A comprehensive collection of news and information about composites.
Posted by: Sara Black30. 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 Gardiner28. 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.
Prosthetic limbs fabricated from composites are among the SBIR-funded projects
that are garnering more attention.
Out of the 21 topics released online in the U.S. Department of Defense (DoD) fiscal year (FY) 2014.3 Small Business Innovation Research (SBIR) funding solicitation, only one directly lists composites. The description for “Replacement Nose Fairing Material” is listed below. Instead, most of the research topics deal with sensors, microelectronics or modeling and computing, though the Navy’s subgroup includes “Optimization of Advanced Wireless Textiles” and “Advanced Textile Manufacturing Using 3D Printing”.
For the composites industry, the take-home is to note the push to integrate sensors into everything, from cargo containers to clothing to the next generation of night vision goggles. In the case of containers — the Defense Threat Reduction Agency’s (DTRA) topic “Smart Materials to Indicate Personnel Presence in Proximity to Container” — the DoD would like to replace cameras, infrared sensors and visual inspection by guard forces with a means to maintain security that does not require staffing and is not easily disabled. The research description suggests that integrated/embedded sensors will need to detect multiple signatures, for example motion, body heat and molecular compounds emitted during breathing.
Another interesting topic is the Defense Advanced Research Projects Agency’s (DARPA) “Energy Harvesting for Next Generation Neurotechnology”. Basically the DoD wants to advance Neuroprosthetics — which already can actuate prostheses based on closed-loop sensing and computation — by replacing batteries with biomedical energy harvesting technologies. This also reflects a larger trend outside the military. Bionics are here. They are still expensive and in development, but they are no longer science fiction. Both of the devices in the videos below from Ekso Bionics and BeBionic use carbon fiber composite laminates.
Prosthetics has always been a market for composites, but with advances in electronics and injured troops returning from Iraq and Afghanistan, the push to improve this technology into self-powered neuroprosthetics that are actually affordable has ramped significantly.
Finally, there is another round of funding available for awards in 2014, this one known as the DoD FY 2014.B Small Business Technology Transfer (STTR) Solicitation. Of the 13 topics included here, only DARPA’s “Revolutionary Airlift Innovation” implies composites, seeking unmanned gliders to perform cargo lift operations from ship to unsecured shore areas. The Missile Defense Agency (MDA) topic "Failure Avoidance in Microelectronics Due to Coefficient of Thermal Expansion (CTE) Mismatch of Substrates and Adhesives” reflects a large trend in the printed circuit board (PCB) industry — reportedly the largest consumer of glass fiber — to develop higher laminate performance and thermal capacity as electronics get smaller and more sophisticated. Watch for our full-length feature on that in the October issue of Composites Technology magazine.
NAVY N143-130 Replacement Nose Fairing Material
DESCRIPTION: The Nose Fairing provides hydrodynamic and aerodynamic stability during launch and flight. The Nose Fairing provides a direct interface during onload and offload of the missile while supporting the entire weight of the missile. Navy Strategic Systems Programs (SSP) desires to develop a replacement material with the following parameters:
Service Life Goal - 50 years
Nominal Thickness - 0.5 inch
Tensile Strength – Longitudinal > 8.0 ksi Property quantified to B-Basis**
Tensile Strength – Hoop > 2.5 ksi Property quantified to B-Basis**
Bending Strength – Longitudinal > 5.0 ksi
Shear Strength > 1.6 ksi Property quantified to B-Basis**
Internal material damping - Loss Factor = 0.01 or higher
Radio Frequency Transparent in the GigaHertz region of the electromagnetic spectrum (EM) spectrum
Density - 0.58 gm/cc.
Manufacturability – Must be able to form into a complex curvature (doubly curved shell of revolution)
**At least 90 percent of the population of values is expected to equal or exceed the B-basis mechanical property allowable, with a confidence of 95 percent.
1) Payload Fairing. http://en.wikipedia.org/wiki/Payload_fairing
2) Nose Fairings on Rockets and Ballistic Missiles. http://www.gpo.gov/fdsys/pkg/GPO-CRPT-105hrpt851/pdf/GPO-CRPT-105hrpt851-2-6.pdf
KEYWORDS: Strategic Missiles; Composite Materials; Materials Development; RF transparent structural materials; Ultrastrong materials; Nanocomposites
TPOC: Roderick Santander
2nd TPOC: David Olson
GS Caltex, a little-known South Korean petrochemicals company based in Seoul, made a name for itself this week when it was reported to be in talks with electric car specialist Tesla Motors Inc. over the potential supply of long fiber-reinforced thermoplastics for use in Tesla vehicles. GS Caltex calls the material long carbon fiber-reinforced thermoplastic (CLFT). Properties of the material (fiber length, resin type, etc.) are unknown as yet.
