基于纳米压痕法的羟基磷灰石/聚乳酸复合材料力学性能表征

采用准静态和动态纳米压痕技术研究了羟基磷灰石/聚乳酸（HA/PLA）复合材料在微纳尺度的表面力学性能。在静态模式下研究了保载和卸载时间对模量和硬度测试结果的影响。结果发现,当保载时间小于45 s时,由于蠕变使保载和卸载时间对测试结果产生显著影响;保载时间短且卸载时间长时,在卸载段会形成"鼻子",为了避免"鼻子"选择保载时间为45 s。在动态模式下研究了材料的动态力学性能,结果表明,存储模量和硬度均随着压入深度的增加而减小。压痕和划痕实验结果均表明：HA显著提高了PLA的力学性能,与纯PLA相比,9wt% HA/PLA复合材料的模量增加了35.5%,硬度增加了44.7%,蠕变深度下降了9.5%,相同载荷下的最大划痕深度和残余深度均小于纯PLA,表现出良好的弹性恢复能力和抗变形能力。

Mechanical properties of hydroxyapatite/polylactic acid composites based on nanoindentation method

Quasi-static and dynamic nanoindentation techniques were performed to study the surface mechanical properties of hydroxyapatite/polylactic acid (HA/PLA) composites on the nanoscale. The mechanical responses(modulus and hardness) of the composite were obtained by changing the loading and holding time in the static mode. The effects of these experimental parameters on nanoindentation measurement were also discussed. It is found that the loading and unloading time have a significant effect on the experimental results due to creep deformation when the holding time is less than 45 s. It is also found that a "nose" may appear in the unloading segment of the load-displacement curve during nanoindentation when the holding time is short and the unloading time is long. The holding time was set to 45 s in order to avoid the influence of the "nose". The dynamic nanomechanical properties of the material were investigated in the dynamic indentation mode. The results show that the storage modulus and hardness decrease with the increase of the indentation depth. Both nanoindentation and scratch test show that HA improves the mechanical properties of PLA obviously. Comparing with pure PLA, the modulus and hardness of 9wt% HA/PLA composite enhance by 35.5% and 44.7%.The creep depth of 9wt% HA/PLA composites decreases by 9.5%. The maximum depth and residual depth are fewer than that of pure PLA under the same load, showing the greater elastic recovery and resilience of HA/PLA composites.