Feature Article
Feature on composite cars written by Richard Stewart
for Composites Technology magazine.
Composites Provide Concept Cars With
Short Cut Toward Start of ProductionDesign flexibility, low-cost tooling, resistance to corrosion and dents seen as valued attributes.
By Richard Stewart
In the automotive industry, the use of polymeric composites
has been increasing steadily over the past three decades. But
nowhere has the application of composites grown as rapidly
as it has among builders of lightweight alternative vehicles.
These include affordable “world cars,” engineered for econo-
mical manufacture and assembly in nations with emerging
economies; downsized commuter and personal cars, typically
weighing less than 1,000 pounds; and ultralight neighborhood
electric vehicles (NEV), designed to operate at low speeds in
closed communities and on city streets.
Plastics and composites are used extensively in these vehicles,
even for structural members such as frames and roof supports,
eliminating the need to purchase expensive metal stamping
equipment. The design flexibility, strength and durability of
polymeric materials have enabled these niche vehicles to move
swiftly from their introduction as concept cars right into pro-
duction. The plastic/composite car is very much a reality today.PARADIGM FEATURES
PULTRUDED FIBERGLASS
The world's first car to make extensive use of plastics and
composites is the Paradigm, a four-door, five-passenger sedan
scheduled for production late this year [2000] in China.
Developed by Automotive Design & Composites Ltd. (San
Antonio, Tex.), the car has an FRP composite chassis made of
pultruded fiberglass/vinyl ester epoxy frame members and a
body formed from vacuum thermoformed (non-reinforced)
thermoplastic body panels.
“Using plastics and composites together is the key to man-
ufacturing these vehicles,” says Michael Van Steenburg, founder
and CEO of the company. “Plastics have all the processing
versatility that the auto industry is looking for, and composites
have the strength to handle the load.” The Paradigm and other
vehicles developed by his company were designed from the
ground up as a marriage of these materials, he notes. He put
the total cost of tooling for the Paradigm's chassis and body
at about $100,000.
The chassis is constructed of a center beam and two outside
beams, joined by five cross-car frame members. These com-
posite rails, with a tensile strength of 75,000 psi, are twice as
strong as steel at a quarter of the weight. They are formed by
injecting resin into a die through which continuous glass fibers
are pulled. The pultrusions, with a ratio of 70% glass to 30%
resin, are post-formed into the load-carrying beams. Epoxy/glass
pultrusions also support a thermoformed tub, the central
structure of the chassis.
Pre-colored body panels, produced on rotary vacuum-forming
machines from a three-layer co-extruded sheet, are assembled
to the chassis using two-sided adhesive tape from 3M (St. Paul,
Minn.). That forms a plastic-composite unibody structure.
Brunswick Technologies, Inc. (Brunswick, Maine) supplies
fiberglass materials. Dow Chemical (Midland, Mich.) supplies
vinyl ester epoxy.
Changes designed to make the Paradigm even more manufac-
turable are planned before production starts, according to Van
Steenburg. For one, a thermoplastic resin matrix will replace the
thermoset epoxy as material of choice for the pultrusions, he
relates.
The decision to switch was made on the basis of recyclability
and the ability to use vibrational welding rather than adhesives to
join the members. A PBT resin with properties similar to vinyl
ester has been developed by an undisclosed supplier. “We try
to avoid adhesives when we can,” Van Steenburg confides.
“Welding is more efficient and provides a good, strong bond
because you don't have a dissimilar material between the two
parts.”
The Paradigm, just over 15' long and weighing less than
1,800 pounds, will be powered by a parallel hybrid drivetrain,
which combines a two-stroke gasoline engine with an electric
motor to produce 105 hp. First-year production of the car is
expected to total 5,000, after which the Chinese plant will ramp
up to an anticipated 30,000 cars a year by 2002.PLASTIC & COMPOSITE
SPORT UTILITY VEHICLE
Van Steenburg's company also developed the Baja, a sport
utility vehicle with a molded thermoset composite chassis and
pre-colored thermoformed thermoplastic body panels. Weighing
only 1,200 pounds, the vehicle can carry as many as eight people.
It was designed for use in damp environments of the Caribbean
and other coastal areas in Central and South America where the
effects of corrosion show up on new cars after only a couple years,
he observes.
