Chapter 14 - Processing of Polymer Matrix Composites and Rubber

resin transfer molding (RTM)

refers to a closed mold process in which a preform mat is placed in the lower mold section, the mold is closed, and a thermosetting resin, example polyester, is transferred into the cavity, under moderate pressure to impregnate the preform. another form of transfer molding for PMC

curing

required of all thermosetting resins used in FRP laminated composites. accomplishes cross linking of the polymer

hand lay-up

shaping method in which successive layers of resin and reinforcement are manually applied to an open mold to build the laminated FRP composite structure. oldest open mold method for FRP laminates.

mandrel

special tooling that determines the geometry of the filament wound part

polar winding

1 of 2 basic winding patterns in which the filament is wrapped around the long axis of the mandrel

helical winding

1 of the 2 basic winding patterns in which the filament band is applied in a spiral pattern around the mandrel at a helix angle

fiber reinforced composite (FRP)

can be designed with high strength-to-weight and stiffness-to-weight ratios

reinforced reaction injection molding (RRIM)

closely related to reaction injection molding but includes reinforcing fibers, typically glass, in the mixture.

bulk molding compound (BMC)

consists of similar ingredients as those in SMC, but the compounded polymer is in billet form rather than sheet. fibers are shorter typically 2-12mm (0.1-0.5in)

mat

formed from fibers. a felt consisting of randomly oriented short fibers held loosely together with a binder, sometimes in a carrier fabric

prepregs

impregnated layers of fiber reinforcement are first prepared outside the mold and then laid onto the mold surface. alternative to wet lay-up

wet lay up

impregnation of resin into the fiber mat or fabric accomplished by rolling

sheet molding compound (SMC)

is a combination of Thermosetting (TS) polymer resin, fillers and other additives, and chopped glass fibers (randomly oriented) all rolled into a sheet of typical thickness

polymer matrix composites (PMC)

is a composite material consisting of a polymer embedded with a reinforcing phase such as fibers or powders

spray-up (method)

liquid resin and chopped fibers are sprayed onto an open mold to build successive FRP laminations

cloth

most familiar form of continuous fiber. it's a fabric of woven yarns

filament winding

process in which resin-impregnated continuous fibers are wrapped around a rotating mandrel that has the internal shape of the desired FRP product.

pulforming

pultrusion with additional steps to form the length into a semicircular contour and alter the cross section at one or more locations along the length

they are fabricated with continuous filaments rather than chopped random fiber thus increasing strength and modulus of the final product

How is a prepreg different from a molding compound

roving

a collection of untwisted (parallel) continuous strands; this is a convenient form for handling and processing

pultrusion

a process in which continuous fiber rovings are dipped into a resin bath and pulled through a shaping die where the impregnated resin cures

autoclave

an enclosed chamber equipped to apply heat and/or pressure at controlled levels

contact molding

another name for open mold processes

prepreg

another prefabricated form for FRP shaping operations is ( ), which consists of fibers impregnated with partially cured thermosetting resins to facilitate shape processing

closed mold processes

are preformed in molds consisting of 2 sections that open and close during each molding cycle. 3 categories: 1. compression molding 2. transfer molding 3. injection molding