Automated SRIM preforming is focus for Automotive Composites Consortium.

The Automotive Composites Consortium (ACC), the cooperative technology group formed four years ago by the Big Three automotive builders of Detroit, this quarter will demonstrate prototype production of directed-fiber preforms for structural RIM (SRIM), utilizing a novel, proprietary method that automates the glass preforming process.

In addition to its SRIM preform work, the ACC (based in Troy, Mich.) continues working on automated preforming for front-end vehicle rails produced by the resin transfer molding (RTM) process. The consortium also is launching a new research program that addresses a wide range of factors involved in bonding and joining composite parts, and is nearing the final planning stages of initiating an unnamed SRIM program that will demonstrate production of structural body members. Details on this new SRIM project are expected in coming months.

PREFORMING IS KEY

Dick C. Kowalske, current chairman of the ACC and manager of the Chassis Engineering Department for Ford Motor Co., says SRIM cross-member prototypes utilizing the novel preform production method will be demonstrated by the end of March. (A cross member supports the transmission, engine, suspension and steering.)

While he declines to provide specifics on the new automated preforming process, Kowalske says it produces a directed-fiber glass charge comparable to manually directed, vacuum layup/chopped-glass spray. Cross-member prototypes, fabricated with the new preform, will be molded at the General Motors Corp. research laboratories in Warren, Mich.

Glass preforms for the parts will be made at several vendor sites. As reported previously, manufacturers that have entered into joint-development agreements with the ACC in SRIM composite structure research include GenCorp Automotive, Akron, Ohio; Molded Fiber Glass Companies, Ashtabula, Ohio; CertainTeed Corp., Valley Forge, Pa.; and Bentley Harris Manufacturing Co., Lionville, Pa.

ACC's developmental preforming system may be an extension of composite production technology introduced by GM in 1989. GM presented three types of single-station robotic production cells for fabricating glass preforms. All three cell concepts involved an enclosed plenum chamber where chopped fibers were sprayed onto a flat or contoured preform screen. A robot would either chop and manipulate glass rovings onto the preform screen, or direct the flow of chopped rovings while operating a binder spray gun. The preform screens were placed over a lower enclosed chamber, with a vacuum maintained by a centrifugal fan.

Kowalske says glass preform fabrication represents the key factor in SRIM commercial development. "We want to configure the glass charge so it does the engineering job we want," he says. "We need to determine how a preform reacts as a finished part, and how it will perform in the field."

The ACC recently entered into a joint research agreement with the Composites Automation Consortium (CAC) in Burbank, Calif., for development of an automated system to produce glass preforms for the cross member. Kowalske says the ACC will contribute composite product designs and tooling, while the CAC will provide expertise in production automation. The CAC will utilize manufacturing concepts for directed-fiber preforms based on technology developed at the Battice, Belgium, laboratory of Owens-Corning Fiberglas Corp., Toledo, Ohio.

SRIM molding cycle times do not represent a problem for existing automotive manufacturing technology. Kowalske says the ACC already has demonstrated 6-min cycle times, which would be commercially viable for an annual production yield (one tool, one part) of 50,000 SRIM units. Based on current technology capabilities, SRIM is expected to continue as a relatively low-volume production domain for automotive in the near term, he says, estimating a range of no more than 20,000 to 100,000 units annually for any SRIM application. Thus, the productivity of existing SRIM molding technology could support current commercial demand.

Automated assembly of glass preforms is vital to the success of another ongoing program for the ACC: testing and development of RTM glass/vinyl ester front-end vehicle rails. Front rails are the structural members located beneath a car's fenders that support the engine and manage energy absorbed in a frontal collision. (ACC is studying composite part performance during 35-mph crash tests.)

Along with its efforts in preform fabrication, Kowalske says the ACC continues to seek improvements in the entire SRIM process, including temperature control, mold-filling analysis, and development of various resin systems.

FASTENING, BONDING R&D

A new research program launched in December will examine a range of topics in fastening and bonding of composite parts. Kowalske identifies this as a crucial body of knowledge requiring greater study and definition. Bonding/fastening technology could become the critical element in determining the successful application and growth of composites in the automotive field, he says. The lack of a reliable database and engineering standards for composite fastening and bonding techniques "could hold up potential automotive applications," he says.

The ACC's bonding/fastening research will explore adhesive types and their application; the design, quality and predictive success of composite joints and connection points; and aging/impact field studies of composite joints.

Kowalske says there are two major constraints that must be satisfied in this program: the end-use part performance must be flawless, from the point of view of consumers; and the technical specifications must be acceptable to OEMs in terms of their assembly and fabrication. One target of the program will be to establish standard test methods that could verify the quality of bonded composite parts.