2003-2004 Assessment of the Army Research Laboratory (2005)

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7 Weapons and Materials Research Directorate INTRODUCTION The Weapons and Materials Research Directorate (WMRD) was reviewed by the Panel on Armor and Armaments. The directorate was formed in 1996 by the merger of the Materials Technology Laboratory and the Ballistics Research Laboratory, which had been independent directorates prior to the formation of the Army Research Laboratory (ARL). Most of the WMRD staff and facilities are located at Aberdeen Proving Ground (APG), Maryland, with additional research cells located at the ARL complex in Adelphi, Maryland, and at ARL Centers of Excellence at the University of Delaware, Johns Hopkins University, Rutgers University, and the University of Massachusetts at Amherst. WMRD has three divisions that are reviewed by the Panel: Materials, Terminal Effects, and Ballis- tics and Weapons Concepts. In addition, WMRD includes the ARL Robotics Program Office and the Army Electromagnetic Gun Program Office. WMRD also is responsible for the Robotics Collaborative Technology Alliance (CTA). Tables A.1 and A.2 in Appendix A respectively characterize the funding profile and the staffing profile for WMRD. CHANGES SINCE THE PREVIOUS REVIEW WMRD is about the same size in both personnel and budget as it was at the previous biennial review. A major improvement in effectiveness has been achieved by filling nearly all of the acting branch chief positions with permanent appointments. The Materials Division recently has been reorganized into four branches: 39 

40 2003–2004 ASSESSMENT OF THE ARMY RESEARCH LABORATORY • The Multifunctional Materials Branch works chiefly on nanomaterials, polymers, elastomers, and electronic materials. The bulk of WMRD’s basic research (6.1) funding for materials is allocated to this branch. • The Survivability Materials Branch focuses on lightweight armor, advanced materials for ar- mor, and mitigation of vehicle ballistic shock. • The Ordnance Materials Branch focuses on penetrator materials, high-gravity physics of fail- ure, gun-projectile material interactions, and electromagnetic gun materials. • The Materials Applications Branch works on corrosion engineering, failure analysis of compo- nents, signature-reduction materials, cost modeling of materials, pollution reduction, and ad- vanced manufacturing methods. According to the division Chief, this reorganization was performed to make the branches more cus- tomer-focused and to break up some concentrations of personnel that had been based on place of previous employment. ACCOMPLISHMENTS AND OPPORTUNITIES Most Significant Advances Remarkable advances have been made in the development of a blast-deflection, active protection system that will protect the Future Combat System land vehicle against a number of threats. This development is nearing the stage at which a number of its critical components can be field-tested. This system is discussed below in more detail. The Panel and the Board consider the electromagnetic armor effort to be a real gem within the ARL’s program. The theory and computational work that ARL has brought to this problem is a good example of how developmental research is most effectively done. By developing its own computation models, the team was able to get to the heart of the physical issues in a way that is hard to accomplish with a large and general type of code. Understanding of the underlying physics governing the electro- magnetic disruption and breakup of metal shaped-charge jets appears to be well in hand. Both analytic and numerical models have been developed, are providing a sensible solution of induced instability growth and material dispersion, and have been subjected to some experimental validation. Further verification and validation studies are certainly encouraged to support further development and to provide confidence in the numerical codes and models. Interactions with workers on the Sandia National Laboratories Inertial Confinement Fusion program or the Lawrence Livermore National Laboratory’s National Ignition Facility, where similar issues are being investigated, could prove fruitful. A computer code has been developed for the prediction of the failure of fibrous composite materials under high-rate loading conditions. The model, based on a continuum mechanics-based description that involves more than 30 material parameters to be determined from experimental measurements, gives quite good predictions for the difficult problem of failure due to the oblique impact of a projectile on a laminated plate. The marketer of a major finite element code has made the computer code available commercially. In its present form, the model appears to be limited to small deformations. Two major opportunities to use materials technology as an enabler to advance the warfighting capability of the soldier are discussed in more detail below: (1) the development of a process to produce phased-array antennas from thin-film dielectric materials and (2) permselective membranes to replace bulky and expensive chemical protective suits now worn by the soldier. Other developments that have been transitioned to service are the following: 

