|M.Sc Student||Dganit Shacham|
|Subject||Effect of Filler Particles Sonication on the Mechanical|
Behavior of Composite Materials
|Department||Department of Materials Science and Engineering||Supervisor||Professor Emeritus Siegmann Arnon (Deceased)|
|Full Thesis text|
When manufacturing high-performance polymer bonded explosive (PBX), it is necessary to mix crystalline explosive powders with polymers, plasticizers and other ingredients, and to process the resulting composition into a homogeneous, uniformly dense compact. Both processing and final product properties are affected by the particle characteristics of the crystalline explosive powder. Content of solid particles in the polymer, particle size distribution and particle shape are all key parameters which influence the rheological and mechanical properties of the final composite. Controlling particle size and shape enables control of the properties of the energetic composite.
The current study focuses on the rheological and mechanical behavior of highly filled PDMS [poly (dimethyl siloxane)] with energetic particles of HMX (cyclo tetramethylene- tetranitramine), considering the effect of particle size and shape.
One of the methods to change particles' morphology is by using ultrasonic energy. In this method, energy in the form of ultrasonic waves is introduced to create cavitations in the vicinity of the particles, suspended in an organic carrier fluid, gradually shaping the particles. The ultrasonic process parameters such as ultrasonic frequency and power, fluid density and viscosity etc., enables to influence the powder shape and size.
The objectives of the current work were to investigate the feasibility of using the ultrasonic technique for shaping HMX particles, followed by testing the influence of particles' morphology on the rheological and mechanical properties of an energetic composite. The research demonstrated that the ultrasonic technique provides adequate control of particle morphology. The sonication of HMX particles results in the erosion of the particle surface, resulting in rounder particles and a change in their size distribution.
The change in particle morphology has a significant impact on the rheological properties of the composite in its pre-cross-linked form, increasing the maximum solid loading in the composition and lowering the composite viscosity for a given solid loading.
The influence of morphology on mechanical properties is quite moderate. Particle size affects the composite's mechanical properties more significantly than particle shape.