DLP 3D Printing: Mechanical & Strain-Sensing for Carbon Nanotube Reinforced Composites

Researchers from Spain continue the trend for the development of new combinations of materials, detailing their study in the recently published ‘ Mechanical and Strain-Sensing Capabilities of Carbon Nanotube Reinforced Composites by Digital Light Processing 3D Printing Technology .’
While there have been numerous studies regarding carbon nanotube (CNT) reinforced composites—from improving materials to creating sensors for wearables , to e-textiles , and much more—here, the authors perform a more unique study regarding mechanical properties and strain sensors, with the ‘development of a conductive ink for DLP 3D printing technology with self-sensing capabilities based on a commercial photocurable resin doped with CNTs.’
Noting that 3D printing is making huge impacts within the industrial world, and in many other applications too, the authors state quite accurately that there is ‘a wide field for improvement.’
Composites are becoming increasingly popular in the 3D printing arena as users on all levels are able to meet their needs better for varying research, projects, and manufacturing of stronger parts.
“In particular, carbon nanotube (CNT) doped resins has been the subject of numerous studies in the last decades due to their great mechanical, thermal, and electrical properties,” state the researchers. “Their addition in low contents into an insulator resin allows the formation of electrical percolating networks inside the material, leading to an increase in electrical conductivity of the material of several orders of magnitude.”
Structural health monitoring (SHM) is a primary application able to benefit from such materials, as sensors can detect strain damage in metallic gauges. Previously, a variety of 3D printing studies have involved CNTs as fillers in developing parts with electrical properties, elastic strain sensors, shielding devices, and flexible electronics.
In this study, the researchers varied CNTs as they assessed the effects on conductivity. Next, the potential for strain sensing was investigated as the authors evaluated the impacts of load state and post-curing treatments.

Gap distance between rolls during calendering process.

A B9Creator was used for 3D printing six samples for the study with CNT content of 0.030, 0.050, 0.075, 0.100, and 0.150 wt %.

“The most relevant printing parameters were 30 µm of layer thickness and 5.12 s of exposure time per layer, except for those specimens with a 0.150 wt % CNTs, where the exposure time was increased to 6.84 s,” stated the authors.
“This is due to the higher CNT content that induces a more prevalent UV light shielding effect caused by CNTs, reducing UV radiation exposure of the photoinitiator and leading thus to an underexposure condition. On the other hand, overexposure conditions were observed for specimens with CNT contents below 0.100 wt % and longer UV light exposure times than...