Description: The nondestructive characterization of advanced composites, such as carbon-fiber reinforced polymers (cfrp), by electromagnetic means is well established. What is needed to advance the state of the art are sophisticated inversion algorithms that allow layup and impact damage to be determined in localized regions, which means that more traditional methods of model-based inverse methods must be replaced by voxel-based inverse methods. Thus, one will be able to better distinguish such things as delaminations from fiber-breakage due to impact damage, or other parameters that characterize the mechanical of the cfrp structure, such as elastic modulus and Poisson's ratio on a voxel-by-voxel basis. This information can then be input to damage evolution models. We describe two such methods, bilinear conjugate-gradients and set-theoretic estimation. The challenge is to extend these methods to anisotropic materials. We do that in this project, and will develop the algorithms for inclusion in our proprietary eddy-current, VIC-3D(R) during Phase II. In addition, we continue our program of discovering and exploiting parallelism in VIC-3D(R) to speed up the modeling and processing that involve massive data generation.

Benefits: NASA LaRC already owns a copy of VIC-3D(R) which it uses for modeling forward and inverse problems in eddy-current NDE. With the enhancements proposed in this project, NASA LaRC will be able to extend its modeling capability to more accurately characterize damage conditions in cfrps, as well as run large problems more efficiently.

There are 35 commercial and university research institutions around the world that own copies of VIC-3D(R) which they use for the same purposes as NASA LaRC. The will have the same advantages with the enhanced version of VIC-3D(R). Furthermore, aerospace companies, such as Boeing, that are developing vehicles that use advanced composites, such as cfrps, will be able to use the enhanced version of VID-3D(R). The enhance code can also be used to support the manufacturing of advanced composites. Purdue University is developing a Center for Composites Manufacturing and Simulation which is part of a $250 million US Dept. of Energy initiative to support President Barack Obama's National Network for Manufacturing Innovation. Advanced manufacturing represents 25 percent of the Indiana economy, and the State of Indiana has a strong background in composite materials research, development and manufacturing, with about 50 companies across the state contributing to this sector. Though VTL is not a part of this consortium at this time, we expect that our Phase II research will yield an enhanced version of VIC-3D(R) that will not only support the work of this consortium, but would lead to an invitation for VTL to join it.