Materials Sciences and Applications, 2011, 2, 319-330
doi:10.4236/msa.2011.25042 Published Online May 2011 (
Copyright © 2011 SciRes. MSA
Design with Ultra Strong Polyethylene Fibers
Roelof Marissen1,2
1DSM Dyneema, Urmond, The Netherlands; 2Delft University of Technology, Faculty of Aerospace Engineering, Delft, The Nether-
Received January 4th, 2011; revised March 11th, 2011, accepted March 23rd, 2011.
Ultra strong polyethylene fibers can be made by gel-spinning of Ultra High Molecular Weight Polyethylene (UHMWPE).
Such fibers exhibit extraordinary properties. They show very high tensile strength and stiffness and low density. On the
other hand, the axial and transverse compression strength is low. This is a large difference with other advanced fibers
like glass and carbon fibers. Additionally, the fibers are chemically inert and the bonding strength to other materials
like resins is weak. Moreover, the coefficient of friction is very low, so the fiber is extremely slippery. Another property
is viscoelasticity; the fiber elongates due to creep at higher loads or temperatures. This exceptional combination of
properties explains why gel-spun UHMWPE fibers are not always applied in straight forward ways, e.g. like glass and
carbon fibers in composites. On the other hand, weaknesses like the limited compression strength are related to very
damage tolerant behavior on a micro scale. This opened application areas like providing of cut resistance. This paper
describes some established applications and shows the relationship between the properties and the applications. Fur-
thermore, some emerging applications are discussed and it is demonstrated how weaknesses can be turned into advan-
Keywords: Tensile, Compression, Friction, Creep, Density, Impact
1. Introduction
Very strong fibers have found various applications in
technology. Glass fibers were about the first non-metallic
fibers with strength levels exceeding 2 GPa. Structural
application of glass fibers in composites is well estab-
lished. Such composites are lightweight and high-strength
materials. Carbon fibers were developed later and are
stronger, stiffer and lighter than glass fibers. Carbon fiber
reinforced plastics are superior construction materials
with unsurpassed specific strength. Polymer fibers could
initially not reach strength levels that are comparable to
glass and carbon fiber s. However, so lvent based sp inning
technologies enabled the development of ultra strong
polymer fibers. Two classes of such fibers can be distin-
guished. One class is based on rigid rod molecules. Well-
known products are Kevlar®, Twaron® or Zylon®. The
molecular chains of these fibers exhibit some bending
stiffness. The other class is made of the very flexible
polyethylene molecules. A well known trade name is
Dyneema® from DSM. Spectra® is a similar fiber from
Honeywell. The interaction between the polymer mo-
lecular chains is low for polyethylene. Therefore, very
long chains are necessary to provide sufficient load
transfer between the macromolecules. Such a polyethy-
lene with long chains is called Ultra High Molecular
Weight Polyethylene (UHMWPE). The gel spinning
process starts from a high temperature solution of UHM-
WPE. Cooling causes crystallization from the solution,
thus a gel is obtained, containing polymer crystals and
solution. These crystals contain disentangled molecular
chains. The disentanglement is conserved during the re-
moval of the solvent. These disentangled chains can be
unravelled during a subsequent drawing process. The
drawing ratio is very high (about 100) and thus causes
extreme orientation of the UHMWPE chains. The paral-
lel oriented chains are again arranged in a crystalline
configuration. The crystallinity is high. Demco et al. [1]
analyzed various phases with NMR. Roughly summa-
rized about 90% of the fiber material is crystalline. The
longitudinal chain orientation “translates” external ten-
sion loads to loads on the strong covalent bond s between
the carbon atoms of the chains, and this explains the high
tensile strength of the fibers. More detailed information
on the production and properties of such fibers is des-
cribed in earlier publications, e.g. by Smith and Lemstra
[2], and Jacobs [3]. An early application field that was
anticipated during the development of these very strong
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
polymer fibers was the use as reinforcement in compo-
sites. However, this application remains limited due to
low axial compression strength of the polymer fibers.
