Administration of the FAA Center for Excellence for Advanced Materials in Transport Aircraft Structures (AMTAS)

In December 2003 the Federal Aviation Administration (FAA) announced a joint award to the University of Washington and Wichita State University to create a new Air Transportation Center of Excellence for Advanced Materials (JAMSCOE). This award established a center led by the UW and named the FAA Center for Advanced Materials in Transport Aircraft Structures (AMTAS). Academic members of AMTAS include the UW, Washington State University, Oregon State University, and Edmonds Community College. As lead institution of AMTAS, the UW is responsible for overall administration of AMTAS, oversight of AMTAS projects conducted by all academic members, and hosting of an annual AMTAS Conference. This proposal requests FAA funding necessary to administer AMTAS. As in all other AMTAS proposals, the FAA funding requested will be matched on a 1:1 basis from non-federal sources.

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Development of Reliability-Based Damage Tolerant Structural Design Methodology

The purpose of this proposal is to develop a new design approach to quantify the reliability of aerospace structures. In this approach, the “Level of Safety (LOS) of an existing structural component is determined based on a probabilistic assessment of in-service accumulated damage and the ability of non-destructive inspection methods to detect such damage. Specifically, the discrete LOS for a single inspection event is defined as the compliment of the probability that a single flaw size larger than the critical flaw size for residual strength of structure exists, and that the flaw will not be detected. The cumulative LOS for the entire structure is the product of the discrete LOS values for each damage type Present at each location in the structure. This approach can be utilized to develop a design process which evaluated the equivalent LOS of an existing structure, and use this value in the design of a new structure which matches or exceeds the existing LOS value. The LOS method enables the characterization of uncertainty associated with damage accumulation, inspection reliability and residual strength of the structure.

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Combined Global/Local Variability and Uncertainty in Integrated Aeroservoelasticity of Composite Aircraft

We propose to the FAA to develop analytical, computational and experimental capabilities to address “Combined Global/Local Variability and Uncertainty in Integrated Aeroservoelasticity of Composite Aircraft”. Computational capability development will focus on quantification of effects on stiffness of key local effects in composite structures, global aeroelastic/aeroservoelastic analyses capable of evaluating variations and uncertainity to such local effects, and integrated local/global modeling capability of uncertain composite structures. Capabilities for simulation of the effects of control surface nonlinearities on aeroelastic and aeroservoelastic behavior of full scale airplanes will be developed and used to study effects of nonlinearity and uncertainty mechanisms and guide maintenance practices. Simultaneously, an experimental structural dynamic/aeroelastic testing capability will be developed at UW, and tests will be planned & conducted to study the effects of damage on stiffness of components and models.

Improving Adhesive Bonding of Composites through Surface Characterization

An investigation of three surface preparation processes for co-bonding on the surface chemistry and subsequent bond performance in composite material.

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Course Development: Maintenance of Composite Aircraft Structures

The goal of this proposal is to develop, in conjunction with AMTAS academic and industry partners, a syllabus and course material for a short course addressing the maintenance of composite aircraft structures.

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Standardization of Analytical and Experimental Methods for Crashworthiness Energy Absorption of Composite Materials

The proposed research will develop a set of standardized procedures for the experimental and numerical characterization of the crush behavior of composite materials. Recent findings have identified the key factors preventing the introduction of polymer composites in primary crash structures as the lack of adequate design guidelines, accurate simulation tools, specialized test methods for energy absorption, and an available material database. The proposed research plans to address all of these factors in a uniquely integrated fashion. Initially the research aims to develop a test standard with which to characterize the Specific Energy Absorption (SEA), featuring a corrugated web coupon. The results using this specimen will be compared systematically against the values measured using a flat plate specimen with dedicated anti-buckling fixture, C-channels, and square tubes using identical material and processing conditions. The method will then be used as benchmark to compare the accuracy of material models and progressive failure criteria within mainstream commercially available finite element codes (LS-DYNA, ABAQUS Explicit and possibly PAM-CRASH). This unified and integrated investigation will be used to generate a set of accessible numerical guidelines for the industry to build on. Lastly, the standard will be used to generate design guidelines and to systematically characterize the material systems and forms. This effort provides direct support to the current standardization efforts of CMH-17 (former MIL-HDBK-17) and will aim to result in a test method for standardization by ASTM Committee D30.

