Associate professor, University of Missouri, Rolla, MO
Research engineer, NASA Langley Research Center, Hampton, VA
An experimental study of cracked-lap-shear specimens was conducted to determine the influence of adherend stacking sequence on debond initiation and damage growth in a composite-to-composite bonded joint. Specimens consisted of quasi-isotropic graphite/epoxy adherends bonded together with either FM-300 or EC 3445 adhesives. The stacking sequence of the adherends was varied such that 0°, 45°, or 90° plies were present at the adherend-adhesive interfaces. Fatigue damage initiated in the adhesive layer in those specimens with 0° and 45° interface plies. Damage initiated in the form of ply cracking in the strap adherend for the specimens with 90° interface plies. The fatigue-damage growth was in the form of delamination within the composite adherends for specimens with the 90° and 45° plies next to the adhesive, while debonding in the adhesive resulted for the specimens with 0° plies next to the adhesive. Those joints with the 0° and 45° plies next to either adhesive had essentially the same fatigue-damage-initiation stress levels. These stress levels were 13 and 71% higher, respectively, than those for specimens with 90° plies next to the EC 3445 and FM-300 adhesives.
Paper ID: CTR10314J