Compressive Instabilities in Metal-coated Polymer Microtrusses

Lightweight structures directly contribute to the sustainability of aviation, as their use reduces the structural weight of aircraft which in turn reduces fuel burned during flight. One family of lightweight structures are metal-coated polymers. Hybrid polymer-nanometal microtrusses are a member of this family. These structures are fabricated by 3D printing complex truss-like structures out of polymer material, and electrodepositing nanocrystalline metal onto the polymer. Recent work has shown that buckling instabilities govern the strength of these systems. Hence this study focuses on modelling local shell buckling, one of the critical buckling mechanisms. In studying filled-shell buckling, hollow-shell buckling theory provides the framework for the behaviour of the shell as it undergoes buckling in a filled cylindrical shell. However, a model for the core must be realized. The Southwell stress model is used to develop an energy model of the core as it is subject to radial displacements, and the Timoshenko energy method is then utilized to determine the axial buckling load for a filled cylindrical shell. The models developed in this thesis include a fundamental model where the shell and core are fully adhered, a non-adhesion model where the shell and core are not adhered, a hollow-core model where the core is partially hollowed out along its axis, and an inelastic model where the shell behaviour is inelastic. These models are later verified through finite element analysis. Experiments on dogbone specimens also revealed some practical implications that must be considered when attempting to validate these theories. In addition, optimization for minimum mass design was carried out using the newly-developed models. The results of these studies indicate that while the new models are theoretically sound, there are still aspects of metal-coated polymer structures which bear investigating. Fine-tuning of the present models is warranted, which may include more complex curve fitting procedures for determining the model constants or the use of numerical techniques other than finite differences. In addition, the manufacturing processes for these structures must be improved prior to their use as primary structural elements in aerospace applications.

Department dc:contributor.department

Aerospace Science and Engineering

Year dc:date.issued

2019

Author dc:creator

• Bhaga, Bharat

Advisor dc:contributor.advisor

• Steeves, Craig A

Handle dc:identifier.uri

http://hdl.handle.net/1807/95751

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/95751