Transient analysis of laminated composite and sandwich plates with embedded delaminations using GLPT

Delamination is the most common damage type of laminar composites. It is of the great importance that perfect bonding between faces and the soft-core of sandwich plate remain intact under different types of dynamic loading. This paper explains the transient response of laminated composite and sandwich plates with embedded delaminations. For this purpose, numerical model is derived using Reddy's Generalized Laminated Plate Theory. This theory assumes layerwise linear variation of in-plane displacement components, while transverse displacement is constant through the thickness. Cross sectional warping is accounted. Jump discontinuities in displacement field, which represent the delamination openings in three orthogonal directions, are implemented using Heaviside step functions. Linear kinematic relations and Hooke's constitutive law are considered. Equations of motion are derived using Hamilton's principle. Numerical solution based on the proposed theory is obtained using the enriched finite elements with four or nine nodes. Governing partial differential equations are reduced to a set of ordinary differential equations in time using Newmark integration schemes. The equations of motion are solved using constant-average acceleration method using the originally coded MATLAB program. Effects of delamination size and position through the plate thickness on transient response are commented. Also, illustrative comments are given about the influence of shear deformation on transient response. Different forcing functions are investigated. After verification of the proposed model for the intact plates, the variety of new results for delaminated plates is presented as a benchmark for future investigations