Microtruss Design for Strength and Energy Absorption

The question of information flow within an inverse design problem is tackled with focus on thermodynamically irreversible phenomena, i.e. strength and energy absorption. Microtruss materials are used as a platform for the study as their individual building units, i.e. struts, possess uniform geometry, known properties, and can be tuned to achieve a desired level of performance; a much simpler task than attempting to design bulk microstructure. Elements of compositing are utilized to alter the performance of the microtrusses, namely nanocrystalline nickel electroplating and carburizing. In terms of strength, both compositing approaches produced microtrusses with superior performance. Additionally, the strength property was optimized using classical optimization approaches since the strength is determined by the onset of the first failure mechanism to be activated; a task that can be completed using conventional analytical models, such as the Shanley-Engesser buckling equation. The problem becomes more complicated for energy absorption since the onset and progression of the deformation and damage need to be readily describable analytically, which is not possible due to the distortion and deformation of the collapsing struts, i.e. geometrical and material non-linearities need to be considered. A primarily experimental approach is therefore followed to first identify the active failure mechanisms and their influence on the energy absorption property. The carburized microtrusses were modified with post-carburizing heat treatments such as tempering and decarburizing to enhance their post-buckling behavior and energy absorption capability. The nickel-coated microtrusses were plated using various plating conditions to control the hardness, thickness, composition, and adhesion of the coatings. With the proper plating parameters, nickel-phosphorous coatings introduced pre-buckling damage that nearly eliminated the post-peak softening in conventionally buckled microtrusses and resulted in an enhanced energy absorption response placing these hybrid microtrusses ahead with the top commonly reported energy absorbers in literature, such as foams and honeycombs.

Department dc:contributor.department

Materials Science and Engineering

Year dc:date.issued

2019

Author dc:creator

• Abu Samk, Khaled

Advisor dc:contributor.advisor

• Hibbard, Glenn D

• Carburizing
• Electroplating
• Energy Absorption
• Microtruss
• Optimization
• Strength

Handle dc:identifier.uri

http://hdl.handle.net/1807/97300

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/97300