JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 55

being pulled from their creels into the
machine process. The creels can be
manually set to create a small amount of
tension on each tow by adjusting small,
low-torque brake assemblies. This may
include spring-applied manual brakes,
or other manually-applied brakes that
will require some attention from the
machine operator, or the tension on
the tows may reach a point where they
break.
Some machines may now include a load
cell roller that will measure the total
tension of all of the tows in a process as
they travel across the idler roll. This gets
a little closer to closed-loop control, but
the operator still needs to make coarse
adjustments to the tow brakes to try and
equalize the tension of all of the tows.
To solve the two aforementioned
problems of manual and inconsistent
control, the tows of material can be
pulled into a nip tensioning device.
Since the pressure across the nip is
loaded with equal pressure from front to
back, and the length of all of the tows is
equal from the exit of the tensioning nip
to the entrance of the process nip, the
tows will all exit the tensioning nip at
equal tension. Using load cell feedback
to control the total tension of all of
the tows, measured at a load cell idler
roll downstream from the nip stand,
the amount of tension can be trimmed
using a brake
to develop a
small amount
of torque at
the nip. The
tension on
each tow will
remain constant no matter what the
diameter of
the tow material on each
of the creels.
If some of
the creels are
Fig. 9: Multi tow tension
new complete
control during processing

rolls and some are partial, it will not
matter in this case because there are no
changing diameters at the nip. The diameter change takes place at the creels,
in a different tension zone.
By selecting a desired tension to be applied to each tow, e.g. 0.25pli, you can
determine the tension setpoint required
to best run the tows exiting the nip
control by multiplying the 0.25pli times
the width of all of the tows together. So
if there are a total of 240 tows coming
from this bank of creels, and the width
of 240 tows is 60 inches, you simply
multiply 0.25(pli) times the 60 inches
of width, or 15
pounds.
So in this example, the tension
setpoint would
be 15 pounds.
If the individual
tows need to be
0.50pli, then the
tension setpoint
would be 30
pounds, and so
on. Now when
Fig. 10: Unwind tension
control
you run the tows
through the nip,
the control system will monitor the tension and make minor adjustments to the
torque device (the brake) to maintain
tension at the selected setpoint.
The next tension zones, upper and lower
unwind tension in this instance, are
load cell-based unwind tension control
zones. These webs are upper and lower
paper carrier sheets in this case. The
tension on these webs is created by
the brake mounted at the centre of the
unwind rolls. As the paper unwinds, it
wraps around load cell rollers. The tension signal from the load cells is sent to
a closed-loop tension controller where
the actual tension is compared to the
setpoint selected by the machine operator. If the actual tension varies away
from the setpoint, the controller makes
the appropriate changes to the torque

at the brake to bring the tension back to
the setpoint. Since this is a closed-loop
system, the tension will remain at, or
close to the setpoint from full roll to
core, and this will remain true roll after
roll. In this case, each tow is fed into an
extruder where the product is extruded
between the two sheets.
From here, we go to the next tension
zone, the top paper carrier rewind.
Since this material is not that important, and is basically waste, the control
does not need to be that precise. You
only need to be able to wind it without
breaking the web. An open-loop control
system might be used in this application. An ultrasonic diameter sensor, or
proximity sensors, can be used to monitor the diameter of the roll as it builds,
and increase the torque slightly as the
roll builds.
The next tension zone is just downstream from where the top carrier sheet
is pulled from the extruded product. A
poly unwind is used to control the tension on a poly web to cover the extruded product. It is important to note that
the tension applied to the poly web will
be substantially
less than the bottom carrier paper
(remember, the
bottom carrier is
still under closedloop tension conFig. 11: Open loop rewind
trol). The paper
zone
carrier is a fairly
strong material, and is not extensible at
all. The poly layer is very extensible, so
the tension applied to this layer needs to
be precisely controlled at a tension that
is a fraction of the tension required for
the paper. If the poly is pulled too tight,
the web necks down. When the roll is
rewound, the roll may look fine but during storage or curing, the poly will try
and get back to its relaxed state. This can
cause wrinkles or starring of rolls. If the
poly is not tight enough, again, you may
find wrinkles in the web after curing.

No99 September 2015 / jec

composites magazine 55



Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #99 - September 2015

Cover
Edito
Point of view: The future of mass production
Contents
Companies & Business
In brief
Interview UCI - “Our aim is to ensure bicyclers are safe to race”
Agenda of Events
Applications
Recreational aviation - A recreational airplane as advanced as the latest widebodied aircraft
Sports & leisure - Cork, flax and green epoxy: a perfect balance for a skateboard
Medical - Lightweight emergency medical cot
Market
Natural fibres - Tending towards optimism
SPECIAL JEC FORUMS
Interview - MIT-NECST Lab: a research consortium dedicated to composites in Aeronautics
Conferences - Gain insight into the JEC 2015 Forums conferences programme
FEATURE WIND ENERGY
Wind energy - Double-digit growth continues
Design - A wind turbine without blades
Simulation - Visualizing RTM behaviour using advanced 3D CAE technology
Permeability - Optimizing fabrics for wind blade infusion
Automation - Automation strategies in rotor blade production: preforming vs. direct textile layup
Recycling - Recycling decommissioned composite wind blades
Platform - An internet aid for advances in wind turbine blade design
Research & Development
Graphene - Gambling with graphene, will it pay off ?
Thermal expansion - Boeing simulates thermal expansion in composites with expanded metal foil for lightning protection of aircraft structures
Technology & Innovations
Heating - Power transfer in complex shape heated moulds or functional composites
Manufacturing - Tension control in composites manufacturing
3D printing - A fully biodegradable flax fibre-reinforced thermoplastic filament for 3D printing
RTM/LCM - Fast production epoxies for lightweight automotive composites
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Cover
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 2
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Edito
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Point of view: The future of mass production
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 5
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Contents
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 7
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - In brief
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 9
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 10
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Interview UCI - “Our aim is to ensure bicyclers are safe to race”
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 13
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Recreational aviation - A recreational airplane as advanced as the latest widebodied aircraft
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 15
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Sports & leisure - Cork, flax and green epoxy: a perfect balance for a skateboard
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Medical - Lightweight emergency medical cot
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 18
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Natural fibres - Tending towards optimism
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 20
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 21
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Interview - MIT-NECST Lab: a research consortium dedicated to composites in Aeronautics
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 23
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Conferences - Gain insight into the JEC 2015 Forums conferences programme
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 25
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Wind energy - Double-digit growth continues
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 27
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Design - A wind turbine without blades
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Simulation - Visualizing RTM behaviour using advanced 3D CAE technology
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 30
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 31
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 32
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Permeability - Optimizing fabrics for wind blade infusion
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 34
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Automation - Automation strategies in rotor blade production: preforming vs. direct textile layup
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 36
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 37
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Recycling - Recycling decommissioned composite wind blades
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Platform - An internet aid for advances in wind turbine blade design
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 40
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Graphene - Gambling with graphene, will it pay off ?
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 42
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 43
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 44
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Thermal expansion - Boeing simulates thermal expansion in composites with expanded metal foil for lightning protection of aircraft structures
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 46
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 47
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Heating - Power transfer in complex shape heated moulds or functional composites
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 49
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 50
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 51
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Manufacturing - Tension control in composites manufacturing
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 53
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 54
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 55
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 56
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 57
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 58
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 3D printing - A fully biodegradable flax fibre-reinforced thermoplastic filament for 3D printing
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 60
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 61
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - RTM/LCM - Fast production epoxies for lightweight automotive composites
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 63
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 64
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - Index
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - In the world
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 67
JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 68
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