A comprehensive collection of news and information about composites.
Posted by: Jeff Sloan25. September 2014
New CompositesWorld logo.
Sept. 23 was the Autumnal Equinox (here in the northern hemisphere), which means that fall has officially begun. The leaves on the trees are starting to change, adopting the yellow hue that portends of cooler weather to come. The summer's flowers are feeling the change as well, beginning their slow fade until the first frost.
Not to be outdone by Mother Nature, change is in the air at CompositesWorld (CW) as well. We are in the process of an image makeover that involves all of the products under the CW brand, including the CW Blog, the CW Weekly newsletter, the CW EXTRA newsletter, the CW conferences, our magazines and the CW website.
From the CompositesWorld front yard, metaphorical leaves changing.
We'll be rolling out the new branding in a few weeks. But in the meantime, we thought we'd offer you a taste of what's to come. We are proud of the new look, and hope that you will appreciate the graphical evolution.
In the meantime — and no matter the logo under which we operate — we'll keep providing the same reliable, authoritative composites content that you've come to know and love.
Compression molded thermoplastic composite clips like this one are seeing increased use in aerospace and other end markets. Thermoplastics are proving uncommonly attractive throughout the compoosites industry.
ITHEC 2014 (Oct. 27-28, Bremen, Germany) is a unique expert conference focusing on structural thermoplastic lightweight constructions in aerostructures, automotive and energy applications as well as hybrid materials and technologies. Over 350 international participants are expected, including leaders in the newest technology developments.
The accompanying International Exhibition on Thermoplastic Composites will present new lightweight concepts, materials trends and innovative manufacturing technologies.
Professor Dr.-Ing. Lothar Kroll, member of the ITHEC steering committee and head of the Institute for Lightweight Structural Construction at the Chemnitz Technical University (Chemnitz, Germany) sees innovations in lightweight construction increasingly based on the synergetic combination of a wide variety of materials. In order to address the current issue of separate material handling processing, multiple process steps and expensive joining technologies, the MERGE Excellence Cluster is developing efficient-resource mass-production manufacturing of high-performance, multi-functional structures. Kroll describes, “active components such as sensors, actuators and generators are integrated as electronic modules with in-line and in-situ processes to attain next-stage highly functional lightweight structures." This topic will be presented on Day Two of the conference.
On Day One, Johnson Controls (Burscheid, Germany) will discuss its work in the CAMISMA project to design and manufacture a hybrid carbon fiber/polyamide/metal seat back structure using recycled fibers, novel in situ polymerized unidirectional and nonwoven preforms, glass-reinforced direct long fiber injection material and steel inserts, which are integrated and attached via a one-shot combined thermoforming and injection molding process to cut weight over 40 percent vs. metal with comparable cost, cycle time and safety performance.
Other highlights include:
“Automobile CFRP Production and Potentials for Thermoplastic Composites” keynote from BMW (Landshut, Germany)
“Smart Production of Hybrid Material Automotive Structures at the Wolfsburg Open Hybrid LabFactory”
“New Concepts for Structure Parts Based on Short Fiber-reinforced Injection Molding” by Airbus (Hamburg and Bremen, Germany)
“Development of RTM TP with Low Viscosity Thermoplastics” by CETIM (Nantes, France)
“Recent Japanese Activity in CFRTP for Mass Production Automobiles”
“Electro Bonded Laminates for High Performance 3D Morphing Structures” by ETH Zurich (Switzerland)
“How to Qualify an Offshore Thermoplastic Composite Pipe System” by Airborne Oil & Gas B.V (Ijmuiden, NL)
“Latest Developments in Thermoplastic Composites for Automotive Applications” by FAURECIA (Paris, France)
The Erlangen carrier developed by the Institute of Polymer Technology (Lehrstuhl für Kunststofftechnik or LKT, Erlangen, Germany) illustrates the latest in-line processes for joining metals to plastics and fiber-reinforced composites, offering reduced cost and time via In-Mold-Assembly (IMA) compared to Post-Mold-Assembly (PMA).
This technology is advancing rapidly, with companies like injection molding machine manufacturer KraussMaffei (Munich, Germany) seeing not only a burgeoning market for hybrid solutions, but also increasing opportunity to replace traditional materials with reinforced thermoplastics which offer more complex geometry, faster cycle times and integration not just of different materials but also of production steps like joining and finishing, where color can be integrated into the molding operation vs. post-mold painting.
