Prepreg process specifications

Autoclave processing is a process in which individual prepreg plies are laid up in a prescribed orientation to form a laminate (Fig. 5.9). The process involves consolidation of the laminate, which generally results in a three-dimensional flow field. Similar to the IP process the fiber bed is not stationary in the AP process hence, its movement has to be specifically considered when the appropriate conservation equation for this process are developed. If it is assumed that the resin has a relatively constant density (i.e., the excess resin is squeezed out before the gel point is reached) then the appropriate conservation of mass equation for this consolidating system is Equation 5.12. 

Thermal and mechanical properties of HiPerComp composites have been measiued at various stages during their development. Consequently the data presented here differs somewhat from previously published data summaries [1] since the material system and processing techniques have continued to evolve with time. The data presented here for Prepreg HiPerComp was mostly measured as part of the DOE-sponsored Continuous Fiber Ceramic Composites (CFCC) program on material fabricated in 2000 and 2001. Data for the Slurry Cast HiPerComp material was measured in 2003. Please note that this data is presented for informative purposes only, and should not be construed as, or used for, engineering specifications. 

A special, easy to use, process aid adhesive , fully miscible with a variety of resin matrices, specifically developed for tacking prepregs, fibres, or for example RTM preforms into a mould or on to a mandrel. Available in different widths. 

During the quahfication of a new laminate material, it may also become necessary to perform prepreg-specific tests to verify its quahty. The most commonly tested properties of prepregs are resin content, flow during mutilayer processing, and gel time. Details about additional properties and all corresponding test methods can be found in IPC-4101. 

To facilitate the many choices of laminates and their associated properties, industry standards groups such as the IPC have defined minimum performance specifications and have issued several specifications to inform the selection process. Some of the most commonly used material specifications are those that deal with laminate,prepreg, and copper foil. IPC lOl, Specification for Base Materials for Rigid and Multilayer Printed Boards, and IPC-4652, Metal Foil for Printed Wiring Applications, are the primary specifications for clad laminates, prepregs, and foils. Another specification, IPC- 4104, Specification for High Density Interconnect (HDI) and Microvia Materials, deals with many of the new materials for HDI, such as epoxy-coated microfoils, as discussed in this chapter. 

This adhesive had to be formulated to match the cure cycle of the composite skins as the panels were produced by a one-shot process, i.e. the curing of the prepreg skins and the bonding to the honeycomb core took place at the same time. It also needed to have some degree of flame retardancy to meet the requirements of the aircraft manufacturer s specifications, for example the BMS 4-17 [38] specification of Boeing. 

To fabricate continuous fiber-reinforced plastics that meet design specifications, the fibers should be uniformly distributed within the plastic matrix and, in most instances, all oriented in virtually the same direction. This section discusses several techniques (pul-trusion, filament winding, and prepreg production processes) by which useful products of these materials are manufactured. 

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