EPDM/PP热塑性动态硫化橡胶高温疲劳性能研究

Study on High-Temperature Fatigue Properties of Dynamically-Vulcanized Thermoplastic EPDM/PP Rubber

针对三元乙丙/聚丙烯热塑性动态硫化橡胶,进行常温及高温(60℃)下应变比R为0的单轴拉伸疲劳试验,以最大主应变为损伤参量,使用幂律模型较好地拟合了疲劳寿命曲线,发现高温下疲劳寿命有较大提高.此外,使用数字显微镜与扫描电镜观察疲劳断面,发现疲劳断面分为光滑与粗糙两个区域,在峰值载荷较低、疲劳寿命更长的断面表现出更多分层,推测较低的峰值载荷作用下产生更多的二次裂纹导致裂尖钝化,从而提高了疲劳寿命.相同应变峰值载荷作用下的高温疲劳断面粗糙区分层更多,但光滑区却更大.高温下材料软化,应变能下降,在形成主裂纹之前形成更多的断面分层,延缓了快速断裂阶段,从而提高了疲劳寿命.

Uniaxial tensile fatigue tests of dynamically-vulcanized thermoplastic EPDM/PP rubber under zero strain ratio R at both room temperature and high temperature(60℃)were carried out.The fatigue life curve was well fitted using a power-law model with the maximum principal strain as the damage parameter.It was found that the fatigue life at high temperatures was improved.In addition,the fracture surfaces were observed using digital microscopy and scanning electron microscopy.The surfaces could be apparently divided into smooth and rough regions,with more delamination in surfaces corresponding to lower peak loads and longer fatigue lives,which presumably results in more secondary cracking leading to blunting of the crack tip,thus increasing the fatigue life.High-temperature fracture surfaces under the same peak strain load show more rough delaminations but larger smooth regions.It is inferred that the material softening and the decrease in strain energy at high temperatures result in more fracture delaminations before the formation of primary cracks,leading to the delay of the rapid fracture phase and thus the increase of the fatigue life.