Carbon and glass fibers can sustain large axial compres-
sion stress if supported by a sufficiently strong and stiff
well adhering resin, thus all structural loads can be car-
ried. However, polymer fibers tend to respond with plas-
tic deformation under axial compression. The compres-
sion yield strength of rigid rod polymer fibers is typically
around 10% of their tensile strength. The compression
yield strength of high strength UHMWPE is even lower
and is around 1% of the tensile strength. The explanation
is a kind of molecular buckling. This buckling stress is
influenced by the low bending stiffness of the molecular
chains and by the low interaction between the chains.
Consequently, fibers made from rigid rod molecules will
show higher compression strength than polyethylene
fibers. Rigid rid fibers show more chain-chain interactions,
because they contain hydrogen bridges. The Vander Waals
bonds and crystalline interactions between UHMWPE
chains are much weaker than hydrogen bonds. Figure 1
shows a Scanning Electron Microscope (SEM) picture of
gel-spun UHMWPE fibers with kink bands due to com-
pression loading. The kink bands are the microscopic
manifestation of the molecular buckling process. The
limited compression strength explains why such fibers
are hardly chosen as a reinforcement for structural com-
posites. On the other hand, several investigations e.g. by
Marissen et al. [4,5] indicate that hybridizing glass or
carbon fiber composites with gel-spun UHMWPE fibers
can improve the impact resistance, with a small penalty
on flexural strength only.
One of the rare applications of composites with
gel-spun UHMWPE fibers, without a significant amount
of glass or carbon fibers, is for the walls of air cargo pa-
nels. The walls are connected to an aluminum frame at
the edges of the container and only initial indentation
causes real bending stresses and the associated compres-
sive stresses. Larger indentations will cause membrane
stresses that are tension by nature. The membrane
stresses are transferred to the aluminum corner frame.
Consequently, compression strength of the panels is
hardly needed. Stiffness and impact strength are required.
Air cargo containers are subjected to severe impact loads
during their handling on airports. Gel-spun UHMWPE
fibers provide the stiffness and excellent impact resis-
tance at low weight. The low weight is desired in view of
fuel cost savings and saving of carbon dioxide emissions
during flight. Lightness in aviation is of extreme impor-
tance. Every kilogram mass saved on flying equipment
saves a multitude of kilogram’s fuel consumption per
year, and accordingly saves carbon dioxide emission.
Figure 2 shows examples of such air cargo containers.
Figure 1. SEM picture of kink bands in compression loaded
gel-spun UHMWPE fibers.
Figure 2. Two air cargo containers with panels made from
gel-spun UHMWPE fibers and a Turane resin (Courtesy
DoKaSch Aircargo equipment GmbH Staudt, Germany).
The colored panels in these containers replace aluminum
sheets at about half the panel weight, yet offering about
triple impact resistance. Thus a considerable redu ction of
repair costs is obtained.
Kink bands are common for high strength polymer fi-
bers. However, they are reversible in UHMWPE fibers.
They disappear under subsequent tensile loading, without
causing noticeable damage. The tensile strength hardly
decreases if kink bands were present in these fibers. On
the other hand, the compression yielding may be related
to the fiber’s damage tolerance on a microscopic scale.
Glass and carbon fibers behave like elastic rods and
bending fracture of those rods occurs if the elastic
strength limit of the material is exceeded. High strength
polymer fibers will rather show compressive yielding
than fracture. The highest toughness may be expected for
the fibers with the lowest compression yield strength.
Indeed, such effects can be observed. Figure 3 shows a
SEM picture of a knot in a single Dyneema® filament.
Extreme curvature and transverse deformation is visible,
yet signs of tensile fracture are absent. Figure 4 shows a
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
Figure 3. SEM picture of a knot in a Dynee m a® filame nt.
Figure 4. SEM picture of a Dyneema® filament stretched
over the cutting edge of a razor blade.
Dyneema® filament that is stretched over the cutting
edge of a razor blade. Again extreme curvature occurs.
The filaments deform in the transverse direction and ra-
ther spread out over the blade than being cut.
