Application of IR Thermography for Studying Deformation and Fracture of Paper

The deformation and fracture of paper have long been investigated from various points of view using many methods. Phenomena such as sound emission and thermal change occurring with the deformation have also been examined. Paper is a planar material and its thermal conductivity is low and further its specific heat is high; thus, the thermal change shown in surface temperature using IR thermography can be investigated related to the mechanical behavior. Advanced thermography with extensive computer memory and various imaging processes enables us to investigate the process of the deformation and fracture of paper. In this paper, studies on the fundamental thermodynamics of paper material are first critically introduced, discussing the effects of defects and unevenness of paper formation. Secondly, uneven thermal distribution and its time-sequential changes during the fracture toughness testing of paper are presented; that is to say, stress concentration and crack development at the notch tip which occurred during the deformation of paper with a notch could be visualized as serial images using IR thermography. The results helped to develop fracture toughness testing of paper and further gave an understanding of the fracture toughness of paper itself.