Date of Award
Doctor of Philosophy (PhD)
This dissertation is to study the stress and strength of a finite laminated plate containing a circular hole subjected to tension. Efforts were made in three aspects: theoretical modeling, computer simulation using finite element method, and experimental evaluation using unidirectional and crossply Scotchply laminates. The stress concentration factor, normal stress distribution and tensile strength of laminates with various hole sizes and gage lengths were investigated. Theoretically, two models were proposed to describe the normal stress distribution of a laminate with finite width and finite length. By defining a width correction function and a size correction function, the normal stress in a laminate with finite width and finite size was predicted in terms of the normal stress in an infinite laminate. The introduction of width correction function and size correction function was based upon the elastic solutions of finite and infinite isotropic plates containing a circular hole. Experimental work was performed on laminated specimens made of unidirectional and crossply Scotchply laminates. Width effect, or hole size effect, was studied using 2&inches; wide specimens with hole size varying from 0.1&inches; to 1.5&inches; (the corresponding d/W ratio from 0.05 to 0.75). Specimens with different lengths were tested. Both initial tensile strength and ultimate (rupture) strength were obtained for specimens with various hole sizes and gage lengths. Strain gages were also used in several specimens to check normal stress distribution. Finite element method was extensively used in the stress analysis of the unidirectional and crossply laminates in this study. COSMOS software was utilized which has the capability to model laminated composites. Composite quadrilateral plate elements were used for the laminates. A total of 29 cases were analyzed to obtain the stress concentration factor, normal stress distribution, and initial tensile strength for laminates with various hole sizes and lengths. The results of this study showed that the proposed models provide better stress and strength predictions than existing models. The predictions from the proposed models agree well with the experimental data and results from the finite element analysis.
Zhao, Yi, "Stress and Strength of Laminated Composite Containing a Circular Hole." (1998). LSU Historical Dissertations and Theses. 6880.