[a] 1IntroductionMany plastic-bonded explosive(PBX)applications use precision-made componentsw ith requirements of thermal and mechanical integrity throughout the lifetime of the part. This is the basis for av ariety of PBX characterization studies that correlate engineering response with formulationa nd environmental variables, includingt hermal changes associated with storage and aging. TATB, triaminotrinitrobenzene, is an insensitive explosive [1].I nr ecent years, there has been increasing interest in the use of TATB-basedP BX composites due to the safety advantages derived from their insensitive nature.D etails can vary (i.e. with binderp roperties or particle-size distribution), but generally speaking, TATB is ar emarkably safe explosive that detonates only in the presenceo ft riggering shocks in appropriately-engineered configurations.I nadvertent detonation is extremely unlikely.TATB crystals are sheet-like and graphitic in nature.K olb and Rizzo measured highly anisotropic coefficient of thermal expansion (CTE) values for TATB single crystals [2]. They also showedt he effects of different binders on the thermal properties of TATB-basedc omposites [3].F or decades since, various observations have beenm ade [4][5][6][7] showing that solid pressings of TATB, with and without binder,c an possess highly anisotropic CTE and irreversible expansion( ratchet growth).C unningham [ 4] and Cady [5] measured anisotropic CTE in specimens removed from larger PBX pressings, providing strong evidence that the compactionp rocess induces preferred TATB orientation. The cause of these observationsw as confirmed by Schwarz et al.[6] using transmission X-raya nalysis, where the preferred orientation of TATB crystals in pressed PBX 9502 (95 wt-% TATB) charges was quantified and correlated directly with the observed anisotropy in the PBX 9502 CTE. Schwarz also proposedamodelf or how compactionm ethods and geometry are responsible for the direction and magnitude of TATB texture. The quantified TATB texture has similarlyb een correlated with anisotropy in ratchet growth magnitudes [7].Observations and models of ratchet growth [8-10] have typicallyi nvolved the iterative applicationo ft hermal excursions while monitoring the irreversibleg rowth, usually as Abstract:T ATBi sa ni nsensitive high explosive, attractive for use because of its safety aspects. TATB compactions, with or without binder,u ndergoi rreversible volumee xpansion (or ratchet growth)u pon thermal cycling. In the past, experimental elucidation of this phenomenon has focused on irreversiblee xpansion as af unction of the number of thermal excursions over ag iven temperature range, where growth is asymptotic with increasing cycle number.I nt his paper,w ed emonstrate that ratchet growth also occurs as af unction of time at constant temperature, and that growth is substantial at elevated temperatures. We have measured strain response in PBX 9502, aT ATB-based composite, by performing thermal-cycling tests with different durations at high temperature. Irreversible...