|
|
||
|
|
|
|
From:
Luyang Shan (Dept. of Civil and Environmental Engineering, Washington State University),
“Explicit buckling analysis of fiber-reinforced plastic (FRP) composite structures”, PhD Dissertaion, May 2007
ABSTRACT: Explicit analyses of flexural-torsional buckling of open thin-walled FRP beams, local buckling of rotationally restrained orthotropic composite plates subjected to biaxial linear loading and associated applications of the explicit solution to predict the local buckling strength of composite structures (i.e., FRP structural shapes and sandwich cores), and delamination buckling of laminated composite beams are presented.
Based on nonlinear plate theory, of which the shear effect and beam bending-twisting coupling are included, the buckling equilibrium equations of flexural-torsional buckling of pultruded FRP composite I- and channel beams are established using the second variational principle of total potential. The critical buckling loads for different span lengths are measured through experiments and compared with analytical solutions and numerical finite element results. A parametric study is conducted to evaluate the effects of the load location, fiber orientation, and fiber volume fraction on the buckling behavior.
The first variational formulation of the Ritz method is used to establish an eigenvalue problem for local buckling of composite plates elastically restrained along their four edges and subjected to a biaxial linear load, and the explicit solution in term of rotational restraint stiffness is presented with a unique harmonic shape function. A parametric study is conducted to evaluate the influences of the biaxial load ratio, rotational restraint stiffness, aspect ratio, and flexural-orthotropy parameters on the local buckling stress resultants of various rotationally-restrained plates. The applicability of the explicit solutions of restrained composite plates is illustrated in the discrete plate analysis of two types of composite structures: FRP structural shapes and sandwich cores.
The delamination buckling formulas are derived based on the rigid, semi-rigid, and flexible joint deformation models according to three corresponding bi-layer beam theories (i.e., conventional composite, shear-deformable bi-layer, and interface- deformable bi-layer, respectively). Numerical simulation is carried out to validate the accuracy of the formulas, and the parametric study of the shear effect is conducted to demonstrate the improvement of flexible joint model. The explicit buckling solutions developed facilitate design analysis and optimization of FRP composite structures and provide simplified practical design equations and guidelines for buckling analyses.
Page 19 / 114