STP640

    Experimental Methods to Determine Locus of Failure and Bond Failure Mechanism in Adhesive Joints and Coating-Substrate Combinations

    Published: Jan 1978


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    Abstract

    The strength of an adhesive bond is assessed by means of several physical tests in which a load is placed on the joint until failure occurs. The durability of adhesive joints is evaluated by still other techniques where the bond is tested, usually under load, in salt spray, high humidity and temperature, or other environments deleterious to the bond. Regardless of the strength of the joint, a complete description of joint performance must include how and where the bond failed.

    Ion scattering spectrometry (ISS) and secondary ion mass spectrometry (SIMS) combined with scanning electron microscopy (SEM) are capable of determining the true locus of failure in an apparent interfacial bond separation. Methods using an electron beam, such as Auger electron spectroscopy (AES), are useful for analyzing evaporated metal films and the metal or alloy surface in adhesive bonds but are of limited use for examining the adhesive side of a failure, because of heating, which rapidly destroys the specimen surface. X-ray photoelectron spectroscopy (XPS), sometimes called electron spectroscopy for chemical analysis (ESCA), provides not only elemental analysis but also gives information on how the elements are combined in the adhesive, adherend, and interfacial regions. Results using these and other techniques are discussed for failure surfaces obtained by lap shear, peel test, and wedge test methods. Advantages and limitations of various methods are discussed.

    Keywords:

    adhesion, adhesive bonding, thin films, failure locus, bond failure, adhesive joints, surface characterization, ion scattering spectrometry, secondary ion mass spectrometry, scanning electron microscopy, Auger electron spectroscopy, X-ray photoelectron spectroscopy


    Author Information:

    Baun, WL
    Research chemist, Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio


    Paper ID: STP38623S

    Committee/Subcommittee: C24.30

    DOI: 10.1520/STP38623S


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