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BMayer@ChabotCollege.edu • ENGR
-
45_Lec
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28_Composites.ppt

1

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Bruce Mayer, PE

Registered Electrical & Mechanical Engineer

BMayer@ChabotCollege.edu

Engineering 45

Composite

Materials

BMayer@ChabotCollege.edu • ENGR
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45_Lec
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28_Composites.ppt

2

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Learning Goals


Composites


List The CLASSES and TYPES

of Composites


When to Use Composites Instead of
Metals, Ceramics, or Polymers


How to Estimate Composite

Stiffness & Strength


Examine some Typical Applications

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3

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Terms & Classifications


Composite


MultiPhase
Material with Significant
Proportions of Each Phase


Phase Components


MATRIX


DISPERSED Phase


Matrix


The CONTINUOUS Phase


The Matrix Function


transfer stress to other phase(s)


Protect other phase(s) from

the (corrosive) Environment

Reprinted with permission from

D. Hull and T.W. Clyne,
An
Introduction to Composite
Materials
, 2nd ed., Cambridge
University Press, New York, 1996,
Fig. 3.6, p. 47.

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Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Terms & Classifications cont.1


Composite
Classifications


M
MC


Metal
Matrix Composite


C
MC


Ceramic

Matrix Comp.


P
MC


Polymer

Matrix Comp.


Dispersed Phase (DP)


Function = To Enhance the

Matrix Properities


MMC
: increase
σ
y
, TS/
σ
u
, creep resistance


CMC
: increase K
c

(fracture toughness)


PMC: increase E,
σ
y
, TS/
σ
u
, creep resistance


Classes: Particle, fiber, structural

BMayer@ChabotCollege.edu • ENGR
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5

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Composite Taxonomy

Composites

PARTICLE Reinforced

FIBER Reinforced

STRUCTURAL

LARGE

Particle

DISPERSION

Strengthened

Continous

(Aligned)

DIScontinous

(Short)

Laminates


Sandwich

Panels

Aligned

Randomly Oriented

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6

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Composite Survey


Particle
-
I

60

Adapted from Fig.
10.10,
Callister 7e
.
(Fig. 10.10 is
copyright United
States Steel
Corporation, 1971.)

-
Spheroidite


steel

matrix:

ferrite (

a

)

(ductile)

particles:

cementite



(

Fe

3

C

)

(brittle)

m

m

Adapted from Fig.
16.4,
Callister 7e
.
(Fig. 16.4 is
courtesy Carboloy
Systems,
Department,
General Electric
Company.)

-
WC/Co


cemented


carbide

matrix:

cobalt

(ductile)

particles:

WC

(brittle,

hard)

V

m

:



10
-
15vol%!

600

m

m

Adapted from Fig.
16.5,
Callister 7e
.
(Fig. 16.5 is
courtesy Goodyear
Tire and Rubber
Company.)

-
Automobile


tires

matrix:

rubber

(compliant)

particles:

C

(stiffer)

0.75

m

m

Particle
-
reinforced

Fiber

-
reinforced

Structural


Examples

BMayer@ChabotCollege.edu • ENGR
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7

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

ReInforced ConCrete


Concrete is a
PARTICLE
ReInforced
Composite


Matrix = PortLand
Cement


3CaO
-
SiO
2

+

2CaO
-
SiO
2



Dispersed Phases


Sand+Gravel
Aggregate


60%
-
80% by Vol


Steel ReInforcing
Bars (Rebar)


A type of FIBER
Reinforcement


Improves Tensile &
Shear Strength

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8

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

More ReInforced Concrete


Concrete
≡ gravel + SAND + cement


Why sand and gravel? → Sand packs into

gravel VOIDS


Reinforced concrete
-

Reinforce with steel
reBAR

or
reMESH


Increases TENSILE strength
-

even if Concrete
matrix is cracked


PreStressed

concrete
-

reMesh

under tension
during setting of concrete. Tension release
puts concrete under COMPRESSIVE Stress


Concrete is much stronger under compression.

BMayer@ChabotCollege.edu • ENGR
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45_Lec
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28_Composites.ppt

9

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Composite Survey


Particle
-
II


Composite Material Elastic Modulus, E
c


Two “Rule of Mixtures” Approximations

Data:

Cu matrix

w/tungsten

particles

0

20

4

0

6

0

8

0

10

0

150

20

0

250

30

0

350

vol% tungsten

E(GPa)

lower limit:

1

E

c

=

V

m

E

m

+

V

p

E

p

c

m

m

upper


limit:

E

=

V

E

+

V

p

E

p

(Cu)

(

W)

“rule of mixtures”

Particle
-
reinforced

Fiber

-
reinforced

Structural


Rule
-
of
-
Mixtures Applies to Other Properties


Electrical conductivity,
σ
elect
: Replace E by
σ
elect


Thermal conductivity, k: Replace E by k.


