Possibility of defects detection by ir thermography in multi-layered polyaramide materials used for military applications

Recently the composite materials have been often applied in designs of light ballistic protections as the progress in domain of polymers chemistry has made possible the production of materials providing efficient protection against small arms bullets and fragments. Usually the composites apply textile materials joined with plastic what creates multi-layered composite materials used for personal ballistic protections (vests and helmets for shots and fragments protection) and armours of car vehicles and stationary objects. This type of composite materials is largely made on the basis of very resistant aramid and polyethane fibres joined with phenolic and polyurethane resins and other elastic mixtures. These materials are characterized as lightweight, non-corrosive and easy to form what makes them fit well to the surface, which they have to protect. Defects, which can appear in this type of multi-layered composite materials usually, are inaccuracies in gluing the composite layers and stratifications and delaminations occurring under hits of fragments and bullets. A method that possibly can be used to non-destructive testing of this type of materials and detection of internal defects deploys infrared thermography. In order to determine the potential use of thermal methods the specialized software was developed for computing 3D (three-dimensional) dynamic temperature distributions in anisotropic multi-layered solid body with subsurface defects. The paper includes some results of simulation representing possibilities for the use of IR thermography methods to test such composite materials.