A quick post to share an experiment I did back in 2016 in cooperation with Qinghua Wu. Qinghua’s research is mainly about 3D-printing chitosan, a natural polysacharride which is the structural element in the exoskeleton of shrimps and other crustaceans. Chitosan has several very nice properties, it is completely natural, it is biocompatible and is an antibacterial agent. However, it has the big disadvantage of only being able to sustain low loads especially when it is hydrated. Qinghua is also able to 3D print films of this polymer using the solvent cast 3D-printing method so we decided to investigate how a crack grows in this material.
We took a rectangular shaped film of chitosan, and covered it with a mist of black paint dots using and air gun. We then precracked it using a razor blade. The material is then inserted in a tensile testing machine and a stereocamera rig was setup in front of the tensile testing machine.
The black paint dots were used as a speckle pattern for the DIC algorithm after the test. It was thus possible to obtain the displacement and strain fields while the crack is growing.