Effect of Bond Quality on Crack Growth Resistance of Adhesively Bonded Composite Joints Under Static and Cyclic Loading
Cohesive failure is preferred over adhesive failure in bonded joints. Cohesive failure can be defined in terms of mechanical properties of adhesive, while adhesive failure is a property of adhesion strength between two bonding surfaces. Although the benefits of bonding apply to both metallic and non-metallic materials, the use of bonding has proven particularly attractive for fiber-reinforced composites due to the complications involved with bolted attachment of composites. Bonding of composite parts is challenging since the interface (adhesive) failure or adherend failure should be avoided. The present work considers cohesive, adhesive and adherend failure in shear, so that the effect of bond quality on mode II crack growth can be better understood. Failure modes for weak bonds were observed to be adhesive failure in static and fatigue loading. Strong bonds showed cohesive failure for fatigue loading. However, in static loading, strong bonds with a tough adhesive had a cohesive-adherend mixed failure mode and strong bonds with the standard adhesive had a cohesive-adhesive mixed failure. The fracture toughness for strong bonds in comparison to weak bonds, increased by 100 % for a tough adhesive and 50 % for a standard adhesive. The fatigue crack growth rate for weak bonds increased with a decrease in adhesive toughness.
Author: Preetam Mohapatra
Conference: SAMPE Seattle 2017