1. New Methodology
Heat Pipe Thermally
Enhanced (HPTE) Mandrels
In Filament Winding
Applications

2. Heat pipes
Well
Established in
Automotive
Tooling
1

3. Heat pipes
What value does heatpipe
technology bring to
mandrel design and
filament winding process
optimization?
1

4. Heatpipe Operating Principles
2

5. Heatpipe Features & Benefits
 Heatpipes transfer large amounts of thermal energy rapidly.
 Heatpipes are intrinsically Isothermal.
 Heatpipes redistribute localized energy inputs.
 Heatpipes have an Intuitive, remediating response to locally
generated energy deficit and surplus transients. (sinks and
exotherms)
 Heatpipes require no electrical power or mechanical
connections.
 Heatpipes are sealed systems.
4

6. HPTE Mandrels
“In Oven” Convection
Oven Curing of
Filament Wound Tube
Sections
3

7. Current “In Oven”
Cure Challenges and Limitations
 The cure sequence usually occurs in a heated
convection oven or radiant energy environment.
 Energy is provided to the surface of the
resin/filament composite through the heated
oven atmosphere at low watt density.
 A large percentage of energy produced by the
oven is vented and not efficiently utilized.
3

8. Current “In Oven" Filament Winding
Cure Challenges and Limitations
 The mandrel is not directly heated.
 The mandrel is the last component to be heated.
 The cure is initiated at the outside surface of the
winding, sealing the outer surface of the tube
section, trapping gasses and vapour liberated during
the cure cycle.
 Trapped gasses and vapours contribute to
delamination and porosity.
3

9. HPTE Mandrel Testing Cell
5

10. Traditional Mandrel Test Results
Transient Temperature Curves for the Hollow Mandrel
140
Top (2")
Mid (33")
120 Bottom(60")
Delta T (bottom-top)
100
Surface Temp. (deg.F)
80
60
40 Date: Jan. 9, 09
Sand Bath Temp. 350 Deg. F
Heat Transfer Rate: ~12W.
20 Mandrel OD. 1.875".
Mandrel Length: 72".
TC location is the distance from the top.
0
0 5 10 15 20 25 30 35 40 45
Time (Min.)
6

11. HPTE Mandrel Test Results
Transient Temperature Curves for the Mandrel-Isobar
260
240
220
200
180
Surface Temperature (deg. F)
160
140
Top (2")
120
Date: Jan. 8, 09
100 Mid (33")
Sand Bath Temp. 350 Deg. F
80 Bottom (62") Heat Transfer Rate: ~210W.
Mandrel OD. 2".
60 Delta T (bottom-top) Mandrel Length: 74".
40 TC location is the distance from the top.
20
0
-20
0 10 20 30 40 50 60 70 80 90 100
Time (Min.) 7

12. HPTE mandrels thermodynamic
features in conventional
oven curing applications
 Exposed surfaces of the HPTE mandrel absorb thermal energy
from the oven and transfer it directly to the mandrel.
 This absorbed thermal energy is immediately redistributed
throughout the HPTE mandrel.
 The redistributed thermal energy results in a dynamically
isothermal mandrel.
 The heated isothermal mandrel provides an optimum uniform
cure platform providing thermal energy from I.D. to O.D. of the
tube section.
8

13. HPTE mandrels in convection
oven curing applications
thermodynamic benefits
 The mandrel is now thermally uniform. (isothermal) and super
thermally conductive and reactive to the ambient temperatures
within the oven.
 Resident energy within the oven is absorbed through the
exposed ends of the mandrel, heating the mandrel directly and
efficiently.
 Because both the I.D. and O.D. surfaces of the winding are now
actively heated, the cure cycle time is reduced.
 The heated mandrel draws resin to the I.D. of the winding
resulting in a tube section with a homogeneous, resin rich,
nonporous surface on the tube inner diameter.
9

14. HPTE Mandrels
“Out of Oven”
Induction Curing of
Filament Wound Tube
Sections After
Winding
3

15. Induction cure sequence using
a HPTE Mandrel winding and curing a 3” I.D.
Tube section with ½” wall using
carbon fiber epoxy prepreg
14

16. HPTE mandrels in induction
heated “out of oven”curing applications
 The induction heating coil is situated proximate to the
mandrel permitting unimpeded mandrel rotation.
 Induction heating is relatively instantaneous and intense.
 RF energy is invisible to the uncured resin and filament
but fully sensed by the metal mandrel.
 Significant thermal energy per unit time can be provided
to the mandrel which then intimately transfers that energy
to the uncured composite resulting in significant energy
efficiencies.
10

17. Testing Cell for Induction heating of
both a HPTE Mandrel
and a Traditional Mandrel
11

18. 3” Standard hollow mandrel:
Thermographic study with induction heat
187.70 ºF
12

19. 3” HTPE mandrel: Thermographic
study with induction heat
183.02 ºF
13

20. Traditional hollow mandrel vs. HTPE mandrel
64” X 3” rotating at 100 RPM and heated by an
induction coil providing 850 Watts
Time lapse video sequences

21. HPTE Mandrels
“Out of Oven”
Induction Curing of
Filament Wound Tube
Sections While
Winding
3

22. Video of a cure while winding sequence using
a HPTE Mandrel winding and curing
a 3” I.D. tube section wound
of carbon fiber epoxy prepreg
15

23. HPTE mandrels in induction
heated “out of oven” curing applications
 The mandrel now provides the uncured composite with
100% of the thermal energy requirement. The cure begins
at the mandrel surface and continues through to the tube
section outside diameter.
 Curing from the inside diameter to the outside surface
allows volatile vapours generated during the cure
sequence to be liberated to atmosphere reducing porosity.
 Resin is drawn to the hottest surface during the cure
resulting in a resin rich non porous I.D.
10

24. SAMPLE A Induction Cure vs. SAMPLE B Oven Cure
CT Scan Defect Analysis

25. A: Induction Cure
Marker

26. B: Oven Cure

27. A: Induction Cure
B: Oven Cure

28. Sample A: Induction Cure
Volume: 1288.8789 mm3
Defects: 2.7777 mm3
Porosity: 0.21505 %
Defect Volume Distribution vs. Defect Count

29. Sample B: Oven Cure
Volume: 1452.3339 mm3
Defects: 2.7764 mm3
Porosity: 0.19080 %
Defect Volume Distribution vs. Defect Count

30. Sample A: Induction Cure
Volume: 1288.8789 mm3
Defects: 2.7777 mm3
Porosity: 0.21505 %
Volume: 1452.3339 mm3 Sample B: Oven Cure
Defects: 2.7764 mm3
Porosity: 0.19080 %
Defect Volume Distribution vs. Defect Count

31. Technology providers
for this project
 Ameritherm Div of Ambrel Corp, Springfield NY
Induction power supply and coil
 Chino Works America, Chicago Illinois
Infrared sensor and process controller
 McClean Anderson, Schofield Wisconsin
Filament winding machine and laboratory
 TCR Composites, Ogden Utah
Prepreg epoxy filament materials
 Acrolab Ltd, Windsor Ontario, Canada
HPTE mandrel
16

32. Thank you
Joseph Ouellette
Director, Advanced Research
& Development
Acrolab Ltd.
Advanced Thermal Engineering /Research and Development
Windsor, Ontario, CANADA
www.acrolab.com