Composite Manufacturing Quiz

Manufacturing of Composites - MECH 415/6521

• Course is taught by Suong V. Hoa
• Course is offered by Concordia Center for Composites, Mechanical and Industrial Engineering, Concordia University
•  Focuses on the introduction to the manufacturing of composites

General Characteristics of Manufacturing Composites

• Requirements for a good composite piece:

  • Good bonding between matrix and fibers
  • Proper orientation of fibers
  • Sufficient volume fraction of fibers
  • Uniform distribution of fibers within the matrix
  • Proper curing or solidification of the resin
  • Limited voids and defects
  • Good dimensional control of the final part

• Good bonding = better strength and stiffness

• Poor bonding = stress concentration, dry spots

• Partial bonding can help absorb impact energy

Fiber Orientation

• Fibers tend to be wavy (microwaviness)
• Overlapping
• Misalignment due to liquid flow during manufacturing
• Reinforcement along thickness direction (pinning, 3D weaving)
• Hard pressing with stiff rollers
• Molding over complex geometries
• Human errors during Hand Lay Up

Fiber Volume Fraction

• Vf = Vf / Vc (Vf = volume fraction of fibers, Vc = volume fraction of composite)
• E = EfVf + EmVm (E = composite modulus, Ef = fiber modulus, Em = matrix modulus)
• 1 = Vf + Vm + Vv (1 = total volume, Vf = volume fraction of fibers, Vm = volume fraction of matrix, V v = volume fraction of voids)

Uniform Fiber Distribution

• Resin rich area
• Fiber to fiber contact

Proper Curing of the Resin

• Curing for thermosets
• Consolidation for thermoplastics

Limited Amounts of Voids and Defects

• Less than 1% voids

Good Dimensional Control of the Part

• Images of parts with good and poor dimensional control

Metal versus Composites Manufacturing

• Different manufacturing methods for metals (compared to composites)
• Composite manufacturing process breakdown (schematics)

Functions of Constituents

• Fibers
• Matrix
• Interface

Advantages of Fiber Form

• Stronger than bulk form
• More fabrication techniques
• Flexibility in forming
• Stretching, drawing, solvent removal

Disadvantages of Fiber Form

• Requirements of large number of fibers
• Need to be bonded together to provide good mechanical properties
• Need for high fiber volume fraction
• Small inter-fiber spacing (leading to stress concentration)

Matrix Materials

• Functions of the matrix:
  • Aligning the fibers
  • Transferring load between fibers
  • Assisting fibers in providing compression strength and modulus
  • Assisting fibers in providing shear strength and modulus
  • Protecting fibers from environmental attack

Interface

• Two main requirements for good interface:
  • Compatibility (depends on surface energy)
  • Availability (depends on speed to be on site)

Volume Fraction and Weight Fraction

• Vf = Vf / Vc
• Wf = Wf / Wc
• Percent (%) and Parts per hundred (phr)

How are Composite Structures Made?

• Diagrams illustrating the composite manufacturing process breakdown (schematic)

Different types of Matrix Materials

• Polymer matrix composites
  • Carbon/epoxy
  • Glass/epoxy
  • Glass/polyester
  • Kevlar/epoxy
• Metal matrix composites
  • Silicon carbide/aluminum
  • Carbon fiber/aluminum
• Ceramic matrix composites
  • Carbon/carbon
  • Carbon/alumina
• More polymer matrix composites than other types (due to compatibility)

Different types of Polymer Matrix Materials

• Thermoset matrix composites
  • Carbon/epoxy
  • Glass/epoxy
  • Glass/polyester
  • Kevlar/epoxy
• Thermoplastic matrix composites
  • Carbon/PEEK
  • Carbon/PPS
  • Glass/nylon
• More thermoset matrix composites than thermoplastic matrix (due to availability)

