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Compression Failure of Trabecular Tantalum Scaffolds
the elastic moduli of AM-fabricated trabecular Ta deformation and fractures appeared on the outside of the
scaffolds with porosities of 65%, 75%, and 85% were 3.0 AM-fabricated trabecular Ta scaffolds with porosities
± 0.2, 2.2 ± 0.3, and 1.1 ± 0.1 GPa, respectively, and their of 65%, 75%, and 85% under compressive loads. Most
yield strengths were 35.7 ± 0.8 (σ ), 19.5 ± 0.6 (σ ), and microcracks occurred at conjunctions, and the rest of
y1
y2
11.9 ± 0.5 (σ ) MPa, respectively. The yield strains of all them appeared on the struts. The fractured struts were
y3
tested samples lie in the range between 1% and 2%. twisted greatly. Figure 11 displays the SEM micrographs
of the ductile fracture surface of AM-fabricated Ta
3.3. Material failure study sample after tensile fracture failure. The interior collapse
Figure 8 illustrates the geometrical morphologies of characterizations of AM-fabricated trabecular Ta scaffolds
trabecular Ta scaffolds with porosities of 65%, 75%, and with porosities of 65%, 75%, and 85% under compressive
85% under compressive strains of 0, 20%, and 50%. They loading are shown in Figures 12-14, respectively. Optical
demonstrated ductile deformation during compression microscope (OM) photographs indicate that both the strut
tests, and no macroscopic cracks were found with a strain distribution on the polished cross-section of annealed
up to 50%. Figure 9 shows the stress–strain curve and and unannealed specimens that underwent compression
failed specimen of trabecular Ti6Al4V scaffold obtained are consistent with the uncompressed specimen (control
from the previous study . An obvious shear fracture group), which facilitates the identification of collapse
[36]
band along the inclination of 45° with respect to the characterizations of trabecular Ta scaffolds. In comparison
loading direction was found on the trabecular Ti6Al4V with the control group, only part of the struts inside
scaffold. SEM micrographs (Figure 10) suggest that strut porous Ta scaffolds deformed plastically or fractured

Table 2. Compressive mechanical properties of AM-fabricated trabecular Ta scaffolds and human cancellous bone
Testing specimen Porosity (%) Yield strength (MPa) Elastic modulus (GPa)
Ta scaffolds 65 35.7±0.8 3.0±0.2
75 19.5±0.6 2.2±0.3
85 11.9±0.5 1.1±0.1
Human cancellous bone 50 – 90 6.6 – 36.2 0.88 – 3.4 [2,31-35]

Figure 8. Geometric morphologies of trabecular Ta scaffolds with porosities of 65%, 75%, and 85% under strains of 0, 20%, and 50%,
respectively.

118 International Journal of Bioprinting (2022)–Volume 8, Issue 1