Mechanical and adhesion testing methods of thin films

4 Mechanical and adhesion testing methods of thin films 

With ever-increasing demands imposed by the use of coated implants and devices for dental, orthopedic, and maxillofacial applications, robust and reliable techniques are required for their mechanical characterization. There have been significant advancements in the techniques and equipment capable of extracting the adhesion behavior and mechanical properties of thin films, particularly with the increasing trend toward deposition of nanometer-thick films on smaller devices. 

Three- and four-point bending methods have been used to evaluate interfacial fracture energy quantitatively and to characterize the interfacial fracture between dissimilar 

The four-point bending method requires a simple bend bar of the coated substrate with a notch machined in the coated layer (Fig. 6.1). The four-point bend delamination 

When the specimen is loaded, a crack is initiated from the notch and propagates to the interface as the bending moment increases. For a sufficiently weak interface bond, the crack deflects and propagates symmetrically along the interface at a constant load. The interfacial fracture energy (y) can be determined using  

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