Another special feature of gel-spun UHMWPE fibers
is that the melting point is much lower than that of other
high strength fibers. Polyethylene is just a low melting
polymer. A typical melting point of normal non oriented
UHMWPE is about 135˚C. However, the rather perfect
longitudinal orientation of the molecular chains in the
crystals causes some increase of the melting point. Typi-
cal melting point is about 150˚C, it is slightly depending
on specific crystal morphologies. Detailed discussions on
morphology are presented by Demco et al. [1]. Still
150˚C is low compared to other high performance fibers.
This limits the application area. However, it also offers
new unique processing options. Gel-spun UHMWPE
fibers can be fused under pressure at a temperature some-
what below the melting point. Such a sintering process
enables the production of “matrix free composites” with
a slight loss of fiber properties only. Ward et al. [6,7]
published on the fusion of highly oriented polyethylene
fibers. Ward stated that local partial melting of the fibers
is important for fusion. His patent mentions a preferred
pressure range of about 5 - 20 Bar [7]. However, gel-
spun UHMWPE fibers can also be fused without notice-
able melting. This can be done at much higher pressures.
Pressures of more than 100 Bar should than be chosen.
The long crystals of the different fibers can be fused un-
der sufficient pressure. Indeed, the lo w transverse strength
of the fibers allows deformation and creation of intense
contact between the fibers. A slight rearrangement of
molecular chains under pressure may cause fusion of
crystals with parallel orientation. Figure 5 presents a
SEM micrograph of a cross section showing partly fused
fibers being deformed from circular to about hexagon
shapes. Some boundaries are still visible; others have
disappeared indicating complete fusion.
Polyethylene is “the simplest polymer”, it contains
only covalent carbon bonds in the chains, and hydrogen
atoms as side groups. The absence of other bonds, like
ester- or amide bonds implies the absence of properties
related to those bonds. So polyethylen e (and UHMWPE)
fibers are non-polar and insensitive to hydrolysis. This
means a good chemical resistance, but also poor bond ing
to resins and dyes. Some activation of the surface is pos-
sible, e.g. with corona or plasma treatments. However,
providing very strong bonding to resins, or providing
saturated colors to the fibers were as yet unsuccessful.
The above discussion shows that properties and useful
technology application of high strength polyethylene
fibers is very different from application of other fibers.
This paper describes some applications of high strength
polyethylene fibers. Firstly, some established applica-
tions are briefly presented and discussed in Chapter 2. A
Figure 5. SEM picture of fused Dyneema® filaments.
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
more extensive presentation of established applications
has been presented previously by Vlasblom and Van
Dingenen [8]. Secondly, more recent applications are
discussed in Chapter 3. This chapter also presents some
“laboratory principles” that did not yet find wide spread
commercial application, but may inspire engineers to
utilize the peculiar properties to the advantage of tech-
nology innovation. In all cases the chosen fiber is the
Dyneem a® fiber prod uc ed by DSM.
2. Well Established Applications of Ultra
High Strength Polyethylene Fibers
2.1. Armor
Stopping fast projectiles with high strength fibers is well
accepted technology. Flexible bullet resistant vests are
made from fibrous sheets. Hard armor plates can also be
made from fibers. Various slightly different views are
possible regarding the physics on the projectile stopping
mechanism. The view by Cunniff [9] is chosen here,
mainly because it is elementary and straight forward.
Cunniff argues that the quality of fibrous armor will be
related to the amount of armor that contributes to the
projectile catching effect. This contibuting amount in-
creases with increasing sonic speed in the longitudinal
direction of the fibers, so with an increasing (E/ρ)1/2 val-
ue, where E is Young’s modulus and ρ is density. An-
other factor is the amount of deformation energy that can
be “consumed” by that contributing amount of material.
That energy will be proportional to (σfr εfr), where σfr is
the fracture stress and εfr is the fracture strain. The final
equation by Cunniff is obtained by multiplying the
amount of contributing material and the energy con-
sumed by that material:
fr fr
 
where U is an armor performance parameter. Very high
strength fibers show approximately linear stress strain
behavior, especially for the high loading rates which are
typical for ballistics, so ε = σ/E and εfr = σfr/E. Substitu-
tion of this last relationship in Equation (1) yields:
Equation (2) contains elementary fiber properties only.
