Fabrication and Design of Multifunctional Energetic Structures Using Gradient Architectures (original) (raw)
Related papers
2005
A new Materials by Design approach to creating energetic materials using Functionally Graded Materials (FGMs) concepts has recently been developed in a joint collaboration between the University of Maryland (UMD) and Indian Head-Naval Surface Warfare Center (IH-NSWC) through the Center for Energetic Concepts Development (CECD). This approach has been facilitated by previous efforts at IH-NSWC to apply a new process, known as Twin Screw Extrusion (TSE), for continuously manufacturing energetic polymer composites. It takes advantage of the continuous nature and superior mixing characteristics of the TSE process to manufacture a new concept for propellants and explosives: Functionally Graded Energetic Materials (FGEMs). For example, conventional geometricallycomplex homogeneous grains for solid rocket motors can be replaced by a geometrically-simpler cylindrical FGEM configuration with an axial gradient in the energetic material formulation. The simpler geometry does not have the undes...
Composites Part A: Applied Science and Manufacturing, 2006
The development of new energetic materials is a time-consuming, laborious, and sometimes dangerous process. Batch approaches are most commonly used, especially for energetic materials consisting of polymer composites. Recently, a manufacturing technology known as Twin Screw Extrusion (TSE), has been demonstrated to increase the safety and affordability for manufacturing composite energetic materials. This technology is also ideally suited to manufacturing graded polymer composites through transient operating and/or feed conditions. In this paper, the TSE process is employed to fabricate graded polymer composites in a combinatorial approach for developing new energetic materials. Graded composite energetic materials with 79 to 87% solids loading of Ammonium Perchlorate are processed. The dependence of burning rate properties on the variation in composition was determined through strand burning tests. These results were compared with a conventional design of experiments approach using the Kowalski algorithm. The correlation of composition to properties over a range of compositions between the new combinatorial approach and the conventional design of experiments approach validates the use of TSE processing as a combinatorial approach to developing new energetic materials. Because the TSE process is used to manufacture both energetic and non-energetic composite materials, the combinatorial approach can also be applied to the development of new polymer composites for non-energetic applications.
The International Journal of Advanced Manufacturing Technology, 2024
This study introduces a new method for fabricating biphasic architectured structures using self-developed hybrid material extrusion (MEX) process. This approach involves filling the voids of closed-cell structures with a powder material in a single process. The architectured structures were 3D printed using thermoplastic polyurethane (TPU) and subsequently filled with polyamide 12 (PA12) powder in two distinct configurations: partially filled (50%) and fully filled (100%), named as biphasic architectured structures. Experimental and numerical uniaxial quasistatic compression tests were conducted on partially filled and fully filled local and global closed-cell architectured structures, and their results were compared with those of empty architectured structures. The comparative analysis revealed that the partially filled structures, representing a transitional phase, exhibit enhanced properties which is influenced by the amount of powder filling within the structure. A substantial enhancement in stiffness and specific energy absorption (SEA) was observed in the consolidation phase. The fully filled architectured structures exhibit rapid increase in its loading response, characterized by high stiffness and SEA. Furthermore, this study paves the way for future exploration into strategic filling of multiple powders in different regions, thereby tailoring the mechanical and functional responses. Potential applications include manufacturing components and equipment that absorb energy, provide impact protection, and offer vibration damping and soundproofing capabilities.
An elasto-viscoplastic analysis of direct extrusion of a double base solid propellant
Advances in Engineering Software, 2010
In this study, three-dimensional modelling of extrusion forming of a double base solid rocket propellant is performed on Ansys finite element analysis program. Considering the contact effects and the time dependent viscous and plastic behaviour, the solid propellant is assumed to obey the large deformation elasto-viscoplastic material response during direct extrusion process. The deformed shape, hydrostatic pressure, contact stress, equivalent stress, total strain values are determined from the simulation in order to get insight into the mechanical extremity that the propellant has undergone during processing. Hydrostatic pressure and contact stress distributions have been found to be important parameters due to safety reasons of the nitro-glycerine content in the bulk of the propellant.