The Baja's hood, bumper covers, dashboard and removable half
doors are vacuum-formed of thermoplastic material. Thermoset
composites are used to mold other components, including a lower
chassis tub. A steel subframe, which might later be replaced by a
pultruded frame similar to the one on the Paradigm, supports the tub.
An upper roof structure is bonded to the tub. The composite parts
are molded using a vacuum-assisted resin transfer molding
(VA-RTM) process, using a 50/50 ratio of vinyl ester epoxy and
glass.
A modular design, the Baja can be assembled and shipped in
two crates, which qualify as auto parts and avoid an import-vehicle
tariff. The front and rear modules, divided at the firewall, can be
assembled in half an hour, says Van Steenburg. Powered by a
60-hp gasoline engine, the vehicle can deliver impressive fuel
economy of 50 mpg.
Another plastic-composite vehicle, a multi-purpose truck called
the MPT, is under development by Automotive Design & Com-
posites. It features a pultruded chassis as well as a pultruded pickup
bed. The fiber-rich pultrusions enable the vehicle to provide a two-
ton payload capacity in a vehicle that has a curb weight of less than
1,600 pounds, according to Van Steenburg. The box is assembled
from three pultrusions, the floor and two sidewalls, which are
vibration-welded together. The pickup box forms a unit body with
the rear of the thermoformed cab, which is bonded to a pultruded
roll-cage structure.
“We're going to a single pultrusion for the pickup bed as soon as
we get a big enough machine,” says Van Steenburg, noting that the
company wants a machine that can produce pultrusions as large as
10' x 10'. “That would let us do bus structures, van boxes, bridge
beams and other large pultrusions.” Quotes from machine builders
are running between $1 and $2 million, he notes.
A joint venture company has been formed to market manufactur-
ing facilities to produce the MPT in Mexico, Bolivia, Ecuador and
Guatemala. The first plant, with a planned annual capacity of 1,200
vehicles, is being built in Monterrey, Mexico. Reportedly, the entire
first-year's production has been pre-sold.WORLDSTAR GEARED
FOR MICROFACTORIES
Composite Automobile Research Ltd. (El Cajon, Calif.) has dev-
eloped the WorldStar, a lightweight, inexpensive utility vehicle. It is
made with fewer than 500 parts and features a glass-reinforced
polyester structure on a tubular steel frame. The body is produced
with open molds, using spray-up and hand lay-up processing.
The laminate is applied over colored gel coat, which eliminates
the need to paint the vehicle. Structural foam and balsa wood are
sandwiched in the laminate to provide additional reinforcement where
needed. A total of 25 open molds are used to manufacture the
WorldStar in its various body styles, including pickup truck, van,
cargo box and 11-passenger bus.
The company is also in the business of selling turnkey manufac-
turing plants in developing countries to produce the WorldStar
using local semi-skilled labor. A joint venture operation is
expecting to set up two dozen factories in Columbia, Venezuela,
Ecuador and Panama this year. The basic WorldStar manufacturing
unit is a modular micro-manufacturing facility, built in a space as small
as 10,000 sq. ft., that can turn out a vehicle a day, according to
spokesman Boyd Marshlain.
“We provide our license holders with all the body molds, steel-
forming jigs, and tools they need to produce the composite compon-
ents and the tubular steel structure. We also sell the parts and
materials to assemble the vehicle,” he explains. Parts include a 62-hp
remanufactured and warranted VW engine, which the company
sources from several suppliers.
“Fiberglass composites are ideal for vehicles in the countries we're
targeting. Composites are lightweight, very durable, and don't rust
or dent easily.” The WorldStar successfully completed a series of
crash tests, suffering only minor damage after frontal and broadside
crashes, Marshlain related.
Chopper guns are not included in the microfactory package since
few workers would have the skills or experience needed to use the
equipment in the start-up plants. Hand lay-up is the method recom-
mended by the company for license-holders, relates Kevin Jackson,
shop foreman. “This vehicle is simple to build using hand lay-up. We
provide everything needed to easily make a car in eight hours.”
Between 100 and 200 hours of labor are needed to build each
WorldStar. Raw materials and parts to produce the car cost manu-
facturers about $4,000, and the vehicle is expected to sell for under
$7,000, varying according to the cost of labor.ELECTRICITY POWERS
VARIETY OF VEHICLES
General Motors introduced its EV1, the world's first production
electric car at the end of 1996. The two-passenger sports coupe
weighs 2,970 pounds, including the 26 lead-acid batteries. Vehicle
weight was minimized by the use of composites and plastics. The
doors, roof, hood and truck lid are compression molded from sheet
molding compound (SMC).
