Semi-analytical Study On The Composite Laminated Structures With Interlaminar Interfacial Damage

Based on the damage severity, the interlaminar interfacial damage form of composite laminated structures can be distinguished into bonding imperfections and delaminations. For bonding imperfection, there are displacement differences, or displacement jumps, between the layers despite non-zero continuous interfacial stresses. For delaminations, the upper sublaminates and the lower sublaminates are completely delaminated from each other, which occur on local interfaces where interfacial stresses vanish. The interlaminar interfacial damage, particularly for delaminations, can drastically reduce the stiffness of structures, which will cause a reduction in the natural frequency, buckling load and thermal buckling temperature. Therefore, it is very meaningful to reserch the vibration, buckling and thermal buckling behaviors of composite laminates with bonding imperfections and delaminations.To do that, two kinds of semi-analytical methods were presented based on the state-space approach in this thesis, i.e., the coupled finite element-meshfree radial point interpolation method and the meshfree local radial point interpolation method in Hamilton system. In the state-space approach, two types of variables(i.e., the displacements and transverse stresses) are synchronously considered. An advantage of this approach is that the analysis of laminated structures can be performed without any assumptions on displacements and stresses. By using the transfer matrix technique, the state-space approach provides an exact continuous transverse displacement and stress field across the thickness of the laminated structures. Another distinct advantage of the state-space approach is that the final scale of governing equation is independent of the thickness and the number of layers of a laminate.In addition, the Hamilton function was modified to analyze the buckling and thermal buckling behaviors of imperfect composite and piezoelectric laminates. Several numerical examples for analyzing the bending, vibration, buckling and thermal buckling behaviors of composite and piezoelectric beams and plates with bonding imperfections and delaminations were carried out to validate the present methods, and the present results are in good agreement with pre-existing results.