Prepreg manufacturing processes

The chapter is divided into a section on development of process cycles or plans and a section on in-process control. The tools to be discussed include design of experiments, expert systems, models, neural networks, and a variety of combinations of these techniques. The processes to be discussed include injection molding, resin transfer molding, autoclave curing, and prepreg manufacturing. The relative cost and difficulty of developing tools for these applications will be discussed where data is available. 

P(2) Prepregs should be considered where the design and manufacturing process requires a high fibre volume fraction, low void content and composite premium performance. Elevated temperatures are essential to cure these materials and achieve the highest mechanical properties and environmental resistance. 

Resin Flow Submodel. Resin flow analysis in a manufacturing process provides estimates of resin flow, and fiber and resin distribution and compaction. In the early stage of the autoclave process, after the prepregs are staked and vacuum hagged, the system is pressurized while the temperature is increased in order to minimize the resin viscosity. In this way the resin flow removes the excess resin from adjacent plies and makes uniform the fiber distribution. In the RTM process the dry fibers inside the mold can be considered as a porous medium through which the resin is injected from a single or multiple inlets Darc/s law can he used to perform a two-dimensional flow analysis. Darcy s law can he written as... 

Principal manufacturing process using prepreg materials, and comparison to infusion techniques. 

A flame retardant structural grade epoxy for prepreg manufacture and vacuum bag processing. Cure temperature 160-175 C and a service temperature of 70 C. Meets MIL-R-9300, Type I, Grade D. 

A cyanate ester resin for prepreg manufacture, autoclave and vacuum bag processing, offering high temperature wet condition performance. Cure temperature 175 C and an equivalent hot-wet service temperature. 

A low cost, all-purpose polyester for prepreg manufacture which in-tum offers a cost-effective alternative to wet-lay processes. Approved for radome application. Cure temperature 80 - lOS C and service temperature up to 70 C. 

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