Reliability and Limitations of Compression Testing of Various Biomaterials
Jokinen, Viivi (2017)
Teknis-luonnontieteellinen tiedekunta – Faculty of Natural Sciences
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Tissue-engineered scaffolds should mimic, as closely as possible, the one of the tissues to be replaced. Hence, mechanical tests are of paramount importance. However, as there are various biomaterials, with distinct mechanical properties, performing a conventional compression test is complicated. The objective of this thesis was to study the reliability and limitations of static conventional compression test and compression testing device. Accuracy and reproducibility of the compression tests were considered. The results showed that the compressive properties are dependent on many factors (sample size, microstructure, etc.). Biomaterial’s properties, such as viscoelasticity and brittleness, complicated the compression test and hampered the reliability. Fixed uniaxial compressive platen led to uneven load distribution on sample cross-section area. Careful sample preparation, surface finish or self-aligning platen could improve the reliability. The testing device showed good reproducibility, and accuracy for compressive strength. However, compressive modulus underestimated the results by > 34 %. The strain was measured from the platen displacement that may have caused error in strain measurements. With an optical extensometer, strain could be measured precisely from the center part of the sample. In conclusion, the accuracy and reproducibility of conventional compression test are questionable. The compression test should be performed with caution.