Composite Coil Spring Development and Testing

This paper will present the development of composite coil springs made from glass-fiber-epoxy materials. It will also review the results from prototype springs that have been manufactured and tested. Sardou S.A. has been developing and manufacturing composite structures and components of various designs for over 27 years. This experience, especially with composite torsion springs, has led to development, prototype production, and testing of several designs of composite coil springs. The design takes advantage of commercially available glass fiber and epoxy materials. The development process led to proprietary design methods and computer models to simulate unique configurations and material characteristics. The development process also allows design of composite springs for the same or smaller design volume as steel coil springs with comparable spring characteristics. The manufacturing methods that are used apply existing lost mold and winding processes in unique ways to produce prototype composite coils springs. These methods were also developed considering scaling-up and automation for volume production. Several generations of prototype composite coil springs have been produced and tested. Each generation has advanced the design and manufacturing methods. Several features of composite coil springs including light weight, dynamic response, flexibility of design, and fatigue resistance have been demonstrated through testing. Depending the steel counterpart considered, composite coils springs offer weight saving of about 75%, fatigue life improvement, no rust, no creep, and no notch sensitivity at a cost close to that of a steel spring.