It shows that a cho ice of high strength f ibers is of highest
importance, because strength occurs in the Equation (2)
with the highest exponent. Low density is the next im-
portant property and low Young’s modulus is of some
importance for stopping fast projectiles. Table 1 shows
some elementary fiber properties. Indeed Dyneema®
fibers exhibit very high strength and low density, thus
they are a typical armor material. Of course projectiles
Table 1. Basic fiber properties of a Dyneema® SK75 yarn
with 176 tex.
Tensile strength [GPa]Modulus [GPa] Density [kg/m3]
3.4 110 975
should not be able to travel between the fibers. Therefore
fibrous armor contains two perpendicular fiber directions.
This reduces the splitting between fibers that would al-
low easy passing through of projectiles. Hence fibrous
armor is made from cross plies of fibers. Figure 6
presents an impression of such armor. Indeed many suc-
cessful applications of gel-spun UHMWPE fibers armor
do exist at present. More details on projectile stopping
mechanisms of such armor can be found e.g. in a paper
by Jacobs and Van Dingenen [10], and by Van der Werff
et al. [11]. Van der Werff also provided perspectives on
future performance of fiber-based armor. Laboratory
investigations on fiber production by Van der Werff [12]
and by Wang et al. [13] with very low polymer concen-
trations in the initial solution indicate that strength and
modulus values could exceed the comercial values with
almost a factor two. Equation (2) indicates that the armor
performance can be approximately doubled in terms of
energy absorption. Note that Van der Werff mentioned a
lower number. This is because he argued in terms of
projectile speed. The projectile kinetic energy is propor-
tional to the second order of speed. Making such ulti-
mately strong fibers on an industrial scale is quite a chal-
lenge. Yet, the argumentation elucidates a future poten-
Gel-spun UHMWPE fibers are viscoelastic materials.
At room temperature, elasticity is dominant under short
term loadings (up to days or weeks). However, time-
dependent behavior is dominant under long-term loading
(years). Creep may be considerable under long-term
loading, depending on stress and temperature. The mo-
lecular origin of the creep deformation is mainly the slip
of the individual molecular chains through the crystals.
Some chain scission may not be excluded. However, the
large creep strains that can be observed (> 50%) can only
be explained by chain slip. Indeed, the low interactions
(atomic bonds) between the chains and the rather perfect
longitudinal crystals with few entanglements can allow
such chain slip. Jacobs [3] elaborates extensively on the
various aspects of chain slip and the corresponding creep
The creep of gel-spun UHMWPE fibers is a disadvan-
tage for long-term loaded applications. However, it can
advantageously be used for processing. The creep rate
increases at high temperatures and it is sufficiently high
at temperatures above about 130˚C for processing in suf-
ficiently short time. Figure 7 shows two helmet shells
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
Figure 6. Illustration of fiber cross plies for armor, (a)
Schematic picture of build up, (b) SEM micrograph of a
cross section.
Figure 7. Two helmet shells made by creep-forming of gel-
spun UHMWPE fibers [14].
made by creep-forming, from a type of cross-ply material
as shown in Figure 6. Typically deep drawn helmets of
such material show wrinkles due to the 3-D deformation,
or they have to be made from a kind of “flower-cut”
stack of plies. This cutting provides fiber ends in the
helmet and thus may reduce protection. The creep elon-
gation of the fibers allows 3-D draping without wrinkles.
The helmets in Figure 7 were made at about 130˚C and
they are free of wrinkles and all fibers are intact. More
details on creep forming can be found in [14].
Another way of making helmets also utilizes the typi-
cal features of gel-spun UHMWPE fibers. The po ssibility
to fuse the fibers under pressure at high temperature al-
lows omission of a matrix in “composites” produc ts. This
allows dry filament winding without leading the fibers
through a resin impreg na tion bath . It simplifies th e set-up
considerably and allows fast winding with many yarns
simultaneously. Figure 8 shows dry winding around an
ellipsoid mandrel with about 30 yarns simultaneously.
