High-Performance Composites is read by qualified composites industry professionals in the fields of continuous carbon fiber and other high-performance composites as well as the associated end-markets of aerospace, military, and automotive.
Issue link: https://hpc.epubxp.com/i/101340
INSIDE MANUFACTURING epoxy resin is injected ��� injection time averages about four minutes ��� and the workpiece cures inmold in ~30 minutes at 80��C/176��F. Then the cured tube is demolded and placed back in the shuttle. In the third production stage, also the ���nal step in the LSW process, the tube is moved into the trim cell and cut to length. A 6-axis robotic arm transfers the workpiece from the shuttle to a holding ���xture, where the soul is removed from the core. Then, the ���exible silicone core can be retracted from the part. Next, the 36 | now hollow carbon tube is positioned via robot within a cutting cell that self-seals to contain carbon dust. After a precision diamond saw trims the tube to ���nal size, it is removed from the cell and placed in a bin. A worker collects the binned tubes and performs a series of quality-assurance tests before depositing them at the assembly station. Making precise connections Having mastered the process for ���perfect��� tubes, the next question was how high-performance composites best to connect them. BMC calls its answer, the Shell Node Concept (SNC), ���revolutionary��� because it forms the frame���s nodal points not as one-piece collars, but instead as two bonded half shells. Each half shell���s inner and outer geometries, therefore, are more easily designed to optimize frame loading, and the shell���s ribbed interior (see Step 5, p. 34) de���nes how the adjoined tubes ���t with absolute precision. The shells are injection molded using a 40 percent carbon ���ber/thermoplastic compound (by weight), with ���bers ~4 mm/~0.2 inch in length. The combination of the stiff ���bers and resilient matrix make the shells rigid and light yet shock absorbent. Engineers de���ned the ���ber orientation in each shell, using a CAD-based mold ���ow analysis simulation. The data was used to construct small batches of matched-metal tools. To verify the mold ���ow analysis results, these tools were subjected to a series of tests, including computed tomography, which accurately gauged the wall thickness and inspected the structure for faults. After necessary changes were made, the ���nal metal tools were ready for injection. Injection molding of shells is carried out offsite by a partner company that specializes in the process. The injection molding machine is equipped with the mold of the given shell, and an engineer loads in carbon compound pellets supplied by EMS Grivory (a business unit of EMS-Chemie AG, Domat/Ems, Switzerland). The machine melts and injects the compound. The ���nalized CAD data for the speci���c metal tool enable engineers to visually monitor the formation of the shell���s interior ridges and to control all of the key process parameters (temperature, ���ll time, ���ow rate and ���ow properties). During the molding cycle, these and other data are recorded, enabling further optimization. Molding is completed in minutes, after which the shells are de���ashed and inspected. Back at BMC, the shell halves are hand-placed into an adhesive application ���xture (green ���xture shown in Step 6 on p. 34) that has been mounted onto a carrier. Then they enter an automated workstation, where a robot equipped with an optical monitoring system recognizes each component and de���nes the quantity and location of adhesive before applying it to each part. BMC uses epoxy adhesive supplied by Huntsman