Self-healing composites using thermally remendable polymers and electrical resistive heating

The concept of self-healing composite using thermally remendable polymers and electrical resistive heating was proposed. A series of single-component thermally remendable polymers, mendomers, was introduced. One of the polymers, mendomer 401, was characterized using thermogravimetric analysis (TGA) and dynamic differential scanning calorimetry (DSC). The cure kinetics was studied using the dynamic DSC results. Ageing effect of polymerized mendomer 401 was investigated using Fourier transform infrared (FT-IR) spectroscopy and micro-indentation test.;A thermally remendable composite using mendomer 401 and carbon fabrics was fabricated using compressive molding method. The thermo-mechanical behavior was studied using dynamic mechanical thermal analysis (DMTA). Surface microcracks were induced using three-point bending and they were healed multiple times using electrical resistive heating. The healing behavior was confirmed by disappearance of microcracks using an optical microscope and a scanning electron microscope (SEM). Also, shape memory behavior was observed near the glass transition temperature of the polymer.;A composite panel was fabricated using a two-component thermally remendable polymer, 2MEP4F, and carbon fibers with the lay-up of [0/90/0] by NanoComposix. Vacuum assisted injection molding was used for the fabrication process. The thermomechanical properties were characterized using DMTA. Delaminations were induced using short span three-point bending test and they were healed multiple times using electrical resistive heating. The delaminated area was observed using X-ray micro-tomography before and after healing Shape memory behavior of the composite allowed the delaminated surfaces to have a physical contact, which is essential for healing.;To realize an addressable conducting network (ACN) for thermally remendable composites, metal electrodes were fabricated on carbon fiber composite laminates using various methods. The contact resistances between metal electrodes and the laminate were measured and compared. The microscopic interfaces between carbon fibers and metal electrodes were observed using SEM. Finally, to evaluate structural integrity of the composite panel upon heating using ACN, compressive load was applied to induce buckling. The critical loads were measured w/ and w/o heating and compared with finite element simulations. It is confirmed that resistive heating using ACN does not have a significant detrimental effect on the structural integrity during the healing process of the self-healing composite.