Mode II Interlaminar Fracture Toughness of Flax/Glass/Epoxy Hybrid Composite Materials: An Experimental and Numerical Study

ABSTRACT

The mode II interlaminar fracture toughness characteristics of flax/glass/epoxy hybrid laminates were experimentally and numerically examined. Three types of hybrid composites that are made of flax (F) and glass (G) and with different layup sequences (i.e., Hybrid I [0 _G/0 _F]_8S, Hybrid II [0_4G/0_4F]_S, and Hybrid III [0_4G/(90/0)_2F]_S) were investigated. The experimental results obtained from end notch flexural tests showed that both the mode II fracture toughness and flexural strength of Hybrid I composites were higher than those for Hybrid II & III composites. This was attributed to the presence of bridging in several interfaces of the flax plies and the glass plies in Hybrid I. A second delamination propagation between the flax/epoxy midplane plies was observed in Hybrid II and III and this helped to lower both the mode II fracture toughness and flexural strength. The finite element simulations employed the virtual crack closure technique and the cohesive zone model. The results showed that both methods successfully predicted mode II interlaminar fracture toughness characteristics of the Hybrid I composites, but significantly overpredicted the values for both Hybrid II & III due to the presence of a secondary delamination propagation.

摘要

对亚麻/玻璃/环氧混杂层合板的II型层间断裂韧性特性进行了实验和数值研究. 研究了亚麻 (F) 和玻璃 (G) 三种不同铺层顺序的混杂复合材料 (混杂i[0G/0F]8S、混杂II[04G/04F]S和混杂III[04G/(90/0)2F]S. 端部缺口弯曲试验结果表明, 混杂I型复合材料的II型断裂韧性和弯曲强度均高于混杂型II&III型复合材料. 这是由于在混杂I中亚麻层和玻璃层的几个界面上存在桥接. 在混杂II和III中观察到亚麻/环氧中间层之间的第二次分层扩展, 这有助于降低II型断裂韧性和弯曲强度. 有限元模拟采用虚拟裂纹闭合技术和粘聚区模型. 结果表明, 这两种方法都成功地预测了混杂I型复合材料的II型层间断裂韧度特性, 但由于存在二次分层扩展, 这两种方法都严重高估了杂交II和III的断裂韧度值.

KEYWORDS:

• Flax/glass/epoxy hybrid composite
• mode II interlaminar fracture toughness
• delamination
• ENF test
• virtual crack closure technique
• cohesive zone model

关键词:

• 环氧/亚麻复合玻璃
• II型层间断裂韧性
• 分层
• 测试
• 虚拟裂缝闭合技术
• 粘性带模型

Acknowledgments

This research was supported by the Natural Sciences and Engineering Research Council of Canada – Discovery Grants program (NSERC-DG). The authors would also like to acknowledge the Hunstman Corporation (The Woodlands, TX, USA) for supplying funding and materials. These organizations had no influence on the design, content, or publication of this work.

Additional information

Funding

This work was supported by the Natural Sciences and Engineering Research Council of Canada [NSERC-DG].