Lightweight Garage #13 Composite tunnel reinforcement @ Jeep Grand Cherokee (WL)

The Vehicle

This time we imported a Jeep Grand Cherokee WL75 from America into our lightweight garage. With a length of 5.20 m and a wheelbase of over 3 m, this SUV offers enough space for a third row of seats. The 5.7 L naturally aspirated V8 engine produces up to 357 hp and 357 Nm.

©Automotive Rhythms, Jeep Grand Cherokee L 2021, CC BY-NC-ND 2.0

In addition, depending on the equipment, various all-wheel drives are available, and the Jeep can conquer ramp angles of up to approximately 23°.

The Technology

A novelty in this vehicle is the tunnel reinforcement with a pultruded structure based on elastocoat polyurethane and continuous glass fibres. During the pultrusion process, a semi-finished fibre product (e.g. roving) is impregnated with the resin in an impregnation tank and shaped in the performer into the desired cross-sectional form. This is followed by the curing of the fibre-reinforced composite. In the next step, the profile is pulled out of the preformer and cut to the specified length.

This manufacturing process offers the possibility of producing large quantities of fibre-reinforced profiles economically. Especially by improving the manufacturing process, it was possible to double the output quantity for the Jeep application compared to the industry average.

The Lightweighting Effect

Characteristic material properties in combination with the advantages of the manufacturing process result in a higher specific strength than ultra-high-strength steel. In order to exploit the anisotropic material properties, the material behaviour has been simulated and designed for the critical load case.


The load-oriented design of the tunnel reinforcement results in a weight saving of primarily 40 % and 20 % for the subsystem. The solution was also awarded the Altair Enlighten Award for "Module Lightweighting" for the weight saving of approximately 2.1 kg. And the optimisation also reduced the required package.

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