Experimental And Numerical Study On Buckling Failure Of Laminated Beam Plates With Delaminations

As a new type of composite material,the laminated carbon fiber reinforced composite structures have many advantages that traditional materials do not possess.Due to the deficiency of manufacturing process and transportation collision,various kinds of defects may occur in laminated structures,and delamination is one of the main structural damage forms of the composite laminates.This paper focuses on the experimental study on buckling failure of laminated beam plates containing delaminations.The buckling and post-buckling behaviors of CFRP composite laminated beam plate with delamination was investigated by performing compressive experiments.Finite element simulation was conducted to obtain the buckling modes and critical buckling loads of laminated beam plates so as to compare with the experimental results.The main contents of this thesis are as follows:Firstly,analytical solution of critical buckling pressure of laminated beam plates under compression is derived.By examining the deformation mechanism of the laminated beam plate,differential equation of equilibrium is established.Based on the theory of composite laminates,governing equation of the laminated beam plates is deduced.Deflections of beam plates with simply supported and clamped boundary conditions are solved.Furthermore,the influence of initial imperfection on the performance of the laminated beam plates was inspected.Secondly,the buckling failure of laminated beam plates with single delamination and multiple delamination was analyzed experimentally.In order to investigated the buckling performance of laminated beam plates with delaminations,the delamination was created by embedding teflon plastic film in the laminated beam plates.Laminated composite specimens with different delamination widths,delamination depths and delamination quantities were produced by using the hot pressing machine.The specimens were symmetrically stacked and were categorized into three groups:without delamination,with a single delamination stacked in a sequence of[0/90/0]₆and with multiple delaminations stacked in a sequence of[0/90/0]₈.The buckling,post-buckling and delamination propagation behavior of CFRP laminated beam plates with single delamination and multiple delamination were researched and compressive tests were conducted to obtain the critical buckling loads and post-buckling equilibrium path.The influence of delamination width,delamination depth and delamination quantity on the critical buckling load of CFRP laminated beam plates with delamination was investigated by using the method of control variables.Finally,the finite element simulation is conducted.In this thesis,the ABAQUS finite element software is utilized to simulate the buckling failure of CFRP laminated beam plates with delamination.A 4-partition model and a 7-partition model are adopted for beam plates with single delamination and multiple delamination,respectively in which the laminated beam plates were divided into 4 or 7 sub-plates accordingly.Then sub-plates are bound together to make them be parts of a single whole.A normal hard contact is imposed on the interface of the delamination to prevent the anti-penetration between sub-plates.Results of the buckling load for the laminated beam plates with single and multiple delamination obtained from finite element analysis are validated by comparing with the experimental results.Using the established finite element model,parametric analysis is performed to examine the influence of delamination condition which is more complex on buckling performance of the delaminated beam plates.