Disruptive technologies power small composites aerostructure firms to market party
HPC guest columnist Bob Skillen draws from 25 years of experience in aircraft design and composite aircraft manufacturing in this commentary on the "why?" behind increasingly effective role played by small manufacturers in the composite aerostructures market.
#cuttingtools #space #autoclave
Today, you can whip out your smart phone to check-in at home, read and respond to e-mail, download data and surf the Internet. You can do this in a park, riding a train and, in some cases, on a commercial aircraft flight. Our kids photograph objects with their phones, then reproduce them at home with 3-D printers, using free apps compatible with commercially available CAD/CAM software. The accelerometers and other technology in our personal devices are far superior to what NASA used to get to the moon. A generation ago, none of this was possible. We all know this … in the general sense. But for advanced composites professionals, how does this change the game?
Narrowing the focus
Whether you make a rocket, a race car or a high-tech tennis racket, the common thread is high performance and the common environment is competition. That’s our business. And small businesses in our marketplace have never been in a stronger position.
Small businesses are like small cars. They are much more maneuverable and go farther on less fuel. But, there is much more to the analogy when you factor in the performance gains made possible by the computer revolution. Compared to the first microprocessor, introduced in 1971, modern CPUs are 4,000 times faster and use 1/5,000th of the energy. Today, $1 gets you computing capability that cost $50,000 in 1971!
As this explosion of computer processing capability intersects the maturing composites industry, the practical impact is enormous. The primary driver is capability. Tools that once were available only to primes and OEMs are now affordable and ubiquitous. The capability gap between large and small companies has narrowed dramatically.
The advantages of small business
Business is about satisfying the customer’s need for the best “value.” Although there are several variables in the value equation, cost is never, never an optional ingredient. Small businesses in our industry, equipped with modern tools, are typically in the best position to compete in terms of price. The lean structure, ease of communication and common lack of compartmentalization are all advantages. Operating costs are lower and efficiency is higher. In turn, much of the advanced composites industry centers on high-tech, relatively low-volume production.
Although much has been done to reduce touch labor and cycle times in high-volume industries (e.g., automotive), low-volume production of advanced aerocomposites is still the mainstay. The capitalization of tooling and automated equipment against small parts counts won’t fit the business model in a competitive environment. Technology advances and availability, along with the inherent efficiency of the small business, is a win-win in the advanced composites marketplace.
What is an advanced composite?
The term composite is not very definitive. The adjective, advanced, doesn’t make it much better. To keep it simple, an advanced composite describes the typical composite materials used in the aerospace industry: carbon fiber/epoxy structure with glass transition temperatures above 100°C/212°F. It can be defined by three basic criteria. The first criterion is fiber volume fraction (Fv). Strength-to-weight and stiffness-to-weight ratios are dependent on optimum resin content. Advanced composites, for this discussion, will have Fv values equal to or greater than 55 percent. The next criterion is void content, which is directly related to quality; void content will be limited to less than 1 percent. The last criterion is quality management. The small advanced composites business must have an acceptable quality management system — the aerospace sector requires AS9100 certification. Documentation of processes, procedures and testing are essential to customer satisfaction in terms of part quality. Also, the quality system must be subject to regular audit by an accredited outside agency. Given these criteria, the advanced composite category is much more confining.
Shape, methods and materials
2.1: Creating shapes. Complex shape generation has never been more convenient. Modern CAD software is exponentially more capable and affordable. Capability gains include generation and manipulation of complex surfaces with extreme accuracy. Virtual complex-curvature parts can be compared quickly with design parameters and virtually installed with mating structure in three dimensions. This design capability was once inconceivable and, not long ago, totally out of reach for small businesses.
Similarly, reverse engineering has benefitted from the computer-processing boom. Recreating the surface geometry of legacy aircraft, when spare parts are unavailable and original tooling is long since lost or destroyed, is a good example. Modern scanning equipment and software can convert existing surfaces into CAD models quickly, moving from the real world to the virtual world with staggering accuracy. And this information can be easily transmitted around the globe. The ability to generate and share this data is now common, available and affordable to small firms.
Although it is still compulsory to realize CAD designs in hard master models and tooling, what was once accomplished by skilled patternmakers is now done by CNC machinery, at speeds and with precision that are as accessible and affordable as they are remarkable. Very accurate 3-axis CNC routers with large worktables can be had for less than $100,000 (USD). Further, tool path software for these machines is available as add-on modules to CAD software. More complex, and certainly more expensive, is 5-axis CNC routing. But in many dedicated patternmaking shops, 3- and 5-axis routers have replaced traditional processes. If production volume does not justify an in-house 5-axis router, outsourcing work to a dedicated master modelmaker is a routine and effective alternative. Today, a 3-D model can be attached to an e-mail — never before have such mammoth quantities of technical data been so easily shared.
2.2: Methods and materials (Look, mom, no autoclave). Having designed complex surface geometry, the small advanced composites business must then produce it. Here, modern composite materials and processing methods have eliminated costly capital equipment — most notably, the autoclave.
For many years, high-quality advanced composite parts required elevated-temperature curing under high isostatic pressure. This environment was only available in a heated pressure vessel. But as parts were consolidated to reduce weight and assembly, autoclaves got larger. Because stress in the wall of a pressure vessel is a function of the radius of the cylinder times the operating pressure, large-diameter autoclaves are massive and can cost 30 to 40 times what is required for an equivalent-size ambient-pressure oven. When amortized into the per-part production cost, high-pressure curing of composite parts is enormously expensive. The question is “Is the expense justified?” More and more, the answer is “no.”
There have always been out-of-autoclave (OOA) composites, but high-performance part quality was directly dependent on the autoclave environment, and its value justified the cost. But in recent years, the performance difference between autoclaved and OOA parts has narrowed. Major prepreg suppliers offer OOA materials, and many data have been generated to validate their performance. OOA material performance is approaching parity with autoclaved materials. The value justification for autoclaved parts is difficult to make, especially for new programs. The large “aerospace-grade” composite structure is no longer an autoclave-only proposition. OOA methods and materials have drastically reduced the capital investment and, therefore, have increased the role of the smaller company in our marketplace.
There is little doubt about the increased capability of small businesses in this sector and little argument about their response time and cost advantages. Whether the industry is adapting to this change as rapidly as change is occurring is the question. Change is hard, but the view is definitely worth the climb.
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