Page 159 - IJB-9-3

International Journal of Bioprinting LPBF of AKM/PEEK biological composite

Figure 5. Mechanical properties of the composite samples. (a) Stress–strain curves and the printed tensile parts, (b) yield strength, (c) tensile strength, and
(d) Young’s modulus.

then yield deformation, and final fracture. Since there when the AKM content further increased to 15 wt%, the
was no obvious yield platform on the curve, a line parallel yield strength decreased significantly to 25.10 ± 1.23 MPa.
to the curve in the elastic stage was used to identify the Meanwhile, the tensile strength decreased from 98.74 ±
occurrence of plastic deformation. Compared with the 0.48 to 30.83 ± 0.46 MPa with the increase of AKM content.
composite samples, the pure PEEK sample experienced a The results indicated that the AKM reduces the
larger plastic region. With the increase of AKM content, mechanical properties of the samples. Therefore,
the range of plastic region gradually decreased, and the microstructure tests were performed to delineate the
samples fractured at lower elongation. This suggests that mechanism. The crystallinity (X ) of the composite
the additive AKM reduces the plasticity of the samples and specimens was tested by the DSC experiments (Table 3).
c
makes the sample brittle.
With the addition of AKM particles, the melting enthalpy
The intersection of the tangent line and the stress– (∆H ) of specimens gradually decreased, which means
m
strain curve indicates the stress corresponding to 0.2% reduced crystallinity. This could be caused by two reasons:
plastic strain, which is considered the yield strength (i) with the increase of AKM mass fraction, the thermal
(Figure 5a and b). Figure 5c and d show the tensile strength energy absorbed by PEEK melting of the composite
and modulus of samples, respectively. Specific values are decreases, leading to the decrease of melting enthalpy
summarized in Table 4. When the AKM content increased and crystallinity; and (ii) as a ceramic material, the low
to 5 wt%, the yield strength increased from 55.90 ± 5.19 to thermal conductivity of AKM hinders the heat transfer
58.30 ± 1.61 MPa. Considering the error bar, AKM with and molecular chain rearrangement of PEEK melt in the
5 wt% content did not greatly affect the yield strength sintering process, thus reducing the crystallinity. The
but made the quality of the sample more stable. However, decreased crystallinity is directly related to the change of

Volume 9 Issue 3 (2023) 151 https://doi.org/10.18063/ijb.699