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A comprehensive collection of news and information about composites.

Posted by: Ginger Gardiner

18. 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.



A multi-channel NCU array can continuously analyze prepreg web or even cured parts.
SOURCE: The Ultran Group presentation at JEC 2014.

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.


The relationship between the desired material property and ultrasonic amplitude can be formulated using statistical analysis on experimental results.
SOURCE: The Ultran Group

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:
The water pick up test is conducted as follows. Six strips of prepreg are cut of size 100 (+/-2) mm x 100 (+/-2) mm. Any backing sheet material is removed. The samples are weighed near the nearest 0.001 g (W1). The strips are located between PTFE backed aluminium plates so that 15 mm of the prepreg strip protrudes from the assembly of PTFE backed plates on one end and whereby the fibre orientation of the prepreg is extends along the protruding part. A clamp is placed on the opposite end, and 5 mm of the protruding part is immersed in water having a temperature of 23°C, relative air humidity of 50% +/- 35%, and at an ambient temperature of 23°C. After 5 minutes of immersion the sample is removed from the water and any exterior water is removed with blotting paper. The sample is then weighed again W2. The percentage of water uptake WPU(%) is then calculated by averaging the measured weights for the six samples as follows: WPU(%)=[(-)/)x100. The WPU(%) is indicative of the Degree of Resin Impregnation (DRI).

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.

Posted by: Jeff Sloan

11. September 2014

PCD veined drill, for composites drilling. (Source: Precorp)

This is IMTS week in Chicago, and North America's largest machine tool show does a great job catering to the diverse and demanding requriements of metals cutting, drilling, reaming and other operations, and if the crowds on the show floor are a reliable indicator, we are in the midst of a burgeoning manufacturing economy.

However, if your job is to trim, router or drill composite structures, finding products targeted to your application is a little more challening. Not impossible, but challenging. Indeed, we use many of the same terms to describe composites machining as we do metals machining, but the similarities end there. Composite parts — by definition non-homogenous — behave very differently when cut or drilled by a machine tool, splintering and powdering in the process. At the same time, machining composites comes with its own set of risks, with delamination topping the list.

Because of this, composites require machine tools specially designed for the work, and this is where the IMTS challenge comes in. The fact is that "composites" to many machine tool manufacturers is a foreign word — representing an exotic, small, odd corner of the materials and manufacturing community. However, a little digging through the aisles reveals some big and small machine tool suppliers who've made a name for themselves in the composites machine tool market, including Sandvik Coromant, Precorp (now a part of Sandvik Coromant), AMAMCO, LMT Onsrud, Seco, SGS, Niagara Cutter and others. As a result of work done by suppliers like these, the industry has seen dramatic increases in tool life, cutting quality and industry machining expertise over the last several years. Even CNC software specialist CGTech has gotten in on the act with the development of a product designed to simulate composites machining and drilling.

The biggest consumer of technology for composites machining is the aerospace market, which buys millions of dollars worth of machine tools annually to machine and drill composite fuselage, wing, tail and other structures — primarily for the attachment of fasteners. In this vein, the next big program on the radar is the Boeing 777X, which is being redesigned to include some of the largest carbon fiber composite wings made today. Some of the machine tool suppliers mentioned above are working hard right now to be selected to supply product for 777X wing manufacture — a program that promises to years of potentially lucrative work for the lucky winner(s). 

Of course, planemakers like Boeing and Airbus would like few things more than to rid themselves (mostly, if not completely) of fasteners, and composites bonding and co-curing technology is maturing such that this might be reality in the next five to 10 years. In the meantime, however, we are stuck with the necessary evil of cutting and drilling valuable composite structures, and IMTS is a great place to find the best technology options to get it done.

Posted by: Ginger Gardiner

9. September 2014

The Institute for Lightweight Hybrid Systems (ILH) at the University of Paderborn (Paderborn, Germany) is researching a broad range of technologies for future automotive structures using multiple materials. SOURCE: ILH

In researching a German automotive development project for an upcoming article, I discovered an article titled “Leichtbau ist Hybridbau”, i.e., “Light construction is hybrid construction.” Granted, my ability to correctly understand the text relying solely on Google Translate is dubious, but the gist I got was that instead of looking at either metals or plastics (composites are a subset, as fiber reinforced plastics), increasingly German designers are taking another tack: a hybrid structure using multiple materials.

