A crack healable syntactic foam reinforced by 3D printed healing-agent based honeycomb

Abstract

In this study, a novel grid skeleton (i.e., the 3D printed healing-agent based honeycomb structure) was embedded in a syntactic foam matrix to enable the composites to own crack closing and healing capabilities. There is always a trade-off between crack healing efficiency and overall structural properties. The new type grid skeleton was proposed here to make syntactic foam composites owning excellent crack healing ability without sacrificing overall mechanical properties. The volume fraction of glass microballoons within syntactic foam matrix remained constant at 30%. The reinforcing honeycomb cell sizes varied with a ratio from 3.8, to 5.4 and 7.3, which resulted in various physical and mechanical properties, such as different density and compressive strength. The thermal properties of the syntactic foam composites were tested through Differential Scanning Calorimetry (DSC). The interfaces between the syntactic foam matrix and PCL grid skeleton (i.e., printout) was investigated by the Fourier Transform Infrared (FTIR) spectrum. It displayed that the interaction between those phases were completely in a physical manner. Nano-indentation tests were conducted to study the composite component mechanical properties. Three-point bending tests were conducted to initiate structural level cracks to examine the crack healing capability. Healing efficiency was obtained according to the comparison between specific flexural strength before and after the crack healing event. Under free constraint condition, the 3D printed PCL honeycomb reinforced syntactic foam exhibited promising crack healing performance with healing efficiencies above 80%. This study provided an understanding on the interface property and crack healing mechanisms in the 3D printed honeycomb reinforced syntactic foam system.