scale level that controls training and actuation processes helically oriented chains and entropic chains. The performance of the model is validated by available experiments in the literature. The model may provide a design platform for the use of low-cost artificial muscles in self-healing composites.

NASA EPSCoR Stimuli 2014-15

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EPSCoR Stimuli 2014-15  

NASA Office of Education’s Aerospace Research & Career Development (ARCD) is pleased to release NASA EPSCoR Stimuli, a collection of univers...

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