Abstract
This study investigates damage monitoring and fracture toughness characterization of additively manufactured acrylonitrile butadiene styrene (ABS) embedded with carbon nanotubes (CNTs) under dynamic mode-I fracture loading conditions. A novel modified split-Hopkinson pressure bar (SHPB) setup along with high-speed imaging is used to understand the crack dynamics. Electrically conductive CNTs embedded ABS nanocomposite is referred to as ABS-EC in this study. A modified four-probe resistivity measurement technique is utilized to understand the piezo-resistance response of ABS-EC. The effect of four infill line orientations (0 degrees, 90 degrees, +/- 45 degrees, and 0 degrees/90 degrees) on quasi-static and dynamic mode-I fracture toughness and damage sensing characteristics are studied. Results reveal that the infill line orientations have a significant impact, where with +/- 45 degrees configurations demonstrating superior dynamic fracture toughness (2.54 MPa-m1/2) due to the kinking of the crack along the + 45 degrees/-45 degrees direction and the 90 degrees orientations exhibiting weaker interfaces. Real-time observations of crack dynamics validate these findings, emphasizing the role of filament alignment in determining crack pathways and fracture behavior. Among the four infill line orientations, 0 degrees/90 degrees shows the highest (500%) peak piezo-resistance response, whereas the 90 degrees orientation shows the lowest (95%). Moreover, convection oven annealing is explored, where substantial improvement in static fracture toughness (226% increase) for ABS is observed. However, annealing did not enhance the fracture toughness of ABS-EC because CNTs acted as a barrier to restrict the polymer's molecular chain movement for rearranging the porosity.