Using a fiber Bragg grating technique to investigate temperature cycling strain of pressed TATB‐based polymer‐bonded explosives

Pressed 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB)‐based polymer‐bonded explosive (PBX) exhibits significant anisotropic and irreversible expansion characteristics during temperature cycling, resulting in both safety and service issues. The anisotropic and irreversible expansion properties of PBX have shown to be closely related to the microstructures, including explosive crystals, binders, micro voids, el. Fiber Bragg grating (FBG) technology has advantages of high reliability, accuracy, and sensitivity, which is more conducive to real‐time capture of the changes in strain throughout the temperature cycling. In this study, temperature cycling strain monitoring experiments of PBX pressed under different thermal–mechanical coupling loading conditions were studied using FBG technology. The effect of the pressing parameters on the anisotropic and irreversible expansion characteristics of the PBX's during temperature cycling was measured and analyzed, taking into account potential microstructural factors such as crystal orientation, binders, and porosity. The results indicated that the strain on the side and top of PBX cylinders were distributed with increasing strain in the direction of higher density. The strain stratification was significant during the high‐temperature stage of temperature cycling and was not obvious during the low‐temperature stage. The degree of strain stratification decreased with an increase in temperature cycling cycles and increased with higher pressing temperatures. The anisotropic expansion of PBX cylinders increased with an increase in temperature during cycling and decreased with a reduction in temperature. The axial expansion degree of PBX cylinders pressed under different compression conditions in the later cycles of temperature cycling is consistent with the different crystal orientations intensity inside them.