The polyurethane fenders, quarter panels, rocker panels, wheel
skirts and belly pan are reaction injection molded. The battery tray,
which is a structural component molded of 30% glass/polypropylene,
was named the most innovative use of plastics in 1997 model cars
by the Society of Automotive Engineers.
GM had long been working on the development of electric vehicles.
Its solar-powered Sunraycer won the World Solar Challenge in 1987
across Australia. That led to the Sunrayce collegiate competition for
solar-powered vehicles held every two years in the U.S. These
student-built racers carry photovoltaic arrays, which convert sunlight
to electricity for power.
In constructing the Sunrayce entries, teams utilize composites to
optimize weight and strength. The chassis can be a monocoque design,
which supports the load. Other designers favor a welded tubular-steel
space frame on which to carry a composite body shell. Some teams
favor a combination of the two styles, a semi-monocoque chassis,
using composite beams to support the body.
GM continues its efforts to incorporate advanced propulsion
systems and lightweight materials in vehicles, as evidenced by the
Chevrolet Triax concept vehicle introduced in October at the 1999
Tokyo Motor. Built on a steel chassis with separate body shell
molded of composites and plastic materials, the Triax was devel-
oped in just seven months – from concept to completed vehicle,
reports GM. Horizontal body surfaces of the vehicle are molded
from SMC, while RIM is used on vertical panels.
The body-on-frame chassis design provides a flexible platform
that can accommodate several body styles and 4-wheel-drive drive-
trains. Pickup truck and cargo vehicle bodies are being considered
in addition to the show model's aerodynamic SUV design. Power
choices would include electric, hybrid, and internal combustion,
says GM.
“The beauty of the Chevrolet Triax is its flexibility. It's a clean-
sheet design approach intended to meet the demands of customers
while demonstrating GM's resolve to address environmental issues,”
remarked John F. Smith, GM Chairman and CEO, during an intro-
duction ceremony in Tokyo. The concept vehicle addresses pro-
pulsion, efficiency, mass, aerodynamics, as well as cost, creating a
opportunities for customers regardless of where they live, says GM.
Solectria Corp. (Wilmington, Mass.) has made a name for itself,
both in winning electric-car competitions and in manufacturing and
selling electric vehicles. The company's composite group provides
consulting services, offering advice on conceptual design, processing
and manufacturing, in addition to developing composite-based
prototypes. The company also manufactures and markets equipment
to fabricate preforms from engineered textiles using fiberglass,
carbon aramid, polyethylene and other reinforcement materials.
Solectria introduced its prototype Sunrise, a composite-based
electric coupe in 1997. James Hogarth, former manager of the
Sunrise project and now president of Electric Vehicles Worldwide
LLC (Pittsfield, Mass.), plans to develop composite-based, electric-
powered fleet vehicles for the federal government. The company has
been awarded a $1.35 million federal grant for R&D. Plans call for
producing as many as 20,000 vehicles a year by 2005.PERSONAL VEHICLE
MOLDED FROM FRP
The Sparrow, an electric, three-wheel “Personal Transit Module” is
manufactured by CorbinMotors.com (Hollister, Calif.), using FRP
construction. The company's “.com” name reflects the success of
its online marketing efforts; about half of the sales of the vehicle come
over the Internet, according to Tom Corbin, vice president. Develop-
ment was started on the Sparrow in 1996, and production began
three years later.
Registered as a motorcycle, the single-seat vehicle sells for
$12,900 and measures 8' long and 4' wide. The power pack consists
of 13 lead-acid batteries and provides a range of 40-60 miles, with a
top speed of 65 mph. Curb weight totals 1,300 pounds, including
batteries, which weight 600 pounds. Recharging takes six hours at
110v, two hours at 220v or 200v. Designed as a commuter vehicle,
the Sparrow offers a size and range sufficient for the majority of U.S.
commuters, since 87% travel 18 miles or less to work and 93% drive
alone, according to Corbin.
The monocoque chassis is made up of two main components, a top
tub and a bottom or base tub. Each tub consists of an inner skin and an
outer skin, sandwiching a layer of polyurethane foam, similar to that used
to manufacture surfboards. The foam is injected between the two skins
after they have cured, explains Corbin. He likens the Sparrow driving
experience to “riding down the road fully enclosed in a motorcycle
helmet.”
