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Grant
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase II | Award Amount: 750.00K | Year: 2011

ABSTRACT: Recent developments of advanced hybrid metallic structural concepts have been promising for enhancing durability and damage tolerance (D & DT) of unitized aircraft structures. The Alpha STAR team, comprised of Alcoa, Northrop Grumman (NGC), and Southwest Research Institute, proposes to demonstrate and verify/validate the application of advanced hybrid materials in a realistic large scale military aircraft structure. The proposed effort consists of: (1) design of low cost fiber metal laminates for insertion in lower wing panel of NGC"s conceptual military transport plane; (2) layout, sizing, robust design, manufacture, and test of structural component. The test plan includes static testing to design limit loads, fatigue testing in presence of discrete source damage, and residual strength after fatigue. This effort will apply multi-scale, multi-site virtual simulation progressive failure analysis and metallic/composite material characterization tool, developed and building block validated in Phase I effort. Phase II will utilize the developed analytical tool to achieve robust design considering uncertainties in geometrical, material and fabrication processes. We will verify D & DT performance, weight, and life cycle cost benefits obtained from hybrid materials compared to those of a baseline. We will apply our expertise in hybrid material and aircraft design, advanced virtual simulation, and testing to meet program objectives. BENEFIT: Based on work done in Phase I, the Alpha STAR team (Alcoa, Northrop Grumman Corporation NGC, South west Research Institute SwRI) analytically demonstrated enhanced damage tolerance capability for unitized aircraft structures. A 20% reduction in weight and 20% reduction in life cycle cost (20/20) coupled with improved performance are anticipated from the use of Fiber Metal Laminates (FML). Improved damage tolerance under fatigue loading is obtained with these advanced materials as compared to conventional all metallic construction. NGC, as a premier developer, fabricator and integrator of manned and unmanned aircraft expressed great interest in exploring use of these advanced materials in conceptual military transport aircraft. As demonstrated in Phase I, this work will also lead to expanded use of software simulation-based tools for assessing structures made from advanced material concepts with minimum testing support. The availability of well-established, well verified tools will aid in the certification by analysis of components from advanced materials. This will reduce testing by at least 30% as compared to current standards and will open the way to use these advanced materials to their maximum potential.


Garg M.,Alpha Star Corporation | Abumeri G.H.,Alpha Star Corporation | Abdi F.,Alpha Star Corporation
Materials Evaluation | Year: 2010

A multi-scale micromechanics technique has been proposed to characterize an advanced multi-scale composite system consisting of continuous microscale diameter fibers and matrix that is reinforced/infused with spherical nano-sized silica particles. The technique was used to predict the effective constituent (fiber/matrix) strength and stiffness material properties using limited test data that is available from Uddin and Sun (2008). The effective constituent properties were then used to simulate longitudinal tension and compression and transverse tension unidirectional coupons using combined progressive failure analysis and the finite element method. The predicted ply properties compared reasonably well with the test data within ±4% error.


Grant
Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase I | Award Amount: 99.95K | Year: 2012

A composite software design tool kit is proposed to predict composite properties using micro-mechanics augmented lamination theory. The capability will overcome shortcomings of progressive failure models and will take into account translaminar and interlaminar failure mechanisms. Starting from lamina properties, strength will be predicted for laminates subjected to tension and compression loading. Generation of allowables using scatter in fiber and matrix material properties and fabrication defects will be carried out by use of probabilistic methods to avoid the testing of large amounts of specimens before there is adequate confidence in the material properties. Integration with finite element approach will be accomplished by synthesis of telescoping composite mechanics from fiber and matrix constituents to laminate level. A significant innovation will be the accounting for damage/micro-crack induced anisotropy of the composite matrix properties. Methods to characterize the material properties under strain rate effects will be included. A commercial composite material characterization software MCQ will be enhanced and integrated into commercial (explicit/implicit) FEM codes for structural scale-up. The capability will consider effect of defects (void shape, size, distribution, and fiber waviness) and will rely on a physics-based micro-mechanics approach to reverse-engineer effective fiber/matrix constituent properties using five ASTM ply in-plane tests as input.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase II | Award Amount: 499.66K | Year: 2012

The Phase II STTR technical objective will update, expand, and validate the excellent results achieved in the Phase I"Analysis and Modeling of Foreign Object Damage (FOD) in Ceramic Matrix Composites (CMC"s)"program. The program will evaluate CMC component life capability before and after impact in a realistic operating environment. Predictions will be validated using new experimental impact results at elevated temperatures and NDE measurements of CMC specimens before and after impact. Multi-scale Progressive Failure Analysis (MS-PFA) will use the GENOA commercial software coupled with LS-DYNA/ABAQUS to assess the micromechanical multisite damage evolution process. Updated models will include triangulation, adaptive meshing, microstructure and damage visualization, interface influences, etc. Damage and stress are fully visualized down to the micromechanical level, and show fiber/matrix/ply stress redistribution after damage. Delamination initiation/propagation and damage size versus impact velocity between specific plies will be compared to test results. A high temperature impact test facility and advanced NDE measurement capability will be developed at the University of Akron. Example materials under evaluation are MI SCi/SCi, NASA N24A and S200. Life prediction in an engine environment will be demonstrated before and after impact in a Phase II Option. Close coordination will be maintained with the NAVAIR TPOC.


