SBIR-STTR Award

Recent advancements in industrial Computed Tomography (CT), including improved X-ray detectors and tomographic reconstruction algorithms, have enabled enhanced identification of material anomalies and manufacturing defects. For composite structures, this nondestructive inspection methodology can enable dimensionally-accurate internal structure characterization of a component, facilitating the inspection process of defect distributions in as-built components before they enter service. Despite the advancements, there is an immediate need to develop digital models that are representatively identical to physical parts to enable accurate predictions of the load bearing capabilities of the components. A streamlined workflow is necessary to digitally thread the image segmentation process of the CT scans with the component characteristics (down to the ply level) that are computer simulation-ready. Ideally, the workflow should automatically assign fiber orientations (for fiber reinforced composites), create a volumetric mesh, and define appropriate inputs for different FEA packages, producing a modeling process that is robust and repeatable. Such high-accuracy computational models are expected to capture component-specific defects (e.g., ply interface voids, wrinkles) and further provide a more accurate prediction of stress concentrations and quantitative damage tolerance assessments. This work will be conducted in partnership with Drexel University to leverage its research expertise in composite damage mechanics.

Benefit:
To accurately quantify and predict the criticality and limitations of laminated composite structures in service, it is essential to accurately create digital geometries that are identical to the physical components. While computed tomography (CT) is not new, there is an opportunity to merge the high accuracy representation that is CT with the predictive power of finite element simulations. This will immensely benefit the Department of Defense as it will provide not only predictability of component service life but also facilitate future design and manufacturing considerations of mission critical parts. Successful implementation of a streamlined CT to simulation workflow can become a commercial toolkit to be used in industries that utilize advanced composite parts, providing superior quality control merged with realistic service life predictions.

Keywords:
segmentation, segmentation, Finite Element Analysis, life assessment, ply reconstruction, structural integrity, computed tomography

The objective of this project is to develop advanced capabilities for processing computed tomography (CT) data into finite element meshes suitable for analyzing the structural response of composite structures. This will include incorporation of manufacturing defects and damage sustained in operation which is detectable in the CT data. This will be done by developing new geometry-based segmentation techniques that can directly construct geometry from CT image data as well as developing robust capabilities to determine fiber orientation and ply stacking sequences from the image data. These capabilities will be combined with existing capabilities for segmentation-based geometry construction and mesh generation capabilities (with suitable enhancements as needed) to produce an overall system which can efficiently build complete finite element input data suitable for analysis purposes.

Benefit:
The technologies developed in this project will be able to be applied to a wide variety of DON/DoD platforms and programs (as well as other agencies such as NASA and commercial users). The use of composite materials for structurally critical parts will continue to increase along with performance requirements. Although in many ways composite parts are more damage tolerant than metallic parts, variability in the manufacturing process along with the lack of understanding of how this affects the potential failure modes of composite structures means that these parts must be overengineered, reducing potential performance and still they may fail to meet their expected service lifetimes in the field. Only in the past few years has CT scanning technology reached a level where it is practical to scan large enough parts at a sufficient resolution to obtain enough information to model the behavior of the as-built structure including manufacturing defects and damage to better understand these issues. Ultimately, we envision that critical parts would be scanned at manufacturing time to fully document the as-built structure and then again at various intervals in service to track the overall health of the structure to fully understand these issues. This would then allow the realization of a true digital twin of such a structure which can be validated against such data.

Keywords:
Damage, computed tomography, Mesh Generation, Composite