11.1 Introduction

Adhesive tests are used for a variety of reasons including: [1]

• Comparison of properties (tensile, shear, peel, flexural, impact and cleavage strength, durability, fatigue, environmental resistance, conductivity, etc.).

• Quality checks for a "batch" of adhesives to determine whether the adhesives are still up to standard.

• Checking the effectiveness of surface and/or other preparation.

• Determination of parameters useful in predicting performance (cure conditions, drying conditions, bond-line thickness, etc.).

Testing is important in all aspects of materials science and engineering, but it is especially so in adhesives. Such tests evaluate not only the inherent strength of the adhesive, but also the bonding technique, surface cleanliness, effectiveness of surface treatments, etchings of surfaces, application and coverage of the adhesive, and the curing cycle.

This chapter first discusses in a general manner the various types of testing carried out in adhesive joints. Only the more important types are covered. Following this discussion, a compilation of 53 subject areas is listed, with all relevant ASTM methods and practices and SAE Aerospace Recommended Practices (ARPs). Chapter 12 provides fairly detailed discussions of the contents of each method or practice, with two exceptions.

11.2 Tensile

Pure tensile tests are those in which the load is applied normal to the plane of the bond line and in line with the center of the bond areas (Figure 11.1). ASTM D897-01 (see below for this and all standards discussed) is one of the oldest methods still in the ASTM book on adhesives. The specimens and grips called for...