ADHESIVES, GLUES AND SEALANTS
What is nondestructive testing?
Nondestructive testing are defined as those tests based on physical phenomena, whose objective is to obtain information on defects or on state of a material without causing any chemical, dimensional, or mechanical damages in the material itself.
Non-destructive tests carried out in an adhesive bonding set their objective in:
Ensuring directly the adhesive bonding between 2 substrates being able locate and evaluate certain defects.
Carry out maintenance checks of bonded joints in its life.
The main advantage of nondestructive test is the ability to see and localize certain defects that can occur in a real adhesive bonding, but currently they cannot describe the behavior of the zone of adhesion between the substrate and the adhesive, and also cannot obtain the mechanical characteristics of the adhesive in the joint.
Among the defects that can be identified by the use of nondestructive testing, we can cite:
Delaminating in the area of adhesion between the substrate and the adhesive.
Bubbles inside the adhesive.
Pores on the outside and inside of the adhesive.
Wrong adhesive thickness.
Concentrations of moisture or water present inside the adhesive.
Degree of crosslinking or cure of the adhesive.
Ageing of the adhesive bond
Among the different methods or instruments that can be used to perform NDT adhesive bonding, we can cite:
Inspection by immersion (Leak Test)
X-rays or neutrons-ray
Nuclear Magnetic Resonance
Nondestructive testing advantages
Identification, quantification and localization of defects such as pores, bubbles, delamination, etc…
The adhesive bonding does not undergo any kind of aggression and can take place in the real bonded joint.
Full or partially sampling of the adhesive bonding, depending on the quality requirements plan.
Early detection of the defect, the possibility of remedy the defect before his life in use.
Detection of defects during the life of the product in use, being able to perform maintenance operations extending shelf life.
Disadvantages nondestructive testing
Identification and standardization of the technique for nondestructive test based on the defects to be found, each method allows you to find certain defects.
Staff using nondestructive tools must be qualified and trained.
Not allows the observation or making statements on the adhesion of the area of adhesive bonding.
Not allows direct measurements on the mechanical properties of the adhesive bonding (resistance to fracture, elongation, modulus of elasticity ...)
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