Mechanics of Architectured Tubes

Architectured material systems offer the ability to control a system's response through the spatial arrangement of material. Material may be connected by discrete linkages or segmented by discrete cuts in such a system. This thesis serves as an investigation of the deformation and load response of architectured material systems in tubular configurations. Specifically, segmented tubes composed of interlocking building blocks and corrugated tubes formed from thin sheets of material are of interest.

Interlocking, segmented tubes, or topologically interlocking material (TIM) tubes, are considered as assemblies of convex polyhedra. Multiple aspect ratios of tubes are considered with identical building block size. The load response to diametral indentation is obtained by finite element analysis and experimentation on additively manufactured tubes. Finite element models consider both an idealized scenario, where contacts between building blocks are stiff, and a realistic scenario, where there are much softer contacts between building blocks and a limit on shear stresses due to friction at contact interfaces. The mechanics of the deformation of TIM tubes are quantified by stress distributions and energies obtained from finite element models. It was found that interlocking between building blocks grants segmented systems increased stiffness, strength, and toughness. The response of TIM tubes varied with tube aspect ratio and contact conditions between blocks. An analysis of thrust-lines in the assembly with finite element results led to the formulation of a model to predict the load response of interlocking, segmented tubes. This model was found to fit idealized FE-model results, and, with the addition of slip between building blocks to the model, experiment results.

Corrugated tubes are considered to be formed from stacks of sheet metal plies. Corrugations are formed one-by-one with a high-pressure fluid and forming machinery. The manufacturing process of these tubes is recreated in a finite element model. With this manufacturing model, the as-formed geometry and residual stress and strain profile of the tube are obtained. Finite element models of corrugated tube loading are created such that their initial state is the result of the manufacturing model. The response of corrugated tubes can then be investigated under the consideration of effects from manufacturing. Including the effects from manufacturing was found to influence the corrugated tube stiffness and yield force. Altering the ply thickness used to form tubes was also found to influence the corrugated tube stiffness. Certain fatigue failure locations were only predicted when including the effects from manufacturing in finite element simulations. Thus, the effects from manufacturing a corrugated tube were found to play a significant role in the tube's load response and failure.