The introduction of new materials into automotive manufacturing has often been dictated by how fast such materials can be processed in the production line.
Right from the first cars until the present, steel has been the preferred option for structural components requiring high strength. But, with the need to produce lighter cars being driven by the CO2 emission regulations imposed for new car builds, this is likely to change.
In order to assess the current shift, it’s useful to have a brief look at the evolution of automotive materials use.
The first commercialised car was designed in 1885 by Karl Benz. The tubing was made of steel and a driver compartment was created using panels of wood (although there was no bodywork as we now understand it).
The car was powered by a 0.75hp petrol engine connected to three steel wheels and solid rubber tyres. Lightweighting was clearly an issue even then, as Benz declared he wanted to design a “dwarf in terms of weight, but a titan in terms of power”.
Benz was also responsible for the first production car (1200 units) in 1894 and a new generation of commercialised cars was born. Crucially, the process of varnishing wooden bodywork to make it sufficiently resilient was both time-consuming and expensive.
In 1912, Budd, a US metal and die-stamping company, fabricated the first all-steel car which quickly resulted in an order for 70,000 cars from Dodge Brothers. These cars were less expensive to manufacture, required considerably less production time and were stronger than the wood/steel combination. And the introduction of the integrated moving production line by Henry Ford in 1913 meant that cars could be produced in far greater volume than previously.
The first experiments with light weight materials were made during the First World War when cast aluminium was introduced by the American automobile manufacturer Marmon and was widely used for building aircraft.
Perhaps Marmon realised the benefits of lightweighting when the manufacturer won the first-ever Indianapolis 500 race in 1911 when their engineer/driver invented the rear view mirror and thus became the first driver to race without a riding mechanic to watch for cars from behind – a significant saving on weight!
From the beginning, motorsport was an important vehicle for popularising innovations and showcasing the performance capabilities of automobiles. Indeed, fiberglass composites were first used on Bill Tritt’s Lancer sports car in 1951. Shortly afterwards, Lotus developed its first dedicated production car, the Elite, in 1959 which featured both lightweight fiberglass body and structure and weighed only 773kg.
The Stout Scarab was the first “minivan” made with fiberglass panels. However, its production volume was always intended to be low, and it was far too expensive to be accessible to the general public.
In today’s high-mass production, conventional steel alloys have partly been replaced by high strength steel which makes steel still a leader in the construction of car bodies. However, since the oil crisis of the 1970s, followed by the global pressure on fossil fuel resources, manufacturers have been increasingly aware of the need to build lighter vehicles in order to enjoy better fuel efficiency.
The use of aluminium alloy started to become more widespread but, in most cases, it costs more than steel: OEMs searching for cheaper alternatives realised plastics have a significant role to play in relation to sacrificial parts, such as bumpers, rather than metal.
Today’s car weight vs the past
Even though the correlation of lightweight components with better fuel efficiency has been understood for decades, the development of new electronics, safety features and entertainment requirements has meant that overall the reduction of weight from new materials has been more than countered by the addition of more technology.
This therefore implies that more effort will have to be expended in order to make the weight savings required, while still meeting safety and environmental regulations as well as consumer expectations.
Taking a concrete example of car mass, Ford’s Model T, launched in 1908, weighed 544-680kg for 3.4m length and 1.68m width. Today, a similar size car such as the Ford KA, weighs 870kg for 3.6m length and 1.65m width.
Nevertheless, with environmental studies showing a correlation between lower weight vehicles and lower CO2 emissions, there is considerable impetus to pursue the lightweighting trend (1).
Introduction of carbon fibre by OEM’s
Today, to counteract the problems associated with finding a material lighter than steel but really strong for body parts, carbon fibre composites might seem to be the obvious choice. Ten times stronger than steel and eight times stronger than aluminium, it is much lighter than both metals.
Again, early adoption of the material comes from Formula One where its high cost is less of a factor than its properties. However, some car manufacturers have started to introduce carbon fibre in their production lines.
In 2013, BMW launched the i series which is its first production electric car with a body made of carbon fibre composite. BMW’s first attempt at an electric car, the 1602e, was used as a shuttle at the Munich Olympics in 1972 but the huge weight of its lead-acid batteries (350kg) meant that it would never make it into production.
The Korean automotive manufacturer, Hyundai, also presented a concept car in 2014 at the Geneva Motor Show; the Intrado. This was a hydrogen fuel cell car with a carbon fibre body.
The principle of carbon fibre composites seems to be accepted. But, in order to see carbon fibre in everyone’s cars tomorrow, effort needs to be made to reduce its cost.
R&D companies and universities are working on this challenge and are also trying to solve the issue of recycling. Carbon fibre composite life cycle analysis suggests that without recycling, this material won’t be a green alternative (2).
Also, the size of the vehicle can have a greater impact on the materials selected for manufacturing. Bigger vehicles such as aeroplanes and buses where the power to weight ratio is crucial, is an area where advanced lightweight materials will play a key role.
(1) Reducing CO2 Emissions from New Cars: A Study of Major Car Manufacturers’ Progress in 2006 (http://www.transportenvironment.org/sites/te/files/media/2007-11_car_company_co2_report.pdf published in 2006)
(2) Impacts of Vehicle Weight Reduction via Material Substitution on Life-Cycle Greenhouse Gas Emissions (http://pubs.acs.org/doi/abs/10.1021/acs.est.5b03192?journalCode=esthag extract published in 2015)