Numerical Simulation Of Interfacial Debonding In Fiber Reinforced Composites Under Fatigue Load

Fiber Reinforced Composites(FRCs) have been widely utilized in many fields during recent years.Unlike other materials,the interfacial fatigue behaviour is associated with the overall properties of FRCs.It is shown that the service life of materials and structures will be shortened by fatigue damage,and even economic losses and casualties will be increased.Interface takes a very important role in FRCs properties,and hence the interfacial fatigue behaviour of FRCs is a concern in composites science and technology.The investigations in this thesis are listed as follows:(1)A numerical technique is proposed to simulate the interfacial fatigue debonding of FRCs while the interface damage on debonded interface is taken into account.The technique is a combination of finite element method,numerical differentiation and fracture mechanics,and it is carried out by the aid of the secondary development of the finite element package ANSYS.The analytical results are verified against the numerical results,while some errors caused by the assumptions in the analytical solution are discussed.Further,the effects of the non-uniform degradation of matrix stiffness are considered.(2)For a new FRC with functionally graded fiber coating,a power-law model is introduced to describe the elastic modulus gradient along the radial direction,and then the mono-interfacial fatigue debonding of the two interfaces is studied both analytically and numerically(i.e.,coating/matrix and coating/fiber).In addition,the predictions of the composite strain related to interfacial debonding and stochastic matrix crack spacing are provided.(3)Taking the interface damage on debonded interface into account,a numerical technique is proposed to simulate the bi-crack propagation of FRCs.Bi-interfacial debonding and interfacial debonding accompanied with matrix annular cracking under cyclic load are investigated.(4)In the simulation of concrete/rebar interface debonding,the freeze-thaw damage of concrete and the corrosion of steel are considered,and concrete beams strengthened with FRP are employed as an engineering application.In a word,an available numerical approach is proposed to evaluate the reliability of materials and structures under fatigue load in the present investigation,and some helpful guidelines are provided for the use of new materials.