Materials, 2021
Functionally graded lattice structures have attracted much attention in engineering due to their excellent mechanical performance resulting from their optimized and application-specific properties. These structures are inspired by nature and are important for a lightweight yet efficient and optimal functionality. They have enhanced mechanical properties over the uniform density counterparts because of their graded design, making them preferable for many applications. Several studies were carried out to investigate the mechanical properties of graded density lattice structures subjected to different types of loadings mainly related to tensile, compression, and fatigue responses. In applications related to biomedical, automotive, and aerospace sectors, dynamic bending and rotational stresses are critical load components. Therefore, the study of torsional properties of functionally gradient lattice structures will contribute to a better implementation of lattice structures in several s...
New extrusion process for manufacturing radial functionally graded polymer materials
Usually additives, fillers and reinforcing materials are homogeneously distributed in plastic profiles when they have undergone conventional extrusion processes. However, in many applications it would be advantageous to place these substances in sufficient quantities where required by the subsequent application of the profile. This is where functionally graded materials start from since they have no homogeneous composition or distribution of fillers along one dimension. These materials have different compositions along the part's cross-section based on its application. Nowadays functionally graded materials are already used in various material combinations, e.g. metal and ceramic, for special applications such as aerospace, nuclear energy and chemistry. The production of functionally graded materials on a purely polymeric basis is only possible under laboratory conditions or with discontinuous processes so far. For this reason, the SKZ is currently developing an innovative continuous extrusion process for radial functionally graded polymer materials. The produced round profiles of two polymers display a smooth radial transition between the two components over the part's cross-section and a homogeneous composition in the extrusion direction. This can be achieved by using a rotating mask in the melt flow, which forms a spiral layer structure and a subsequent concentric mixing by a rotating cluster in the flow channel.
Additive manufacturing of ammonium perchlorate composite propellant with high solids loadings
Proceedings of the Combustion Institute, 2019
The effective solid propellant burning rate in a rocket depends on surface area and propellant composition. Currently, the surface area geometry in a rocket is limited to what can be practically cast using molds, etc. Additive manufacturing (AM) could allow the production of unique propellant grain geometries, however printing propellants with high solids loadings and viscosities is not readily possible using currently available printers. A new AM direct write system developed recently in our laboratory, is capable of printing visibly low-void propellants with high end mix viscosities into highly resolved geometries. The system was used to print ammonium perchlorate (AP) composite propellants at 85% solids loading using hydroxyl-terminated polybutadiene (HTPB) and a UV-curable polyurethane binder. The change in HTPB propellant viscosity with time after mixing was measured and the microstructure of the strands was evaluated with X-ray tomography scans. The burning rate of printed and cast strands was measured to compare the quality of the strands at high pressure, since propellants with significant voids should catastrophically fail due to flame spreading. The printed samples burned in a planar fashion up to pressures of 10.34 MPa with consistent rates that were comparable to the cast propellants. The HTPB propellant used was not optimized and showed some porosity due to gas generation, but strands printed with the UV binder exhibited extremely low porosity. A strand printed with no gaps in one half and gaps in the other failed catastrophically where intended at high pressure, demonstrating the ability to spatially grade propellants. This new system can produce adequate strands of composite propellant with high solids loadings without the addition of solvents, special binders (low viscosity, thermal softening, etc.), or restricting use to formulations with lower viscosities, and enables the fabrication of complex propellant grain geometries.
Thermal and acceleration load analysis of new 122 mm rocket propellant grain
Scientific Technical Review
In order to achieve very strong inter-ballistic requirements, a unusual free standing rocket motor propellant grain was designed, with variable channel diameter. Due to its very high length, it was expected for the grain to be exposed to dangerous combination of different loads during the design phase. Structural analysis of viscoelastic propellant grain is always very complex and it differs substantially from an elastic analysis, because the propellant mechanical properties depend on temperature and strain rate. The most complex case in the analysis occurs when multiple loads operate simultaneously. In this paper, the structural analysis has been done during the initial period of rocket flight, when the grain is under very fast load due to acceleration and at the same time under a slow load due to surface pressure, created as a result of temperature dilatation. In the absence of data on mechanical properties of the new propellant composition, the properties over the whole time-temperature range were estimated comparing by a similar composition that have been completely tested earlier. Using finite element method (ANSYS program) two different design solutions were examined and the more reliable one was adopted.