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Software Toolset for Rapid Finite Element (FE) Mesh Generation of As-Built Large Laminated Composite Structural Components


TECHNOLOGY AREA(S): Materials, Air Platform

OBJECTIVE: Develop a software toolkit enabling automated generation of Finite Element (FE) meshes to rapidly assess structural capability of as-built and damaged composite structures from Computed Tomography (CT) scan data that accurately captures ply layers, ply-orientations, ply drops, and fiber-resin densities. The mesh should include manufacturing defects such as waviness, air pockets, porosities, and other CT-revealed observable anomalies/defects/damages.

DESCRIPTION: Advanced rotors for vertical lift aircraft and wings on many U.S. Navy fixed wing aircraft are complex assemblies made primarily from composites. CT scans can provide the foundation for analyses of these structures that accurately model manufacturing defects and the quality of a repair. The references cited demonstrate algorithm technologies capable of transitioning CT scans into composite structural FE models. An FE model that accurately captures the in-situ condition of a questionable manufactured part will improve speed, accuracy and consistency in disposition instructions for these non-conforming wings and rotor blades. An FE model that accurately captures the in-situ condition of a new repair will provide stress and strain comparisons to adjacent authorized high stress locations of identical materials. The span of flaw sizes between what is acceptable and what is unacceptable is very large in complex composite structures. Converting the CT scans with authorized manufacturing defects into an FE mesh will provide an analytical stress threshold for assessing these gray areas and for developing repairs to the scanned component. The proposed solution should address the following key requirements:(A) The ability to generate accurate subsurface geometry data for a composite structure that includes all manufacturing defects such as wrinkles and voids at ply interfaces. (B) The ability to automate the conversion from geometry data to structural FE models, where the structural FE models will reveal the influence of these defects on strength and fatigue performance for do-no-harm repairs, life-improvement design changes, and disposition instructions.The finite element mesh must be applicable to progressive damage analysis of laminated composite structure including manufacturing defects such as wrinkles, marcels, foreign object debris, and ply interface voids. Besides developing possible repairs for field-damaged components, brand new parts will benefit from this software toolkit. Manufacturing processes used to produce thick composite structures can generate defects that could impact their performance and service life. Determining disposition instructions for these new components involves Material Review Board (MRB) efforts that can be long and tiresome. Existing tools used to measure defects with the attempted recreation of these defects in test coupons can result in a perpetually delayed decision about the part’s acceptability. The difficulty in assessing defects may result in storing the rotor blades or wings in a warehouse until technological capabilities become available to determine what actions to take: scrap, repair, or sell as-is.Rapidly built structural diagnostic FE models for evaluating structural integrity using an automated interpretation of the nondestructive measurement data will fill a necessary technological need. FE modeling of the entire data-driven blade or wing assembly will assist in determining the margins of safety for flight qualification. CT conversion of field-damaged large parts to an FE model that captures undamaged adjacent authorized manufacturing defects will provide stress limit thresholds for safely establishing repairs to the component scanned. CT data conversion of flawed new components will greatly assist in MRB decisions. The FE mesh can provide a model for design modifications. This project will merge state-of-the-art nondestructive measurements with composite durability and damage tolerance analyses into an add-on toolkit package for a commercial FE software program.

PHASE I: Demonstrate a semi-automated transition of CT-based measurements of a rotor blade section or wing section to a high-fidelity FE mesh that captures the composite material structure including ply-orientations with a refined mesh surrounding the to-scale, three-dimensional manufacturing defects. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Integrate the automated analysis toolkit into a commercial finite element modeling software for use in high performance computing centers. Demonstrate progressive damage and structural fatigue analysis capability on a rotor blade or wing.

PHASE III: Perform full-scale testing on NAVAIR-supplied structures to validate progressive damage predictive capability. Make any corrections identified during full scale testing and finalize toolkit. Transition software toolkit into fleet overhaul facilities, fleet support teams, and OEM commercial markets.This technology will assist aircraft, automotive, and recreational vehicle industries that use advanced composite materials. This toolkit will assess the strength of prototype composite structural designs and will identify static and fatigue test procedure limits for those prototypes. This toolkit will improve speed, accuracy, and consistency in material review board decisions on non-conforming composite parts.

KEYWORDS: Composite Wings, Rotors, CT Scan, Finite Element, Damage Progression, Manufacturing Defects, Composite Repairs, Computed Tomography


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