Thesis
3D printing and finite element modeling of auxetic re-entrant structures for impact applications
Washington State University
Master of Science (MS), Washington State University
07/2019
DOI:
https://doi.org/10.7273/000000091
Handle:
https://hdl.handle.net/2376/119152
Abstract
Additive manufacturing technologies such as fused filament fabrication (FFF) enable
us to manufacture meta-structures with more complexity and design freedom on relevant scales. As previously reported for foam materials, a stiffness gradient can be
implemented in an auxetic re-entrant structure by varying the cell height within the
structure. This gradient is anticipated to be beneficial for energy absorption at different impact velocities. Thus, this work investigates the impact behavior of graded
re-entrant structures.
Appropriate models are necessary to simulate 3D printed re-entrant structures under
static and dynamic loading conditions. Acrylonitrile butadiene styrene (ABS) was selected as the model material to print the test specimens and the structures by FFF.
Quasi static tensile and compressive tests were performed in the lower strain rate
range; the test data was then complemented with dynamic data of conventionally
produced ABS and a constitutive model was calibrated. A dynamic explicit finite
element (FE) model was set up in order to simulate the stress-strain response of reentrant structures for different angles under compression. This model was checked by
quasi static compression tests of printed auxetic structures. An FE model was then
set up to conduct optimization on the structures under impact loading with varying
velocities.
Good agreement between the simulation and experimental stress values was found
for the compressive deformation characteristics of auxetic re-entrant structures with
different angles, especially in the elastic and instability phases of the response. Further improvements of the FE model were achieved for higher re-entrant angles by
accounting for the printing imperfections such as radii. Positive effects of stiffness
gradient on the impact accelerations were observed from the optimization results,
but the local optima were within small tolerances of the design parameters. Future
investigations could focus on reducing the cell size and a full validation of the FE
model before application.
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Details
- Title
- 3D printing and finite element modeling of auxetic re-entrant structures for impact applications
- Creators
- Florian Baertsch
- Contributors
- ABOUTALEB AMELI (Co-Chair)Thomas Mayer (Co-Chair)Robert Eberlein (Committee Member)CHANGKI MO (Committee Member) - Washington State University, Mechanical and Materials Engineering, School of
- Awarding Institution
- Washington State University
- Academic Unit
- Engineering and Applied Sciences (TRIC), School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Format
- pdf
- Number of pages
- 180
- Identifiers
- 99900590963801842
- Language
- English
- Resource Type
- Thesis