This trend seems to have exploded over the past 3 to 4 years in Germany. Even Volkswagen, which has proudly touted cutting 23 kg/51 lb from the Golf VII using high-strength steel — not carbon fiber — has also formed the Open Hybrid LABfactory, as explained by Prof. Dr. Jürgen Leohold, Head of Volkswagen Group Research:

"For the large-scale light alone is not feasible with expensive lightweight materials. Rather an intelligent multi-material mix is ​​required for success in the market, which enables new methods suitable for mass production. With our partners in the Open Hybrid LABfactory we are developing hybrid multi-material structural components, made of plastic, metal and high-performance fibers in a single production step."

This public-private project claims to include the entire value chain from carbon fiber to finished part, staffed with approximately 200 employees from more than 30 companies contributing technology expertise via  shared, cooperative R&D in a new 7,000 m2/74,350 ft2 facility located near Wolfsburg, Germany (VW headquarters).  

SOURCE:  Open Hybrid LABfactory website.

The Open Hybrid LABfactory website announces its first three research programs:

  • ProVor - Functional Integrated Process technology for prefabrication of FRP-metal hybrids — Research and implementation of a production technology for pre-assembly of load-adapted FRP-metal preforms for the technical press processing.
  • Trophy - Thermoplastic, roll formed sections in hybrid construction (BMBF) — Development of a continuous process for the production of profiles with variable cross-sections and bends in fiber-composite-metal hybrid materials with a thermoplastic matrix for new vehicle concepts.
  • MultiMaK - development of design and assessment tools for use meet ecologically optimized multi-material automotive component concepts in mass — Development of methods and tools for analysis and comprehensive evaluation (economic, ecological, technical) product and process chains for the use of multi-material lightweight-based materials in high volume.

 

Open Hybrid LABfactory objectives and partners. SOURCE: ILH

The slide above showing the lab’s many partners is from a presentation labeled “Form-flexible Handling Technology for Automation in RTM preforming” (CFK Convention on June 17, 2013) given by Dr.-Ing. Annika Raatz, leader of the Assembly and Production Automation Research Group at the Technische Universität Braunschweig. She describes joint research between the Institute of Machine Tools and Production Technology (Institut für Werkzeugmaschinen und Fertigungstechnik, IWF) and the Institute of Joining and Welding (ifs), also at TU Braunschweig, to developed automated preforming for resin transfer molding (RTM) which integrates the functions of handling, draping and bonding into one machine system.

Dr. Annika Raatz describes research at the Institute of Machine Tools and Production Technology (IWF) automating RTM preform operations via FormHand, a new tool which uses a form-flexible gripper with integrated heating. SOURCE: “Form-flexible Handling Technology for Automation in RTM preforming” by Dr. Annika Raatz, TU Braunschweig.

David Vink, the author of “Leichtbau ist Hybridbau”, says that the Open Hybrid LABfactory facility will be operational in 2015 and that TU Brunschweig is working on hybrid hoods that are 30 percent lighter than steel, using 0.2mm/.008 inch thin steel plate as a jacket around a carbon fiber reinforced plastic (CFRP) core.

Vink goes on to describe two more hybrid lightweighting projects in Germany. The first is led by the Institute for Lightweight Hybrid Systems (ILH), established in 2012 at the University of Paderborn. ILH is  working to develop metal structures reinforced with CFRP that do not require “glue, rivets or screws.” A carbon fiber/epoxy prepreg is stamped along with sheet metal at 0.2 to 0.5 N/mm pressure in a die preheated to 180°C/356°F, the epoxy curing in 2 minutes. A post-cure of 30 minutes in a 180°C oven occurs simultaneously with hardening of the CDL powder coating on the metal sheet. ILH has developed shaped sandwich structures comprising a base steel sheet, a carbon fiber composite core and a cover sheet of aluminum or steel. It claims weight is reduced by 35 percent vs. pure steel with one-quarter to one-fifth the thickness yet same strength and crash behavior. The project is reportedly supported by Benteler-SGL (Ried im Innkreiss, Austria), Johann Meier tooling and Audi (Ingolstadt, Bavaria, Germany). Vink notes that the Benteler’s local Paderborn facility has already developed a metal B-pillar with local CFRP reinforcements. Its goal is 150,000 pillars, sills or roof frames per year with a 96-sec cycle time.

