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Non-destructive testing on composite parts

News International-French

29 Jul 2011

New automation tools and an advanced composites engineering environment support both a wide range of design methodologies and simulation of manufacturing processes.

(Published on June-July 2005 – JEC Magazine #18)




Recent years have seen dramatic and fundamental changes in composites engineering. These changes have been led in part by the aerospace industry, which has seen steady, progressive innovation at Airbus in Europe as well as a commitment to composite materials design and manufacture on the Boeing 787 Dreamliner programme in the U.S. and Japan.


The evolving field of composites design


With the changes have come challenges, however. First of all, with the increased use of composites for aero-structures and the greater size and complexity of individual parts, engineers need software with more flexible design capabilities. For example, the design tasks involved in creating a composite fuselage are far different from those required to create an inlet duct or a strut. For this reason, a one-size-fits-all tool ends up being a poor fit for all three projects, and software that is supposed to help the designer work efficiently can itself become a hindrance.


Design methodologies vary widely, not only part to part, but even from one region of a design to another. Engineers creating largescale parts, for instance, often subdivide the part into zones. For designs with particularly complex surfaces or performance requirements, engineers also may need to define a series of grids, each of which has a particular characteristic or performance requirement.


Second, because composite parts have grown larger and more complex, there is a need for automation of repetitive tasks. The design of composite parts involves detailed documentation of everything from material characteristics to manufacturing sequences and instructions. This information is vital to a host of people involved in the creation of the part, including designers, stress analysts, purchasers, and manufacturing engineers. For a part involving hundreds of plies, manually entering this information is time-consuming and prone to error. In the event of a redesign, the cost of re-entering this information is significant.


Finally, the need for simulation has increased. The surfaces of aerospace parts are often complex, and the strength requirements they must meet are stringent. Engineers must verify, early in product development, that a part design and its manufacturing process are optimal. Accurate capture of design data and early simulation of as-manufactured parts enable product developers to prove out designs digitally, avoiding the costs associated with redesigning and with iterative physical prototyping.



In response to the demand for greater design, automation, and simulation capabilities, the software used for composites design and manufacture has become more flexible as well, incorporating new design techniques and providing data and simulation for a range of materials and manufacturing processes. The use of software such as FiberSIM® enables engineers to work in the optimum mode to create each part, automate repetitive design tasks, and manufacture high-quality products in less time.


Manufacturing simulation


The most recent release of FiberSIM includes the option of an Advanced Composite Engineering EnvironmentTM (ACEE). The object of the ACEE is to provide software tools for the full range of tasks, methodologies, and manufacturing processes that engineers designing in composites may encounter. The engineer may then select the methods appropriate to creating the design at hand.


Among the new design functionalities in the software are:
- Zone-based design for structural components – spars, for instance. The software now provides engineers with flexible ways to quickly create zones that define the requirements of different regions of a part. The software automatically generates plies that take on the characteristics of their zones, such as boundary, material, and orientation. This capability automates a repetitive design task and reduces time formerly spent manually defining laminates.
- Grid-based design for large, complex aero-structures such as fuselage sections and wing panels. Grids are subsets of zones that provide an additional level of granularity to manage very complex design and manufacturing constraints. Engineers can specify laminate requirements and define plies using a profile that stipulates how ply boundaries drop off or stagger between adjacent zones. The software then automatically creates the corresponding ply boundaries and transitions, eliminating what was formerly a painstaking, error-prone manual process.
- Variable-offset surface modelling. One of the advantages of designing with composites is that plies of a specific material type and orientation can be placed on portions of a part that require greater strength. On such parts, the surface created by the built-up plies varies in thickness. Tasks that require accurate representation of these surfaces, such as creating mock-up solids and inner mould lines, were previously done manually. Automated design tools in the ACEE generate variable offset surfaces for the part. Engineers can then automatically account for manufacturing tolerances and ply thickness when they generate mock-up surfaces for interference checking, mating surfaces that model where two parts join together, and tooling surfaces for manufacturing.
- Smart darting and splicing. The process of creating darts and splices has always been heavily manual. Earlier versions of the software provided some automation, but inserting a new ply required the engineer to redefine by hand all the staggered darts and splices in the sequence following the insert. FiberSIM® 5.0 allows engineers to define the darts and splices of the first ply, then define the rules for staggering subsequent darts and splices. The software populates the design with darts and splices, and it automatically updates the staggering if an additional ply is inserted into the laminate. On a small part, this tool saves significant engineering time; on the design and redesign of a large-scale aero-structure such as a fuselage, it is vital.



Manufacturing processes


In addition to the ACEE, this composites engineering software has retained the simulation capabilities of previous releases, including simulations of ply lay-up, resin transfer moulding, and fibre placement.


New tools available with the software can simulate manufacturing processes such as drape forming, tape placement and forming or stamping. The simulation tools provide engineers with increased confidence at the design level that the part will be producible, meet all requirements and perform optimally in the field.


Simulation tools give designers and structural engineers the capability to evaluate in advance the efficacy of the manufacturing processes selected for a product. The tools also help companies to avoid surprises such as unanticipated material behaviour or manufacturing difficulties, which could lead to delays and cost overruns.




Instead of trying to force designers to follow a single path and accept limited manufacturing processes, FiberSIM® and its Advanced Composite Engineering Environment reflect the way that engineers think about product development. The software supports the complete range of composite materials and manufacturing processes, providing maximum design flexibility, efficiency, and ease of use. By speeding the design process, the software leaves engineers free to focus their expertise on design innovation, process selection, and part quality.