A Modular Integrated Front End with a Structural RIM Beam/Support - A Case for the Directed Fiber Preform Process

A Modular Integrated Front End (MIFE) has been designed, prototyped and tested. The backbone of the MIFE is a structural RIM (SRIM) beam/support, which incorporates the bumper beam, the radiator support, headlamp cans, turn signal and side marker lamp supports and reinforcement brackets. With the SRIM process, it was possible to integrate these 20 plastic and stamped steel components into one part resulting in a weight savings of 13 Kg (28.5 lbs). The bumper beam is a closed section utilizing urethane foam cores. The MIFE also includes a full urethane fascia and a urethane foam energy absorber. The MIFE successfully passed 8 kph (5 mph) pendulum and barrier tests as well as the 4.8 kph (3 mph) pendulum corner test. The directed fiber preform process was judged to be the only practical method of making the very complex preform required for this design.

IN THE late 1970's Davidson started looking at further integration, specifically bumper beams, to complement its urethane fascia and urethane foam energy absorber (Davisorb^tm) product lines. None of the materials and processes then available fitted in with Davidson's RIM capabilities. In the mid 1980's SRIM was introduced. The SRIM process with it's inherent product versatility in terms of the availability of different types of resins, different types of fiber glass preforms and the ability to vary the levels of glass loading was ideal for the degree of integration considered necessary. A generic beam tool of a W-shaped configuration, which could be adapted for a closed section, was built to evaluate the available material systems and glass types. The data developed with this beam tool provided the confidence to proceed with a more complex beam/support structure. A generic concept was developed showing the degree of integration possible and the resultant cost and weight savings. This concept was presented to several OEM's and a prototype development program was initiated. This program was jointly funded by Davidson Exterior Trim Textron and the OEM. The three parts included in this MIFE program are shown in Figure 1.

In the early stages of SRlM development, it was felt that SRIM might not be competitive for simpler bumper beams when evaluated against a stampable thermoplastic or SMC. Therefore, the decision was made to look at more complex geometries which would not be feasible with those processes and also offered more cost and weight savings through the greater degree of integration possible. However, with the introduction of lower cost resins, SRIM can be competitive with other materials in many different applications.

This prototype program, as with many other plastic development programs, was made

more difficult by the fact that we were demonstrating our MIFE development on a production vehicle and therefore were making a direct substitution of plastic for steel, rather than designing a brand new part to take the best advantage of plastics inherent properties and capabilities. The optimization of composite properties was not fully realized because of these inherent design restraints. Even under these conditions, however, a considerable weight savings was achieved. Determination of cost savings is dependent on OEM manufacturing costs which were not fully available to Davidson. However, with the best information available and using very conservative cost data, the cost savings of the MIFE vs. current construction was in excess of 6%.

The commitment of Davidson Exterior Trim Textron to the SRIM process led to the design, development and building of a directed fiber preform machine with a 1830 mm (72˝) diameter screen, capable of making a preform for a complete beam/support. This machine was not available in time for the development program discussed herein and therefore, we had to use multiple preform sections as discussed in the preform section.