The breadth and depth of thermoplastic composites information being offered at ITHEC make this an event well worth attending!
Teijin introduced this passenger cell concept in 2011 to demonstrate the capabilities of its 60-second carbon fiber/thermoplastics manufacturing process. Since then, we've seen and heard little about the process.
In March 2011, carbon fiber manufacturer Teijin (Tokyo, Japan) generated a lot of composites industry buzz when it announced that it had developed a 60-second process for the manufacture of carbon fiber/thermoplastic composite automotive structures. The company reported that the process uses press forming and was based on three intermediate material forms: Unidirectional carbon fiber, isotropic carbon fiber and long fiber thermoplastic pellet.
Then, in December 2011, Teijin announced that it and General Motors (GM) had created a joint venture to work on this high-speed molding process together. Soon after, in early 2012, Teijin opened the doors of the Teijin Composites Application Center (TCAC) in Auburn Hills, Mich., USA, where GM/Teijin joint-venture/co-development work would be done.
Both companies played their cards close to the vest regarding details of the process and its application. In what would prove to be a voluminous discourse on this topic, GM officials told CompositesWorld at the time that the goal was development of a production part: "A timeline for this development process has not been set, GM said, but acknowledged that integration of carbon fiber composites in a production vehicle would require 'from ground up' design and enigneering to optimize material use and minimize weight."
Since then, there has been virtually no information revealed about the Teijin/GM process, and queries by CompositesWorld have gone unanswered. We have, on occasion, run into composites professionals who have been in the TCAC and have seen the process, but are bound by a non-disclosure agreement (NDA). We did, however, enjoy one fact-filled exposition from one person who had knowledge of the process: "The 60-second cycle time is legitimate. Sorry, that's all I can tell you . . ."
Then, about a year ago Teijin reported that this high-speed process had been named Sereebo (Save the Earth, Revolutionary & Evolutionary Carbon) and was being used by Nikon to make structural parts for a digital SLR camera.
Finally, fast-forward to last week (Sept. 16), when a new press release was issued by Teijin. It said, in essence, "We're still working on this process, it's called Sereebo, it's been used by Nikon and our joint venture with General Motors continues." It is, effectively, a press release that says very little. Or, it might say much.
Secrecy and protection of proprietary information is not uncommon in the composites industry. In fact, the composites industry is infamous for its buttoned lips and NDAs — almost every composites fabricator has, or thinks he/she has, a secret sauce of some sort that provides competitive advantage. Teijin and GM certainly deserve much credit for having kept the lid on this process for as long as they have.
The issuing of a say-nothing press release like the one Teijin sent last week might be a way of reminding the market that an important technology is still in the works and is still none of your business. And this might have been prompted by BMW's openess regarding the carbon fiber process it developed for the manufacture of its i3 and i8 cars, which have entered the market to much fanfare over the last year.
What we hope, however, is that Teijin and GM's silence is not indicative of problems with the Sereebo process. The combination of thermoplastics, carbon fiber and compression molding is promising for automotive and getting much attention from a variety of material and equipment suppliers. The composites industry would benefit greatly from a high-speed, thermoplastics-based manufacturing process that uses technology (press molding) that has familiarity in the automotive industry already.
It would be an encouragement to the composites and automotive industries alike if the next Teijin press release announced that Sereebo was being used to mold production parts for a near-future GM car or truck.
Posted by: Jeff Sloan23. September 2014
Sierra Nevada's Dream Chaser.
After months of speculation and breath-holding, NASA finally announced last week the recipients of its Commercial Crew Transportation Capability (CCtCap) grant money, designed to fund development of space vehicles to transport U.S. astronauts to and from the International Space Station (ISS).
There were three companies, and their craft, vying for the funds: SpaceX (Crew Dragon), Boeing (CST-100) and Sierra Nevada (Dream Chaser). Only two of three would be picked to receive funding and speculation suggested that SpaceX would be a winner, with Sierra Nevada likely to take the second spot. On Sept. 16, however, we got the news that the odd man out was Sierra Nevada. Boeing was awarded $4.2 billion to further development of its CST-100 and SpaceX was given $2.6 billion for its Crew Dragon.
