Typically, the burning surface of a composite solid propellant is controlled through grain geometry and formulation. However, combustion studies of grains constructed from different propellant formulations at fine scales (nominally 1 mm) are not readily accessible in open literature. With additive manufacturing, such configurations can be investigated easily. Propellants with a faster burning inner layer (enhanced with either 1 wt.% iron oxide or 5 wt.% nanoaluminum) were 3D printed between two layers of slower burning 85 wt.% ammonium perchlorate/hydroxyl-terminated polybutadiene propellant. The dynamic combustion behavior of the layered propellant was investigated at pressures ranging from 3.45 to 10.34 MPa. Overall, an increase in the burning surface area, without interlayer delamination, was observed. The driving force behind the propellant surface area increase was the difference in the burning rate between the layers. In addition, the nanoaluminum propellant layer had a more stable burning rate exponent than the cast nanoaluminum propellant. Overall, only a small addition of catalyzed propellant was needed to increase the burning rate of the bulk material. The results of this study lay the foundation for functionally grading propellant grains, which could tailor the thrust profile of solid rocket motors and gun propellants.

通常，通过颗粒的几何形状和配方来控制复合固体推进剂的燃烧表面。然而，在公开文献中尚不容易获得由不同推进剂配方制成的细颗粒（标称尺寸为1mm）的细粒的燃烧研究。通过增材制造，可以轻松研究此类配置。将具有较快燃烧内层（用1 wt。％的氧化铁或5 wt。％的纳米铝增强）的推进剂3D打印在较慢燃烧的85 wt。％高氯酸铵/羟基封端的聚丁二烯推进剂的两层之间。研究了层状推进剂在3.45至10.34 MPa压力下的动态燃烧行为。总的来说，观察到燃烧表面积的增加，而没有层间分层。推进剂表面积增加背后的驱动力是各层之间燃烧速率的差异。另外，纳米铝推进剂层具有比铸造的纳米铝推进剂更稳定的燃烧速率指数。总体而言，仅需少量添加催化推进剂即可提高散装材料的燃烧速率。这项研究的结果为功能分级的推进剂颗粒奠定了基础，该颗粒可以调整固体火箭发动机和火炮推进剂的推力曲线。