Postbuckling Analysis of Delaminated Composite Plates Under Compression (Composite Laminates)

Failure mechanics of delamination problems in composite laminates under compression is investigated. The failure modes in general may include prebuckling, postbuckling, delamination growth and final failure. Buckling load is determined by solving an eigenvalue problem using a subspace iteration technique. The Riks-Wempner iterative scheme is then used to determine the associated postbuckling load-displacement path. Owing to local buckling of the delaminated ligament, interlaminar stress transfer and strong material anisotropy, the singular stress field near the crack-tip must be considered for crack stability study. A rotational, singular hybrid finite element approach is taken for studying crack-tip stresses during postbuckling. Formulation of the element stiffness matrix is based on the assumption of small strain, large rotation and the recently developed laminate elasticity solution. The variational principle of a modified hybrid functional is employed for derivation of equilibrium equations in each incremental step. Comparisons of the results obtained from the present method and conventional finite elements are made to demonstrate the accuracy and efficiency of the present approach. Influences of eigenfunction truncation, and size of the rotational singular hybrid element on solution accuracy and convergence are studied. An analysis of symmetric graphite-epoxy composite laminates subjected to in-plane compression is attempted. Effects of fiber orientation and crack length on buckling instability and postbuckling behavior are studied. Mixed-mode stress intensity factors in delaminated (theta)/-(theta)/-(theta)/(theta) composite systems are calculated during postbuckling. Based on a critical mode-I fracture criterion, delamination stability is also investigated.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Theoretical and Applied Mechanics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Yuan, Fuh-Gwo

• Engineering, Aerospace

Identifier

(UMI)AAI8701664

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/71691