Mixed-Mode Failure Analysis of a Unidirectional Carbon/EpoxyComposite and Ahesively Bonded Composite Systems Using the Modified Losipescu Test Method

采用改进的Iosipescu试验技术对单向碳/环氧复合材料的混合模式断裂机制进行研究。本文将对复合材料板间断裂机理进行数值和实验分析。本研究将广泛采用有限元方法研究双轴应力条件下复合材料Iosipescu试件层内裂纹的混合模态应力强度因子和能量释放率。此外，粘合复合材料系统将使用新设计的Iosipescu夹具在混合模式加载条件下进行测试。将对Iosipescu试件中的粘结接头进行线性和非线性有限元计算。本研究的根本意义在于有助于理解碳纤维/环氧复合材料在双轴应力条件下的板间断裂机制。此外，该研究将为研究先进粘接系统的复杂破坏现象提供新的见解。实际意义在于，通过对新设计的双轴试验技术进行全面的数值和实验研究，该试验将有很大的潜力成为许多先进复合材料体系混合模式破坏和断裂分析的标准。

Research will be conducted to investigate mixed mode fracture mechanisms of a unidirectional carbon/epoxy composite material using the modified Iosipescu test technique. Intralaminar fracture mechanisms in the composite will be analyzed numerically and experimentally. The research will use finite element methods extensively to study the mixed mode stress intensity factors and the energy release rates associated with intralaminar cracks in the composite Iosipescu specimens tested under biaxial stress conditions. In addition, adhesively bonded composite systems will be tested under mixed mode loading conditions using the newly designed Iosipescu fixture. Linear and non-linear finite element calculations of the adhesive joints in the Iosipescu specimens will be performed. The fundamental significance of this research is that it will contribute to the understanding of intralaminar fracture mechanisms in carbon fibre/epoxy composites caused by biaxial stress conditions. Moreover, the study will provide new insights into the complex failure phenomena of advanced adhesive joint systems. The practical significance is that after comprehensive numerical and experimental investigations of the newly designed biaxial test technique, the test will have great potential to become standard for mixed mode failure and fracture analysis of many advanced composite systems.