Лако-красочные материалы — производство

A major feature of the fracture mechanics argument is that the fracture energy, Gc, for a given joint, tested at a stated rate and temperature, is independent of the test geometry employed. In principle therefore, and with appropriate modifications, almost any test configuration could be used. In practice, certain geometries lend themselves particularly to analysis […]

Adhesives and adhesive bonds are very weak in peel, so that peel tests can discriminate rapidly between different surface pretreatments, particularly after, or during, environmental exposure (e. g. Brockmann(53)). Various forms of the peel test are described in several texts (5, 25, 37, 54-56), which are all essentially variations on the common theme depicted in […]

Despite the fact that adhesive joints are rarely designed to be loaded directly in tensile mode, tensile tests are common for ‘evaluating’ adhesives. The axially-loaded butt (or ‘poker chip’) joint geometry, as recommended by ASTM D897(52), is depicted in Fig. 4.11. A close look at the stress state induced within this joint indicates clearly a […]

Lap shear. The lap shear joint is that used almost universally in testing adhesives or surface preparation techniques. It owes its popularity to its convenience of manufacture and test, as well as to the fact that the adhesive is subjected to cleavage as well as to shear. It thus simulates, in a way that torsional […]

Real joints do not consist of simple, separate, elastic materials with a clear, mathematical geometry. The adherend surface is usually rough, and the thickness and properties of the primer (if applied) and adhesive layer are often difficult to regulate and to determine. There also exists some debate as to whether the in-bondline, or thin-film form, […]

The complete characterisation of an adhesive requires that its response to various load, time and environmental conditions be determined. Renton(32) says that useful data are: (1) stress-strain response (in shear and tension) at a constant strain rate to failure (2) cyclic stress-strain response versus the number of cycles to failure (3) creep response (4) combined […]

Quantitative data requirements for stuctural analysis depend on the design approach and, therefore, the type of analysis to be performed. However, all the theoretical methods for predicting joint strength require: (1) adherend tensile modulus (E) and Poisson’s ratio (v) (2) adhesive shear (Ga) and tensile (Ea) moduli, and Poisson’s ratio (va) Additionally, analyses which allow […]

General remarks It is evident that a large number of parameters are involved in the fabrication and testing of bulk adhesive specimens and adhesive joints; these must be controlled if meaningful experimental data are to be obtained. Joint tests evaluate not only the mechanical properties of the adhesive, but also the degree of adhesion and […]

Closed form solutions. Structural adhesive joints are generally designed to be loaded in shear so that treatments of joint analyses are confined essentially to the transfer of load by shear, with some consideration of the transverse normal stresses induced by eccentricities in the load path. In the simplest case the adhesive and the adherends are […]

General considerations The adhesive, which can be likened to plastic material, represents a low modulus interlayer and is likely to be the weakest link in a structural joint. Exceptions to this might be when one or both substrates are concrete subjected to forces other than compression, or if thin sheet metal adherends are involved. Design […]