hand lay-up of woven mat or chopped strand mat in open mold

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Fabrication Processes for Polymer Matrix Composites

*Programmable Powdered Preform Process (P4)

****Thermoplastic Molding

****Resin Infusion (RI)

**Automated Fiber Placement (AFP)

*Reinforced Reaction Injection Molding (RRIM)

****Liquid Composite Molding (LCM)

**Pultrusion

*Filament Winding

****Compression Molding

**Autoclave

*

**

Open moldHand Lay-upSpray-up

HybridWovenChoppedContinuousProcess

Type of fiber Reinforcement

Hand Lay-up of Woven Mat or Chopped Strand Mat in Open Mold

For development work, prototypes, large components, small quantities

Resin

MatGel Coat

Wax coating on mold ( or mold release)

Mold

Roller

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Chopper-Spray Gun

Prepreg tape - fibers pre-impregnated with matrix resin and partially cured in tape form

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Hot-Melt Prepegging Process

Courtesy of SACMA

Autoclave Molding ( Thermosetting Polymers)

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Autoclave-Style Press Cure

Filament Winding

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Natural Gas Vehicle (NGV) Composite Fuel Tank

• Filament wound composite wrap• Operating pressure 3,000 psi

Source: Brunswick Composites

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Courtesy of McClean Anderson, Inc.

Courtesy of McClean Anderson Inc.

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Roll wrapping of composite tubes

From A. L. Browne and N. L Johnson, Proc. ASCAnnual Technical Conference, Philadelphia, PA, 2005

SMC Machine

From Reinhart, et al., 1987

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Compression Molding with Matched Metal Dies

For production of large quantities

Heated Die

Prepreg Tape or Sheet Molding

Compound (SMC)

Molding with SMC• 3-5 day maturation period to reach desired

molding viscosity• Limited shelf life-about two weeks• Charged placed in steel mold• Mold heated to • Mold closed under 800-1200 psi pressure• Cure time 30-150 seconds• Mold opened and part ejected• Part placed on cooling rack

F°−° 325250

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Compression Molding

Heated Die

Premix or Bulk Molding

Compound (BMC)

Pultrusion Process

• Thermoset matrix resin (e.g., polyester, vinyl ester, etc.)

• continuous fibers coated by pulling through premixed thermoset resin bath

• resin-coated emerges from other end of die• limitation: part geometry cannot change

along length (e.g., I-beams, channel sections, etc.)

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Pultrusion Process

Resin Bath

Heated Die

Fiber rovingPuller

Pultruded fiberglass composite structural elements.(Courtesy of Strongwell Corporation)

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Large (3 m x 3 m) interlocked composite grid structure fabricated from pultruded carbon/epoxy ribs and rib caps (Tsai, 2001)

Pultrusion Process

• Automotive Applications– Drive shafts (General Motors)– Fuel tank stiffeners (Chrysler)– Side panels for buses (Greyhound)– Bumper beams (Chrysler - discontinued)– Leaf springs (Ford, General Motors -

discontinued)

Source: D.J. Evans, “Pultruded Products: An Automotive History”, Proc. 6th Annual ASM/ESD Advanced Composites Conference, Detroit, Michigan, Oct. 8-11, 1990, PP. 327-331.

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Thermoplastic stamping (Thermoplastic Molding)

• Thermoplastic resin matrix (e.g., polypropylene, nylon, PPS, PEEK)

• Fiber reinforced thermoplastic blank is heated in an infrared oven

• After heating to above the melting point, blank is quickly placed in matched metal die

• Die closed and part formed under high pressure (1,500-3,000 psi)

• Typical cycle times 30-90 seconds, depending upon part thickness

• High forming pressures limit use of foam cores due to crushing

Conveyor Belt Mold

Press

Infrared Oven

Blank

Thermoplastic stamping (Thermoplastic Molding)

