The document discusses advances in composite materials technology, detailing their properties and applications compared to conventional materials. It covers the mechanics of laminated composites, design considerations, manufacturing processes, and various applications across industries including aerospace and automotive. Additionally, it highlights the importance of material characterization, performance assessment, and the integration of computer-controlled manufacturing methods in optimizing composite component production.

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Advances in Composites
Technology
Materials; Mechanics; Design; Manufacturing; Applications

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• Composite materials offer several outstanding
properties compared to conventional materials
– Example: Specific strength Vs Specific stiffness space
• We define composite as a combination of two or
more chemically distinct and insoluble phases.
The properties and performance of these
engineered materials are far superior to those of
the constituents acting independently
– Example: Glass fiber reinforcement of Polymers
(Plastics): Improves strength to weight ratio, creep
resistance, fatigue life, and fracture toughness.
Advances in Composites Technology
Materials

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• The reinforcement may be a chopped strand mat; woven
fabric, roving.
• Fiber Reinforced Polymer Matrix Composites (PMC)
• Fiber Reinforced Metal Matrix Composites (MMC)
• Fiber Reinforced Ceramic Matrix Composites (CMC)
• Commonly used fibers: Glass, Graphite (Carbon), Aramid
(Kevlar), Boron etc.
• Commonly used Polymer Matrix materials: Polyester,
Epoxy, Phenolic, Silicone, Polyimides, (upto 300oC),
PEEK, etc.
• Tehrmosets Vs thermoplastics

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• Commonly used Metal matrix composites: Boron, Carbon,
silicon carbide or Alumina (fibers) in aluminum alloys,
magnesium alloys, titanium alloys, Zinc and Copper alloys
(matrices). Short fibers, wiskers, particulate reinforcement
and Carbon Nano Tubes (CNT) also employed.
• Stiffness, strength, thermal conductivity, creep resistance,
thermal expansion coefficients are all ANISITROPIC
(direction sensitive). Measuring these properties have to
respect anisotropy
• To provide a design manual approach (formulae, tables,
charts) to composite components is not yet possible
• Test methods to characterize composite materials (i.e to
measure thermal/physical/ mechanical properties) deserve
special attention

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Advances in Composites Technology
Mechanics
• Mechanics of laminated composite materials and structures
is quite complicated due to Heterogeneity, Anisotropy,
Nonlinearity, and the concurrent manufacture of materials
and components
• Mechanics of composites Provides a methodology to
predict, stiffness, strength and service life of laminated
composite materials, components and structures
• Finite Element Modeling and Engineering Analyses of
laminated composite structures is essential for component
design and performance assessment

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• Special issues: Hygro-thermal expansion effects,
free edge effects on the properties of composite
materials and on the behaviour of composite
structures/components
• Strength prediction of composite laminates by
itself is a special topic. It involves failure criteria
and failure mode identification and ply stiffness
degradation options
• Prediction of the behaviour of laminated
composite structures up to failure demand finite
element analysis. Usually combined geometric and
material nonlinearly is implied.
– Example: Burst pressure of a filament wound fiber
reinforced plastic pipe

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• Although at first sight mathematical nature of the
presentation is daunting, time invested in coming
to terms with the Mechanics of composites and the
FEM in general and a General-Purpose Program
(Ex:ANSYS) in particular will pay rich dividends
• Understanding the behaviour of generic structural
elements such as laminated composite beams,
plates and shells and how it differs from those
manufactured from metallic materials is
fundamental for successful application of
composites for the more demanding duties.

