Integrating design-to-production environments for aerospace composites

Upfront inclusion of performance and lifecycle requirements creates a better-engineered product. One challenge to accomplishing this in aerospace is the scale and complexity of wings, fuselages, and overall airframe structures. Many disciplines have a hand in design, using a range of analysis tools: finite element analysis (FEA), computational fluid dynamics (CFD), other multiphysics domains, system-wide engineering, and management methods.

However, disciplines with deep expertise are often separated by communications silos that interrupt flow, introducing opportunities for manual interpretation and errors. Integrating and automating digital capture of knowledge and data are important, particularly with composites – materials that have proven their value for strength and lightweighting.

Improving cost, speed, and production repeatability for composite laminates requires moving best-case design scenarios from the production floor back to the analysis and validation engineers. Stress analysts can shorten the design-to-manufacturing cycle by accounting for preferred production methods and system capabilities upfront in their analyses. There has always been give-and-take between upfront and downstream processes, but the burden of analysis is now shifting to proving what works best for manufacturing – machine performance, observed defects, and creating composite fiber geometries at faster speeds.

Incorporating manufacturing feedback

High-performance computing is driving computer-aided design/computer-aided engineering (CAD/CAE) systems, tool simulations, and machine controls for automated- and robotic-layup equipment. Stock materials and custom material formulations are advancing in tandem. Optimized wings and fuselages are evolving through topology and sizing-optimization software that shortens weeks or months of calculations to hours or days. This faster environment enables rivers of information to flow upstream, permitting customer-specific manufacturing approaches to inform early design-tool applications in CAD and CAE.

In this scenario, Collier Research Corp.’s HyperSizer software serves as an analysis hub calculating strength using OEM and supplier data for tow placement, fiber direction, machine turning, and steering-radii limits for ply layup – and by communicating with automated fiber placement (AFP) software such as CGTech’s Vericut Composite Programming (VCP) or Ingersoll Composite Programming System (iCPS) for evaluating laps and gaps, tolerances, and potential fiber wrinkling issues. As manufacturing successfully tests speeds and limits, this real-world information (the as-manufactured model) returns to design for correlation and simulation:

• What are the tradeoffs between tape width and steering radius, between experimental geometries and strength?
• How do these parameters combine with the material behavior of the resins and tape, the customer-specific pathway to innovation and final product?

With data from manufacturing feeding back to design analysis, time-tested case scenarios (templates) and fresh finite element analysis (FEA) results can help determine if new variations of the manufacturing design pass stress and weight requirements, and by what margin of safety. The design can be further tweaked until the optimal balance has been struck between ideal manufacturing and certification requirements.

The influence of manufacturing on design occurs from day one. The iterative cycle between design and manufacturing is shorter and the data captured in digital form is also more accurate.

Designing for certification

Such accuracy is of critical importance for flight certification. To achieve this, meshes are imported from the global finite element model (GFEM) into the software. Structural-component CAD data surfaces for fuselages, wings, etc., are meshed into shell, beam, and solid elements in FEA software such as Nastran, Abaqus, ANSYS, and OptiStruct along with the accompanying loads. Weight-bearing items are optimized for strength and positive margins of safety covering all potential failure modes.

Next, HyperSizer software optimizes the entire structure for manufacturing ply compatibility; the lightest design is determined at this stage as well as the most practical layup. Early manufacturing data guides upfront stress analysis for a quicker path to the most efficient layup sequence, which also sets conditions to help develop future automated processes.

Extensive evaluation of ply compatibility, entailing analysis of ply drop-offs and ply adds is just part of arriving at the most manufacturable configurations. Multiple team members can analyze and review options in the software database from their workstations. This is part of the growing communications loop that cuts time off design stages that are still partially sequential. Insights and final results are stored to document airworthiness certification.

Despite a long history in engineering of conducting hand-offs between silos of experts, contemporary digital engineering tools are interconnecting and bringing data and people together. Efforts by former CAD vendors to offer true science platforms for engineering have been crucial, from their significant investments in model-based definition to multiphysics. Subsets within the engineering market – such as Collier Research Corp., CGTech, and others working to bridge AFP composite automation/simulation with design tools – are also dedicated to integrating important processes beyond where they may already overlap. Down in the root CAD files, where our analyses circle back to update FEA models, data interoperability suppliers are aiding the move to all-digital by ensuring clean transfers and data integrity between different modeling engines and disciplines.

Accelerating composites’ timetable

Recognizing the industry growth of composites in commercial aerospace, defense, and private space ventures, the National Institute of Aerospace (NIA) manages the Advanced Composite Consortium (ACC) to promote material, design, and manufacturing advances. The long-term goal is reducing development and certification times by 30% within these markets.

While advances are already taking place in these discrete areas, integrating and automating these elements is vital to achieving affordable outcomes, high product quality, durability, and faster turnaround.

The ACC programs (see sidebar) are operating more efficiently and collaboratively in supporting stakeholders in the industry. During the analysis-and-optimization design phases, these programs are increasingly addressing advances in technologies such as AFP, along with changing parameters in layup and curing methods. Integrating these process approaches early and iteratively will help engineers improve quality and consistency in laminate fabrication, resulting in fewer defects and lower costs while streamlining the path to certification to reach those 30% faster goals sooner.

Collier Research Corp. 
www.hypersizer.com 

About the author: Craig Collier is president of Collier Research Corp. He can be reached at craig.collier@hypersizer.com or 757.825.0000.