Springs in PARALLEL

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10

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

Composite Survey: Fiber
-
I


Fibers very strong


Provide significant strength improvement
compared to pure matrix
-
material


Example: fiber
-
glass


Continuous glass filaments in a

polymer matrix


Strength due to fibers


Polymer simply holds them in place

BMayer@ChabotCollege.edu • ENGR
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11

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

Fiber Materials


Whiskers
-

Thin
single crystals
-

large length to
diameter ratio


graphite, SiN, SiC


high crystal
perfection


extremely strong,
strongest known


very expensive



Traditional Fibers


polycrystalline or
amorphous


G
enerally polymers
or ceramics


Ex: Al
2
O
3

, Aramid,
E
-
glass, Boron,
UHMWPE

BMayer@ChabotCollege.edu • ENGR
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12

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Composite Survey: Fiber
-
II


Fiber Materials



Whiskers

-

Thin single crystals with


large length to diameter ratio


graphite, SiN, SiC


high crystal perfection


extremely strong,

strongest physical form known


very expensive to produce

Particle
-
reinforced

Fiber
-
reinforced

Structural



Fibers



polycrystalline or amorphous



generally polymers or ceramics



Ex: Al
2
O
3

, Aramid, E
-
glass, Boron, UHMWPE



Wires



Metal


steel, Mo, W

BMayer@ChabotCollege.edu • ENGR
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13

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

aligned

continuous

aligned random

discontinuous

Adapted from Fig.
16.8,
Callister 7e
.

Fiber Alignment

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14

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

ISOstress & ISOstrain


isoSTRAIN

Tensile strength and
elastic modulus
when fibers are
parallel

to the
direction of stress


isoSTRESS

Tensile strength and
elastic modulus
when fibers are
perpendicular

to the
direction of stress

BMayer@ChabotCollege.edu • ENGR
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15

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

Composite Survey


Fiber
-
I


ALIGNED, CONTINUOUS Fibers


Examples

Fiber
-
reinforced

Particle
-
reinforced

Structural

Metal:
g

(Ni
3
Al)
-
a
(Mo)


by eutectic solidification.

From W. Funk and E. Blank, “Creep
deformation of Ni
3
Al
-
Mo in
-
situ
composites",
Metall. Trans. A

Vol. 19(4),
pp. 987
-
998, 1988. Used with
permission.

matrix:

a

(Mo)

(ductile)

fibers:

g



(Ni

3

Al)

(brittle)

2

m

m

Glass w/SiC fibers


formed by glass slurry


E
glass

= 76GPa; E
SiC

= 400GPa.

(a)

(b)

From F.L. Matthews and R.L.
Rawlings,
Composite Materials;
Engineering and Science
, Reprint
ed., CRC Press, Boca Raton, FL,
2000. (a) Fig. 4.22, p. 145 (photo
by J. Davies); (b) Fig. 11.20, p.
349 (micrograph by H.S. Kim, P.S.
Rodgers, and R.D. Rawlings).
Used with permission of CRC

Press, Boca Raton, FL.

BMayer@ChabotCollege.edu • ENGR
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16

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Composite Survey


Fiber
-
II


DISCONTINUOUS, RANDOM, 2D (Planer) Fibers

Fiber
-
reinforced

Particle
-
reinforced

Structural


Example: Carbon
-
Carbon


Process: fiber/pitch, then
burn out at up to 2500C.


Uses: disk brakes, gas
turbine exhaust flaps,

rocket nose cones.



Other variations:


Discontinuous, random 3D


Discontinuous, 1D


Fully Aligned

Adapted from F.L. Matthews and R.L.
Rawlings,
Composite Materials; Engineering
and Science
, Reprint ed., CRC Press, Boca
Raton, FL, 2000. (a) Fig. 4.24(a), p. 151; (b)
Fig. 4.24(b) p. 151. (Courtesy I.J. Davies)
Reproduced with permission of CRC Press,
Boca Raton, FL.

