December 8^th, 1999              

Strengthening a carbody - with foam

Mazda Motor Corporation has developed a "world first" new technology to strengthen a vehicle’s body without adding weight.

It involves resin foam being filled into parts of the vehicle body frame, increasing body strength and substantially improving safety in collisions, with very little increase in overall weight.

Fully developed by Mazda, the technology was first made possible by the development of a strong structural foam and then a unique method of filling the resin foam into the body frame cavities.

A newly designed body frame structure enables the structural foam to be spread more effectively and makes the technique even more practical.

The idea of pouring resin foam into vehicle body frames to increase body strength or reduce body vibration and noise has existed for sometime. However, the existing technologies have not increased body strength to the extent of improving occupant safety in collisions.

Conventional methods use thicker steel or reinforcements and are attached to the body frame to increase strength and improve collision safety. However, these methods result in weight increases, failing to satisfy an important vehicle engineering objective: weight reduction and improvement in collision safety at the same time.

The idea of the new technology evolved from the fact that body strength will increase drastically if the body frames are prevented from folding on collision. The crushing energy from a collision impact would be effectively released if weaker portions of the body frames were reinforced by strong structural foam.

In order to be effective, the structural foam has to be able to withstand compressing pressure and have strong adhering power. This new structural foam developed by Mazda has been designed to do just that: withstand high compressing power while having strong self-adhesive power after it inflates in the body frame.

In the production procedure, the resin foam material in sheet form is attached inside the body frame. From the heat of the painting process, the foam then inflates to fill up the inside of the frame.

The main advantages of the new technology are as follows:

1. Because the technology does not require reinforcement of the body frame with steel pieces, and when it is used in "B" pillars, it has a body strength in collisions equivalent to that of those reinforced with steel pieces it will result in a weight reduction of about 6 kilograms per vehicle.
   
2. Since this technology avoids the use of steel (material) reinforcements and the use of press dies in making such materials (steel), related parts costs are therefore reduced by approximately 10%.

This technology has been applied for the first time in the Freestyle Door System* of the "RX-EVOLVE" concept car, exhibited at the recent Tokyo Motor Show.

This car, although possessing no "B" pillar, boasts a strong body and top class performance against side collision. Mazda is planning to apply this technology to mass production vehicles in the future, and pledges to continue working on further improvements to body strength and body safety, "MAGMA"** and reduction in vehicle weight.

*Freestyle Door System means a front hinged front side door and rear hinged rear side door system having no "B" pillars, realizing a wide-open entrance space.