Date of Award


Access Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering


Aerospace Engineering

Committee Chair

Dr. Marwan Al-Haik

First Committee Member

Dr. Sirish Namilae

Second Committee Member

Dr. Ali Tamijani


The research presented here involves an attempt to model the viscoplastic response of 3D printed carbon fiber composites made using the Mark Two 3D printer by Markforged. The ability to manufacture composites through the use of 3D printers is relatively new and contains gaps in the various mechanical properties of the material, of interest is the viscoplastic response.

Due to the fabrication method, the properties of the composites cannot be assumed to be similar to that of conventionally made composites as the fused deposition in printing alters the material properties. In order to understand the effects of the printed fiber orientation on the viscoplastic response, four different configurations were to be tested: 0ᴼ, 45ᴼ, 90ᴼ, and a mixed 0ᴼ/45ᴼ/90ᴼ laminate. The model that is investigated in this paper was developed at NASA by C.T. Sun and Thomas Gates. In order to utilize this model, and determine the material properties of the composite, data had to be gathered from a series of tensile and stress relaxation tests. A third type of test, creep, was also performed in order to validate the model predication of creep at different temperatures and loads.

The viscoplasticity model presented in this paper was able to get rough estimations of the creep response for the 3D printed carbon fiber with Onyx thermoplastic composite. The model seems to be more accurate at the lower temperatures for both stiff and less stiff composites. The model also seemed to be more accurate at all temperatures with the stiffer specimens, which would exhibit a weaker creep response.