Advances in Ceramic Armor XI

The Ceramic Engineering and Science Proceeding has been published by The American Ceramic Society since 1980. This series contains a collection of papers dealing with issues in both traditional ceramics (i.e., glass, whitewares, refractories, and porcelain enamel) and advanced ceramics. Topics covered in the area of advanced ceramic include bioceramics, nanomaterials, composites, solid oxide fuel cells, mechanical properties and structural design, advanced ceramic coatings, ceramic armor, porous ceramics, and more.

• Language: English
• Publisher: Wiley
• Release date: Nov 24, 2015
• ISBN: 9781119211600

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Preface

I had the pleasure of being the lead organizer for the 13th Armor Ceramics Symposium in 2015 at the 39th International Conference on Advanced Ceramics and Composites. I am very grateful for the guidance and support that was provided by Jeff Swab, Andy Wereszczak, and the organizing committee in putting this symposium together. Consistent with the history of this symposium, we strived to create a program that would foster discussion and collaboration between researchers from around the world in academia, government, and industry on various scientific issues associated with the topic of armor ceramics.

The 2015 symposium consisted of approximately 68 invited, contributing, and poster presentations from the international scientific community in the areas of synthesis & processing, manufacturing, materials characterization, testing & evaluation, quasi-static & dynamic behavior, modeling, and application. In addition, because of their importance for the foreseeable future, this symposium also had special focused topic sessions on Advanced Materials Characterization, Intergranular Films, and ceramic armor research by the Netherlands Organisation for Applied Scientific Research (TNO). Based on feedback from attendees, the 2015 symposium was a success, and the manuscripts contained in these proceedings are from some of the presentations that comprised the 13th edition of the Armor Ceramics Symposium.

On behalf of Jeff Swab and the organizing committee, I would like to thank all of the presenters, authors, session chairs, and manuscript reviewers for their efforts in making this symposium and the associated proceedings a success. I would also especially like to thank Andy Wereszczak, Vlad Domnich, Mike Golt, Steve Kilczewski, Kris Behler, Victoria Blair, Jonathan Ligda, Jim McCauley, and Nitin Daphalapurkar for hosting and chairing the symposium when we were unable to due to remnant effects of Sequestration. Last, but not least, I would like to recognize Marilyn Stoltz and Greg Geiger of The American Ceramic Society, for their support and tireless efforts without which the success of this symposium would not be possible.

JERRY C. LASALVIA

Symposium Chair, Armor Ceramics

Introduction

This CESP issue consists of papers that were submitted and approved for the pro-ceedings of the 39th International Conference on Advanced Ceramics and Composites (ICACC), held January 25-30, 2015 in Daytona Beach, Florida. ICACC is the most prominent international meeting in the area of advanced structural, functional, and nanoscopic ceramics, composites, and other emerging ceramic materials and technologies. This prestigious conference has been organized by the Engineering Ceramics Division (ECD) of The American Ceramic Society (ACerS) since 1977.

The 39th ICACC hosted more than 1,000 attendees from 40 countries and over 800 presentations. The topics ranged from ceramic nanomaterials to structural reliability of ceramic components which demonstrated the linkage between materials science developments at the atomic level and macro level structural applications. Papers addressed material, model, and component development and investigated the interrelations between the processing, properties, and microstructure of ceramic materials.

The 2015 conference was organized into the following 21 symposia and sessions:

The proceedings papers from this conference are published in the below seven issues of the 2015 CESP; Volume 36, Issues 2-8, as listed below.

Mechanical Properties and Performance of Engineering Ceramics and Composites X, CESP Volume 36, Issue 2 (includes papers from Symposium 1)

Advances in Solid Oxide Fuel Cells and Electronic Ceramics, CESP Volume 36, Issue 3 (includes papers from Symposium 3 and Focused Session 5)

Advances in Ceramic Armor XI, CESP Volume 36, Issue 4 (includes papers from Symposium 4)

Advances in Bioceramics and Porous Ceramics VIII, CESP Volume 36, Issue 5 (includes papers from Symposia 5 and 9)

Advanced Processing and Manufacturing Technologies for Nanostructured and Multifunctional Materials II, CESP Volume 36, Issue 6 (includes papers from Symposia 7 and 8 and Focused Sessions 4 and 6)

Ceramic Materials for Energy Applications V, CESP Volume 36, Issue 7 (includes papers from Symposia 6 and 13 and Focused Session 2)

Developments in Strategic Ceramic Materials, CESP Volume 36, Issue 8 (includes papers from Symposia 2, 10, 11, and 12; from Focused Sessions 1 and 3); the European-USA Engineering Ceramics Summit; and the 4th Annual Global Young Investigator Forum

The organization of the Daytona Beach meeting and the publication of these proceedings were possible thanks to the professional staff of ACerS and the tireless dedication of many ECD members. We would especially like to express our sincere thanks to the symposia organizers, session chairs, presenters and conference attendees, for their efforts and enthusiastic participation in the vibrant and cutting-edge conference.

ACerS and the ECD invite you to attend the Jubilee Celebration of the 40th International Conference on Advanced Ceramics and Composites (http://www.ceramics.org/daytona2016) January 24-29, 2016 in Daytona Beach, Florida.

To purchase additional CESP issues as well as other ceramic publications, visit the ACerS-Wiley Publications home page at www.wiley.com/go/ceramics.

