Analysis of the notched coating adhesion test

An analysis of the notched coating adhesion (NCA) test is presented. This s imple adhesion test method is appropriate for measuring the interfacial fra cture toughness of some classes of coatings and open-faced adhesive bonds. The NCA specimen consists of a single substrate coated with a thin layer of adhesive. The coating is notched to sever the coating and induce sharp int erfacial debonds, and the specimen is then loaded in tension. The substrate strain at which coating debonding occurs is recorded and used to determine the critical strain energy release rate. Yielding of the substrate is perm itted, and does not significantly affect the calculation of the strain ener gy release rate. Analytical and finite element analysis are used to quantif y the available strain energy release rate for both steady state and latera lly-constrained cases. The available strain energy release rate is shown to be quite insensitive to the initial debond length. The specimen geometry r esults in a mode mix which causes the adhesive to debond along the interfac e.