Viscosity of Thermoset and Thermoplastic Materials

• Table of materials, viscosities, temperature
• Units: Centipoise, Pa-sec

Schematic of thermoset resin molecules

• Images of various stages of thermoset resin molecule formations

Polyester Production

• Chemical reactions and formulas for polyester production

Example on Cross Linking of Polyester

• Calculations and formulas for determining the mass of polyester obtained from different reactants

Initiators

• Table of names and chemical structures of commercial organic peroxides

Polyester Cross Linking

• Diagram illustrating the chemical reactions involved in polyester cross-linking

Atomic Bond Energy

• Table of different atomic bonds and their energies (in kJ/mole)

Example on Heat Generation and Temperature Increase

• Calculations related to heat generation and temperature increase during polymerization process for different materials

Different Types of Reactants

• Chemical structures and formulas for different reactants (e.g., ethylene glycol, orthophthalic acid, maleic acid)

Polyester use and Storage

• Container for shipping and storage, Shelf life, Pot life, Inhibitors, Accelerators, Prepregs, Coupling agents, Fillers

Epoxy

• Commonly used resin for advanced composites
• Good adhesive strength
• Low shrinkage
• Operating temperature up to 140 °C

Diglycidyl ether of bisphenol A (DGEBPA)

• Chemical structure of this epoxy-based product

Formation of epoxy resin

• Chemical reactions with diagrams for creating various epoxy systems

Specialty Epoxy Resins

• Diglycidyl ether of bisphenol A (DGEBPA)
• Epoxy Novolac (Epoxidized Phenolic Resin) – DOW DEN 438
• Tetraglycidyl ether of Tetrakis (Hydroxyphenyl) Ether – SHELL EPON 103

Diluents

• Reduce resin viscosity
• Improve shelf/pot life
• Lower exotherm
• React with resin, become part of cured system
• Butyl glycidyl ether, Cresyl glycidyl ether, Phenyl glycidyl ether

Curing Systems for Epoxies

• Amines
• Anhydrides
• Tertiary amines and accelerators

Amine Curing Agents

• Table listing amine curing agents, hydrogen equivalent weights, and viscosities at 25°C

Amine curing agents

• Chemical reactions with diagrams for amine curing systems

Stoichiometric Ratio

• Calculations and formulas to determine the appropriate ratio of amine to epoxy for curing

Anhydride Curing Agent

• Chemical structure and reaction for phthalic anhydride (PA) curing systems

Tertiary Amines and Accelerators

• Reactions and diagrams for tertiary amine curing systems
• EMI accelerator

Relative Concentration

• Large excess of epoxy
• One reactive epoxy site for one reactive hardener site
• One epoxy molecule for one hardener molecule
• High excess of hardener

Cured Epoxy Resin Systems

• Aromatic rings
• Cross-link density
• Lower cross-link density improves toughness, lower shrinkage
• Higher cross-link density improves chemical resistance, higher heat distortion temperature

Pot Life

• Prepregs- Shelf life

Quality Control

• At the liquid stage: Measure viscosity
• At the solid stage: Degree of cure
• Chemical principle: FTIR, Acetone wipe
• Electrical principle
• Mechanical principle: Barcol hardness test, DMA, Ultrasonic, Shrinkage measurement
• Thermal principle: DSC test

Degree of cure and rate of cure

• Equation

Vinyl Ester Resin

• Chemical structures of different vinyl ester resins

Vinyl ester resin formation

• Chemical reactions for vinyl ester resin formation, with additional reactants and catalysts

Polyimide

• High temperature stability (up to 350°C)
•  Epoxies stable up to 177°C

### Bismalimide (BMI)

• Cured at 177°C
• Post-cured at 246°C for complete cure.
• Properties significantly higher than epoxies

Phenolic Matrix

• High-temperature applications
• Made by reaction between phenol & formaldehyde
• Brittle & high shrinkage
• Fillers are used to reduce brittleness
• Used for electrical switches, auto molded parts, billiard balls
• Used as liner for rocket nozzles