After completion of the winding process, a hot knife is
used to separate the wound ellipsoid shape in two pre-
forms. The fibers melt at the cutting location and thus are
welded together, yield ing two shaped pr eforms. Figure 9
shows the “welded” cut line. The resulting halves are
stable preforms that can be shaped and consolidated to
helmet shells in a hot press. The disadvantage of the low
melting temperature is turned here into an advantage, as
it allows the simultaneous cutting and fusion of the edges.
Thus a practical production of stable preforms is possi-
2.2. Cut Resistance
Gel-spun UHMWPE fibers are difficult to cut. Figure 4
gives an impression on a part of the physics of cut resis-
tance. However, cut resistance in actual prod ucts is much
more complex. The angle between the blade and the fi-
bers is important as well. Protective textiles are often
hybrids with other fibers. Gel-spun UHMWPE fibers are
rather stiff as compared to other polymer fibers. Blending
with very elastic fibers helps to make products like
gloves even more comfortable. Blending may also im-
prove the cut resistance. If the very stiff gel-spun UHM-
WPE fibers are blended under tension with a stretched
elastic fiber, the gel-spun UHMWPE fibers will form
loops after relaxation of the tension. Loops remain al-
most free of stress until the cutting blade has stretched
the loop completely.
A striking property of cut resistant gloves made from
gel-spun UHMWPE fibers is their comfortable cool
feeling. Indeed such fibers have a very high thermal
conductivity along the fiber axis. Thus, excessive heat
from the hands is easily transferred to the usually colder
environment. The combination of cut resistance and cool-
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
Figure 8. Filament winding w ith many yarns.
Figure 9. Preform with “fiber weld” at the cutting location.
ing is especially attractive in suits for sh ort track skating.
The suits offer protection against the sharp skates in case
of falling and collision accidents. The suits also provide
good tran sfer of ex cessiv e heat th at is typically gen erated
in high level exercise. An article by S. Shen et al. [15]
highlights this behavior on very small scale. Of course,
the conductivity is even larger fo r the perfect crystals that
can be made on nano-scale, as compared to industrial
scale. However, the less perfect large scale industrial
grade of their fibers is already on the market for years,
e.g. Dyneema®. It is not uncommon that ultimate pro-
perties are approached on small laboratory scale, where
properties associated with large scale industrial produc-
tion are somewhat lower.
2.3. Ropes, Cables, Wires and Nets
The combination of high tensile strength, stiffness, low
density and damage tolerance (as illustrated in the Fig-
ures 3 and 4), make gel-spun UHMWPE fibers ideal
material for tensile structures that are subjected to fre-
quent handling. Ropes and cables are used in various
designs and dimensions, varying from thin lines for kites
and fishing lines to very thick cables for offshore moor-
ing. The density of about 0.975 g/cm3 makes cables al-
most weightless under water, thus they do not have to
carry their own weight in deep water mooring.
Parallel fusion of the fibers at increased temperature,
but below the melti ng point allows the prod uct i on o f wire
like monolines that are attractive for fishing. Figure 10
shows a SEM picture of such a wire. The individual fi-
laments can still be recognized to some extent. Yet it
behaves as a single line. Nets for fishing and fish farming
can be made from gel-spun UHMWPE fibers. Again,
lightness and small size at high strength are attractive.
The bite resistance makes them especially suitable for fish
farming. Nets for air cargo pallets show high strength
and lightness and thus allow for a reduction of fuel con-
Gel-spun UHMWPE fibers show low friction coeffi-
cients. Measurement results of friction coefficients (μ)
yield somewhat varying values. A coefficient of friction
μ = 0.05 is not uncommon. Karuppiah et al. [16] investi-
gated the effect of crystallinity on the friction co efficient
of UHMWPE. They found reduced friction for increasing
crystallinity. Consistently, the very high crystallinity of
gel-spun U H MWPE fib ers explains the low coefficient of
friction. It can be speculated that this is related to the
lower mobility of the molecular chains in the crystal.
