TECHNOLOGY AREA(S): Materials/Processes

ACQUISITION PROGRAM: Naval Ordnance Safety and Security Activity (NOSSA)

OBJECTIVE: Develop lightweight materials and associated structural components to produce a more efficient means to construct Earth Covered Magazines (ECMs) while keeping the same or higher level of protection capability, making it easier to maintain and upgrade them, and enabling the military to fabricate the munition structure under field conditions.

DESCRIPTION: The defense technology based on the weapons effect phenomenology can increase the functions of weapon storage structures by adopting new generation structural members with improved energy absorption. The design of ECM storage facilities has been standardized by developing several typical models. The primary components of the ECM structure are concrete walls, concrete roof, basement, blast door, and earth cover. Design details very typical of hardened structure design before 1945 are employed. Few changes to this design concept have been made, and the standard design is still being used, even though there have been important technical developments in blast resistant structure design concepts.

The Navy seeks innovative, advanced materials specifically found advantageous for enhancing blast resistance, which will be considered to replace the standardized heavy concrete structures of the past and will afford for deployment of much more lightweight and easily constructed ECMs. This new approach to the design of ECMs is to employ modular components fabricated from composite structural components, which has many advantages for various types of munitions storage facilities both at a base and in the field. The material or structural members will be developed to maximize blast effect resistance and then, three types of structures will be designed to show the applicability, efficiency and feasibility of the developed material/component� to ECM design and construction. Various ECM standard designs are currently being used. The general dimension of the ECM in rough measure is in the range of 30 ft. X 30 ft. X 30 ft. to 100 ft. X 100 ft. X 30 ft., with normal concrete thickness of more than three ft. Tunnel and standalone ECM module type have totally different measurements. Cost and function shall be evaluated by comparison with Navy standard design of concrete structures to show efficiency.

The development is planned in three steps � composite material development, module development, and module application to the ECM. Based on selected or developed composite material, a structural module will be developed. A Lego-type module integration, which will be assembled to the ECM, will be designed by computer simulation and validated by full-scale testing. Full-scale structural testing, assembled by developed modules, can hardly be conducted in this project due to limited cost. Instead, the construction procedure can be precisely reviewed by using building modeling information (BMI) techniques to acquire preliminary information about construction procedure and detail cost.

PHASE I: Identify the blast resistant capacity through energy absorption mechanism of the various materials followed by a study of the participation of the identified foams in composite members. The developments in Phase I shall include:
- Efficient blast resistant composite components based on high-fidelity physics-based (HFPB) analytic simulations shall be generated.
- Lab tests for dynamic material characteristics of the materials for energy absorption function shall be conducted.
- Materials shall be identified by using test results to show the contribution of each material in composite action.
- HFPB analysis shall be conducted to show efficiency of the identified material model against the frequency and magnitude range of the blast load. The results of Phase I research shall give solid insight about the practical applicability of the members when it is applied to the magazine or related hardened structures in extensive and comprehensive research in Phase II.

The Phase I Option, if exercised, will include the initial design specifications and capabilities description to design a prototype solution in Phase II.

PHASE II: Based on the results of the Phase I, with sufficient and convincible insight of the application of composite materials to the magazine and related hardened structures, practical design and validation through integrated member testing. Develop a comprehensive new generation design of ECMs. Ensure that the components and modules can be deployed for the construction of different ECM structures requiring hardened capacity or a high level of blast resistance. Include:
- Development of a module design suitable for fabrication from the results of HFPB analysis for materials and structural components.
- Development of structural designs in accordance with the design guidelines specified by UFC (Unified Facility Criteria) and DDESB (Department of Defense Explosives Safety Board) technical notes.
- Testing of optimal designs of the composite material with three different levels of blast resistant capability according to the applied blast loadings in reference to the ECM design guideline.
- Consideration of a modular concept of the ECM structures to control the local damage and make the maintenance effective and efficient.
- Full scale detonation testing of integrated modules with the boundary conditions and connection conditions for validation of the development, which is the basic module to the structural assembly.
- Production of standard drawings of the three structures with the modular concepts in the same format as the conventional design. Provide the construction and fabrication simulation with BMI technology.

PHASE III DUAL USE APPLICATIONS: The developed design of the practical structures will be extended to more standard designs those were established before 1980�s.� Also, the developed and validated structural members and integrated modules will be assembled by modeling and simulation (M&S) and BMI to check any remaining practical problems to be solved.

The developed design of the practical structures can be extended to more standard designs those were established before 1980�s. Also, the developed and validated structural members and integrated modules will be assembled by modeling and simulation (M&S) and BMI to check any remaining practical problems to be solved. It can be applied not only the new construction of the new generation magazine structures but for the pure protection of the commercial structures.� According to the protection level adjustment, enhancement of the magazine storage capacity can be pursued by the developed design.

REFERENCES:

1. Gama, B. A., Bogetti, T. A., Fink, B. K. et al. �Aluminum foam integral armor: a new dimension in armor design.� Composite Structures, vol. 52, no. 3-4, 2001, pp. 381-395. https://www.sciencedirect.com/science/article/pii/S0263822301000290

2. Deshpande, V. S. and Fleck, N. A. �Isotropic constitutive models for metallic foams.� Journal of the Mechanics and Physics of Solids, vol. 48, no. 6, 2000, pp. 1253-1283. https://www.sciencedirect.com/science/article/pii/S0022509699000824

3. Zhang, X.and Cheng, G. D. �A comparative study of energy absorption characteristics of foam-filled and multi-cell square columns.� International Journal of Impact Engineering, vol. 34, no. 11, 2007, pp. 1739-1752. https://www.sciencedirect.com/science/article/pii/S0734743X06002235

4. Wu, Youcai, Magallanes, Joseph M., Choi, Hyung-Jin and Crawford, John E. �Evolutionarily Coupled Finite-Element Mesh-Free Formulation for Modeling Concrete Behaviors under Blast and Impact Loadings.� Journal of Mechanical Engineering, Vol. 139, Issue 4, April 2013. https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000497

KEYWORDS: Magazine Structure; Blast Loading; Energy Absorption: Composite Material; ECM Modular Design; ECM Modeling and Simulation; Full Scale Detonation test; Earth Covered Magazine; ECM