Carbon Matrix

• Made from carbon fibers reinforced phenolics.
• Porous material can be re-impregnated.
• Pyrolysis (charring)
• Process may take up to 6 months
• High-temperature applications
• Liners for rocket nozzles, tiles for space shuttle nose cones, aircraft, race car, and truck brakes
• High energy absorption (specific heat)

Thermoplastic Matrix

• No shelf life
• Short processing cycle
• Higher ductility than thermosets
• Repairable
• Recyclable
• Higher viscosity than thermosets
• Requires high temperature for processing
• Tapes are stiff and boardy

Two types of Thermoplastic Resins

• Industrial thermoplastics (up to ~80°C) – Polyethylene (PE), Polyvinyl Chloride (PVC), Polymethylmethacrylate (PMMA), Polypropylene (PP), Polystyrene (PS), Acrylonitrile Butadiene Styrene (ABS)
• High-performance thermoplastics (up to ~300°C) – Poly-ether-ether-ketone (PEEK), Poly-ether-ketone-ketone (PEKK), Poly-ether-imide (PEI), Poly-phenylene sulfone (PPS), Poly sulfone

Thermoplastic Matrix- Fabrication

• Difficult due to high viscosity (compared to epoxy)
• Shear thinning
• Comingled fibers
• Power impregnation

Fillers

• Cost reduction
• Shrinkage reduction
• Improvement of mechanical properties
• Improvement of flame resistance
• Colorants, pigments

Metal Matrix

• Aluminum, titanium, magnesium, copper
• Short fibers such as SiC- particles, whiskers, fibers
• Piston ring inserts, pistons, connecting rods, high-temperature applications

Ceramic Matrix

• Oxides, carbides, borides, nitrides
• Short fibers such as SiC- particles, whiskers
• Made by chemical vapor deposition
• High-temperature applications

Polymer Nanocomposites

Structure of Clay Sheets

Clay sheets with intercalating ions

Different levels of clay structure

Replacing positive ions with long omium ions

Dispersion techniques

• High-pressure mixing technique

X-Ray pattern for samples mixed

• Relative intensity, 29 degrees

Minimum distance of particles

• Microscopic images and distribution plots of particle size

TEM of samples mixed

• Microscopic images

Variation of strain energy release rate

• Graph of strain energy release rate versus clay loading, with data points for different methods

High-speed mixing (10,000 rpm)

X-Ray Diffraction pattern

• Graph showing X-ray diffraction data for various samples and methods

Strain energy release rates

• Graph showing strain energy release rates for epoxy/clay samples
• Related to high-speed mixing method

Procedure to incorporate modified epoxy into long continuous carbon fibers

• Pictorial representation of procedure

Improvement in fracture toughness

Improvement of fatigue lives

Possible applications

• Barrier properties (obstruction to diffusion of small particles: CO2, flammability resistance).
• Fracture resistance

Carbon nanotube configurations

• Images

Three-roll milling machine

Variation of electrical conductivity

• Graph showing electrical conductivity versus CNT weight fraction

Possible applications

• Enhance electrical conductivity (lightning strike resistance, conductive adhesives).
• Uses for strain measurement
• Defect detection in composite structures

Aggregately conductive materials

• Diagrams illustrating different types of conductivity

Vessel with one layer

• Calculations and equations

Vessel with two layers

• Calculations and equations

Vessel with n layers

• Calculations and equations

Example on relative concentration

• Calculations and formulas related to epoxy resin and DETA amine concentration

Relative concentration

• Summary of concepts related to relative epoxy/hardener concentrations

Cured epoxy resin systems

• Aromatic rings, cross-link density, considerations influencing toughness, shrinkage, and chemical resistance

Lay up

• Methods for depositing layers of prepregs to create a laminate; considerations for avoiding sticking, resin flow, and volatile release

Curing and Consolidation

• Steps in curing and consolidation during the composite manufacturing processes, involving molecular cross-linking and layer compaction
• Factors determining cure percentage