Lower mobility implies lower interaction between the
sliding parts. The low friction causes some difficulties
regarding connections of ropes and connections to ropes.
On the other hand, the relative sliding of filaments allo ws
bending of ropes with little damage. Thus bending fati-
gue resistance of such cables is large. Smeets et al.
present some quantitative results on bending fatigue of
gel-spun UHMWPE cables [17].
Figure 10. Monofilament made by fusing gel-spun UHMWPE
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
3. Recent and Emerging Technology with
Ultra High Strength Polyethylene Fibers
3.1. Medical Applications
Dyneema Purity® is a very clean grade of gel-spun
UHMWPE fiber. It is a fairly recent development, based
on a proprietary spinning process. Dyneema Purity® is
an ideal material for interactions with the human body,
both during demanding surgeries, and over the longer life-
span required for implantable devices. The high strength,
softness and abrasion resistance are very valuable assets
in demanding applications like sports medicine. The ma-
terial’s low elongation and fatigue resistance offer a su-
perior alternative to traditional materials for surgeons and
device manufacturers. Some typical uses include: high-
strength sutures, ligament repair, arthro scopic procedures,
motion-preserving spinal applications, trauma and surgery
of the spine. A striking example is rotator cuff repair.
Thousands of rotator cuff repair shoulder surgeries with
Dyneema Purity® have been performed already with good
results and this surgery is becoming standard practice.
The wear resistance and the possibility for thermal fu-
sion suggest the use of this pure variant as a liner in arti-
ficial implantable joints. Such joints may not only pro-
vide good wear-resistance, but the fused fibers will also
provide high strength and resistance to cracking that is
still observed sometimes after long term in vivo use of
conventional joint materials. A young company named
Cartificial explored this field. The results were very en-
couraging. Unfortunately, testing of medical devices is
very expensive and this start-up company did run out of
cash before the commercial potential was established
sufficiently and the company was discontinued. Yet, the
potential might be materialized later.
3.2. Kite Based Wind Energy
Wind turbines provide an increasing part of electric en-
ergy production. A much lighter alternative for wind tur-
bines are kites. Although many practical problems have
to be solved, kites are potentially more powerful and
more effective energy gener ators than convention al wind
turbines. Ockels is one of the pioneers of this concept,
see e.g. Podgaets and Ockels [18]. His kite based ladder
mill design should generate approximately 100 MW.
Many concepts for kite based energy generation have
already been proposed. All kite based energy generation
systems will require lightweight cables, allowing much
“handling”. The high tenacity (specific strength) and
damage tolerance of g el-spun UHMWPE fiber will make
it a first choice material for the required cable systems.
3.3. Connections
The low friction coefficients of gel-spun UHMWPE fiber
were discussed before. The low coefficient of friction
makes gel-spun UHMWPE fibers notorious for knot
slippage. The friction coefficient of fibers against steel is
about 0.1. The fiber-fiber friction coefficient is about
0.05 only. The behavior of knots suggests that these
numbers may even decrease under high normal forces.
Strong knots in gel-spun UHMWPE fibers require addi-
tional loops. A square knot that provides good hold in
conventional fibers behaves as a “large force sliding
knot” in gel-spun UHMWPE fibers. This may be imprac-
tical for standard connections. However, it may be turned
into a great advantage. A square knot can be used to
connect parts with a loop. Subsequently, the loop can be
tensioned by a large mechanical force at the end of the
fibers. The strong fibers will allow that large force.
About 10% of this force will be transferred through the
square knot to the loop, thus tensioning the connected
parts considerably. Most of this tens ion will remain after
removing the force at the ends. An additio nal square kno t
(or optionally more knots) will cause a durable fixation.
Variations of this procedure are under development for
surgery, allowing for a safer procedure involving tempo-
rary fixation, optionally adjustment, and final fixation.
A variation of this slip-block technology is the use of
auxiliary features. A system that is easily tensioned and
provides excellent holding power is based on the use of
small metal rings. An assembly of two or three rings can
be used.