(b)

view onto plane

C fibers:

very stiff

very

strong

C matrix:

less stiff

less strong

(a)

fibers lie

in plane

BMayer@ChabotCollege.edu • ENGR
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17

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Composite Survey


Fiber
-
III


CRITICAL fiber length for

effective stiffening & strengthening:

Fiber
-
reinforced

Particle
-
reinforced

Structural


The Equation
Balances (want
PullOut



Tear)


The Fiber Load capacity →
σ
f
•[
A
CylXsec
] =
σ
f
•[
π
d
2
/4]


The Fiber Pull
-
Out Force→

c
•[
A
CylSurf
] =

c
•[
π
d•l
]


Stronger Fibers → need LONGER fiber


Stronger Fiber
-
Matrix Shear
-
Bond →

need SHORTER Fiber


fiber
length

15

f
d

c
fiber diameter

shear strength of

fiber
-
matrix interface

fiber strength in tension

BMayer@ChabotCollege.edu • ENGR
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18

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Fiber Lengths cont.


Example: FiberGlass


Need Fiber Lengh > 15mm


Reason for length Criteria → examine Extreme cases


Very Short Fiber has very little hold
-
in force

and would PULL
-
OUT (Fiber PULLS OUT before Fracture)


Very Long Fiber would take almost all the axial load

(Fiber FRACTURES before PullOut)


fiber
length

15

f
d

c
Shorter, thicker fiber:


fiber
length

15

f
d

c
Longer, thinner fiber:

Poorer fiber efficiency

Better fiber efficiency

Adapted from Fig.
16.7,
Callister 6e
.

BMayer@ChabotCollege.edu • ENGR
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28_Composites.ppt

19

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

Composite Survey


Fiber
-
IV


Estimate E
c

and TS


Valid for LONG Fiber
Condition:

Fiber
-
reinforced

Particle
-
reinforced

Structural


The Elastic Modulus in
Fiber Direction


fiber
length

15

f
d

c
efficiency factor


E
c
=
E
m
V
m
+
KE
f
V
f

Typical Values for K:


Aligned 1D: K = 1

(anisotropic)


Random 2D: K = 3/8

2D

isotropy)


Random 3D: K = 1/5

(3D

isotropy)


TS in fiber direction

(1D, Aligned) by VOLUME
Weighted Average



(
TS
)
c
=
(
TS
)
m
V
m
+
(
TS
)
f
V
f
BMayer@ChabotCollege.edu • ENGR
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20

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

Composite Survey


Structural


Stacked and bonded fiber
-
reinforced sheets


Orthogonal stacking sequence: e.g., 0
°
/90
°


benefit: balanced, in
-
plane stiffness


Sandwich panels


low density, honeycomb core


benefit: small weight, large bending stiffness


Structural

Fiber

-
reinforced

Particle
-
reinforced

honeycomb

adhesive layer

face sheet

Similar to Composite Beam

Lab Exercise

BMayer@ChabotCollege.edu • ENGR
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21

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

Composite Benefits


Ceramic Matrix
Composites →
Better FRACTURE
TOUGHNESS

fiber

-
reinf

un
-
reinf

particle
-
reinf

Force

Bend

displacement


Metal Matrix
Composites →
Improved CREEP
RESISTANCE

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22

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

Composite Benefits cont.1


Polymer Matrix Composites →

Better E:
ρ

(Stiffness:Weight) ratio

E(GPa)

G=3E8

K=E

Density,

r


[Mg/m

3

]

.1

.3

1

3

10

3

0

.01

.1

1

10

10

2

10

3

metal/

metal alloys

polymers

PMCs

ceramics

BMayer@ChabotCollege.edu • ENGR
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23

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Specific Strength


The PRIMARY
Motivation for the
Use of Composites
→ Hi
-
Strength,

Hi
-
Stiffness &

Lo
-
Weight


Thus Two Important
Metrics


Specific STRENGTH


Similarly The
Specific STIFFNESS


Now Specific Weight

Weight
Specific
Strength
S

=

Weight
Specific
Modulus
Elastic
S
E

=
3
N/m
in

g

=
r
g

Where


ρ



Density in kg/m
3


g


Acceleration of
Gravity (9.81 m/s
2
)

BMayer@ChabotCollege.edu • ENGR
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24

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Specific Strength cont.1


Now Determine
Units for S
σ

and S
E

by Way of Examples


For 7075 Al in the
Heat treated State



u

= 83 ksi


g

= 0.101 lb/in
3


For Kevlar
-
49
(Aramid Fiber)