JINGYANGWANG, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China

SOSHUKIRIHARA, Osaka University, Osaka, Japan

Volume Editors

July 2015

TNO’s RESEARCH ON CERAMIC BASED ARMOR

Erik Carton, Geert Roebroeks, Jaap Weerheijm, André Diederen and Manfred Kwint

Group Explosions, Ball istics and Protection, TNO P.O. Box 45, Rijswijk, The Netherlands

ABSTRACT

Several specially designed experimental techni ques including an alternative test method have been developed for the evaluation of ceramic based armor. Armor grade ceramics and a range of combined materials have been tested using 7.62 AP rounds. Using the energy method [12] the dwell-time and total energy absorbed from the AP core were determined. In additional tests ti me-resolved fracturing of the ceramic tile (fragments) was recorded using high-speed video at one million frames per second. Also the particle size distribution of the fragments were measured in order to determine the total fracture surface area. The information provided by the results of all tests has resulted in an energy-based engineering model that allows calculation of the dwell-ti me, erosion and residual velocity of an AP-core. The model predicts the mass and velocity of residual AP cores rather well assuming a failure period during which the intact ceramic material transfers into a massively broken medium. The model does not require detailed mechanical properties of the ceramic materials. This reflects the difficulty within the ceramic armor research community to find a relation between mechanical properties and ballistic efficiency of armor ceramics. The developed engineering model creates a renewed understanding of the relevant phenomena, that could explain the ballistic efficiency of ceramic armor.

INTRODUCTION

Over the last years TNO’s Laboratory for Ballistic Research has focused its R& D on the subject of armor ceramics, as a component of an armor system, as well as on ceramic based armor; a combination of ceramic and other materials together forming an armor system. The optimization of ceramic based armor systems is targeted by the armor community to obtain more weight efficient protection. However, armor ceramics are still not very well understood, hence there may still be a lot to gain if one can determine the main mechanisms that occur during the short interaction time between a high speed projectile and a ceramic-based armor. TNO’s research has been limited to 7.62 AP rounds and therefore is mainly focused on body-armor applications, however the scope will be expanded to vehicle armor in the coming years.

Generally speaking ceramics are an effective class of armor materials as they can both erode a hard projectile (core), hence change the nose shape and reduce its mass, and project the impact forces over an area much wider than the projectile diameter. The latter will reduce stress by spreading forces exerted on the backing material, preventing its local failure thereby allowing a large volume of backing material to be involved in the projectile-target interaction.

Over the years relationships between the mechanical properties and the ballistic efficiency of armor grade ceramics have been searched for. The unique combination of mechanical properties of ceramics like high hardness, compressive strength, stiffness and relative low density are frequently mentioned to rationalize the use of ceramics in armor. However, even after decades of use the relation between mechanical properties and ballistic (protection) efficiency is not fully understood. This may be explained by also considering some other relevant mechanical properties of ceramic materials like their modest tensile stre ngth and brittle fracture behavior. This combination of mechanical properties results in early failure and negligible energy dissipation by fracturing of ceramic materials. It is the main reason ceramics are not used stand-alone in armor applications. Ceramics generally are supported by a backing material that is ductile and capable to absorb (residual kinetic) energy. Often metal plates or polymer fiber materials (like fabrics and composite) are used as backing material in armor systems. Hence, armor ceramics are often tested in combination with a backing material that influences the projectile-target interaction. This influence complicates the search for a unique relation between a mechanical property of the ceramic and its ballistic efficiency [1]. To complicate things further, the projectile-target interaction not only depends on intrinsic material properties of the ceramic and its backing material. Many researchers have shown that extrinsic properties, like tile dimensions, pre-stressing and confinement also have a large influence on the ballistic behavior of a ceramic-based armor system [2-5].

Figure 1 shows a schematic representation of the impact of a core of a bullet with a (bare) ceramic tile. The ceramic has high enough compressive strength to initially withstand the dynamic loading by the impacting projectile (a high strength core with conical or ogive nose shape). Hence, the first interaction phase is dwell; the interface velocity between projectile and ceramic is zero (U=0). The tail of the projectile still has the impact velocity (V), thus the length of the projectile will reduce with a velocity V-U=V. As an AP core consists of a brittle material, the failure strain is very low resulting in erosion rather than deformation of the core material. In the second image of figure 1, the eroded fragments/particles of the projectile nose can be seen to spray from the high pressure impact area below the projectile. The ceramic tile itself does not yield, and only responses by bending generating a linear strain distribution over the tile thickness inducing a compressive stress at the strike-face and a tensile stress at the rear of the tile. During the dwell phase the ceramic suffers from impact damage and/or erosion on the strike-face by the radial movement of the eroding projectile, as well as internal failure by comminution, micro-and macro-cracks. The internal damage of the ceramic tile is shown in yellow in figure 1. At a certain moment the internal damage has propagated throughout the tile thickness. This allows a localized flow of fragments and formation of a conical plug. From this moment on, the ceramic can flow axially reducing the dynamic loading (as U>0) finally eliminating the erosion of the projectile when U=Vr, with Vr the residual velocity of the projectile. This transition in penetration velocity (from zero to U=Vr) marks the end of the dwell phase (tDwell,end). The axial flow of fragments can be seen at the rear of the tile as this initiates an out-of-plane movement resulting in a fragment cloud that is pushed out by the residual projectile (with mass mr and velocity