Altair has big ideas on tiny technology

Bruce Sabacky, head of research and engineering at Altair, holds tape casts of anode and electrolyte used to make the company's monolithic-design solid-oxide fuel cell. The experimental setup in the background is a functioning test cell running rigorous thermal cycles.

Altair Nanotechnologies has completed a second set of tests demonstrating the potential of solid-oxide fuel cells based on nanomaterials.

In the testing, a monolithic fuel cell was stressed through several startup/shutdown cycles without deterioration in power or adverse effects of the structure. Based on the testing, Altair believes that a monolithic fuel cell (a stack of fuel cells produced in one monolithic structure) is feasible and can be fabricated in a single firing.

The entire fuel cell—including connectors, electrolyte, anode, and cathode—was constructed of micro- and nano-sized materials produced by Altair, some costing less than $20/kW. (The current state of development puts the overall SOFC cost at $1200/kW, according to Altair.) A gas-impermeable membrane 20 µm (800 µin) thick is sandwiched between the porous cathode and anode.

Altair says the advantages of its nanomaterial-derived fuel cells include:

• Lower material costs
• Reduced fabrication costs
• The possibility of using traditional hydrocarbon fuels in fuel-cell power generators.

The recent test, using hydrogen as the fuel, demonstrated good matching of thermal expansion properties among the components.

"Altair has convincingly demonstrated that its nanomaterials can solve the classic materials mismatch problem that has been experienced by other fuel-cell manufacturers and now will focus its efforts on incorporating catalysts currently being developed by the Massachusetts Institute of Technology," said Rudi Moerck, President of Altair.

"The ability to use commercial tape-casting techniques for fabrication of fuel cells, along with the ability to fabricate fuel cells in a single monolithic structure, will provide the basis for future mass production of fuel cells employing Altair's techniques and nanomaterials."

- Patrick Ponticel

CFT from Polygon opens new doors

CFTs can be used for structural (as shown here) or for nonstructural purposes.

Continuous Fiber Thermoplastics (CFTs) are the first production-capable material using continuous, nonbroken filaments in a thermoplastic resin matrix at high fiber volumes (55-60% F_v), according to Polygon Co. They can be used in sheet-molding applications or in a process known as "pultrusion."

Pultrusion, Polygon says, is similar to extrusion except that the former affords the use of high volumes of continuous filaments. Because of these high fiber volumes, the profile must be "pulled" through the process as opposed to extruded. Pultrusion generates both symmetrical and nonsymmetrical shapes that have constant geometries along the length of the profile. The CFT process introduces thermoplastic resins into the cross section of the profile, resulting in a pultruded profile that has good mechanical properties such that the finished CFT profile can compete with high-strength metal extrusions, according to the company.

Unlike either short- or long-filled thermoplastic resins, CFT materials have 100% of their fibers continually connected throughout the axial direction of any profile; no break exists in the fiber architecture. As such, they can optimize the design advantages of a traditional composite material with the processing and product advantages of thermoplastic extrusions, Polygon says.

The design migration from conventional metals to engineered thermoplastics has many times provided an opportunity for design solutions using fiber-reinforced thermoset composite materials, which offer superior strength-to-weight properties but little of the design flexibility of either metals or filled thermoplastics. CFT materials offer good strength-to-weight properties while also providing post-forming, joining, and secondary attachment operations that have not been available with traditional materials until now, according to Polygon.

There are basically three types of materials available to a design engineer: natural (e.g., wood), metals, and synthetics (primarily engineered plastics). A subcategory of synthetics is fiber-reinforced plastics (FRPs), which were developed in the late 1940s. (The FRP industry has come to be known as the "composites" market.) CFT materials hold the potential to bridge the gap between unfilled thermoplastics and metallic materials—specifically in applications for which impact, durability, and cross-sectional strength are issues.

Impact tolerance is one area in which CFTs are better than conventional composite materials, according to Polygon, and the "shattering" associated with conventional fiberglass products is not an issue with CFTs. Suitable applications include hood, doors, dashboard, and similar automotive panels. Higher-elongation materials such as TPU-based CFTs can be incorporated into structural systems such as cockpits, bumper bars, or side-collision stiffeners for which the combination of light weight, ease of installation, and energy management is important.

The mechanical modulus values of CFT vary, depending on choice of resin matrices. A CFT material with TPU as the resin matrix at 55% F_v has a tensile strength of 980 MPa (142 ksi), tensile modulus of 43 GPa (6200 ksi), longitudinal flexural strength of 1340 MPa (194 ksi), and longitudinal flexural modulus of 44 GPa (6400 ksi). Transverse flexural strength of an all-uniaxial material, also with TPU as the resin matrix, offers a resulting value of 151 MPa (21.9 ksi).

With the CFT process, other thermoplastic materials can be co-extruded to cover or provide a detail feature. Examples include abrasion-resistant coverings, unique colorants, and cosmetic features such as ribbing for grips.

Polygon says there are three main areas of application for CFTs. One is the replacement of extruded thermoplastic materials that cannot meet structural or other mechanical requirements. Another is replacement of metallic extrusions that are problematic due to corrosion, weight, or damage tolerance. The other is for applications requiring a combination of high strength-to-weight ratios in conjunction with good durability.

While a 100% pure CFT material across an entire cross-sectional area is an option, an even better design approach involves a CFT-stiffened application, in Polygon's view. This approach integrates a CFT material—be it in the form of a rod, angle, or flat—into a lower-strength and typically lower-cost thermoplastic. The result is a profile that has high-strength continuous fibers oriented only where needed throughout the profile. A possible application would be a rectangular profile measuring 2 x 4 x 0.16 in (51 x 102 x 4.0 mm) for use as an energy management member. Four CFT rod reinforcements 0.70 in (18 mm) in diameter would be placed in each corner of the engineering thermoplastic extrusion. While maintaining the same 0.160 in (4.0 mm) wall thickness, the CFT reinforcements would increase the stiffness of the profile by 30-45% with minimal cost increase. One could then consider decreasing the wall thickness to reduce costs.

- Patrick Ponticel

Vibracoustics sees MCU growth

By the end of the decade, MCU will have replaced rubber as the most used body mount material, according to Vibracoustic.

As North American vehicle manufacturers drive to make them quieter and more comfortable, light trucks and sport utility vehicles will, by decade's end, employ more microcellular urethane (MCU) than rubber in body mount applications.

That's the forecast for the yellow polymer foam from Rod Hadi, Director of Engineering and Advanced Product Design at Vibracoustic North America. He said MCU offers improved vibration damping, greater durability, longer material property retention, reduced weight, and improved packaging—at a competitive price. MCU body mounts can be easily tuned and optimized by changing the material's density, eliminating the need to change chemistries or part geometry, as well as the associated prototyping and tooling costs and delays, Hadi noted.

Tests conducted on a light truck in which production rubber body mounts were replaced with MCU mounts showed an interior noise reduction of 3 dBA at the driver's right ear, a 20% reduction in vibration measured at the seat track, and a 20% reduction in weight. Already in production at Vibracoustic for several SUVs including the Ford Sport Trac and the Ford Explorer Sport, MCU body mounts are being evaluated by the three largest light truck manufacturers for future applications.

- Patrick Ponticel