processing methods for composites

University ofAlberta

MANUFACTURING TECHNOLOGY FOR FIBRE-REINFORCED POLYMERIC

COMPOSITES (FRPC)


FRP MANUFACTURING

• General Manufacturing Objectives:- to form required shape and size - to properly ensure that the reinforcement phase is completely encapsulated by the resin phase

- to eliminate voids and entrapped air- to ensure the proper fiber direction and fiber-resin

proportion- to produce homogeneous distribution of

reinforcement phase (uniformity)


FRP MANUFACTURING

Most Common Manufacturing Methods for Fiber

Reinforced Polymeric (FRP) Composites:

- Hand Lay-up

- Spray-up

- Compression & Resin Transfer Molding (RTM)

- Pultrusion

- Filament Winding


HAND LAY-UP

Two Main Methods of Hand Lay-up:• Wet Lay-up:

- dry reinforcement (fiber mat or woven cloths) is first applied to the mold, and then is saturated with liquid resin

• Dry Lay-up: - reinforcement and resin (thermoset) are applied simultaneously as a pre-impregnated fiber tape (prepreg)- the resin in the prepreg sheets is ‘B’ staged (i.e. solidified and tacky but only partially cured)


HAND LAY-UP

Source: Wittman and Shook, Hand Lay-up Techniques in “Handbook of Composites”, (Ed. G. Lubin), Van Nostrand Reinhold, 1982

Wet Lay-up Technique


HAND LAY-UP

Wet Lay-up MethodAdvantages:

- good method for limited runs or prototyping (flexible and low capital costs)

Disadvantages: - highly manual fabrication method- quality of part is worker dependent (may not be

repeatable)


HAND LAY-UP

Example of Dry Lay-up Technique (Cylindrical Parts using Rolling Table)

Source: J. Wolodko, “Biaxial Fatigue and Leakage Characteristics of Fiber Reinforced Composite Tubes”, Ph.D. Thesis, University of Alberta, 1999


HAND LAY-UPDry Lay-up Method

• Advantages: - superior part quality and repeatability (used by aircraft industry)- method can be automated using tape placement machines (but expensive >$1M)

• Disadvantages: - requires elevated temperatures to cure the resin and

applied pressure to consolidate the part (i.e. autoclave or oven/shrink tape)

- material and storage costs are expensive


Automated Tape-Laying Equipment


SPRAY-UP

Spray-up Technique

Source: Wittman and Shook, Hand Lay-up Techniques in “Handbook of Composites”, (Ed. G. Lubin), Van Nostrand Reinhold, 1982


SPRAY-UP• Advantages:

- fast process- reinforced resin can take on any contour- can be automated

Disadvantages: - produces short fiber reinforcement (low strength

applications) - requires specialized equipment- spray area requires necessary ventilation


RESIN TRANSFER MOLDING (RTM)

• General Method: - in a two part mold, the fiber reinforcement (mat, cloth, porous foam or preforms) is stacked/placed in the mold- the mold is closed and resin and hardener are either injected or drawn (via vacuum) into the fiber reinforcement- polymer phase is cured (at room or elevated temperatures, depending on resin system used)

Preforms: Fiber network which has the general shape of the part but is still permeable to resin flow (i.e. skeleton structure) - fabricated separately by textile technologies (braiding, etc.) or spray-up (using less resin), and is used for fast production of parts.



Source: B. Jang, “Advanced Polymer Composites: Principles and Applications”, ASM International, 1994

Schematic of RTM Process


• Advantages: - can produce complicated shapes (depends upon drapability

of reinforcement)- can produce a “near-net” shape (which does not require

any further machining) - can be a fast process (depends on pressure and

reinforcement type)- can be performed by hand or fully automated (flexible)

• Disadvantages: - requires a closed mold and injection/vacuum system- for higher processing speeds, high pressure steel molds

and equipment are required (expensive)



Manufacturing of Textile Preform

Preforms: Fiber network which has the general shape of the part but is still permeable to resin flow (i.e. skeleton structure) - fabricated separately by textile technology such as braiding, and is used for fast production of parts.


PULTRUSION

• General Method: - dry fiber rovings (strands) are continuously pulled through a resin bath and forced through dies to form various cross-sectional shapes- often the surface is reinforced with cross-ply cloth/veils to prevent matrix cracking (splitting) along the fiber direction- polymer phase is cured continuously at elevated temperatures (specialized fast curing resins)- sections are automatically parted at required lengths (can produce long sections)


Pultrusion Process and Available Shapes


PULTRUSION• Advantages:

- produces very strong structural members (unidirectional continuous fibers) which can be used when the applied loading is known to be in the fiber direction (i.e. uniaxial or bending loads) - very fast process

• Disadvantages: - expensive and complex machinery required (extensive capital investment)- pultruded parts not very good under torsion and transverse loading (shear)


FILAMENT WINDING

• General Method: - continuously apply reinforcement and resin system on to a rotating mandrel, one band of roving at a time - the applied fiber angle is determined by the relationship between the mandrel rotation and movement of the traversing carriage- trapped air is reduced by applying tension to the fibers- polymer is cured at room or elevated temperatures depending upon process and polymer used- upon removal from mold, final trimming or machining of the part may be required


FILAMENT WINDING

Two Main Methods of Filament Winding:• Wet Winding:

- dry fiber rovings are passed through a liquid resin bath, then continuously applied to the part through a pay-out eye

• Dry Winding: - reinforcement and resin (thermoset) are applied

simultaneously as a pre-impregnated fiber tow (towpreg)- the resin in the towpreg rovings is ‘B’ staged (i.e.

solidified and tacky but only partially cured)


FILAMENT WINDING

Wet Winding Technique

Source: B. Jang, “Advanced Polymer Composites: Principles and Applications”, ASM International, 1994


FILAMENT WINDING

Dry Winding Technique


FILAMENT WINDING• Advantages:

- good method of producing shells of revolution (e.g. pipe, tubing, vessels and tanks) with very high strength (continuous fibers) - can produce parts with complex profiles along its length and irregular cross-sectional shapes (e.g. rectangular tubing)- relatively fast process (automated)

• Disadvantages: - expensive and complex machinery required (extensive capital investment)- difficult to wind angles along mandrel axis


FRP MANUFACTURING SUMMARY

Selecting a Manufacturing Method for Fiber Reinforced Polymeric (FRP) Composites:

- Hand Lay-up and Spray-up can be performed with simple equipment, and are good methods for limited production runs and prototyping.

- Automated Tape Lay-up, Rasin Transfer Molding,Pultrusion and Filament Winding require expensive equipment to produce parts, but with faster production rate and pre-fabricated products are available off the shelf (e.g. beams and tubing)


APPLICATIONS OF FRP COMPOSITESAerospace Applications:


APPLICATIONS OF FRP COMPOSITES

Evolution of Composite Material Application at Airbus



Major Advanced Material Candidate for Airbus A380



Optical bench for space application, made from carbon-fiber/epoxy laminates designed with a near zero coefficient of

thermal expansion



Automotive Applications: body parts, driveshafts, springs, bumpers and CNG tanks



Formula Raced Car with a Carbon-Fiber/Epoxy Chassis



Chemical Processing/Petroleum: pipe, downhole tubing, storage tanks and pressure vessels



Recreation: racquets, golf clubs, hockey sticks, fishing rods, boats and bicycles



Construction: grating, beams, scaffolding and infrastructure repair

processing methods for composites

Documents