Abstract

This work is motivated by ongoing efforts within the Smart Materials, Adaptronics, and Shock Laboratory (SMASH Lab) at Brigham Young University (BYU) to develop variable-stiffness, external fixators using 3D-printed tensegrity structures. In the process of designing and evaluating these systems, the need arose to accurately model the nonlinear mechanical behavior of thermoplastic polyurethane (TPU), the primary material used in prototype fabrication. This thesis investigates how accurately a calibrated Ogden material model can predict the nonlinear mechanical response of TPU in 3D-printed tensegrity structures. Experimental data were used to calibrate the parameters of the hyperelastic constitutive model through nonlinear optimization. An experimental test apparatus was developed to characterize the force-displacement behavior of TPU-based tensegrity structures under controlled loading conditions. Model predictions were compared against independent experimental measurements to assess predictive accuracy. Agreement between simulation and experiment was quantified using root-mean-square error (RMSE). Discrepancies were reduced using a correction factor. Limitations of the model such as hysteresis and recovery were discussed. Results demonstrate that the calibrated Ogden model captures the overall nonlinear response of the TPU tensegrity structures with good accuracy. These findings establish the effectiveness of hyperelastic constitutive modeling for describing the behavior of 3D-printed TPU systems. While this study focuses on tensegrity structures, the calibrated Ogden modeling framework is readily extendable to other 3D-printed systems utilizing TPU.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2026-06-20

Document Type

Thesis

Keywords

hyperelastic constitutive model, Ogden material model, thermoplastic polyurethane (TPU), additive manufacturing, mechanical characterization, nonlinear material behavior, tensegrity

Language

english

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