一、引 言 本研究的目的在于进一步认识无规短纤维SMC复合材料系统在不同的周期疲劳加载方式下的疲劳裂纹传播问题。具体目的是:(1)研究断裂力学参数对SMC复合材料中疲劳裂纹增长问题的适用性;(2)获取这种材料中关于周期裂纹传播速率的定量数据和相关机理;(3)验证不同疲劳加载模式对裂纹增长速率的影响;(4)为进一步研究复合材料中疲劳裂纹增长力学提出合适的模型。 对缺口无规短纤维SMC-R50复合材料进 I. INTRODUCTION The purpose of this study is to further understand the problem of fatigue crack propagation under different periodic fatigue loading methods for SMC composite materials with random short fibers. The specific objectives are: (1) to investigate the applicability of fracture mechanics parameters to fatigue crack growth in SMC composites; (2) to obtain quantitative data and related mechanisms for the propagation of periodic cracks in this material; and (3) to verify that different fatigue Loading mode on the crack growth rate; (4) to develop a suitable model for further study of fatigue crack growth mechanics in composites. Notch random short fiber SMC-R50 composite material into