Potential for lightweight (y-axis) vs. large-scale production capacity (x-axis) of FRP (gray), aluminum (green) and steel (blue) materials in automotive structures.
SOURCE: University of Paderborn, ILH

Vink also describes work by the Institute for Lightweight Structures and Polymer Technology (ILK) of the Technical University Dresden AG (TUDAG). ILK was a participant in the BMBF (German Ministry of Education and Research) funded InEco project with partners including steel producer ThyssenKrupp (Essen, Germany), plastics supplier Evonik (Essen, Germany) and lightweight research center Saxony LZS. The resulting affordable and sustainable urban electric vehicle InEco was presented at the 2013 Frankfurt Motor Show and Composites Europe (Sep 17-19) and K Show plastics (Oct 16-23) trade fairs, both in Düsseldorf. It used a multi-material design to achieve significant parts integration, reducing components by 70 percent vs. conventional designs. During this project ThyssenKrupp established its TechCenter Carbon Composites and its Carbon Components business unit, the latter producing CFRP wheels which are 30 to 50 percent lighter vs. standard alloy versions.

The Audi R8 e-Tron combines an aluminum front section with a
multi-material space frame which also contains CFRP.
SOURCE: Audi, David Vink article “Leichtbau ist Hybridbau”

As a demonstration actually nearing commercialization, Vink puts forth the Audi R8 e-Tron, which he says will have an aluminum front body but a Multi-material Space Frame (MSF) for ultra-lightweight. The high-voltage battery unit includes both aluminum and CFRP and is load-bearing along with the CFRP luggage compartment tray described as “wavy” (see above image). Vink says Audi refers to the outer skin as “almost” made of CFRP but the passenger compartment and front cover (hood?) are very much CFRP, the latter reportedly having up to seven layers of carbon fiber mats. Vink says Audi plans to bring the R8 e-Tron to market this year.

There are two new hybrid lightweight construction projects at Karlsruhe Institute of Technology (KIT): “HyPro” and “KraSchwing”. These are funded by the German state of Baden-Württemberg as part of its extensive strategy to promote lightweight construction in its region.

HyPro is developing technology for economically efficient production of hybrid metal, plastic and composite automotive structures using RTM and is coordinated by KIT’s Institute of Production Science. Partners include Fraunhofer Institute for Chemical Technology (ICT) in Pfinztal near Karlsruhe and six industrial companies. Researchers are studying RTM process steps – layout, pre-forming, infiltration, and post-processing – with a focus on pre-forming of continuous fiber textile semi-finished products in combination with metallic elements. The head of the HyPro project Professor Jürgen Fleischer explains, “Draping, positioning, and fixing of the fiber mats during pre-forming result in the basic structure of the component.” KIT reports that another focus is tool technologies for resin impregnation of the preforms and sealing of the mold. The results will be validated using a demonstrator constructed by project partner Porsche AG (Stuttgart, Germany).

The second project, KraSchwing, pursues optimizing technology for joining fiber-reinforced and metallic hybrid lightweight components, specifically aiming to improve the stability of both bonded and innovatively screwed structures under dynamic loading. Partners include the German Aerospace Center (DLR) in Stuttgart, the KIT Institute of Vehicle System Technology (FAST), and the Institute for Natural Sciences and Medicine (NMI) in Reutlingen, with six other enterprises.

Karlsruhe Institute of Technology (KIT) is pursuing a wide range of hybrid lightweight construction research, including enabling fastener technologies. SOURCE: KIT.

In total, the Baden-Württemberg state government is funding five joint research projects on hybrid lightweight construction worth roughly EUR 1.63 million. “The funded projects contribute decisively to the automation of production processes or the joining of hybrid lightweight components. Enhanced cooperation of science and industry in innovation partnerships paves the way towards a rapid transfer of viable lightweight construction technologies from research to the industrial production of marketable products,” says the Minister of Science Theresia Bauer.

KITe HyLITE, another of the state-funded hybrid lightweighting projects is directed by the Institute for Automotive Systems Engineering and Institute of Lightweight Technology in Karlsurhe and pursues combining long fiber thermoplastics (LFT), metals and continuous fiber reinforced plastics along specific technology corridors.

  • Project A — LFT Hybrids
  • Project B —  Multi-PUR
  • Project C —  Inno-RTM
  • Project D — In-Situ Comp
  • Project E —  Fiber Handling

Fraunhofer also participates in the project.

MERGE is yet another lightweight structures research organization, this one emphasizing the integration of multiple functions. It aims to merge technologies for mass-production, comprising plastic, metal, textile and what it terms “Smart Systems” into resource-efficient processes and products. Over 100 researchers from six interacting “research domains” are participating, with EUR 31 million in funding from 2012 to 2017.