WEAPONS AND MATERIALS RESEARCH DIRECTORATE 41 • A modular artillery propellant charge system; • A barrel-reshaping process to improve the accuracy of 120 millimeter tank cannons after exten- sive service; • A water-dispersible polyurethane chemical agent-resistant coating made available to paint ven- dors; and • A new formulation of polymer resin that will reduce the styrene emissions in the fabrication of polymer matrix composites. Opportunities and Challenges Progress similar to that made in active protection systems and electromagnetic armor has not been made at the same rate in developing light-armor systems for vehicles and for personnel. This is, by nature, a more difficult problem than the above weapons systems. In this area, close coupling between understanding the physical modes of armor failure through experimentation and realistic modeling of the failure event is crucial. Better integration of the mechanics- and materials-oriented research staff is perhaps called for. The staff of WMRD is to be commended for their efforts to achieve a better balance between experimentation and modeling. This has certainly been achieved by the mechanics-oriented staff, but among the materials-oriented staff there is an opportunity to enhance their research by greater use of modeling. This is not necessarily a call for greater use of complex quantum mechanical models, al- though they certainly have a role in modern-day materials science. However, with the wealth of model- ing talent available in ARL generally and in WMRD specifically, the opportunity exists for extensive in- house training. CONTRIBUTIONS TO ARMY NEEDS AND THE BROADER COMMUNITY Contributions to Army Needs The technical program of WMRD is uniformly high in quality, and the work seems focused and relevant to the Army’s needs. The speakers making presentations to the Panel tended to communicate well within the expected style, which tends toward overly colorful and busy viewgraphs. Added to this propensity is a real pressure, in such briefings, to communicate the message that “a lot of things were done,” rather than to tell a clean technical story. Also, the uniformity in viewgraph, poster, and presen- tation style suggests that a significant amount of coaching took place before the briefings. While this is not all negative, it should be recognized that every element of imposed control has an associated cost. In a research environment, freedom of expression and creativity produce large rewards. It may be better to allow a bit more personal latitude at the expense of losing the united front. However, one form of uniformity that the Board would appreciate would be the inclusion in every presentation of the level of personnel and funding devoted to each project since its inception. The management of WMRD continues to be very responsive to the suggestions for improvement provided by the Panel. For example, in the previous biennial report, the suggestion was made to include the plug shear failure mode in the composites analysis software. This year, it was part of the software package that has just been completed and marketed to the public. The staff appear to have taken to heart the suggestion that modeling should be proven out by experimentation. They have worked hard to balance the presentations with laboratory tours and poster sessions. The Panel and the Board agree that WMRD’s high level of partnership with universities is good, and 

42 2003–2004 ASSESSMENT OF THE ARMY RESEARCH LABORATORY it is a hallmark of the research done within the Materials Division. However, it was often hard to appraise ARL’s contribution versus that of the university or contractor to the overall progress of the various projects. This was due in part to the way that the contributors were credited, by listing all contributors at the end of the talk. A more thorough breakdown of credit would make this aspect clear. Examples of WMRD’s contribution to Army needs include the following: • Development of thin-film dielectric materials, • Research on active protection systems, • Transitional work in permselective membranes, and • Direct assistance to the troops in Iraq. Thin-Film Dielectric Materials Development Previous research had developed a powder processing route for making barium-strontium titanate (BST) components for phase shifters at a price low enough to allow consideration of the replacement of all communications antennas with this technology. However, scale-up work showed that the bulk components required too high a power level to be operationally economical. Therefore, attention was focused on making the phase shifters with thin films of BST. The advantages of a phased antenna are that it provides a greater range of communication across multiple communications systems from 20 to 45 gigahertz with high data rate capability. This capability results in a highly mobile communications system for the digital battlefield of the future. An important additional advantage is that it provides increased survivability to the communications command centers because of the low profile of the antennas. The major obstacle to this system development has been the high cost of antenna components made from ferroelectric materials. To make this development eco- nomically feasible to the Army, the cost per installation must be reduced from several hundreds of thousands of dollars per vehicle to tens of thousands of dollars. This is an excellent example of a case in which materials science and engineering can provide an enabling breakthrough. Through substantial team effort, a process has been developed for producing magnesium doped BST thin films using a metal-organic solution deposition technique. Careful studies have been made of microstructure, surface morphology, interface bonding, and dielectric and insulating properties. The manufacturing process appears to have appropriate economics, although not much was revealed about this during the presentations to the Panel. Meticulous tests were carried out with respect to tolerance for high vibration (fatigue failure), shock, stress, and elevated temperature (thermal fatigue). The experi- ments seem to have been well planned and carried out. However, there was a distinct absence of any use of modeling to guide the direction of the research. The Panel suspects that more attention to modeling might have advanced the progress of this important program. For example, some modeling might have pointed out that the approach originally applied to making monolithic components would have been limited by power (high voltage) considerations. The progress reported on thin-film dielectric materials development was very encouraging. How- ever, one problem remains before the phased arrays can be field-tested. Thin films are notorious for problems with residual stresses being built in during fabrication, and this system is no exception. Residual stresses as high as 2 GPa have been measured. These stresses lead to the formation of voids and cracks, with failure of the structural integrity of the array. Careful measurements of residual stress are being made, and these are being correlated with processing conditions. It is expected that, with further work, the residual stress problem can be minimized. 

