INTEGRATED FLUID RESERVOIRS FOR MICROVASCULAR
HEALING IN SANDWICH COMPOSITE MATERIALS
J. Tye 1, C. Hansen 1
1
Advanced Composite Materials and Textile Research Laboratory, University of Massachusetts Lowell, 1 University Ave, Lowell MA 01854, USA – email: Christopher_Hansen@uml.edu
Keywords: microvascular, sacrificial fibers, sandwich composites, damage sensing
ABSTRACT
Microvasculature is a pervasive architectural feature in biological systems because fluid transport enables many critical biological functions, including healing of tissue damage. In engineering contexts, embedded microvascular networks permit self-healing of greater damage volumes and multiple damage events due to improved access to healing agents. To date, these healing agents have been supplied by reservoirs external to the material structure, which add complexity and parasitic mass. Here, we address this shortcoming by integration of healing fluid reservoirs into honeycomb core sandwich composites that autonomously transport healing fluids via microvascular pathways to damage sites.
The microvascular networks are fabricated via sacrificial fibers, which were pioneered by Esser-Kahn et al. (2011). This work utilizes the same polylactide and tin oxalate catalyst fiber chemistry, which depolymerizes in situ at 200°C. We improve the fiber treatment and evacuation process by direct filament extrusion rather than the previous chemical swelling technique. Filaments are extruded at rapid rates (>10 m/s) using a single-screw extruder, thereby speeding fiber manufacture while reducing cost and eliminating chemical waste. Isothermal thermogravimetric analysis indicates improved filament decomposition kinetics, which we attribute to improved catalyst dispersion within the filament.
Sacrificial fibers are successfully woven into the textile face sheets and the resulting microvascular pathways permit transport of healing fluids between the core and the face sheet networks. Fluids are successfully infiltrated into and recovered from the honeycomb compartments, with demonstrated recovery efficiencies greater than 95%. Fluids can be initially pressurized via compressible air and sealed into internal fluid reservoirs to successfully provide a passive mechanism to transport healing agents from the core cell reservoirs to incident damage sites. The repeatability is shown to be dependent on the structural orientation of the damage and the fluid reservoirs.