Figure 11 shows a schematic picture of a clamping
method with a three ring clamping system. The dimen-
sions are optimized for a Dyneema® cable of 1400 tex
(1400 gram/kilometer). The upper ends in the figure are
the tension ing ends. The lo wer ends are co nnecting ends,
e.g. parts of a loop to be tensioned. The high strength of
the fibers, together with the low friction, allows firm ten-
sioning. On the other hand, the loading force at the con-
necting end presses the rings together and thus prevents
reversed sliding. The extra loop configuration has the
best holding force, about 3000 N for the above mentioned
cable; the standard winding pattern allows easier and
Figure 11. Schematic presentation of ring clamping.
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
Figure 12. Pictures of the installed three-fold ring clamp with extra loop.
faster tensioning. Many variations are possible. All have
in common that the tensioning ends are between the rings
and the loaded ends are around the rings. Figure 12
shows photographs of the assembled rings with the fibers.
Figure 13 shows a variation with two rings.
Connections may be desired to be permanent, but
sometimes it is important that quick release and connec-
tion is possible. Metal shackles, or carabiners are used in
such cases. However, they are heavy and hard. A metal
shackle at the end of a swinging rope can be a hazard. A
recent alternative is a soft shackle. Soft shackles are typ-
ically made of gel-spun UHMWPE fibers. Reasons for
this choice are the high tensile strength and damage to-
lerance. Another reason is that the slippery character of
such fibers allows easy use. Opening can even be done
easily after high loading . The special shape still provide s
a good locking behavior if closed and loaded. Figure 14
shows a LIROS XTR soft shackle in opened and closed
condition. Colligo Marine offers a similar “softie” with
an additional feature for keeping it closed. Such soft
shackles are light, strong and practical in use.
3.4. Hinges
Connecting rigid structures with cables may allow for
some flexibility. The conn ection can be designed in such
a way that the flexibility is optimized. This will create a
kind of cable hinge, or in general a fiber hinge. The fi-
bers may be present as yarns, cables, or fabrics, depend-
ing on the specific design. The use of gel-spun UHM-
WPE fibers in such hinges is especially advantageous. A
rough but effective way of making a line-hinge is to
make a composite plate of gel-spun UHMWPE fibers,
e.g. by impregnating a fabric with a resin and curing the
resin, followed by folding the plate. Indeed, it will not
break completely, only the resin breaks! This is unlike
other composites and it is attributed to the typical fiber
properties. Folding it a few times in both directions and
pressing the fold line creates a strong and flexible line-
hinge in the plate. Another way of making a hinge is
shown in Figure 15. If made from Dyneema Purity® and
a surgical steel quality, it may potentially be used in
arthroplasty as a strong artificial finger joint. Figure 16
shows a possible joint with the kinematics resembling
that of a ball bearing. This could b e an artificial hip joint
that does not generate wear particles. Wear particles are
the cause for loosening of the stem-femur connection on
long term for conventional implants. The four cables
prevent relative translation of both parts, but allow rota-
tion. The body weight will be carried mainly by the low-
er cable. This cable may be designed thicker than the
other ones. The extreme tensile strength of Dyneema
Purity® and the possibility to apply rather thick cables
allow overdesign of the critical cable up to load carrying
capacity of a few tons, whereby creep will be virtually
3.5. Fiber Modifications
Some “weaknesses” of UHMWPE fibers may even be
enhanced. Ropes made of UHMWPE fibers allow fre-
quent bending on winches and sheaves. A lubricating
coating on the fibers may even enhance this effect. A so
called bending optimized fiber was developed this way.
Details are presented by Smeets [17]. Cables made from
this modified fiber show even further improved bending
fatigue properties.
Also the production of gel-spun UHMWPE fibers al-
lows some flexibility. Pigments and other functional
constituents can be incorporated into the fibers during
Figure 13. Ring clamp variation with two rings.
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
(a) (b)
(c) (d)
Figure 14. Closing a Liros soft shackle; a) Initial condition, b) Opening the loop, c) Feeding the knot through the loop, d)
Closing the loop.