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 99.99K | Year: 2010

Continuous fiber-reinforced SiC/SiC ceramics matrix composite (CMC) material is being considered in an advanced gas turbine engine intended for an aircraft or an industrial power generation system, for high temperature capability, possibly with added protection from environmental or thermal barrier coating. CMC engine parts in military/commercial vehicles allow engines to operate at higher temperatures than what a typical superalloy with or without a barrier coating can withstand, and it also significantly reduce engine weight. A successful insertion of CMC’s, particularly in Air Force’s aircraft engines, will also need to sustain aggressive corrosive environment due to “salt” attack on top of considerable damage caused by oxygen and moisture in the combustor fuel. Multidisciplinary physics-based analytical modeling proposed here deals with microstructural damages occurring due to environmental effects, such as, oxidation, recession etc., and it could be an important tool for designing and continually monitoring the health of these critical components in service. Demonstration of such a life prediction tool, which will correlate actual thermochemical and micromechanical damage processes with mechanical response, will shorten the mechanical design and analysis process of CMC components, thereby lowering cost and leading to higher reliability. These benefits will also be relevant for other NASA, DOE and DOD supported CMC application programs for power generation industries where higher temperature and lesser quality fuel will cause these damages to become more severe. BENEFIT: The application of CMC engine parts in military war fighters allows engines to operate in higher temperatures and will reduce the engine weight significantly. Analytical modeling strategy in CMC gas turbine engine design and application is an important complement to test investigation, which reduces test costs and shortens the design-to-production cycle of CMC engines. The proposed development of the micromechanical modeling technique and structural analytical tool will enable its transition to JSF and other military aircraft propulsion systems. Future use may involve hypersonic aircraft and the J-UCAS propulsion systems for weight reduction and enhanced life expectancy. Ceramic matrix composites also leverage large economic and social benefits in commercial application. Catalytic converters alone in the power generation industry enable a $38 billion pollution control business each year and have reduced air pollution by 1.5 billion tons since 1975. Demonstration of commercially available GENOA software, that can successfully predict the composite thermo-chemically-oxidization behavior, will provide the military, the aerospace industry and power generation plants with a verified analytic/design tool. Successful demonstration/verification of a life prediction analytical methodology for engine composites under service environment would reduce future certification costs of an advanced engine structure fabricated with CMC material database for future engine components.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 99.80K | Year: 2010

A significant barrier to the insertion of ceramic matrix composite (CMC) materials into advanced aircraft engines is their inherent lack of toughness under foreign object Damage (FOD) as well as post FOD. Our team will develop and demonstrate a physics-based model for FOD/post FOD in CMC’s. The model will incorporate physical mechanisms associated with impact for two different CMC systems: a) matrix-dominated system and b) fiber-dominated system. Our methodology will address impact and post-impact of both “as-built” and “as-is” CMC’s. It will account for architecture (2D/3D-nano) and CMC manufacturing (layered thickness, void shape/size, interfacial strength, micro-crack formation) taking advantage of the strength and toughness enhancing effect of different length scales of CMC structure. The model will be incorporated into our commercial progressive failure analysis software GENOA, that integrates commercial FEA and enhances their accuracy limitation. It will be validated using available CMC impact test data from NAVAIR SiC/SiC and Oxide/Oxide for a range of FOD tests. We will determine the feasibility for performing impact tests with Acoustic Emission/Electrical Resistance monitoring as damage assessment and health monitoring techniques that relates to damage model and life prediction. In Phase II high temperature impact testing will be conducted to further validate our model.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 79.97K | Year: 2013

Ceramic Matrix Composite (CMC)'s are highly susceptible to interlaminar shear failure at elevated temperatures. Therefore, interlaminar properties, critical design limitation of CMC should be assessed accurately with appropriate test methods to ensure overall structural reliability/integrity of components in Naval gas turbine engines. AlphaSTAR proposes to develop rigorous, precise, and innovative test methods, and validated FEM based Fracture Toughnesses (FT) methodology, that guides tests, and assist customization of the standardized delamination growth CMC test methods. To address the need a comprehensive/systematic approach is proposed that involves the application of the latest advanced FT analysis/modeling and experimental techniques. The focus in Phase I is on:1) room/elevated temperatures modeling of technically sound and marketable testing technique for accurate characterization of delamination resistance such as crack tip micro-cracks; crack growth resistance (Mode I/II, mixed mode), as well as predicting high temperature FT when only tests are available at room temperature; and 2) to identify/implement modifications to ASTM test methods working with OEM design engineers. Following the initial redesign of test method and testing in Phase I, further development, data generation on one or more specific materials, and efforts for standardization of procedures will be pursued in Phase II.


