Issue: Sep 2011


Advanced technology of automotive front-end



by Tony Davison

Before the advent of European sports cars being imported to the United States, highways in that country were traversed by large heavy hulks of automobiles that somewhat jokingly held the reputation of being like Sherman tanks. Everything was heavy about them, from power train to the knobs on the radio. Up to the very recent past cars were manufactured from the ground-up in one assembly line; nothing really had changed from the time of Henry Ford in the very early 1900s. In other areas of manufacturing, especially electronics, miniaturization and modulations were becoming watchwords, as more attention was being paid to the need to have space and conserve natural resources.

Europe and Japan already realized that there needed to be a change in how automobiles were being manufactured, as peoples in these regions already were experiencing high fuel costs, and they were living in much more crowded areas. It was only logical to bring in manufacturing practices to the automobile industry, and the first wave of that came with European “sports cars” and economy cars. The U.S. lagged by at least ten years, introducing similar but inferior models, such as the Chevette and Pinto in the early 1970s. The Mustang and the Camero, albeit smaller than their larger predecessors, still weren’t as small as the Toyota Corolla of 1971, Honda Civic, fiat Spider, or the VW Beetle. They certainly don’t rank in the category of “compact” or “economy” cars, as a visit to any major parking lot, rental car agency, or street in Europe or Japan will immediately reveal.

Europe and Japan also led the way to modularization, as well as miniaturization, front-end modules (FEM) being a major step forward. Two major factors driving FEM development were the need for weight reduction, brought on by increasing fuel costs, and the observation that vehicle assembly procedures were bulky and inefficient. Smaller cars demand lighter components, simply because the engines are not as powerful.

Material density and size are the main factors contributing to weight and strength. The main goal in design to make a material less dense and miniaturized, while retaining functionality and durability. However, overall cost of manufacturer still is the baseline consideration by most manufacturers. Corporate Average Fuel Economy (CAFE) regulations [1] also will be a factor. These U.S. regulations were enacted in 1975 in response to the 1973 Arab oil embargo and mandated auto manufacturers to construct vehicles with lower fuel usage.

Three basic ways of constructing a front-end module (FEM) are using current materials, (mainly metal), all non-metal (mainly composites), or a combination of both. The central goal is to have a lower weight but stronger assembly that is durable but environmentally friendly. FEMS initially has a steel carrier but developments in composite design have helped transition construction from a hybrid design to more composite-based assemblies.

Material and weight considerations 

Lift up the suspension and steering assemblies of the front-end and you’ll realize that they are one of the heaviest assemblies of the automobile. Only the engine and transmission weigh more (and the differential in older cars). Just about every part contributes to the weight, but of particular notice are brake assemblies (particularly rotors and callipers), ball joints, power-assisted steering units, and the material out of which the linkage is made – usually dense steel. Plastics, metal alloys, ceramics, and composites are changing all that.

Plastics 

Plastics saw their advent with Bois Durci (French for "hardened wood") in 1855, made from finely ground cellulose together with an adherent, such as egg or blood albumen, or gelatine. The mixture is compressed to a dense form using steam. Synthetic ivory was under the trade name of Parkesine and won an award at the 1`862 World’s Fair in London. This is made by treating cellulose with nitric acid (part of the process making nitroglycerine) and dissolving this cellulose nitrate, or pyroxilin, in alcohol and hardened by heating it. Bakelite was invented in 1912 by Leo Hendrik Baekeland, a Belgian-born American and was the first plastic, not being created from molecules not found in nature. World War I brought polyvinyl chloride, with polyamide (nylon) following in the 1930s, and hosts of other during and following World War II. Synthetic rubber saw its advent in that war, and since then, we have developed a plethora of synthetic materials, including biodegradables and organic-synthetics. Which then are used in making cars lighter and stronger? Surely, anything lighter and stronger than the present usually metal-based materials is better.

Thermoplastic resins provide the material most commonly used in the most common matrices that are filled with polypropylene (PP) and nylon polyamide (PA). Early FEM materials consisted of compression moldable glass-mat thermoplastic (GMT)
composites with chopped-fiber matting. Plastics manufacturing in other applications was using injection molding, and this technology was transferred to FEMs, along with pelletized long fiber thermoplastics (LFT), the first being PA, and winding up with PA. Currently, there is inline-compounded (ILC) injection, or compression-molded direct-LFT (D-LFT) as a major material of choice [2].

For lighter cars, manufacturers like Mercedes and Hyundi are using injection-
moulded pelletized LFT-PP for their all-composite FEMs. These FEMs have the capability of deforming better, thus preserving the main part of the car during a crash. LFT also provides the needed stiffness and allows for the creation of mounting points for system components.

Fiber reinforced plastics 

Everyone has heard of fiber glass and knows that strands of a material mixed with any other substance that hardens in a homogeneous way will strengthen it. This is the principle behind fiber reinforced plastics. Not only is the substance lighter than metal, it often can be just as strong or stronger. At the Shanghai Auto Show this year, the Chinese displayed an all-plastic front-end module (FEM) made out of a long glass fiber polypropylene (LGFPP) resin. Their claim is that the weight reduction is about 40%.