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Thermoplastic Stamping

Heated blank loaded into mold

Mold closing, compressing material to

fill cavity

Co-mingled fiber/thermoplastic matrix yarn

Thermoplastic fibers which form matrix after melting

Reinforcing fibers

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Thermoplastically stamped E-glass/polypropylene Twintex® composite

isogrid panel and steel mold

Manufacturing of Specimens

• Laboratory sized composite isogrid and orthogrid panels (305 mm x 264 mm) made from co-mingled E-glass/polypropylene (Twintex® by Vetrotex)

• Used a grooved mold thermoplastic stamping process (Goldsworthy and Hiel, 1999)

• Co-mingled unidirectional roving used for ribs• Co-mingled woven fabric used for skins

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Reinforced Reaction Injection Molding (RRIM)

Constituents:• Chopped glass fibers• Thermosetting resin, typically polyurethane• Fillers, internal mold release agents, etc.

Reinforced Reaction Injection Molding

Resin +

Fibers

Hardener

Mix Head

Heated Mold

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Molding Process:

• Two liquid reactant streams, one containing chopped fibers, are mixed by impingement under pressure in a mixing head just before injection into a closed mold where polymerization occurs (e.g., polyisocyanate and polyol, the precursors for polyurethane)

• Low viscosity liquids, so pressure in mold is low, typically 50 psi

• Cycle time typically no more than several minutes• After demolding, polyurethane typically post

cured for 1 hr. @

≈

°120

Resin Transfer Molding

Mold

Dry Fiber Mat

(preform)

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Resin Transfer Molding

Resin

Injection of resin into fiber mat in mold

under pressure

Courtesy of Ford Motor Company, Research Staff

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Examples of Automotive RTM Application

Experimental Ford Ranger two Piece RTM Truck Cab

Experimental Ford Ranger Two Piece RTM Truck Cab

• RTM continuous random strand mat glass fibers/vinyl ester resin matrix over urethane rigid foam core

• RTM cab has 2 pieces compared with 100 piece steel cab

• Beam structure integral with body skin panels (semi-monocoque)

• Weight 157lb compared with 189lb for steel cab

• Passed 35 mph front barrier crash test

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Experimental Ford Ranger Two Piece RTM Truck Cab

• Bending and torsional stiffness 1.75 to 2.5 times greater than those of steel cab

• Passed 16,000 mi rough road durability test• NVH characteristic as good or better than

steel cab• Passed roof crush resistance and seat belt

anchorage tests

Source: R.E.Bonnett, R.A.Carpenter and S.W.Gallagher, SAE Paper No. 900306, 1990.

Seeman Composites Resin Infusion Molding Process (SCRIMP)(Source: TPI Composites Inc.)

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• References on Fabrication of Composites:

– Composite Materials Handbook, Schwartz

– Handbook of Composites, Lubin– Composites Engineering Handbook,

Mallick

Critical Issues in Design, Manufacturing and Performance – Current ACC

Technology Programs

• Material Test Standards– Development and publication of “Test

Procedures for Automotive Structural Composite Materials” to provide reliable design data

– Development of durability test methods (fatigue, bolt load retention, impact damage tolerance, environment effects)

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Technology Programs• Joining Technology

– Development and verification of a general methodology to optimize performance, reliability and durability of adhesively bonded joints in composite structure

• Crash Energy Management– Development and demonstration of technology

required to apply production feasible structural composites in crash energy management applications


Technology Programs

• Composite Processing– Development and demonstration of cost-

effective, high-volume manufacturing technology to produce reliable structural composite parts (focus on Liquid Composite Molding)

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ACC Focal Project – Automobile front end structure

• RTM braided/continuous strand mat/chopped fibers/vinyl ester resin with polyurethane foam cores

• Shock tower durability tests showed performance superior to steel

ACC Focal Project

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ACC Focal Project

Future Opportunities in Automotive Composites

• New and improved methods for high speed, low cost processing needed to compete with steel

• Design for assembly and disassembly: part integration, reduction of part count, reduction of number of joints and fasteners

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• Composite automotive primary structures not widely used yet, but have great potential if issues such as high speed, low cost manufacturing, crash energy management and damage tolerance are resolved


• Advanced thermoplastic matrix materials (e.g., PEEK, PPS, PEI, PS) offer many advantages such as fast cycle times, excellent temperature and moisture resistance, recyclability, unlimited shelf life, and excellent toughness, but they are relatively new and expensive, and more research is needed.

