Arthropod cuticle: Time-lapse 3D imaging to assess toughening and failure mechanisms

Abstract

This thesis concentrates on one of the least studied mechanical properties of cuticle – toughness. In particular, it investigates how cuticle microstructure impacts crack propagation, and the toughening mechanisms cuticle possesses to protect the vulnerable soft tissues contained within the exoskeleton. I use time-lapse 3D nCT imaging with in situ mechanical tests to investigate toughness and damage progression in arthropod cuticle. In addition, I develop new methodologies of standardised sample preparation and hydration preservation to perform quantitative analysis of fresh locust tibiae and beetle elytra. The results obtained in this thesis have shown that it is possible with these techniques to analyse toughening in fresh and dry cuticles, by qualitative visualisation of the interaction between microstructure and crack propagation and quantitative measurement of toughness values from standardised test samples. It was shown that microstructure is responsible for the numerous extrinsic toughening mechanisms present in cuticle, of which many were previously unreported, and that hydration is responsible for improving the effectiveness and frequency of their occurrence. Furthermore, it was found that the exocuticle contributes little to toughness and that the difference in angle between the crack direction and the fibre orientations of a lamina directly affected the toughening capability of that lamina. To summarise, this thesis displays how a combined approach using state-of-the-art 3D imaging, in situ mechanical testing, sample preparation and hydration preservation techniques can provide us with new insights in how arthropod cuticle shape, microstructure, composition and mechanical properties interact.

Date of Award	3 Jan 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Philip Withers (Supervisor), Shelley Rawson (Supervisor) & Russell Garwood (Supervisor)