Resin kinetics

• • Various chemical reaction formulas and diagrams of epoxy and DETA molecule interactions

Degree of cure—Rate of cure

• Relationships and equations

Typical DSC curve for epoxy

• Graphical representation of heat flow versus time curve for different epoxy resins

Heat Transfer and Energy Balance

• Equations for composite thermal conductivity
• Data table of materials' properties

Heat generated

• Calculations and relationships related to heat generation during composite processing

Kinetic equations

• Equations for degree of cure and rate of cure, with different conditions
• Graphs/figures illustrating the kinetics of curing process

Different types of reactants

• Chemical structures/diagrams for various chemical reactants (ethylene glycol, orthophthalic acid, maleic acid)

Mold filling

• Equations/concepts regarding mold filling during LCM processes
• Diagrams illustrating flow patterns

Radial flow

Pressure

• Flow rate, flow front velocity, filling time
• Table of values and relationships related to pressure and filling times
• Consideration for various flow types (linear to convergent/divergent flow types)

Coefficient of Permeability

• Relation/equation between permeability, flow direction, material system, and fiber volume fraction
• Related table of permeability values for different materials

Permeability measurement

• Diagram/representation of design for measuring permeability.
• Description of two types of permeabilities (Rectilinear and Radial Flow)

Injection strategies

• Point injection.
• Edge injection.
• Peripheral injection.

Estimation of required filling time

• Calculations for determining filling time in different injection strategies (Point, Edge, Peripheral)

Ways to reduce fill time

• Decreasing viscosity (increase temperature).
• Increasing pressure (beware of potential fiber washing & deflection).
• Changing the reinforcement
• Reducing flow length (additional inlets)

Factors that affect the validity of equations

• Fiber washing, Race tracking at edges, Significant mold deflection, Significant cure pressure during injection, Non-Newtonian behavior of resin flow, Binder dissolution in resin (increase in viscosity), Preform variation

Problems and issues related to mold filling

• Summary of various issues related to mold filling in composite manufacturing processes.
• Specific concerns related to fiber variability, preform characteristics, and process conditions

Two types of flow in the preform

• Diagrams showing two types of flow observed/possible in fibrous preforms: Macro flow and Micro flow

Race tracking

• Diagram showing undesirable resin flow behavior (race tracking) and how it impacts resin-rich/dry-spot patterns

Occurrence of voids

• Considerations related to air/void removal and their impact
• • Flow rate management with pressure to avoid air ingress

Fiber wetting

• Importance of fiber wetting, relationship to time and surface tension of components

Maximum mold filling time

• Concepts related to gel time and related parameters (e.g., NIP time) associated with mold filling

In mold cure

• Essential process of curing composite resins within a mold cavity, needing controlled reaction speed to prevent/limit negative outcomes

Considerations for curing

• Residual stresses, warping, void formation, and surface quality in curing systems
• Related defects in curing

Different types of resin flow and fiber deformation

• Diagrams describing different flow types (e.g., Resin percolation, Transverse flow, Interply slip, Interply shear)

Autohesion

• Molecular bonding at interfaces, leading to interface healing.
• Reptation theory, including relevant equations.

Degree of autohesion

• Formulas related to autohesion, considering time and viscosity
• Discussion related to different molding methods, how it will affect autohesion and its significance

Solidification

• Factors and parameters associated with the solidification (cooling) phase
• Degree of intimate contact and impact related to material/process parameters
• Equations associated with solidification

Bulk consolidation

• The pressure required for bulk consolidation (formula/concept)
• Impact of parameters on bulk consolidation (e.g., modulus relationship to different pressures and variables including number of layers and/or pressure/temperature )

Resin flow

• Percolation, transverse flow, intraply and interply shearing, cooperative flow.
• Equations and diagrams illustrating these types of flow associated with a fibrous preform in a composite system.