And to bring it round full-circle, whereas the Open Hybrid LABfactory is supported by the German state of Lower Saxony, Baden-Württemberg has its own:  Active Research Environment for the Next generation of Automobiles, or ARENA2036. Launched on June 3, the flexible research ARENA2036 factory for the car of the future — 2036 is the automobile’s 150th anniversary — is dedicated to realizing new, resource-efficient and competitive production models. Its website explains that lightweight automotive components in the future are not only based on fiber-reinforced plastics but also metals. Weight and cost savings will be achieved by integrating not only materials during manufacture, but also multifunctional properties such as sound and thermal insulation as well as sensory and electrical systems. Currently, there are four main projects:

  • LeiFu — Intelligent lightweight with functional integration
  • DigitPro — Digital prototype: new materials and processes
  • ForschFab — Research Factory: production of future
  • Khoch3 — Creativity, cooperation, competence transfer

Though one of the presentations and the video below are in German, they give a good idea as to the future of automotive composites where Leichtbau ist Hybridbau.

Posted by: Sara Black

30. August 2014

Ten months….that’s a lot of time, in my book. I have been casually observing the replacement of a bridge near my home in Colorado, a bridge over a tiny stream on a road that leads to a park. The existing bridge was demolished, and new abutments built, followed by placement of six steel girders, with several cranes, then a poured concrete deck. Once the deck was fully cured (under blankets and tarps), work progressed slowly on the parapets and access aprons, and finally, this week, an asphalt cover was placed. It took nearly one year to build a very small, two-lane bridge with a span of approximately 30 feet.

Well, it may be that the project posed some difficult challenges that took extra time, and the Colorado winter certainly didn’t help speed things along. But I couldn’t help but think, every time I passed the construction site, about the many stories we’ve published over the years about composite material solutions for bridges. The main point of those stories has always been that the bridge is built by a composites fabricator, off-site, and delivered in a modular fashion, allowing installation to be accomplished in days, or even, hours. The on-site labor savings is significant, heavy cranes aren’t required, the road opens sooner….surely the time and effort savings of that scenario outweigh the higher material cost — yes?

Unfortunately, the answer seems to be “no” more often than not. The tried-and-true methods of cured-in-place concrete persist in many departments of transportation, even though the Federal Highway Administration (FHWA) has been pushing, for four years now, accelerated bridge construction (ABC) initiatives under the name Every Day Counts (EDC). EDC is a collaborative effort that involves the FHWA, the American Association of State Highway and Transportation Officials (AASHTO), state departments of transportation (DOTs), local agencies, and industry, and is aimed at reducing overall project delivery time and impacts from onsite construction. Among the many ABC alternatives (which include better planning, fee structure changes and greater right-of-way and utility flexibilities), is a construction concept called Prefabricated Bridge Elements and Systems, or PBES.

PBES include not only the structural components of a bridge that can be built at offsite locations, like a composite deck, but also components that can be constructed without traffic disruption adjacent to construction sites, given sufficient room and access. Examples include full-depth precast concrete deck panels, steel grid decks, aluminum deck panels, modular beams with decks, full-width beams, prefabricated truss spans, precast segmental spans, pier elements, abutment and wall solutions and miscellaneous items, such as prefabricated parapets and approach slabs. They also could include preassembled composite superstructures or complete bridges.

Ben Beerman of the FHWA wrote about PBES for CompositesWorld in 2012 (http://www.compositesworld.com/columns/prefabricated-bridge-elements-and-systems-an-opportunity-for-composites), but even the FHWA itself is struggling with convincing entities to adopt the concept. “PBES often cost more at the bid stage, and they require planning and coordination,” says Scott Reeve, president of Composite Advantage (Dayton, Ohio, USA), a composite bridge design and build firm. “But, they have less potential for change orders that inflate the final costs of long projects.” He points to an example of how PBES can accelerate a project significantly: the Mitchell Gulch bridge construction project, ironically, located in the State of Colorado. A deteriorated timber structure on a secondary road in Douglas County, Colorado needed replacement, and CDOT and designer Wilson and Company (Denver, Colo., USA) seized the opportunity to use precast concrete modules, including precast concrete deck girders that acted as the actual bridge deck. After significant upfront planning, advance part production and preliminary site work that didn’t disrupt traffic, the old bridge was swiftly demolished starting at 7:00 pm on a Friday night (with demolition completed in 5 hours). The completed precast elements were then put in place in a complex choreography, and by Sunday afternoon of the same weekend, paving was underway (here’s a link to that case study story on Mitchell Gulch, on the FHWA Web site:  https://www.fhwa.dot.gov/hfl/co2story.pdf).