Whether and to what extent Tesla employs CLFT in its vehicles, this news raises an interesting question that’s come up in the last few months as the automotive industry wrestles with the challenge of integrating composite materials into new vehicles. The question is this: If use of continuous carbon fiber in cars is too expensive, and if manufacturing processes are too slow, might long fiber-reinforced thermoplastics provide the stepping stone automakers need to start the migration to composites?
There’s much to like in long-fiber technology. First, the primary manufacturing process in which it’s used is injection or compression molding, both of which the automotive industry understands and has familiarity with. Second, several machinery suppliers, like Engel, Arburg and KraussMaffei, are working on injection technologies designed to minimize fiber shear, thus elongating fiber length in finished parts. This increases part strength and durability.
Third, there is at least some research that shows that even chopped carbon fiber provides a substantial fraction of the strength supplied by continuous carbon fiber. George Husman, chief technology officer at Zoltek (St. Louis, Mo., USA), reported at SAMPE Tech in Seattle last spring on research he’s done that shows just 0.7 mm of carbon fiber length provides 70 percent of theoretical modulus of continuous carbon fiber.
Such data require substantiation, but if it’s valid then it wouldn’t be hard to see that a long fiber-reinforced thermoplastic might easily find several homes in a car — at least in semi-structural parts, if not fully structural parts.
CW will investigate this further. Look for a more complete report soon.
For the past 100 years, protection for ground-based armored fighting vehicles and their occupants has basically mean more armor. Weapons’ ability to penetrate armor, however, has advanced faster than armor’s ability to withstand that assault. As a result, achieving even incremental improvements in crew survivability has required significant increases in vehicle mass and cost.
Increasingly heavy, less mobile and more expensive armored vehicles hinder rapid deployment and maneuverability in often challenging environments. Moreover, larger vehicles are limited to roads and require more logistical support. They are also more expensive to design, develop, field and replace. The U.S. military is now seeking innovative and disruptive solutions to ensure the operational viability of the next generation of armored fighting vehicles.
DARPA has created the Ground X-Vehicle Technology (GXV-T) program to disrupt the current trends in mechanized warfare. GXV-T seeks to investigate revolutionary ground-vehicle technologies that would simultaneously improve vehicle mobility and survivability through new approaches including detection avoidance and evasion of engagement and targeted hits.
GXV-T’s technical goals include the following improvements relative to today’s armored fighting vehicles:
“GXV-T’s goal is not just to improve or replace one particular vehicle—it’s about breaking the ‘more armor’ paradigm and revolutionizing protection for all armored fighting vehicles,” said Kevin Massey, DARPA program manager. “Inspired by how X-plane programs have improved aircraft capabilities over the past 60 years, we plan to pursue groundbreaking fundamental research and development to help make future armored fighting vehicles significantly more mobile, effective, safe and affordable.”
To familiarize potential participants with the technical objectives of GXV-T, DARPA has scheduled a Proposers' Day on Friday, September 5, 2014, at DARPA’s offices in Arlington, Va. Advance registration is required through the registration website: http://www.sa-meetings.com/GXV-T. Space is limited and registration closes Friday, August 22, 2014 at 5:00 PM Eastern Time or when capacity is reached, whichever comes first. DARPA reserves the right to limit the number of attendees from any individual organization.
The DARPA Special Notice document announcing the Proposers’ Day and describing the specific capabilities sought is available at http://go.usa.gov/Edsh. For more information, please email DARPA-SNfirstname.lastname@example.org.
DARPA aims to develop GXV-T technologies over 24 months after initial contract awards, which are currently planned on or before April 2015. The GXV-T program plans to pursue research, development, design and testing and evaluation of major subsystem capabilities in multiple technology areas with the goal of integrating these capabilities into future ground X-vehicle demonstrators.
The GXV-T program provides the following four technical areas as examples where advanced technologies could be developed that would meet the program’s objectives:
Radically Enhanced Mobility – Ability to traverse diverse off-road terrain, including slopes and various elevations; advanced suspensions and novel track/wheel configurations; extreme speed; rapid omnidirectional movement changes in three dimensions.
Survivability through Agility – Autonomously avoid incoming threats without harming occupants through technologies such as agile motion (dodging) and active repositioning of armor.
Crew Augmentation – Improved physical and electronically assisted situational awareness for crew and passengers; semi-autonomous driver assistance and automation of key crew functions similar to capabilities found in modern commercial airplane cockpits.
Signature Management – Reduction of detectable signatures, including visible, infrared (IR), acoustic and electromagnetic (EM).