Substrate failure shows as torn wood fibers, ripped paper, delaminated composite plies, broken plastic or pulled-off paint layers. In most cases it means the bond is stronger than the part, which is the goal for wood, paper and packaging joints. On painted or plated parts it can reveal that the coating, not the adhesive, is the weak link.
Coupon broke in the composite, first ply came away with the adhesive, so it's substrate failure, not the glue.
Also heard as
- adherend failure
- material failure
Related terms
Fiber tear
Paper or wood fibers torn out and stuck to the adhesive when a bond is pulled apart, showing the bond beat the substrate.
Cohesive failure
A break that runs through the adhesive itself, leaving adhesive on both parts.
Adherend
Each of the parts in a bonded joint; the surface the adhesive has to grip.
Adhesive failure
A break at the interface between adhesive and part, leaving one surface clean or nearly clean.