28 июля, 2015 
Malyar 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, properties of the adhesive are the same as they are in bulk. In service, the applied load will in general be much lower than that applied in the laboratory, thereby imparting an ‘acceleration’ factor to the testing. It is important therefore to try to establish the relation between test life and real life.
Claims are made for the superiority of different specimen geometries or different test conditions, and there exists some
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controversy world-wide over appropriate accelerated ageing procedures for bonded joints. This stems in part from the different objectives of the investigators, their backgrounds, and the different materials and processes involved. Formerly various lap shear joints, tensile butt-joints, and peel specimens were used. More recently fracture mechanics principles have been employed in cleavage specimens, and self-stressed configurations are favoured for durability testing. There remains a need for the development of appropriate, cheap, simple and quantitative test methods in order that adhesive materials may be brought more readily into the compass of general engineering applications. The test coupon approach to quality control is, perhaps, most constructively criticised by Albericci(35) with respect to aerospace applications of adhesives. The observation is made that problems which are likely to arise in the ‘real’ structure simply do not arise in the test coupon, and its validity tends to diminish with the complexity and size of the real component.
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