The question at Colorado-based Sierra Nevada is, "Now what?" Company officials have said that they would like to complete development and testing of the composites-intensive Dream Chaser, and that is probably a good idea, particularly if the company wants to attract funding from elsewhere, like Europe. But going forward will require at least some in-house investment. Employees who worked on Dream Chaser deserve a lot of credit for bringing the craft as far along as they have, and so quickly. We hope that for their sake Sierra Nevada can find new suitors soon so that Dream Chaser can, ultimately, fulfill its promise.
Posted by: Ginger Gardiner18. September 2014
Direct NCU transmission of different single layer CFRP prepregs assessing level of impregnation (LOI). SOURCE: The Ultran Group
Several weeks ago I blogged about 2014 Small Business Innovation Research (SBIR) funding solicitation being short on composites. The Ultran Group (State College, Pa., USA) commented, pointing out that they have a composites-related 2014 SBIR award. Indeed they do, awarded via the U.S. Department of Defense (DOD) and U.S. Air Force titled, “Standard Test Method for Prepreg Resin Impregnation Level.” The goal of the research is to develop standardized test methods for prepreg resin impregnation levels.
My first reaction was, “Don’t they already have a test for this?” and then my eyes kind of glazed over at the words “Standard Test Method”, for which I should be chastised, because the story of what’s going on here is anything but dull. In fact, The Ultran Group has already demonstrated that NCU can detect LOI changes of less than 1 percent. And this technology has the potential for integration into automated tape laying systems, measuring porosity on the fly, real-time.
No trustworthy standard test
According to The Ultran Group CEO Anuj Bhardwaj, “There really is no trustworthy standard method to measure level of impregnation (LOI) in prepreg.” He says the best known method is referred to as the ‘water uptake test’ where prepreg is sandwiched between two layers of coated aluminum and weight is measured before and after immersion in water. The increase in weight equals the amount of water absorbed and is supposed to indicate the level of impregnation or lack thereof. The idea is that if the prepreg reinforcement is fully impregnated with resin, then there is no room for water to be absorbed. But out-of-autoclave (OOA) prepregs are NOT fully impregnated. From my Jan 2011 article “Out-of-autoclave prepregs: Hype or revolution?”:
According to Ridgard, most OOA prepregs for hand layup incorporate dry fiber paths to some degree, which permit air extraction during cure but result in less than 100 percent impregnation.
ACG’s Ridgard explains that in OOA processing, removal of volatiles, which include not only air entrapped during layup but also the moisture (1 to 2 percent) that epoxies absorb when they are exposed to ambient air, involves an “edge-breathing” strategy. The laminate edges must be in contact with the breather and materials must be arranged in a way that maintains air escape paths.
Chris Ridgard, now at Cytec, was one of the first to preach edge breathing for low void content laminates using OOA prepregs. So here is at least one serious issue when you’re testing prepregs for LOI. Hold this thought. I’ll come back to it.
Non-contact Ultrasound (NCU) and inline quality control of composites
The Ultran Group’s web-site features a post titled “Shifting Gears” which gives a good background on their development of NCU. I’ve compiled the highlights:
Ten years ago, NCU was an obscure and nascent technology, unknown to virtually all testing experts. Today, it is quickly growing in adoption as more and more companies are looking for competitive quality control solutions. While ultrasound has been widely used for decades, it has been limited by the need for contact or liquid coupling. The Ultran Group has invested many years of R&D into overcoming these issues and innovating NCU transducer technology. Having delivered its first set of 24/7 in-process testing systems in 2012, the company is now deploying many such systems and is increasingly moving towards providing high-throughput, 100 percent inspection solutions for production quality control.
Continuously monitoring the upper and lower control limits (UCL and LCL) of a manufacturing process allows for instant feedback and control, reducing waste and saving money.
SOURCE: The Ultran Group presentation at JEC 2014.
Prepreg manufacturers already using multi-channel NCU systems
Bhardwaj explains that even though the use of NCU for prepreg LOI measurement is not widely known, “we’ve already sold these systems to leading aerospace-grade prepreg manufacturers for online/inline inspection.” Described as “multi-channel”, these systems use arrays of transducers — 8, 16, 32 or more — with transmitters on one side of the prepreg and receivers on the other (i.e. bottom vs. top) across the entire width of the sheet being manufactured.
The Ultran Group’s software then creates rolling line scans or C-scans of the material/parts being inspected. As shown in the diagram of UCL vs. LCL, it’s relatively easy to then watch for aberrations and react quickly as they start to appear. In fact, the software can do that on its own, with alarms for when measurements are nearing prescribed limits.