That’s 2 days and change, compared to 10 months for my bridge. While the Mitchell Gulch example used precast concrete, Reeve points out that if accelerated bridge methods using PBES can be advanced successfully, “It’s a change for the better. The composites industry will get at least part of that work, as more DOTs adopt this approach.” Our aging infrastructure could really benefit from a faster, and better, refresh.

Posted by: Ginger Gardiner

28. August 2014

Materials Sciences Corp.'s COUNTERVAIL composite material helps cancel vibrations in the Infinito CV high-performance racing bicycle. SOURCE: Bianchi.

Materials Sciences Corp. (MSC, Horsham, Penn., USA) has provided design, analysis, engineering and testing services to the advanced composites industry since 1970. It has worked with the U.S. Army, Navy, Air Force, NASA, and DARPA as well as renowned industry leaders such as Seemann Composites Inc. and McDonnell Douglas (now Boeing) Phantom Works. Its projects span a huge range of topics including multifunctional composites, damage tolerance, fire performance, armor systems, nanocomposites and design allowables methodologies, to name just a few.

One of its latest developments is a low acoustical insertion loss composite for sonar windows using MSC’s proprietary fiber commingling technology. The latter blends acoustical and structural fibers into a tailored fabric and multilayer composite which enables the high-strength, protective sonar dome to mimic the density and acoustical impedance of sea water through which the sonar waves travel. This then minimizes sonar wave scattering for a clearer, more accurate signal.

Now MSC — NOT to be confused with MSC Software, supplier of MSC NASTRAN plus other FEA and simulation products — is expanding its corporate mission to include transitioning its proprietary, innovative technologies from R&D into commercial products. It has already released MSC-CAN composite attachment nails for sandwich structures and LS-DYNA dynamic simulator and database which provides accurate progressive failure modeling of composite structures.

MSC has commercialized MSC-CAN (left) and LS-DYNA (right) failure modeling tool.
SOURCE: Materials Sciences Corp.

But perhaps MSC’s most ingenious product is COUNTERVAIL (globally registered trademark), which combines traditional vibration damping layer concepts with a patented fiber preform to offer “unparalleled” vibration reduction in composite structures. The preform uses a fiber pattern that maximizes the vibrational energy dissipation achieved by an integrated viscoelastic damping layer. Damping performance has been shown to be at least 200 percent better than similar constructions using traditional methods. Lay-ups can be tailored to balance vibration curbing with stiffness and strength. COUNTERVAIL’s performance does indeed look impressive in this video by bicycle manufacturer Bianchi for its new Infinito CV model:

 In fact, the Infinito CV was named “Bike of the Year” by road.cc and also was used by cyclist Lars Boom to win Stage 5 of the 2014 Tour de France race, a stage known for its bike-frame chattering cobblestones.

My thoughts fast forward to the potential solution this new technology may offer for two long-time challenges involving composites: (1) Composite interior panels which are thinner, lighter yet offer reduced transmission of noise into the aircraft cabin; (2) Mitigation of repeated and severe shock loads experienced by Navy SEALs and other occupants of special warfare marine vessels due to high-speed wave impacts.

The latter has caused chronic and acute injuries and risks mission performance. It has also seen huge amounts of money invested into solutions which may not yet offer the performance/price point combination that this new technology could provide. Shock mitigating designs have been proposed for the hulls, decks and seats used in these boats. CW reviewed one example in the 2011 article, “Re-inventing the RHIB: Shock Mitigation”.

Meanwhile, noise transmission from air rushing past an aircraft fuselage is tricky because noise is vibration, which traditionally has been most easily addressed by adding weight — hence, the use of lead around superyacht engine rooms. Viscoelastic materials are a more modern alternative, but they too tend to be heavier than desired in aircraft and must also pass fire, smoke and toxicity (FST) regulations.

COUNTERVAIL, however, may have opened a pathway that could yet be refined to offer a solution. There are so many materials innovations affording improved flame resistance, for example University of Texas’ development of nanoclay fillers used to drop the flammability of polyurethane foam and the latest thermoplastics which offer both FST performance and higher toughness.

I’ve been invited to visit MSC’s newest facility in Greenville, South Carolina. So keep watching for our next report on Materials Sciences Corporation, COUNTERVAIL and where both are headed next.

MSC’s videos on YouTube

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