Experimental Debonding Failure Behaviors of Composite Skin-Stiffener Bonded Specimens

Debonding failure characteristics of the composite skin-stiffener specimens were experimentally investigated. The influences of bonding methods, types of stiffener shape and various secondary bonding parameters were evaluated. Present test results combined with the previous test results[1] showed that the failure displacement of the skin-stiffener specimens well evaluates the skin-stiffener debonding failure strength of the composite stiffened panels. The specimens with an open type stiffener had lower bending stiffness and larger failure displacement than those with a closed type stiffener. Secondary bonding and co-curing with adhesive had better failure strength than co-curing without adhesive film. Secondary bonded specimens failed by adhesive failure and co-cured specimens failed by delamination failure. As the bondline thickness was thinner, the skin-stiffener specimens had higher failure strength. The fillets had no influence on failure strength of the specimens. The influence of the surface roughness was shown according to types of stiffener shape.