The wetness or porosity of carbon fiber prepreg can be directly correlated to ultrasonic signal amplitude in non-contact analysis. SOURCE: The Ultran Group
“UT is very sensitive to a change in the medium through which the sound passes,” notes Bhardwaj, “in this case, the strength of the signal will decrease with increased porosity in the prepreg.” He explains that the prepreggers using these systems have developed their own correlation between NCU transmittance and prepreg LOI, but this knowledge is obviously proprietary to those companies. “This SBIR gives us the opportunity to build independent correlations from the bottom up and make all of this public to the industry,” says Bhardwaj. Basically, the work is to develop calibrations based on investigating the many different transducer and signal variables and then produce curves correlating the transmission signals with porosity, LOI and other prepreg sheet properties. “We have to filter out the noise that we don’t want to measure and show reliability in measuring LOI for prepregs regardless of fiber weights, resin types, etc.” Then, that understanding will be used to draft an ASTM standard test method.
Aurora Flight Sciences (Manassas, Va., USA) is The Ultran Group’s partner in this SBIR development work and both companies will be giving presentations at the upcoming CAMX show (Oct. 13-16, Orlando, Fla., USA).
Anuj Bhardwaj will be presenting “Application of Advanced Non-Contact Ultrasound for Composite Material Qualification” on Wed., Oct. 15 at 10:00 am in Room W221 B. He will be followed by Konstantine Fetfatsidis from Aurora Flight Sciences at 10:30 am in the same location with “Correlation of Prepreg Resin Impregnation Levels to Resulting Composite Part Porosity using Non Contact Ultrasound.”
Water uptake test and OOA composites
Back to this test method and its issues. When I Google’d this, I found a 2014 Hexcel patent that outlines the procedure, which I’ve pasted below. Note underneath the test procedure ranges of test values the patent authors considered acceptable, yet further down the patent recommends prepreg that most preferably has a water pick up of less than 3 percent. Remember, The Ultran Group has demonstrated NCU sensitivity to prepreg LOI of less than 1 percent.
From Patent EP2703141A1:
Water pick up values for the uncured prepreg moulding material and tows of the invention may be in the range of from 1 to 90%, 5 to 85%, 10 to 80%, 15 to 75%, 15 to 70%, 15 to 60%, 15 to 50%, 15 to 40%, 15 to 35%, 15 to 30%, 20 to 30%, 25 to 30% and/or combinations of the aforesaid ranges.
The preferred prepregs contain a low level of voids between the tows. It is therefore preferred that each prepreg and the prepreg stack has a water pick up value of less than 15 % or less than 9 %, more preferably less than 6 %, most preferably less than 3 %.
The U.S. Air Force has estimated the accuracy/repeatability of the water pick-up test to be +/-5 percent, but it wants a test with an accuracy of +/-1 percent and specifically mentions OOA materials:
Partial impregnation is a common practice used to manufacture prepreg materials for the defense industry while full impregnation is used for automated tape materials. The products are used on multiple DoD aircraft platforms to benefit part quality through improved processability. Air transport occurs via different mechanism depending on the product form (dry mid-plane of prepreg verses interstitial gap in tow/tape placement). Successful air evacuation is especially vital to new generation, vacuum bag only (atmospheric pressure only) cured systems. Improved processability translates to improved repeatability and generally improved mechanical performance. (Link to full text)
The Hexcel patent also targets OOA processed prepregs. This makes sense. A company well known for developing OOA composites technology once said, “Pressure solves a lot of problems.” Until now, resin impregnation and porosity could vary and the autoclave basically smoothed out most potential issues. But you can see that OOA prepregs start out with areas of no impregnation. So if you’re getting porosity using an OOA prepreg, how can you be sure it’s your processing variables vs. your raw material? It becomes clearer why this test method is important as the aerospace composites industry steps toward wider use of OOA prepregs, especially in primary structure. You can also see the potential for game-changing quality control in automated tape laying of not just thermosets, but also thermoplastics, which also is a path toward OOA processing and one where real-time, on-the-fly measurement of in situ consolidation and laminate porosity could prove very interesting indeed.
P.S. Research funding for the same basic topic was awarded to Nokomis, Inc. (Charleroi, Pa., USA) for a project titled, “Standard Inline Non-Destructive Determination of Prepreg Resin Impregnation Level.” It is described as directly supporting the Joint Strike Fighter (JSF) program by improving quality control of composite material during manufacturing.