E = 131 GPa


ρ

= 1444 kg/m
3


Find
g


Now Specific Stiffness

3
2
in
lb

101
.
0
in
lb

83000
=

S
3
2
3
14166
81
.
9
1444
m
N
s
m
m
kg
g
=

=
=
r
g
in

10
218
.
8
5

=

S
3
2
9
m
N

4166
1
m
N

10
131

=
E
S
m

10
248
.
9
6

=
E
S
BMayer@ChabotCollege.edu • ENGR
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28_Composites.ppt

25

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

BMayer@ChabotCollege.edu • ENGR
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26

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

S
σ

vs S
E

Comparison


The High DENSITY of Metal Reduces S
σ

and S
E


The Low STRENGTH & STIFFNESS of most
Polymers Reduces
S
σ

and S
E

BMayer@ChabotCollege.edu • ENGR
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27

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Summary


Composite Matls


Composites Classified by:


The Matrix Material


Ceramic (CMC)


Metal (MMC)


PolyMer (PMC)


ReInforcement Geometry


Particles


Fibers


Layers

BMayer@ChabotCollege.edu • ENGR
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Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

Summary


Composites cont.1


Composites enhance matrix properties:


MMC: enhance

y
, TS, creep performance


CMC: enhance K
c


PMC: enhance E,

y
, TS, creep resistance


Particle ReInforced


Elastic modulus can be estimated by the
Rule of Mixtures


Properties are isotropic

BMayer@ChabotCollege.edu • ENGR
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29

Bruce Mayer, PE

Engineering
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Summary


Composites cont.2


Fiber ReInforced:


Elastic modulus and TS can be estimated
along fiber direction By Rule of Mixtures


Properties can be isotropic or anisotropic


Structural:


Based on build
-
up of sandwiches in
layered form


Plys


HoneyCombs

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Bruce Mayer, PE

Engineering
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45: Materials of Engineering

WhiteBoard Work


Prob 16.11


Given IsoStrain,
Longitudinal Loading
for a Continuous
Fiber Composite:


f
m
c
F
F
F
+
=

Then Show


m
m
f
f
m
f
V
E
V
E
F
F
=

Where


F


Force


E


Elastic Modulus


V


Volume fraction


Sub
-
f → “fiber”


Sub
-
m → “matrix”


Sub
-
c → “composite”

BMayer@ChabotCollege.edu • ENGR
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31

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

Bruce Mayer, PE

Licensed Electrical & Mechanical Engineer

BMayer@ChabotCollege.edu

Chabot Engineering

Appendix

E
-
glass

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32

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

E Glass
-

BackGround


http://www.azom.com/details.asp?Articl
eID=764


Background


E
-
Glass or electrical grade glass was
originally developed for stand off insulators
for electrical wiring. It was later found to
have excellent fibre forming capabilities
and is now used almost exclusively as the
reinforcing phase in the material commonly
known as fibreglass.

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33

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

E Glass
-

Composition


Composition


E
-
Glass is a low alkali glass with a typical
nominal composition of SiO
2

54wt%, Al
2
O
3

14wt%, CaO+MgO 22wt%, B
2
O
3

10wt%
and Na
2
O+K
2
O less then 2wt%. Some
other materials may also be present at
impurity levels.

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34

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

E Glass


Key Properties


Properties that have made E
-
glass so popular in
fibreglass and other glass fibre reinforced composite
include:


Low cost


High production rates


High strength, (see table on next slide)


High stiffness


Relatively low density


Non
-
flammable


Resistant to heat


Good chemical resistance


Relatively insensitive to moisture


Able to maintain strength properties over a wide range of
conditions


Good electrical insulation

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35

Bruce Mayer, PE

Engineering
-
45: Materials of Engineering

E Glass


Fibre Strength


Table 1.
Comparison of typical
properties for some common fibres.

Materials

Density (g/cm
3
)

Tensile Strength
(MPa)

Young modulus
(GPa)

E
-
Glass

2.55

2000

80

S
-
Glass

2.49

4750

89

Alumina (Saffil)

3.28

1950

297

Carbon

2.00

2900

525

Kevlar 29

1.44

2860

64

Kevlar 49

1.44

3750

136


BMayer@ChabotCollege.edu • ENGR
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36

Bruce Mayer, PE

Engineering
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45: Materials of Engineering

E Glass


Use in Composites


The use of E
-
Glass as the reinforcement material in
polymer matrix composites is extremely common.
Optimal strength properties are gained when straight,
continuous fibres are aligned parallel in a single
direction. To promote strength in other directions,
laminate structures can be constructed, with
continuous fibres aligned in other directions. Such
structures are used in storage tanks and the like.


Random direction matts and woven fabrics are also
commonly used for the production of composite
panels, surfboards and other similar devices.