The tubs are molded using two-sided clamshell molds made of
polyester/glass composite built on a steel framework. The mold halves
are waxed and gel coat is sprayed on and allowed to cure. Layup
combines 2 oz. mat with 6 oz. cloth; balsa is added to large, flat panels
to stiffen them.
Resin is applied with brushes, and rollers are used to flatten air
bubbles and facilitate impregnation of the fiberglass materials. The
thickness of each skin varies from 1/8” to 5/8” and even thicker in
areas requiring additional reinforcement. Metal plates are embedded
in the laminate to provide attachment points.
Once the laminate has cured, the mold halves are closed, clamped,
and a 9-lb., two-part polyurethane foam is injected between the two
FRP shells. Both tubs are produced in the same manner. A flange
around the bottom perimeter of the top tub overlaps the bottom tub.
They are secured together with an adhesive and metal fasteners. Overall
thickness of the FRP/foam sandwich varies from 1” to 2”. The foam
provides excellent insulation characteristics, notes Corbin.
A transverse, thickened rib in the roof serves as a roll bar. A steel
subchassis is glassed into the bottom of the structure to support the front
axle, independent suspension and two wheels. At the rear, a single, belt-
driven wheel is mounted to a swing arm. The Sparrow's windshield, rear
window and power side windows are made of automotive safety glass.
Only a single door is provided in order to maximize chassis strength,
simplify construction and reduce weight, Corbin explains. It's on the
curb side. That permits maximum impact resistance on opposite or
traffic side, where side collision impact is most likely to occur.
Front and rear sections of the Sparrow are also molded using hand
layup processing and assembled to the main chassis section. The front
section is designed to deform and absorb energy upon impact. Other
FRP body components include the hood, rear wheel skirts, and a hatch
for access to a storage compartment.
“By designing the Sparrow as a monocoque structure, we make the
bottom tub serve three functions -- the chassis of the car, the battery
box and the exterior skin,” Corbin observes. Batteries are carried both
in a molded-in front compartment, where they provide crash protection
in frontal impacts, and beneath the seat.
Production has gone from one unit a day to two, and the company
is ramping up to produce between 7,000 and 12,000 units next year,
according to Corbin. Construction of a new manufacturing facility in
Daytona Beach, Florida, will be completed this spring to handle orders
from the Eastern U.S., Europe and South America.
Another lightweight, three-wheel electric car is manufactured by the
Neighborhood Electric Vehicle Company (Eugene, Ore.). It qualifies as
a motorcycle for registration purposes, but provides 10 cubic feet of
storage capacity. Called the Gizmo, the vehicle carries one person at a
top speed of 40 mph. The vehicle has a range of 25 miles from four
batteries, which take just over three hours to recharge at 110v. Instead
of a steering wheel, the Gizmo features dual side-mounted push/pull
levers called steering handles, which also control acceleration and braking.
Like the Sparrow, the Gizmo's composite chassis serves as the
integrating structure. Two wheels are mounted at the front, and a single
wheel is at the rear. The vehicle has molded FRP chassis sections --
a rounded front cowl, fenders, tail and roof – and incorporates a subframe
of steel tubing.
Removable fabric side panels enclose the vehicle. Without doors or
steering column, the vehicle does not require a heavy chassis, the
company notes, enabling the Gizmo to tip the scales at only 580 pounds
– including batteries. Production started last year after the company spent
a reported $150,000 to create molds and build a prototype.
Innovative vehicles molded of plastics and composites offer people in
developing countries who cannot afford to buy conventional cars and
trucks an affordable path to ownership. Polymeric materials are easy to
mold using inexpensive soft tooling. That enables manufacturers to start
up vehicle production at a fraction of the cost required for a traditional
automobile assembly plant.
These alternative vehicles, engineered specifically for FRP materials,
contain fewer parts than conventional cars and trucks and are inexpensive
to manufacture. Plus, they weigh less, offer better fuel economy, and are
impervious to the ravages of corrosion, which can quickly destroy
automotive sheet metal in many regions.
Lightweight, composite-based electric vehicles show great promise as
environmentally friendly alternatives to conventional ones powered by
internal combustion engines, especially for commuters. In developing nations,
locally manufactured, low-cost vehicles powered by remanufactured gasoline
engines, can help usher poorer populations into the modern age – squealing
tires, racing motors and all.
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