Fiber placement enables production of complex composite structures in a cost-effective manner, and further enables structures exhibiting steered or curvilinear fiber paths. Steered fiber architecture may improve structural efficiency by tailoring local fiber orientation to the local internal load path. Few consider the advantages of fiber steering, due to limitations in available design and analysis tools. This invention addresses integrated design and analysis tools for fiber placement, including robust knowledge-based design software, and optimization strategies for enabling fiber steering as an independent variable with laminate family and laminate thickness. Four independent tow geometric definition methods are demonstrated, including a novel definition for tows within one layer defined relative to tows in alternate layers. Potential weight savings of 3-10% are demonstrated, at no additional cost to manufacture.

This invention also covers a tool currently in development at the University of Kansas. The Steered Composite Analysis and Design System (SCADS) represents an integrated design for manufacturing/fiber steering system for the fiber placement process. Preliminary through detailed design simulation is enabled by producing theoretical paths of individual tows for a set of user-defined manufacturing criteria, to include input tool geometry, tow material and desired path parameters. This detailed tow information historically has resided with the manufacturer of the fiber placement hardware, and thus is not available throughout the design phase. As such, fiber placed components are generally designed as hand lay-up components, preventing a consideration of curvilinear fiber reinforcement and neglecting the requirements of the actual manufacturing process. SCADS allows visualization of actual tow geometry, to include quantifiable computational assessments of common geometric flaws such as tow gaps and overlaps. In addition, SCADS is capable of extracting actual fiber orientations within each layer of a composite structure at discrete locations, providing true local laminate definition for detailed analysis. Additional analytical tool development includes solution methods for materials with continuously varying mechanical properties, to enable optimal curvilinear fiber paths. In particular, we have identified geometric methods to define what we call a "family ply." Although layers oriented at specific angle orientations with respect to one another are common, this is only true for linear orientations. We expand this thought to include local orientation with respect to guiding curvilinear paths. Our approaches for optimizing the family (local orientations) at all locations in a structure are novel. Our approaches for either initial population of family orientations across a part for subsequent sectioning into plies and our approach for "smoothing" a piecewise discontinuous vector plot of desired orientations into a manufacturable path are both novel.

Described tools and processes are the first available to the composite designer that readily allow him or her to evaluate alternate steering patterns during either preliminary or detailed design. Described analytical approaches provide diverse yet straight-forward methods to accomplish a difficult task -- the inclusion of fiber orientation and fiber path as an independent design variable. Availability of integrated design and analysis tools provides a formal process which will enable a divergence from the common practice of designing fiber placed components in the same manner as conventional hand layup components, and will enable consideration of fiber steering. Research activities outlined offer significant increases in design and analysis capability for the fiber placement process, particularly with respect to steered fibers. This increased capability has the potential to offer significant weight savings in composite structural applications, at no additional cost.

File Number: 2003 FY 18 

Web site: http://www.engr.ku.edu/ae/

Other Information: *State of Development* Available for licensing.