Andrew Zeagler

Michigan Technological University


Project Title: Multilayer Metal/Ceramic Laminates for Ballistic Purposes

Advisor: Prof. Jeffrey P. Youngblood

Introduction

Kinetic energy penetrators are currently the most capable weapon in penetrating tank armor. As these weapons improve, there is a need to increase the effectiveness of armor without compromising the weight or volume of the tank. The current solution is steel with ceramic plates and plastic honeycomb. The ceramic plates blunt the tip of the penetrator before being pulverized, and the particles then erode the projectile. The metal layers absorb energy through deformation.

Metal/ceramic laminates absorb energy in the same manner, but have the potential to outperform current armors while being cheaply manufactured. The processing method necessitates use of preceramic polymers, with the material and heat treatment schedule chosen such that high-hardness ceramics remain. It is hoped that multiple cracking in the ceramic layer can be induced by controlling the thickness ratio of the layers.

Project Objectives

  • Synthesize metal/ceramic laminates using metal foils and preceramic polymers
  • Optimize heat treatment schedule such that high-hardness ceramics remain
  • Control layer thickness to promote multiple cracking

Approach

  • Run thermogravimetric analysis on three preceramic polymers
  • Synthesize metal/ceramic laminates of sufficient thickness at optimal heat treatment conditions
  • Determine mechanical properties using various tests

Findings

Through this research it was proven that the novel processing method of heat treating laminated metal foils and preceramic polymers can result in a metal/ceramic composite material. Thermogravimetric analysis was performed on three preceramic polymers: poly(phenyl-methyl-silsesquioxane), polyacrylonitrile and polycarbomethylsilane. It was determined that heat treating poly(phenyl-methyl-silsesquioxane) in air at 725oC leaves silicon and oxygen only (Si2O3). A heat treatment of 275oC in air followed by 620oC in nitrogen is required to form a random network of carbon from polyacrylonitrile. Silicon carbide, along with some graphite, remains after polycarbomethylsilane is heated in nitrogen to 1175oC.

Further analysis supports the above results. FTIR analysis on heat treated poly(phenyl-methyl-silsesquioxane) did not show peaks characteristic of phenyl or methyl groups, whereas analysis performed after lower temperature heat treatments did show these peaks. FTIR analysis could not be performed on heat treated polyacrylonitrile because the sample was consumed, but this indicates that beyond a certain temperature, only carbon remains (and it lacks the order to withstand these temperatures). XRD analysis on heat treated polycarbomethylsilane shows that silicon carbide formed, but also that some graphite developed. The results also confirm that the system was not free of oxygen, as both aluminum and alumina peaks were present.

An in-depth investigation of the mechanical properties of these laminates was not undertaken due to time constraints. If, when this is done, any combination of metal and ceramic exhibits suitable mechanical properties, the effects of layer thickness should then be examined.


Thermogravimetric behavior of poly(phenyl-methyl-silsesquioxane) in different atmospheres.
Aluminum/poly(phenyl-methyl-silsesquioxane) laminate (front) and titanium/poly(phenyl-methyl-silsesquioxane) laminate (back), both heated to 700oC in air for 3 hours.

Contact me: arzeagle@mtu.edu