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Chapter-1
Introduction to Mechanics of Composite
Materials
1.1 Introduction
1.2 Lamina stress-strain relations
1.2.1 Material coordinate system
1.2.2 Arbitrary coordinate system
1.2.3 Modifications to include thermal strains
1.2.4 Hygroscopic thermal analogy

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1.3 Lamina failure criteria
1.3.1 Maximum stress criterion
1.3.2 Maximum strain criterion
1.3.3 Quadratic interaction criterion
1.3.4 Off-axis tensile strength
1.4 Laminate stiffness and strength properties
1.4.1 Lamination theory
1.4.2 Modifications to include shear deformations
1.4.3 Modifications to include thermal expansions
1.4.4 Thermal residual stresses
1.4.5 Strength prediction of composite laminates
1.5 Closure
References

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Lamina stress and strain components in the material
coordinate system

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Off-axis tensile strength

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Nomenclature for a laminate

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References
• Whitney J. M, Structural Analysis of Laminated
Anisotropic plates, Tecnomic publishers, AG, Basel, 1987
• Whitney J M, I.M. Daniel, and R.B.Pipes, Experimental
Mechanics of Fiber Reinforced Composite Materials,
SESA Monograph No.4, society for Experimental stress
Analysis, brook field, 1982
• Tsai S.W. and Hahn H. T, Introduction to Composite
Materials, Technomic, West-Port, 1980
• Pipes R.B and Cole, B.W, On the off-axis strength test of
Anisotropic Materials, Journal of composite materials,
7(1973). 246-256
• Hahn H. T. and Pagano N. J, Curing stresses in composite
laminates, Journal of composite materials, 9(1975) 91-106

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References
• Hahn H.T, residual stresses in Polymeric Matrix composite
Laminates, journal of composite Material, 10 (1976), 226-
278
• Hahn H.T and Kim R. Y, swelling of composite
Laminates, In advanced composite materials-
environmental effects. ASTM STP 658, J.R. Vinson
)Editor), ASTM, 98-120 (1978)
• Petit P.H. and Waddoups M.E. A method of predicting the
nonlinear behaviour of laminated composites, Journal of
composite materials, 3 (1969) 2-19
• Ahmed K. Noor and W.S. Burton, Assessment of shear
deformation theories for multilayered composite plates,
Appl Mech. Rev, 42 (1989) 1-13

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Finite element discretization- A spacecraft
structure

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Finite element discretization- A spacecraft
structure
• The main activities include:
– Structural analysis of spacecraft
static, free-vibration and dynamic
response analysis
– Preparation of mathematical
dynamic models for coupled
analysis with vehicles
– Thermal stress and distortion
analysis
– Analysis of mechanism elements
– Dynamic substructuring
– Shock and acoustic response
analysis
– Correlation studies between test
and analysis results
– Dynamics of flexible spacecraft

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Advances in Composites Technology
Composite Component Design
• Preliminary Design
– Realized as combination of beams, plates and shells
• Detailed design
– Hybrid laminates and sandwich construction may need to be
considered to achieve a higher level of design optimization
– Individual components must be joined together not only to achieve
physical connection, but also to ensure efficient load transfer from
one part to another: Adhesive bonding; mechanical fastening;
welding; etc
– Perturbations in the induced stress fields due to Free edge effects,
Geometric discontinuities and Material discontinuities should be
minimized using Local reinforcement

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• Account should be taken of fabrication induced
influences: curing stresses
• Evaluation of environmental effects on stiffness,
strength, and durability: Hygro- Thermal
expansion
• Damage of composite structures subjected to
lateral impact by itself and its influence on
residual properties is difficult to predict but should
be accounted for:

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Test section of propose fuselage design (units-inches)

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Design and manufacture of composite
structures
COMPOSITE
COMPONENT
Material’s Selection
Manufacturing
Technology
Detailed Analysis
Design Feasibility
Property
Determination
Prototype
Evaluation
NDT

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Advances in Composites Technology
Manufacturing
• To translate composite materials promise into component
performance is the real challenge to the manufacturing
engineering discipline
• Products of nominally the same form but manufactured
through different processes could have markedly different
properties
– Stiffness, strength, thermal, physical, electrical, internal damping,
chemical resistance, surface finish, etc.
• The unit cost of a composite component is strongly linked
to the manufacturing process. The brake down of cost
elements between equipment, tooling, labor and materials
varies greatly as illustrated in the figure to follow