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• Under-the-hood applications: great potential for not only polymer matrix composites, but metal matrix and ceramic matrix composites as well

• Design for NVH with composites: damping designed in, not added as an afterthought

MicromechanicsMacromechanics

FibersLamina

Matrix

Laminate

Structure

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Randomly Oriented Short Fiber Reinforcement

FibersMaterial is Isotropic like steel or aluminum

Strength:= Yield Strength = Ultimate Strength

YσUσProperties are independent of orientation.

Elastic Properties:E = Young’s Modulus G = Shear Modulus v = Poisson’s Ratio

Randomly Oriented Short Fiber Reinforcement

∴

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Unidirectional Continuous Fiber Reinforcement

1

2

Fibers

Material is Orthotropic, not Isotropic

Strength:SL = Longitudinal Strength ST = Transverse Strength SLT = Shear Strength

Properties depend on orientation.

Elastic Properties:E1 = Longitudinal Young’s Modulus E2 = Transverse Young’s Modulus G12 = In-plane shear Modulus v12 = Major Poisson’s Ratio

∴

Unidirectional Continuous Fiber Reinforcement

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Micromechanics of Composites

• Prediction of composite properties based on corresponding properties of constituent materials

• Example: prediction of the longitudinal young’s modulus of a unidirectional continuous fiber composite by “Rule of mixtures”

mmff VEVEE +=1

Where, Ef = Young’s modulus of fiber Em = Young’s modulus of matrix Vf = Fiber volume fraction Vm = Matrix volume fraction

Rule of Mixtures

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Laminate Analysis:

Plies or laminae

Analysis of composite structures such as laminates using effective properties, but not concerned with constituents like fiber and matrix.

Macromechanics of Composites

Review of basic Mechanics of Material Equations

• Equations of static equilibrium based on Newton’s Second Law

• Force-deformation, or stress-strain relationships for the materials

• Geometric compatibility equations or assumed relationships regarding the geometry of deformation

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Composite bar system – series arrangement

For static equilibrium of Bar A which has internal force PA,

Similarly, for Bar B which has internal force PB,

so that

∑ =−= 0Bx PPF

∑ =−= 0PAPxF

PBPAP ==

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The axial elongations of the bars are given by the force-deformation equations

The total axial elongation is

Note: system is statically determinate

AEAAALAP

A=δBEBABLBP

B=δ

BAtotal δδδ +=

Composite bar system – parallel arrangement

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Static equilibrium equation

The axial elongations of the bars are given by the force-deformation equations

But the geometric compatibility equation is now

Note: system is now statically indeterminate

BPAPPorPBPAPxF +=∑ =−+= 0

AEAAALAP

A=δBEBABLBP

B=δ

BA δδ =

Statically indeterminate composite system

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Static equilibrium equation

Geometric compatibility equation

Force-deformation equations

Note: system is statically indeterminate

∑ =+−= 0asFbwFPcoM

asbw δδ =

wEwAwLwP

w=δsEsAsLsP

s=δ

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Composite ring assembly subjected to temperature drop TΔ

Coefficients of thermal expansion

From thin-wall pressure vessel theory

From mechanics of materials, the radial displacements of the rings, and , are related to the corresponding tangential strains, and by

sa αα >

atapr

a=σstspr

s −=σ

arara

Δ=εsrsrs

Δ=ε

arΔ srΔaε sε

Since the rings are bonded together, the radial displacementsmust be equal, so that

srar Δ=Δ

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Tangential stress-strain relationships

Combining the above equations, the problem is reduced to one equation in one unknown, the interface pressure p

After solving for p, the stresses and strains in the rings can be found

TaaEaa Δ+= ασε TssE

ss Δ+= ασε

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

Δ+−=Δ+ TssEstspr

arsrTaaEat

apr αα

hand lay-up of woven mat or chopped strand mat in open mold

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