湿热老化及应变率耦合作用下有机玻璃的微纳米力学性能

Micro-Mechanical Properties of PMMA with the Coupling of Hygrothermal Aging and Strain Rate

采用微压入法在温度85℃、相对湿度85%的条件下,对有机玻璃(PMMA)试样进行加速老化的试验,研究其在湿热老化及应变率耦合作用下的力学性能。实验采用5种不同的应变率,结果表明湿热老化及加载应变率均会影响有机玻璃的性能。其中,湿热老化会增加有机玻璃的蠕变特性,同时对有机玻璃的影响可分为3个阶段:初始阶段(0~10d)、不稳定阶段(10~22d)、稳定阶段(22~33d);对于应变率,高应变率下有机玻璃的弹性模量和硬度较高,而且有机玻璃的粘性变形不能充分释放,转变为保载段更为显著的蠕变变形及较高的初始蠕变应变率。

PMMA sheets were subjected to 85℃and 85%relative humidity for different times and then applied to nanoindentation tests to investigate the effects on PMMA nanomechanics with the coupling of hygrothermal aging and strain rate.The test adopted five strain rates.Results show that both the hygrothermal aging and loading strain rate affect the property of PMMA.The hygrothermal aging increases the creep property of PMMA with respect to unaged sample.Meanwhile,the effect of aging time on PMMA nanomechanics can be divided into three stages:initial aging stage(0~10 d),unstable stage(10~22 d)and stable stage(22~33 d);As for loading strain rate,the elastic modulus and hardness increase as the strain rate increases.Furthermore,at high strain rate,more viscous deformation is accumulated after loading stage,transforming into larger creep deformation and higher initial creep strain rate.