Material Characterization & Experimental Mechanics
The Branch features multiple world-class experimental research facilities designed to evaluate the full breadth of material behaviors under the extreme loading conditions and environments typical of aerospace propulsion and power applications. Materials of primary interest include monolithic ceramics and metallics, neat polymeric resins, and the multitude of fiber-reinforced composite forms generated when each is used as the matrix constituent. The Branch operates over fifty computer-controlled uniaxial and axial/torsional mechanical loading frames designed to investigate a multitude of loading scenarios at the coupon and sub-component levels in a variety of thermal (up to 1650 degrees Celsius or 3000 degrees Fahrenheit) and environmental (e.g., air, inert gases, vacuum, and partial pressures of oxygen) conditions. Many unique facilities and specially designed testing apparatuses are also available to experimentally evaluate and characterize advanced engineering materials.
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Analytical and Computational Mechanics
The Branch develops innovative research methodologies and computer software that are used worldwide by industry, academia, and government organizations for predicting the mechanical and structural response, durability, reliability, and life of advanced material systems. Research areas include structural mechanics, constitutive modeling, composite analysis, durability, reliability, and life prediction modeling. Material systems investigated include high-temperature polymeric, metallic, ceramic, and fiber-reinforced composites. The Branch develops theoretical, empirically based, and integrated, computer-based, design/analysis tools for simulating and assessing the lifecycle performance of critical structural components. Many of the software programs developed within the Branch are used either in conjunction with or as postprocessors to finite element analysis (FEA) programs. In this way, a complete analysis package is provided to design engineers, enabling cost-effective design of more reliable, efficient, and environmentally conscious components
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Advanced Concepts and Failure Assessment
The Branch develops and uses numerous analytical tools and/or software codes for predicting the deformation, fatigue, and fracture of engineering components. For example, traditional fatigue life estimation methods, such as strain-based methods for low-cycle fatigue and stress-based methods for high-cycle fatigue, are routinely evaluated for their applicability to metallic materials used in the hot sections of aerospace propulsion system components. In particular, models are available for assessing fatigue crack initiation lives of metallic materials subjected to isothermal and nonisothermal uniaxial and multiaxial cyclic loading conditions. In addition, analytical crack growth codes such as FASTRAN, NASGRO and others are often used to perform damage tolerance life prediction analysis with the current emphasis on modeling variable amplitude loading behavior for turbine materials under both time dependent and cyclic loading conditions.
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