Effects of defects on the buckling load of rodpack laminates

The composite rod has emerged as a new material form that is currently bein g considered in the design of stiffener reinforced structures for low-cost composite wing and fuselage structural applications. This paper covers buck ling analysis of rodpack laminates with and without defects. Defects consid ered in this study include rods broken in the center, rods split vertically as well as horizontally in the rod layer, and delamination occurring at th e interface between rod layer and unidirectional lamina. A fully three-dime nsional finite element analysis was conducted to investigate the effect of the critical buckling load due to these defects. A closed-form expression o f the bending stiffness for the rodpack laminates was also derived. This ex pression provides better accuracy for evaluating the column buckling for th is laminate. The results indicate that vertical split or broken rods in the rodpack laminates do not affect the buckling load. However, for laminate w ith a horizontal split rod the prediction of the critical buckling load has reduced about 8.7% compared with the laminate without damage.