To further characterize the roles of aluminum and ammonium perchlorate (AP) characteristics in ammonium perchlorate/R45-M hydroxyl-terminated polybutadiene (AP/HTPB)–composite propellants, aluminized and nonaluminized formulations were tested at very high pressures, up to 68.9 MPa (10,000 psi). A total of nine formulations were examined: seven nonaluminized with varying AP distributions, concentrations, and average particle sizes, and two aluminized with varying aluminum concentrations. All nine propellants showed an exponent or “slope” break above 20 MPa (2900 psi) and a postbreak pressure exponent greater than one. Decreasing the AP particle size decreased both the characteristic pressure where the exponent break occurred (or $P^{*}$) and the pressure exponent after the break. AP distribution also affected $P^{*}$, whereas changes in AP concentration did not. The inclusion of aluminum lowered $P^{*}$ compared with the nonaluminized formulations. Additionally, increasing the aluminum concentration appeared to lower the postbreak pressure exponent. The present study provides one of the first fundamental, systematic studies on the exponent break feature of AP/HTPB-composite propellants and adds new data to the limited database available in the open literature on the AP-based, composite propellant burning rate exponent break at very high pressures, with emphasis on the effect of mixture variables and Al on the characteristic break pressure and the postbreak pressure exponent.

为了进一步表征高氯酸铝和高氯酸铵/ R45-M羟基封端的聚丁二烯（AP / HTPB）复合推进剂中铝和高氯酸铵（AP）特性的作用，在非常高的压力下（高达68.9 MPa（ 10,000磅/平方英寸）。总共检查了九种配方：七种未铝化的AP分布，浓度和平均粒径各不相同，还有两种铝化的铝浓度不同。所有九种推进剂均显示出超过20 MPa（2900 psi）的指数或“斜率”断裂，而断裂后的压力指数大于1。降低AP粒径可同时降低发生指数破坏的特征压力（或$P^{*}$）和休息后的压力指数。AP分布也受到影响$P^{*}$，而AP浓度没有变化。铝含量降低$P^{*}$与未铝化的配方相比。另外，增加铝浓度似乎降低了断裂后压力指数。本研究为AP / HTPB复合推进剂的指数折断特征提供了首批基础，系统的研究之一，并为基于AP的复合推进剂燃烧速率指数折断的开放文献中的有限数据库增加了新数据。非常高的压力，重点是混合变量和Al对特征破裂压力和破裂后压力指数的影响。