SITIS Topic Details |
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| Proposals Accepted: | |
| Program: | SBIR |
| Topic Number: | AF103-005 (AirForce) |
| Title: | Modeling and Simulation of Hybrid Materials/Structures for Sustainment Applications | Research & Technical Areas: | Air Platform, Information Systems, Materials/Processes |
| Objective: | Develop finite element models and perform analysis of simultaneous crack initiation/growth in metal layers and delamination of composites layers of arbitrarily configured hybrid materials/structures.
| Description: | For the purpose of this topic, hybrid materials/structures are assumed to be composed of, in part or whole, fiber metal laminates (FMLs). FMLs have been developed over the past several decades, examples of which include, but are not limited to Glare, Arall, or CentrAl. These particular materials exhibit slow crack growth, corrosion resistance, and impact resistance. Military application includes the C-17 aft cargo door (Arall), and commercial application includes the A380 fuselage (Glare). Advanced hybrid structures (AHS) are considered for sustainment of veteran aircraft to take advantage of the tailorability of the material to provide form/fit/function replacement of problematic monolithic aluminum structural components. These FMLs may require layups that are not considered part of the standard family, with varying thicknesses of individual metal layers, potentially different metal alloys, and adhesive combinations with varying fiber volume fraction in the form of pre-pregs.
To effectively consider AHS as replacements for their monolithic metal counterparts, the behavior of the failure modes of the FML must be predicted and validated by coupon, element, subcomponent, and component testing. For current FMLs that exhibit excellent fatigue resistance and impact resistance, the failure mode is characterized by a combined delamination zone between metal and composite layers and a crack in the metal layers. The mixed failure mode exhibits synergy between the delamination and crack: the crack growth rate is affected by the reduction in stress intensity due to fiber bridging in the wake of the crack, which is only possible due to the delamination zone allowing fiber stretching. The mixed mode failure may be significantly altered by a nonuniform (materials, thicknesses, layup) configuration. Successful prediction of the mixed failure mode has been performed for uniform configurations (Glare), and is currently extended to nonuniform thickness layups (CentrAl). Modeling and simulation (M&S) of static and dynamic behavior of arbitrary configurations of FMLs to capture individual layer delamination zones and crack growth is necessary to provide validation of replacement concept capability. Finite element modeling and simulation developed to capture this mixed mode failure is the first step to enabling simulation of various configurations. This capability will require capturing simultaneous crack and delamination growth, including possible nonlinear behavior of constituent materials.
| PHASE I: Models and simulations of multi-constituent material FMLs, potentially incorporating micro-/meso-/macro- modeling techniques, to capture delamination and crack interactions/behaviors. Validation of analysis by comparison with existing models of FML behavior in literature, or experimental data.
| PHASE II: Incorporation of modeling and simulation capabilities in commercial software code as a module or package. Modeling and simulation at the sub-component level to determine residual strength of the damaged structure. Experimental validation of sub-component.
| PHASE III | DUAL USE COMMERCIALIZATION: Military Application: Design and certification of hybrid components as a form/fit/function replacement to problematic monolithic aluminum structures.
Commercial Application: Design and certification of new aircraft that incorporate FMLs in primary load-bearing structures.
| References: | 1. Vlot, A. and Gunnink, J.W., Fibre Metal Laminates – an Introduction, Kluwer Academic Publishers, Dordecht, 2001. 2. Alderliesten, “Analytical prediction model for fatigue crack propagation and delamination growth in Glare,” International Journal of Fatigue, Vol. 29, No. 4, April 2007, pp. 628-646. 3. Beumler, “MoC for A380 Hybrid Structure,” Proceedings of the 2008 ASIP Conference, San Antonio, TX, December 2008. |
| Keywords: | fiber metal laminate, fibre metal laminate, sustainment, glare |
Questions and Answers: |
Q: Regarding Phase II citing "experimental validation of sub-component": |
A: A.) It is up to each proposer as to how relevant experimental data should be collected. The USAF does not anticipate providing data as GFE. |
Q: Is it only necessary to consider delamination at the composite / metal interface, or should delamination of individual composite layers be considered as well? |
A: For the scope of this project, specifically Ph I, delamination between each metal/composite interface should be considered. For the scope of future project, potentially in Ph II, delamination between the individual composite pre-preg layers may be considered, as the failure mode for an "arbitrary" or "variable thickness" hybrid/FML may include such delaminations, particularly if impact is considered for initation. |
Q: Should the modeling of the nucleation of the crack in Al layers be a part of Phase I or the fatigue crack growth for existing cracks should be considered? |
A: The objective of Phase I is the modeling & simulation of mixed mode (crack growth in metal layers & delamination between metal layers and composite layers) failure of fiber metal laminates. Each proposer must consider the best way to accomplish this task. |
As of midnight September 1, questions for solicitations SBIR 10.3 and STTR 10.B will no longer be accepted.
To read the solicitation for full proposal preparation and submission details click here. |