Ngjitësit struktural - Metodat e provës për vlerësimin e qëndrueshmërisë afatgjatë të strukturave metalike të ngjitura

Structural adhesives - Test methods for assessing long term durability of bonded metallic structures

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1.1 This standard specifies test procedures for determining the long-term durability of an adhesive system subjected to environmental and fatigue loads. The procedures are based upon measurement of the crack growth rate and the resistance to crack propagation through the adhesive layer in double cantilever beam type specimens under an applied mode I opening cycling loading. 1.2 The test specimens consist of rectangular metal substrates bonded together with a pre-starter crack in the bondline. For testing joints consisting of relatively thin sheets of metallic substrates the specimen needs to be structurally reinforced by adding layers of compatible material to the back of each adherend substrate in order to prevent permanent deformation, usually referred to as reinforced double cantilever beam (RDCB) test specimen. 1.3 For brevity, the standard relates to testing RDCB specimens, which are essentially more complex in manufacturing than standard double cantilever beam (DCB) specimens. However, the standard allows also for use of single substrate double cantilever beam specimens when the substrate material is available in sufficient thickness. 1.4 The test method has been proven to be particularly sensitive in finding weaknesses within certain adhesive systems and is recommended as a scientific tool to study adhesion properties. This test method may be used to determine: - The fatigue crack growth rate as a function of the mode I strain energy release rate; - The threshold values for negligible crack growth; - The effects of other environmental factors (temperature and/or humidity cycling); - The mode I (peel or crack opening) failure mode of the adhesive joint (cohesive, interfacial, near-surface …).