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Effect of manufacturing
process on component cost

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• Computer controlled machines are developed and
concurrent engineering approaches are applied to
improve the quality, to increase production rate, and
to reduce costs of composite components/products
• Computer controlled filament winding machines are
becoming prevalent (upto 5 axis)
• Computer controlled automated tape laying machines
have been developed to fabricate aircraft structures
• Pre-preg tapes, bulk-moulding compounds and sheet-
moulding compounds should be stored in a deep
freeze

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• The reinforcement may be chopped fiber mats,
woven fabric, roving, or pre-preg tapes. In order to
ensure good bonding between the fibers and
polymer based matrix as well as to protect the
fibers during subsequent processing, fibers are
surface treated (SIZING)
• Short fibers are used for injection molding; milled
fibers are used for reaction-injection molding, and
longer chopped fibers are used in compression
molding
• The over-riding message when considering a
composite material option for a product
development is that component performance is
intimately linked with the manufacturing process.

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A list of manufacturing processes
• Filament winding
• Pultrusion
• Braiding
• Contact molding
• Spray-lay-up
• Matched die molding
• Autoclave molding
• Vacuum/pressure bag molding
• Resin transfer molding
• Reaction injection molding

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Advances in Composites Technology
Applications
• The first application of fiber reinforced
plastics in 1907 was for an acid storage tank
– Phenolic resin was reinforced with asbestos
fibers

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• To translate composite materials promise into
component/structure/product performance the key
issues involved are:
– Material characterization (standard test methods)
– Mechanics of materials and structures
– Component design (finite Element modeling and
engineering analyses)
– Performance assessment (physical prototype tests,
virtual prototyping and test simulation)
– Manufacturing processes
– Quality assurance (NDE)
– Machining and joining techniques

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• Composites are candidate materials to offer
significant improvements in component
performance
• Examples of composites applications include:
– Aircrafts (fixed wing/ Rotary wing)
– Space crafts (launch vehicles/satellites)
– Process plants
– Medical equipments
– Automotive
– Offshore structures
– Wind turbines
– Sports goods
– Marine crafts
– Building industry
– Civil engineering

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Advances in Composites Technology
Case Studies

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Hansa

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Hansa
• Glass/carbon fiber reinforced epoxy structure
• Laminar flow aerofoils: LS (1)-0413 and LS (1)-
0415
• Power plant: Teledyne Continental IO-240B
engine developing 125 BHP@2800rpm
• Cruise speed: 220 km/h
• Stall speed: 75 km/h
• Endurance: 4h

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Hansa
• Cockpit: spacious, 107 cm wide; side-by-side
seating
• Certification: JAR-VLA/FAR-23
• Superb looks, excellent visibility, full dual
controls
• The ideal light aircraft for ab-initio training, sport
and hobby flying
• Will meet the much-felt need of flying clubs for
modern trainers

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Compressor rotor assembly

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Photograph of 3-m-diameter corrugated graphite-
epoxy cylinder

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Graphite-epoxy ring stiffened corrugated cylinder shell assembly

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CFD Critical to Innovative Air Taxi
Design
BENCHmark, The International Magazine for Engineering Designers and
Analysis, NAFEMS, January 2000, p18-23
http://www.nafems.org

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F1 design features
• All carbon composite construction saving around
200 lb. in weight
• Laminar flow wing-giving low drag at high speed
and high lift at low speed
• Mature Pratt and Whitney PT6A turboprop
engine-combining proven reliability with low
noise
• Large cabin cross section-larger than the other
aircraft in its class
• 30% chord Fowler flaps-giving slow stall and
approach speeds

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F1 design features (Contd..)
• Powerful ailerons and full depth rudder-
giving positive sate control at low speeds
• Short take off and landing ability-take off to
50ft in less than 500m
• High rate of climb and a quite engine
installation, minimizing noise footprint
• Unprecedented cruise to stall speed ratio-
330 knot cruise/59 knot stall

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