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Correlation between reference point indentation and mechanical properties of 3D-printed polymers
1Department of Mechanical Science and Engineering, University of Illinois at Urbana Champaign, 1206 West Green Street, Urbana, Illinois 61801, USA.
The Review of Scientific Instruments
|December 8, 2023
Summary
Reference point indentation (RPI) can assess 3D-printed polymer mechanical properties. Initial testing showed strong correlations between RPI parameters and material properties, but these weakened significantly after five years.
Area of Science:
- Materials Science
- Biomaterials Engineering
- Mechanical Engineering
Background:
- Reference point indentation (RPI) is an emerging technique for evaluating material properties.
- Assessing the mechanical integrity of 3D-printed polymers is crucial for their application.
- Long-term material degradation and its impact on mechanical response require investigation.
Purpose of the Study:
- To evaluate the efficacy of two RPI instruments (BioDent and Osteoprobe) in characterizing the mechanical properties of 3D-printed polymers.
- To correlate RPI parameters with established tensile test mechanical properties (elastic modulus, ultimate stress, elongation).
- To investigate the effect of aging (5 years) on the RPI-based mechanical property assessment of these polymers.
Main Methods:
- Utilized BioDent and Osteoprobe instruments for RPI on multiple 3D-printed polymer samples.
- Performed standard tensile tests to obtain elastic modulus, ultimate stress, and elongation.
- Correlated RPI-derived parameters (e.g., unloading slope, indentation distances, bone material strength index) with tensile test results.
- Re-tested aged (5-year-old) polymer samples using the same RPI and tensile testing methods.
Main Results:
- For fresh (Age 0) polymers, strong correlations were observed between elastic modulus and RPI parameters like average unloading slope (r=0.87) and bone material strength index (BMSi) (r=0.85).
- Ultimate stress also showed significant correlations with RPI parameters, including first unloading slope (r=0.85) and BMSi (r=0.81).
- Elongation showed a weak correlation only with average creep indentation distance (r=0.60), while correlations between RPI and mechanical properties were notably lower for aged (Age 5) polymers.
Conclusions:
- Reference point indentation shows significant potential for non-destructively assessing the mechanical properties of 3D-printed polymers.
- The strong correlations observed in fresh polymers diminish substantially after five years of aging, highlighting the impact of time on material response.
- This study provides novel insights into the RPI behavior of aged 3D-printed polymers, a previously unexplored area.
