Interfacial Mode Mixity And Mode-mixity-based Criterion Of Laminated Composites

Composite laminates structure is getting more and more widely used in varies engineering fields,such as aviation, aerospace, marine and automotive, due to its high specific strength and specificstiffness, high performance at fatigue resistance, easy to be designed, good corrosive resistance etc.However, because it has low shear strength between layers and material properties of adjacent layersare discontinuous, which make delamination become the main factor of failure of composite materials,limiting the use of them.Delaminated composite material can be treated as propagation of interfacial crack between twoadjacent layers. Hence, fracture mechanics could be applied to analysis this problem, anddelamination propagation is regarded as resulting effect of crack propagation under different modes ofcrack. This article mainly studied the oscillatory singularity of crack tip of biomaterial interfacialcrack theoretically, summarized main methods to eliminate the singularity of crack tip of biomaterialinterfacial crack, discussed advantages and disadvantages of each method; by introducing variablesΦ₁、Φ₂、Φ’₁, using modified virtual crack closure technique （VCCT）, proposed a method whichsuccessfully exact crack-extension-size-independent components of strain energy release rate（SERRs）, hence, mode mixity which doesn’t vary with crack extension size was obtained. Alsoprogram of mode mixity calculation, which based on MATLAB platform, was written. Bothcorrectness and effectiveness of this method were verified through a typical interfacial crack mode;eventually, functions of interfacial toughness and mode mixity of different materials were establishedby fitting experiment data of interfacial toughness for different materials, based on this, therefore,proposed mode-mixity-based fracture criterion and estimation of initiation and evolution of thedelamination.