Engineers at the University of Glasgow, working with colleagues at the University of Sydney, can now show where a 3D-printed lattice is cracking while the part is still being pulled.
Sensors that read electrical resistance at a few points are enough for a simple part. They cannot show what is happening across a lattice of thin struts and open spaces. The team mixed carbon nanotubes into the plastic, printed rectangular lattices 48 millimetres across, and attached electrodes. They then used electrical impedance tomography, a hospital method that tracks how electricity moves through tissue, to rebuild a picture of the whole part as it was stretched to breaking.
As the lattice stretched, the conductive paths changed, and so did the voltages measured at the surface. A computer turned those voltage changes into maps of where the electrical properties were shifting. The maps placed damage within about one strut of its real location, including tiny cracks the researchers had built into some struts on purpose. The maps also showed damage gathering before the lattice failed. The team checked them against what they could see on the parts.
“Conventional measurements can tell us what is happening at a particular location in a material, or provide an overall, averaged indication of the structural health of the whole structure,” said Professor Shanmugam Kumar of the James Watt School of Engineering. “They cannot show us in detail where damage is developing and how it is spreading.”
The group says this is the first reported use of the method to watch damage inside 3D-printed lattice metamaterials while they are under load. Akash Deep and Professor Andrew McBride at Glasgow wrote the paper with Dr Andrea Samore and Professor Alistair McEwan at the University of Sydney. It is published in Advanced Functional Materials under the title “Full-Field Damage Monitoring in Architected Lattices Using In situ Electrical Impedance Tomography.”
Kumar said further work is needed before the technique is scaled for practical use. The researchers name structural health monitoring, including medical implants, aircraft parts, and car bodies, as the kind of job it would have to grow into.
Source: gla.ac.uk
