In-situ Study On The Structural Changes Of TATB-based PBX Under The Combined Action Of Heat And Power

Polymer Bonded Explosives(PBX)is a class of composites consisting of explosive crystals and a polymeric binder.PBX has been used in a wide variety of civil and military applications due to its explosive performance,safety and moldability.2,4,6-triamino-1,3,5-trinitrobenzene(TATB)is a kind of high-energy insensitive explosives and widely used in PBX.The life cycle environment of PBX is very complicated and includes various forms of thermal-mechanical loading.These thermal-mechanical environments can cause structure changes in PBX,significantly affecting the mechanical and safety performance of PBX.This paper studied structure evolution of a TATB-PBX under thermal-mechanical loading through in-situ experiments.The research contains the following aspects:experiment technology of in-situ thermal-mechanical loading,quantitative characterization method,tests for the feasibility of in-situ experiment technology,and structure evolution and fracture behavior of TATB-PBX at different temperatures.Firstly,this paper built an in-situ thermal-mechanical loading experiment platform based on X-ray computed tomography(X-ray CT),designed an in-situ curved Brazilian test equipment for X-ray CT systems,established a quantitative characterization method for describing crack morphology of TATB-based PBX,and developed an algorithm for analyzing particle structure changes and displacement field in PBX.Secondly,an in-situ curved Brazilian test was conducted using PBX mock materials to preliminarily verify the feasibility and scientificity of the above experiment technology and methods for characterization and analysis.Three groups of specimens including the intact sample,sample with oblique 45°non-through defect and sample with oblique 45°through defect were prepared.It was found that when the defect had a certain angle to the loading direction of Brazilian Test,the loading symmetry of the original test broke and the damage behavior of the sample changed.The influence of non-through defects and through defects on the damage behavior of samples is very different,that is:the non-through defect may result in stratification of the sample.The effect of surface defects on the damage behavior of the samples is mainly concentrated in the defective part;while the part without defects of the non-through defect sample acts nearly as the intact sample.Finally,TATB-based PBX structure evolution in the temperature range from-20? to 70? was studied,and the crack morphology under different thermal-mechanical loadings was quantitatively characterized.The internal particle changes were analyzed.It was found that:(1)PBX failure strain is insensitive to temperatures;(2)With the temperature from low to high,the crack morphology changes from flat to meandering,and the roughness of crack surface changes from rough to smooth;(3)In the low-temperature Brazilian test,the internal particles of the PBX are tend to translate and shear.While at high temperatures,the main form of internal structure evolution in PBX is the expansion of the binder,reduction of particle size and particle reorganization.