蠕变条件下刚性夹杂填充高聚物复合材料的延迟时间-蠕变荷载幂率关系研究

The Power-law Relation Between Retardation Time and Creep Load for Rigid Inclusion-filled Polymer Composite

论文研发了不锈钢短纤维(SSFs)填充聚丙烯(PP)的新型高聚物复合材料,开展了在不同的蠕变荷载下材料的蠕变行为研究.实验证实,在相同的持载时间条件下,蠕变变形与蠕变载荷之间呈非线性关系,这个现象用传统的线性粘弹性理论难以解释.论文采用延迟时间与蠕变荷载相关的观点,对蠕变变形-蠕变载荷的非线性现象进行分析,发现了在对数坐标下延迟时间与蠕变载荷之间存在线性关系,从而得到了延迟时间与蠕变载荷之间的幂律关系.进一步的分析指出,蠕变载荷提升导致延迟时间增加的机理主要由材料体系的损伤所诱发.

A new polymer composite was developed by filling polypropylene（PP）with short stainless steel fibers（SSFs）.Because the elastic modulus of stainless steel is about 140 times of that of polypropylene,the short stainless steel fibers could be regarded as rigid inclusions.To investigate the creep behavior of the polymer composite,experiments were conducted under different creep loadings at a constant strain rate of 10^（-2） s^（-1）.The creep load was set as 10 MPa,15 MPa,20 MPa,25 MPa,30 MPa,and 40 MPa,and the dwelling time was 300 s.The experimental results showed a nonlinear relationship between creep strain and creep load in the same dwelling time,which could not be explained by the linear viscoelastic theory.In order to analyze the phenomenon,the dependence of retardation time on creep load was taken into account.The expression for creep response under constant strain-rate loading was obtained by theoretical analysis.Using this formula to fit the experimental data,the relationship between retardation time and creep load was obtained by the fitting parameters.It was found that the retardation time increases linearly with the increase of creep load in the logarithmic coordinate system,thus the power-law relation was proposed to describe the one between retardation time and creep load.Further analysis indicated that the increase of retardation time with creep load is induced by the micro-damage evolution and the difficulty in relative slip of molecular chain due to creep loading.Meanwhile,from the creep strain rate-time curve under different creep loads,it can be seen that the creep strain rate decreases with the increase of time,and tends to zero.This shows that the viscosity of the composite material is limited,i.e.with the increase of holding time,the viscosity of the material could eventually exhaust.