Tang Haibin, Zhou Guowei, Sun Qingping, Avinesh Ojha, Meng Zhaoxu, Engler-Pinto Carlos, Su Xuming
School of Intelligent Manufacturing, Nanjing University of Science and Technology, Nanjing 210094, China.
Department of Mechanical Engineering, National University of Singapore, Singapore 117575, Singapore.
Compos Struct. 2021 Nov 1;275. doi: 10.1016/j.compstruct.2021.114402. Epub 2021 Jul 27.
With a better balance among good mechanical performance, high freedom of design, and low material and manufacturing cost, chopped carbon fiber chip reinforced sheet molding compound (SMC) composites show great potential in different engineering applications. In this paper, bending fatigue behaviors of SMC composites considering the heterogeneous fiber orientation distributions have been thoroughly investigated utilizing both experimental and computational methods. First, four-point bending fatigue tests are performed with designed SMC composites, and the local modulus is adopted as a metric to represent the local fiber orientation of two opposing sides. Interestingly, SMC composites with and without large discrepancy in local modulus of opposing sides show different fatigue behaviors. Interrupted tests are conducted to explore the bending fatigue failure mechanism, and the damage processes of valid specimens are also closely examined. We find that the fatigue failure of SMC composites under four-point bending is governed by crack propagation instead of crack initiation. Because of this, the heterogeneous local fiber orientations of both sides of the specimen influence fatigue life. The microstructure of the lower side shows a direct influence while that of the upper side also exhibiting influence which becomes more prominent for high cycle fatigue cases. Furthermore, a hybrid micro-macro computational model is proposed to efficiently study the cyclic bending behavior of SMC composites. The region of interest is reconstructed with a modified random sequential absorption algorithm to conserve all the microstructural details including the heterogeneous fiber orientation, while the rest of the regions are modeled as homogenized macro-scale continua. Combined with a framework to capture the progressive fatigue damage under cyclic bending, the bending fatigue behaviors of SMC composites are accurately captured by the hybrid computational model comparing with our experimental analysis.
chopped carbon fiber chip reinforced sheet molding compound (SMC) composites show great potential in different engineering applications. In this paper, bending fatigue behaviors of SMC composites considering the heterogeneous fiber orientation distributions have been thoroughly investigated utilizing both experimental and computational methods. First, four-point bending fatigue tests are performed with designed SMC composites, and the local modulus is adopted as a metric to represent the local fiber orientation of two opposing sides. Interestingly, SMC composites with and without large discrepancy in local modulus of opposing sides show different fatigue behaviors. Interrupted tests are conducted to explore the bending fatigue failure mechanism, and the damage processes of valid specimens are also closely examined. We find that the fatigue failure of SMC composites under four-point bending is governed by crack propagation instead of crack initiation. Because of this, the heterogeneous local fiber orientations of both sides of the specimen influence fatigue life. The microstructure of the lower side shows a direct influence while that of the upper side also exhibiting influence which becomes more prominent for high cycle fatigue cases. Furthermore, a hybrid micro-macro computational model is proposed to efficiently study the cyclic bending behavior of SMC composites. The region of interest is reconstructed with a modified random sequential absorption algorithm to conserve all the microstructural details including the heterogeneous fiber orientation, while the rest of the regions are modeled as homogenized macro-scale continua. Combined with a framework to capture the progressive fatigue damage under cyclic bending, the bending fatigue behaviors of SMC composites are accurately captured by the hybrid computational model comparing with our experimental analysis.
短切碳纤维片材增强片状模塑料（SMC）复合材料在不同工程应用中显示出巨大潜力。本文采用实验和计算方法深入研究了考虑纤维取向分布不均匀的SMC复合材料的弯曲疲劳行为。首先，对设计的SMC复合材料进行四点弯曲疲劳试验，并采用局部模量作为度量来表征相对两侧的局部纤维取向。有趣的是，相对两侧局部模量差异大与小的SMC复合材料表现出不同的疲劳行为。进行中断试验以探索弯曲疲劳失效机制，并仔细检查有效试样的损伤过程。我们发现，SMC复合材料在四点弯曲下的疲劳失效由裂纹扩展而非裂纹萌生控制。因此，试样两侧不均匀的局部纤维取向会影响疲劳寿命。下侧的微观结构有直接影响，而上侧的微观结构也有影响，在高周疲劳情况下这种影响更为显著。此外，提出了一种混合微观 - 宏观计算模型，以有效研究SMC复合材料的循环弯曲行为。用改进的随机顺序吸附算法重建感兴趣区域，以保留包括不均匀纤维取向在内的所有微观结构细节，而其余区域则建模为均匀化的宏观连续体。结合一个捕捉循环弯曲下渐进疲劳损伤的框架，与我们的实验分析相比，混合计算模型能够准确捕捉SMC复合材料的弯曲疲劳行为。