The American Chemistry Council says of fiber reinforced plastics:

Fiber-reinforced polymer composite materials weigh around 50 percent less than steel, though according to a carbon fiber manufacturer, they are characterized by a higher absorption of crush energy per kilogram — 100 kJ/kg, compared to steel’s 25 kJ/kg. On impact, carbon fibers can have four to five times higher energy absorption than steel or aluminium [5].

Such materials are designed to break crack so as to use up impact energy. The Council asserts, “An automotive front-end section built from glass-fiber-reinforced polymer composites passed a key 35 mph barrier crash test performed by the Automotive Composites Consortium (ACC), a research partnership established by DaimlerChrysler, Ford, and General Motors [6].”

Metals 

Light weight metals (such as magnesium and aluminum), alloys and metal structures, such as tubes, being injected with plastics, such as polyphenylene ether/polyamide (PPE/PA) blend for strength, are being used in lie of conventional metals. Compressible steel reduces the consequences of vehicle object/person impact are designed to meet regulations, such as the European Pedestrian Impact Phase Two Standards that took effect in 2010. Magnesium is mixed with aluminum and then formed into geometric structures that have equivalent strength to older designs using conventional steel [7]. Too, with the design of a collapsible front as an ultimate shock absorber, the need for conventional metals and solid construction, with attendant heavy weight, is no longer needed or even wanted, the result being a lighter (often to more than a third of the weight of a regular component) and safer car.

Magnesium, itself, is strong and durable, as well as being lightweight, so as to hold radiator and front-hood latching mechanism. The metal is cheaper than plastics, is fully recyclable, and obviously doesn’t rely on petroleum [8]. Of course, everyone knows about “mag wheels”, and simply lifting one up and comparing it to the weight of a conventional wheel will be convincing enough in arguing for using magnesium as a way to make cars lighter. As a general consideration, magnesium is used for making engine blocks, and considering the strength needed for that component, it is easily seen that it would be satisfactory for front-end components, as well.

In its undated report, “Lightweight Front End Structure”, the Auto/Steel Partnership organization presents front-end rail and bumper construction that significantly reduces weight but sustains crashes just as well as conventional materials. By stamping in reinforcement geometry, with thinner metals, there is significant weight loss but strength as in conventional designs [9]. In addition, strength in the parts is manufactured as needed, rather than having a uniform density.

Hybrid materials 

Heavier vehicles cannot be constructed from purely composite materials, as the technology has not been developed to the point of lowering the cost of construction. Consequently, what we see is a reliance on GMTs. Research is continuing to develop composites with the strength of conventional metals. Developments in adhesives have accelerated FEM design and construction.

Plastics and metals are being united to create building material for components [11].
Where plastics cannot supplant metal in order to reduce weight, the metal can surely be used with the plastic. In one process, metal is drilled with holes and plastic reinforced with fibers uses them into which to hold when covering the metal part [12]. 

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References(Subject is indicated by URL – accessed 22 August 2011)
[1] http://en.wikipedia.org/wiki/Corporate_Average_Fuel_Economy
[2] http://www.nrc-cnrc.gc.ca/eng/facilities/imi/magna-nrc-composites-centre/manufacturing-direct-long-fibre-thermoplastics.html
[3] Courtesy of http://www.nrc-cnrc.gc.ca/eng/facilities/imi/magna-nrc-composites-centre/manufacturing-direct-long-fibre-thermoplastics.html
[4] https://ktn.innovateuk.org/web/polymers/articles/-/blogs/driving-plastics-forward-another-mile-stone-towards-the-all-plastic-car;jsessionid=9AD213EBDB025E2FD69077E5DC86E890.9OphEwv4
[5] http://www.plastics-car.com/frontendvehicle, p. 2

[6] ibid.

[7] http://www.aimme.es/archivosbd/observatorio_oportunidades/super_light_car.pdf

[8] http://www.intlmag.org/showcase/MgShowcase7_Jan09final.pdf

[9] http://investors.smdisteel.org/AM/Template.cfm?Section=Home&TEMPLATE=/CM/ContentDisplay.cfm&CONTENTID=28256

[10] http://investors.smdisteel.org/AM/Template.cfm?Section=Home&TEMPLATE=/CM/ContentDisplay.cfm&CONTENTID=28256

[11] http://www.ptonline.com/articles/plastic-metal-hybrids-make-headway-on-and-off-the-road

[12] http://www.ptonline.com/articles/plastic-metal-hybrids-make-headway-on-and-off-the-road

Resources (Subject is indicated by URL – accessed 22 August 2011)

https://ktn.innovateuk.org/web/polymers/articles/-/blogs/driving-plastics-forward-another-mile-stone-towards-the-all-plastic-car;jsessionid=9AD213EBDB025E2FD69077E5DC86E890.9OphEwv4
http://insciences.org/article.php?article_id=6220 – SuperLight Car
http://www.plastics-car.com/frontendvehicle
http://www.a-sp.org/database/publicationmain.asp - Magnesium
http://www.ncn-uk.co.uk/DesktopDefault.aspx?tabindex=139&tabid=431
http://innovationzealot.typepad.com/files/ct-dec-08-front-end-modules.pdf
http://www.just-auto.com/analysis/review-of-front-end-modules_id104743.aspx
http://en.wikipedia.org/wiki/Fibre-reinforced_plastic

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