Different types of resin flow and fiber deformation

• Different resin flow categories associated with various geometry types or molding methods (e.g, consolidation, matched die, shaping, double curvature)

Autohesion

• Chemical bonding between dissimilar materials at interface
• Concept of autohesion and its role in eliminating interfacial issues
• Reptation theory's application in autohesion phenomenon
• Relevant diagrams/schematics

Degree of autohesion

• Formulas and relevant concepts related to autohesion (considering time and viscosity)
• Different molding methods' impact on autohesion and its implications/considerations

Consolidation, including discussion of the degree of intimate contact and considerations during resin flow. Include details/concepts about autohesion, pressure requirements, and related material properties.

• Description and relevant concepts of bulk consolidation and its relation to the molding process.
• Definitions and considerations of the degree of intimate contact and its impact on the composite system, including relevant factors impacting bonding.
• Pressure requirements and considerations for bulk consolidation, including the effect of different materials.
• Autohesion, including its role in eliminating interfacial gaps in the composite system, and considerations needed.

Thermoplastic Composites: Application, Advantages, and Disadvantages

• Summary of properties, advantages, and disadvantages

Materials for Filament Winding

• Fibers (E-glass, S-glass, carbon, Kevlar, combinations)
• Resins (Epoxy, polyester, vinyl ester) -Viscosity requirements linked to wet winding.
• Curing methods (room temperature or infrared heating methods).

Mold filling/Injection strategies

• In-mold cure
• Various Injection strategies (point/edge/peripheral method)
• Process control
• Flow considerations
• Molding aspects (e.g., considerations impacting mold designs)

Variables affecting mold filling time

• Different factors influencing overall mold filling time
• Approaches (strategies) for reducing filling time
• Factors affecting validity of filling time equations

Problems and issues related to mold filling

• Issues related to preform variability, process conditions, and related materials

Two types of flow

• Diagrams illustrating the two distinct modes of flow in the preform

Race tracking

• Diagram illustrating resin flow behavior in the context of racing (how it impacts resin-rich/dry-spot patterns)

Incidence of Voids

• Factors influencing void formation in mold cavity
• Prevention and management strategies.
• Pressure considerations during mold filling

Fiber wetting

• Importance related to avoiding void formation
• Factors influencing fiber wetting (time, surface tension of components)

Maximum mold filling time

• Concepts, related parameters (NIP time) for specific molding techniques.

In mold cure

• Aspects and factors impacting curing, time and flow, within composite mold cavity, Including considerations related to preventing/limiting negative outcomes

Consideration for curing, defects, their causes, process time impacts, and strategies for minimization

• Overall process issues in curing (residual stresses, warping, void formation, surface defects)
• Potential defects within a molding process.

Analysis of a production AFP machine

• Different steps in AFP machine, including aspects impacting efficiency.
• Issues related to reliability, recovery, tool movement considerations

Challenges in AFP machines (in aerospace manufacturing)

• Considerations impacting process efficiency/effectiveness

Future Outlook—Additive Manufacturing

• Expanding AFP technology, materials associated with additive manufacturing, newer/smaller AFP machinery

Two ends of the spectrum

• Different structural application types associated with AFP/ATL-related designs

Future outlook-- Smaller AFP machine

• Specs for a smaller AFP machine

Outline Thermoset Matrix and Thermoplastic Matrix

• Specific areas of attention and considerations
• Summary information about different composite types

Conclusion

• Summary of successes with thermoset matrix composites
• Considerations for improvements related to speed/efficiency, inspections, and fiber steering.
• Summary elements for thermoplastic matrix considerations linked to heating/temperature, interlaminar shear strength, distortion for structures, and future developments.

Natural Sciences and Engineering Research Council

• Summary information related to the Natural Sciences and Engineering Research Council of Canada, and collaborative projects/research initiatives.

Composite Manufacturing: Methods and Issues of Automation

Test your knowledge on the principles and processes of composite manufacturing. This quiz covers various materials, manufacturing steps, and the chemical properties involved in creating composite materials. From thermoset to thermoplastic matrix composites, challenge yourself and enhance your understanding of this field.