Cohesive Model For Delamination In Composite Multidirectional Laminates With Fiber Bridging

Advanced carbon fiber composite materials are widely used in aerospace and other fields due to their high modulus,high specific strength and outstanding designability characteristic.As one of the most commonly used composite material configurations,due to the relatively weak interlaminar strength,delamination has become one of the most common failure types in composite laminates.Numerical simulation is one of the important methods to study delamination,and improving its objectivity and usability is a hot topic for many researchers.Currently most simulations are focused on the delamination in unidirectional laminates.However,multidirectional laminates are more widely used in the engineering structures,so there is more practical value to simulate the delamination behavior of multidirectional laminates.Different from unidirectional laminates,fiber bridging always exists during the delamination growth in multidirectional laminates,which leads to the increase of fracture toughness as typical R-curve.On the basis of considering the influence of fiber bridging on the delamination behavior in multidirectional composite laminates,this paper studies the delamination simulation of multidirectional laminates specimens fabricated by T700/QY9511.Some innovative research results have been obtained:(1)Based on the microscopic mechanism of delamination failure,a novel trilinear cohesive model with explicit physical meaning and simple parameters has been proposed.The model does not depend on the process of delamination growth,and introduces the mechanism of fiber bridging from the constitutive relation,which can accurately reflect the stress distribution in fiber bridging zone and demonstrates the formation mechanism of delamination resistance.(2)The numerical procedure of the trilinear constitutive relation is developed,and the relative parameters are studies systematically.Based on two-dimensional and three-dimensional models,the general modeling parameters and constitutive relation parameters are discussed.A reasonable parameter research process is proposed,in which the parameter system with strength as the core is determined.The results of numerical simulation of T700/QY9511 multidirectional laminates are very close to the experiment,which demonstrates the validity of the model parameter research scheme.Based on the cohesive zone method,this paper proposes a new trilinear constitutive model,puts forward a reasonable parameters research scheme and realizes the validation of the model and parameters of discussion by combing with the secondary development.The model with clear physical meaning and simple parameters can accurately simulate the delamination in multidirectional composite laminates.The work of this paper provides effective support for the delamination simulation of multidirectional composite laminates.