Heat Pipe Thermally

Enhanced (HPTE) Mandrels

In Filament Winding

Applications

New Methodology

Well Established in

Automotive Tooling

1

Heat pipes

What value does heatpipe technology bring to mandrel design and

filament winding process optimization?

1

Heat pipes

Heatpipe Operating Principles

2

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.

Heatpipe Features & Benefits

4

HPTE Mandrels

3

“In Oven” Convection

Oven Curing of

Filament Wound Tube

Sections

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.

Current “In Oven” Cure Challenges and Limitations

3

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.

Current “In Oven" Filament Winding Cure Challenges and Limitations

3

HPTE Mandrel Testing Cell

5

Traditional Mandrel Test Results

Transient Temperature Curves for the Hollow Mandrel

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35 40 45

Time (Min.)

Su

rface T

em

p.

(deg

.F)

Top (2")

Mid (33")

Bottom(60")

Delta T (bottom-top)

Date: Jan. 9, 09

Sand Bath Temp. 350 Deg. F

Heat Transfer Rate: ~12W.

Mandrel OD. 1.875".

Mandrel Length: 72".

TC location is the distance from the top.

6

Transient Temperature Curves for the Mandrel-Isobar

-20

0

20

40

60

80

100

120

140

160

180

200

220

240

260

0 10 20 30 40 50 60 70 80 90 100

Time (Min.)

Su

rface T

em

pera

ture

(d

eg

. F

)

Top (2")

Mid (33")

Bottom (62")

Delta T (bottom-top)

Date: Jan. 8, 09

Sand Bath Temp. 350 Deg. F

Heat Transfer Rate: ~210W.

Mandrel OD. 2".

Mandrel Length: 74".

TC location is the distance from the top.

7

HPTE Mandrel Test Results

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.

HPTE mandrels thermodynamic features in conventional oven curing applications

8

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.

HPTE mandrels in convection oven curing applicationsthermodynamic benefits

9

HPTE Mandrels

3

“Out of Oven”

Induction Curing of

Filament Wound Tube

Sections After

Winding

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

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.

HPTE mandrels in induction

heated “out of oven”curing applications

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Testing Cell for Induction heating of both a HPTE Mandrel

and a Traditional Mandrel

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3” Standard hollow mandrel: Thermographic study with induction heat

12

187.70 ºF

13

3” HTPE mandrel: Thermographic

study with induction heat

183.02 ºF

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

HPTE Mandrels

3

“Out of Oven”

Induction Curing of

Filament Wound Tube

Sections While

Winding

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

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.

HPTE mandrels in induction

heated “out of oven” curing applications

10

SAMPLE A Induction Cure vs. SAMPLE B Oven Cure

CT Scan Defect Analysis

A: Induction Cure

Marker

B: Oven Cure

A: Induction Cure

B: Oven Cure

Sample A: Induction Cure

Volume: 1288.8789 mm3

Defects: 2.7777 mm3

Porosity: 0.21505 %

Defect Volume Distribution vs. Defect Count

Sample B: Oven Cure

Volume: 1452.3339 mm3

Defects: 2.7764 mm3

Porosity: 0.19080 %

Defect Volume Distribution vs. Defect Count

Sample A: Induction Cure

Sample B: Oven Cure

Defect Volume Distribution vs. Defect Count

Volume: 1288.8789 mm3

Defects: 2.7777 mm3

Porosity: 0.21505 %

Volume: 1452.3339 mm3

Defects: 2.7764 mm3

Porosity: 0.19080 %

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, CanadaHPTE mandrel

Technology providers for this project

16

Joseph Ouellette

Director, Advanced Research

& Development

Acrolab Ltd.

Thank you

Advanced Thermal Engineering /Research and Development

Windsor, Ontario, CANADA

www.acrolab.com