Figure 15. Set of fiber-hinges with one degree of freedom;
rotation around one axis. The size as compared to a 2 Euro
coin illustrates the possibility of design as a potential finger
joint implant.
fiber production. A new implantable blue fiber “Dyneema
Purity® BLUE” was recently developed and presented at
the Medical Design and Manufacturing East Conference
& Exposition (MD&M East) 2010 [19]. Blue fibers pro-
vide improved visibility for surgeons, due to improved
contrast to body tissue.
Another modification of gel-spun UHMWPE fibers is
the incorporation of short thin mineral fibers in the
gel-spun filaments. Figure 17 shows a SEM micrograph
of gel-spun UHMWPE fibers containing a mineral fiber.
The mineral fiber is made visible (lighter grey scale) by
using back scattered electrons. So far, this technique is
only published in patents [20]. The commercial launch
was at Expoprotection in Paris (France) at 4 November
2010. These fibers with incorporated mineral fibers exhi-
bit about twice the cut resist ance of the already cut resis-
tant non modified fibers, without reducing the wearing
comfort. The constitution of the mineral fibers is such
that they will dissolve in the human body, in case they
would be released from the polyethylene filaments
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
(a) (b)
(c) (d)
Figure 16. Fiber-hinge with rotational freedom in various directions. Designed as a potential hip joint implant, (a) View
showing the head rotated in two different positions, (b)-(d) Various views on the inside showing three white cable pairs to
the “equator” and one black cable to the “pole” of the c up.
and would enter the human body.
The above innovations demonstrate that new future
variants of gel-spun UHMWPE fibers are possible and
may become available, allowing even more applications.
4. Discussions
Gel-spun UHMWPE fibers already have numerous ap-
plications in a wide variety of technology fields. How-
ever, also many application trials failed because of
structural limitations of these fibers. This is in contrast to
the situation with g lass or carbon fibers which are exten-
sively applied in composite materials, but application
does not extend much b eyond this technology field. This
creates an almost paradoxical situation: Fibers with most
“complete” properties (tension, compression and trans-
verse strength) are applied in a rather narrow field (com-
Design with Ultra Strong Polyethylene Fibers
Copyright © 2011 SciRes. MSA
Figure 17. Gel-spun UHMWPE fiber filaments with incur-
porated short mineral fibers.
posites), whereas gel-spun UHMWPE fibers with “in-
complete” properties (tension strength only, weak in
compression and in transverse direction) have applica-
tions in many different fields. This paradox is discussed
in some detail below an d resolved to some extent.
Johan Cruijff once stated (in Dutch): “Every disad-
vantage comprises an advantage”. This wisdom was re-
lated to soccer, but it also applies to gel-spun UHMWPE
fibers. Such fibers could roughly be qualified as “having
all properties but one being negligible”. The not-negligi-
ble property is that it allows application of extreme ten-
sion loading. This character is due to the uniaxial mole-
cular structure of such fibers.
However, the lack of other properties can indeed be an
advantage for some applications. The extreme “micro
toughness” as illustrated in the Figures 3 and 4 is related
to the limited transverse stress transfer in the filaments,
thus the tensile stresses are equalized over the filament
cross section. High local peak stresses in the fibers are
thus annihilated. Of course, it is important that the re-
sponse in the weak directions is deformation and not
material separation, so in fact not all non-tension proper-
ties are low. For example, the fracture strain in compres-
sive and transverse direction is high. So weaknesses in
those directions are only apparent in terms of force.
It was demonstrated above that the high tenacity, to-
gether with disadvantages like creep deformation, a low
friction coefficient, and low melting point can all be
turned into an advantage, for specific applications,
enabling the design of products or processes that show
properties with some unique aspects. Finding such possi-
bilities may require creativity but when found, they often
lead to unique advantages. Some opportunities for such
special products or processes are presently known.
However, still a challenge remains. There is no reason to
assume that possibilities for new attractive designs with
such exceptional fibers are exhausted. Moreover, the
gel-spinning process is versatile, and fibers optimized for
specific applications, like ballistic protection, surgery, or
cut resistance can be ( further ) d ev e loped.
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