Cardenas D.,Monterrey Institute of Technology | Elizalde H.,Monterrey Institute of Technology | Marzocca P.,Clarkson University | Abdi F.,Alpha Star Corporation | And 2 more authors.
Composite Structures | Year: 2013

A reduced-order finite-element model suitable for Progressive Failure Analysis (PFA) of composite structures under dynamic aeroelastic conditions based on a Thin-Walled Beam (TWB) formulation is presented. Validation of the PFA-TWB against an integrated PFA model based on a shell formulation and implemented in the commercial software tool GENOA is conducted for static load conditions. A helicopter blade made from composite material and previously used in literature for the discussion of damage propagation is used as the reference case. The failure criteria for the different layers of the composite material used in the PFA-TWB model have been formulated in analogy with the corresponding criteria implemented in the shell formulation. Comparisons between the predictions of both models for progressively increasing load have been conducted in terms of the cumulative overall damage volume in the thin-walled structure, the layer-resolved cumulative damage volume, as well as through spatially resolved damage maps for both models. A strikingly similar damage topology has been found from both models up to load values close to final failure, in spite of the restraining assumptions of the TWB formulation. In terms of damage volume the PFA-TWB models predicts slightly higher values which can be traced back to the inevitable differences in the failure criteria formulation in the one-dimensional and the shell model, respectively. It is shown that a good agreement with the predictions of the shell model in terms of the cumulative damage volume is obtained if the strength values of the composite material are adjusted upwards in a uniform manner by about 10%. Considering the common safety factors usually applied in the design process of composite material the agreement of the TWB and the shell model in terms of damage propagation is considered excellent, allowing for the PFA-TWB to be used in systematic design studies. © 2012 Elsevier Ltd.


Grant
Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase I | Award Amount: 99.98K | Year: 2015

We propose SHM technology integrated with multi-scale, multi-physics analysis to detect fatigue damage precur-sors. We will predict remaining useful life based on nondestructive information. In Phase I, we will investigate the capabilities of our sensing approach in both metallic and composite coupons. For metals emphasis will be given in implementing a multiscale experimental mechanics approach consisting of standard laboratory testing coupled with the multispectral approach developed at Drexel University. To complement this approach we will further perform experiments using miniature mechanical testing with microscopes for direct microstructure evolution measurements. Our approach will provide rich datasets to our computational models that will focus on two major objectives. The first is related to the use of computational mechanics approaches to produce simulation results that have the capability to replicate effects observed by our nondestructive measurements with the additional task to create modeling strategies to feed actual experimental data into such models. The second objective will be to use this approach in a prediction framework that will be based on Probabilistic Structural Risk Assessment (PSRA) and Bayesian updates to determine pathways towards remaining useful life estimates. Our plan for Phase II and commercialization of this approach will be further addressed.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase II | Award Amount: 249.26K | Year: 2015

The Alpha STAR Corporation and the University of Akron STTR Phase II proposal will establish ASTM standards test methods to determine relevant ceramics matrix composites (CMC) delamination crack growth resistance (CGR) material properties (Mode I & Mode II)under service load temperature conditions. Phase Ii will expand on Phase I results, conclusions & recommendations. Emphasis will be on testing techniques and quality specimen preparation that will result in lower test scatter/higher accuracy and high temperature testing with improved non-visual measurements using AE/ER (acoustic emission and electrical resistivity). Phase II will test several class of CMC's coupons (e.g., SiC/SiC, Sic/SiNc, Oxide/Oxide), and ASTM approved test standards with round-robin verification including simple data analysis methods (e.g. modified bean equation). A significant reduction in design time and cost will be achieved by using validated & calibrated virtual testing software that can rapidly assess durability & damage tolerance (D&DT) and reliability of CMC structures based on FAA recommended building block strategy. Robust design optimization technique integrated with multi-scale modeling (damage and fracture evolution) will be used to maximize the ASTM design performance and address the CMC test issues (e.g., zig-zag crack pattern, blunt/sharp notch width effect.

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