WEAPONS AND MATERIALS RESEARCH DIRECTORATE 43 Active Protection Systems Active protection systems are armor systems that intercept a threat before it hits a vehicle. Active protection is an absolute necessity for the Future Combat System, since that system cannot carry sufficient armor to defeat a number of threats, especially the tank-fired, long-rod kinetic energy (KE) penetrator. Because antitank KE rounds move at such high velocities, the time line for sensing, engag- ing, and neutralizing an incoming KE penetrator is less than 1 second. An active protection system is made up of the following components: threat warning sensors, a tracking and fire control component, a countermeasure launcher, the countermeasure, and base armor. Although various active protection systems have been examined, the focus at ARL has turned to blast deflection. A high-explosives warhead countermeasure is launched to intercept, at some appropri- ate engagement distance, the incoming KE threat. Detonation of the warhead generates a blast that loads the KE projectile and causes it to swerve and miss the vehicle. Pacing technologies can be divided into two primary categories: KE projectile tracking and blast deflection. KE projectile tracking challenges include issues related to sensor sensitivity, accuracy, speed, and cost, combined with the complexity of the projectile signature. The challenges for blast deflection include warhead design, creation of the proper blast loading, detonation timing, accuracy, and the available time line. The active protection system work is a well-managed program that has used a suite of analytical and computational tools, combined with well-planned experimentation, to understand, bound, and develop solutions for the various technical challenges. The researchers have developed enabling technology for KE threats that is robust against a variety of KE long-rod projectiles. Further, they have demonstrated the technology against some chemical energy (CE) munitions. Although the time line is considerably less stressing for CE munitions because of their lower velocities, other issues, such as detecting and tracking CE munitions and their very different geometric profiles, result in other challenges. Current efforts are focused on integration of the active protection system onto the vehicle (considerable progress has been made) and further research to improve the effectiveness of the warhead countermeasure (e.g., its size and weight). Permselective Membranes The work on permselective membranes is a materials science effort that is in transition from 5 years of basic research to an applied development of chemical/biological protective clothing. This project typifies the important role that WRMD provides in applying fundamental research to protect the warfighter. Traditional material screening methods were appropriately used to determine permselective membranes to meet a near-term solution for protective clothing. Long-term concepts also have been envisioned. Although it was suggested that this concept may be effective for chemical protection from mustard agents, additional work that is being carried out needs further study to demonstrate effective- ness against a broader class of chemical agents. Much of the current focus of the work on permselective membranes appropriately centers on material processing and commercialization issues. The directorate’s good ties to commercial partner- ships and university research can strengthen this effort. However, there is some uncertainty about the level of interactions and collaborations that the ARL team has with their colleagues at the Natick Soldier Systems Center. The Board suggests that these ties should be reestablished and strengthened. 

44 2003–2004 ASSESSMENT OF THE ARMY RESEARCH LABORATORY Assistance to Troops in Iraq A wealth of knowledge concerning ballistics, weapons systems, and materials resides in the WMRD staff. This expertise has been used effectively when called upon for “quick fixes” to problems that have arisen in Iraq. For example, WMRD staff provided a quick fix to prevent enemy troops from disabling the Abrams tank by shooting up its tailpipe. Another quick fix was to devise and manufacture several hundred armored doors for the High-Mobility Multipurpose Wheeled Vehicle (HMMWV, or Humvee). Contributions to the Broader Community WMRD is well connected to the Army Research, Development, and Engineering Command, which forms the directorate’s main customer groups. Each year the directorate holds an off-site planning conference to learn about the needs of these customers and to discuss their plans for future research. These conferences have been highly successful and should be continued. WMRD, and in particular the Materials Division, maintains a high level of partnerships with universities. Most of these involve near-weekly interactions with the particular university group. Similar close connectivity with the Sandia National Laboratories and the Los Alamos National Laboratory in dynamic modeling was not emphasized or demonstrated. While in past years WMRD has shown good and improving metrics dealing with issues such as papers published, presentations, professional society activities, and educational outreach, no informa- tion of this type was received at the 2004 review. The Panel and the Board recognize the heavy workload imposed on WMRD staff as a result of the Iraq conflict and the pressures brought about by the Future Combat System. Nevertheless, it is increasingly important for research staff to improve and document their professional credentials.