Structure-property Relationships of Composite Coil Springs Processed by Rtm

Textile technology and resin transfer molding (RTM) process have been combined to manufacture composites coil springs. Preforms for coil springs were made by braiding process, in which axial yarns are located in the central region and braiding yarns covered them circumferentially. The geometric and process parameters that are related with the fiber orientation and fiber volume fraction of the braided composites have been identified. The carbon fibers and aramid fibers were utilized for fabricating the spring preforms with the wire diameter <5mm. For the RTM process, braided preform was wrapped into the five-piece mold cavity designed. The resin was injected into the mold at 120C for cure. In order to assess the mechanical performance of the composites spring, an analytic method for predicting the spring constant has been developed. The model prediction compared favorably with experimental results.