Composites Manufacturing - Materials, Product, and Process Engineering Part 8 doc

© 2002 by CRC Press LLC match the coefficient of thermal expansion of the nickel face and provide high thermal conductivity. Integral electrical heating and water cooling pro- vide extremely rapid thermal cycling. Air cooling is used to control the temperature rise at the end of the rapid heat-up to prevent temperature overshoot. Water cooling is used to obtain rapid cool-down at the end of the high-temperature hold. The molds operate in a shuttle press with an integral process control system. 6.8.6.2 Basic Raw Materials For the RTM process, fiber preforms or fabrics are used as reinforcements. There are several types of preforms (e.g., thermoformable mat, conformal mats, and braided preforms) used in the RTM process. The thermoformable mats are produced by more or less randomly swirling continuous yarns onto a moving carrier film or belt and then applying a binder, which is typically a thermoplastic polymer, to loosely hold the mat together. The mat is cut to the desired size and formed under heat and pressure to the shape of the mold. In this process, scraps are produced to get the final shape preform because complicated three-dimensional shapes are produced by cutting the flat mat and then forming it under heat and pressure. Once a shape is formed, the preform maintains its shape. In conformal mats, fabrics or chopped strand mats are placed on the outer layer and spun-bonded core material is placed as core material. These layers are stitched together to form conformal mats. Spun material is placed as a core material to create a low-permeability region in the inside region. In braided preforms, fibers are woven over a mandrel to obtain a three-dimensional fiber architecture. For low-volume FIGURE 6.46 Composite fork for the bicycle. (Courtesy of Radius Engineering, Inc.) © 2002 by CRC Press LLC match the coefficient of thermal expansion of the nickel face and provide high thermal conductivity. Integral electrical heating and water cooling pro- vide extremely rapid thermal cycling. Air cooling is used to control the temperature rise at the end of the rapid heat-up to prevent temperature overshoot. Water cooling is used to obtain rapid cool-down at the end of the high-temperature hold. The molds operate in a shuttle press with an integral process control system. 6.8.6.2 Basic Raw Materials For the RTM process, fiber preforms or fabrics are used as reinforcements. There are several types of preforms (e.g., thermoformable mat, conformal mats, and braided preforms) used in the RTM process. The thermoformable mats are produced by more or less randomly swirling continuous yarns onto a moving carrier film or belt and then applying a binder, which is typically a thermoplastic polymer, to loosely hold the mat together. The mat is cut to the desired size and formed under heat and pressure to the shape of the mold. In this process, scraps are produced to get the final shape preform because complicated three-dimensional shapes are produced by cutting the flat mat and then forming it under heat and pressure. Once a shape is formed, the preform maintains its shape. In conformal mats, fabrics or chopped strand mats are placed on the outer layer and spun-bonded core material is placed as core material. These layers are stitched together to form conformal mats. Spun material is placed as a core material to create a low-permeability region in the inside region. In braided preforms, fibers are woven over a mandrel to obtain a three-dimensional fiber architecture. For low-volume FIGURE 6.46 Composite fork for the bicycle. (Courtesy of Radius Engineering, Inc.) . and then forming it under heat and pressure. Once a shape is formed, the preform maintains its shape. In conformal mats, fabrics or chopped strand mats are placed on the outer layer and spun-bonded. obtain rapid cool-down at the end of the high-temperature hold. The molds operate in a shuttle press with an integral process control system. 6 .8. 6.2 Basic Raw Materials For the RTM process, fiber. and then forming it under heat and pressure. Once a shape is formed, the preform maintains its shape. In conformal mats, fabrics or chopped strand mats are placed on the outer layer and spun-bonded