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Failure of Notched Laminates under Out-of-plane Bending

The design of aircraft structures made of composite materials is heavily influenced by damage tolerance requirements. The problem of predicting failure in notched laminates has been the subjected of numerous studies. In general, these investigations have focused on the response of laminates to in-plane tension, compression or shear. In spite of the fact that out-of-plane bending, twisting, or shear can be an important load situation, very little research has been devoted to this topic. The overall goal of this research is to develop analysis techniques that are useful for the design of composite aircraft structure subjected to general out-of-plane loading. For this project we will limit ourselves to the out-of-plane bending case and focus on some very basic experiments and modeling efforts involving simple structures (center-notched, unstiffened laminates) under pure bending. In partnership with the Boeing Commercial Airplane Company, we will determine the modes of failure of the laminates and evaluate the capability of some currently existing analysis techniques for predicting these failures. Accomplishing our objective will require both experimental and computational efforts.

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Identification and Validation of Analytical Chemistry Methods for Detecting Composite Surface Contamination and Moisture

The primary objective of the proposed work is to verify the reliability and sensitivity of solid-state electrochemical sensors for detecting surface contaminants and moisture on pre-bond surfaces. Sensors, made using the novel concepts applied to solid-state electrochemical materials, were found to be very sensitive in experiments with polyester peel ply samples. However, the method has not been tested for other peel ply samples that may have more or less contamination and/or moisture levels. In addition, the correlation between the features of the signals and surface chemistry condition has not been established. The proposed work will be focused on comprehensive testing and evaluation of the sensors. The proposed work will also be focused on atomic force microscopy (AFM) and chemical force microscopy (CFM) analysis of the sample surfaces prepared with peel ply.

Development and Evaluation of Fracture Mechanics Test Methods for Sandwich Composites

Whereas the development of test methods for fracture mechanics of composite laminates has reached a high level of maturity in recent years, relatively little attention has been given to the development of fracture mechanics test methods for sandwich composites. Of the limited number of investigations performed to date, a majority have emphasized a particular sandwich material or the effects of specific environmental conditions. In general, the test methods proposed for fracture mechanics of sandwich composites have been found to be problematic due to problems in testing, crack propagation, and the analysis of test data.

Emphasis in this research project grant will be focused on the development of fracture mechanics test methods for sandwich composites. The ultimate goal of the proposed research is to establish draft ASTM standards for both Mode I and Mode II fracture toughness of sandwich composite materials.

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Inverse/Optimal Thermal Repair of Composites

The goal of this project is to develop a software tool that can be used in the field to optimize the repair of composites by ensuring that the temperature at the repair can be maintained at a specified level for the required duration. Producing the desired temperature field requires the specification of the heating intensity as a function of position and time consistent with the boundary conditions that exist at the time of repair. Since the boundary conditions are rarely known with sufficient accuracy, one of the project goals is to develop a method to estimate them from a diagnostic thermal analysis/test.

We aim to produce a tool that will tell the technician where to place the heating blankets, what the intensity of heating should be as a function of position, and how long the heating is to be applied. All of these results will come from a dynamic simulation of the heating process and subsequent optimization. The tool will be tested on repairs in the laboratory and in the field.

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Advanced Materials & Manufacturing Training Innovation Center (AMMTIC)

AMMTIC's mission is to develop and implement a strategic business plan that supports a self-sustaining advanced materials and manufacturing innovation facility and organization in Snohomish County and in Washington State that integrates public and private research and training initiatives designed to transform the aerospace and other advanced manufacturing workforce and keeps the United States globally competitive. This project will continue to build upon the current composite, aerospace and other manufacturing training programs currently offered through Edmonds Community College and its affiliates through the joint FAA Center of Excellence partnership.

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