JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 55

Temperature-sensitive joints for water-soluble braiding mandrels

Tab. 1: Joint requirements

Connection of individual elements

backlash free

Torsional moment in the clamping system

25-38 Nm

Tensile force in the clamping system

50-500 N

Compression force in the clamping system

50-500 N

Maximum width of each segment

40 mm

Maximum height of each segment

30 mm

Maximum length of each segment

120 mm

Minimum disassembling temperature

130°C

Maximum disassembling temperature

175°C

Application

reusable

Tab. 2: Features of the joint system

Design

Torsion

Tension

Minimum interference

0.040 mm

0.030 mm

0.034 mm

Maximum interference

0.040 mm

0.033 mm

0.035 mm

Maximum axial force

500 N

-

> 500 N

Maximum torsional moment

21.5 Nm

25 Nm

-

Disassembling temperature

130-175°C

140-175°C

140-175°C

passed

passed

Test results

hubs are made of material with high CTE (aluminium). In contrast,
the shaft is made of an alloy with a low CTE (nickel-iron alloy). The
individual elements are dimensioned to ensure an interference fit between the hub and the shaft at room temperature - the joint is in activated state. Thereby, a backlash- and slip-free force and torque transmission from the releasing hub to the shaft and then to the pulling hub
is possible. As the temperature of the joint system increases, both hubs
expand stronger than the shaft and the tight fit migrates into clearance
fit. The friction force between the shaft and both hubs decreases. At
certain point the friction force becomes lower than the drag force applied by the spring and the shaft is retracted into the releasing hub by
the spring - the joint becomes disassembled. After the system cools
down all elements shrink to their initial dimensions and the joint remains in its disassembled configuration (Figure 2).

Verification
Joints were manufactured and tested to check the applicability of the
above-described concept. The required properties of each joint are
listed in Table 1.
An improved machining approach was selected to increase the reliability of the joint system. First, the hub was machined by turning and
its inner diameter was measured. The dimension achieved was declared to be the nominal (outer) diameter of the shaft. The shaft itself
was machined by turning and subsequent polishing of its surface. Following this procedure, the scale of interference created only depends
on the polishing process.
In several tests, joint systems were each subjected to a load case representing the braiding forces. Then, thermal loads simulating the curing

Fig. 3: Proof of concept and validation structure

process were applied. The test was declared as passed if the joint remained stable while mechanical forces were acting, but disassembled
autonomously at the target temperature, between 130°C and 175°C.
The test results are summarized in Table 2.
The operating principle of the temperature-dependent autonomously switchable coupling allows an irreversible change in state within a
limited-access system. In the initial state, at room temperature, there
is shrinkage fit between the individual coaxially arranged joining elements. Thus, a continuous load path from the releasing hub to the
shaft and then to the pulling hub is created and the transfer of forces
and loads occurs backlash- and slip-free. The developed joint features
high strength in terms of tension, bending and torsion.
Upon reaching a preset temperature, the system reconfigures autonomously. After repositioning of the joint elements, the end-to-end
contact disappears so that no load transfer is possible. Here, the temperature acts as a signal for the disassembling of the joint system. The
required amount of energy is provided by an integrated preloaded
spring. The operational capability of the concept was demonstrated
in experiments (Figure 3) and the functional principle was registered
for patenting [1].
The aim of future work is to identify further areas of application for
compact, autonomously opening or closing joints that have to operate
in closed systems. In addition to the initially targeted production of
reinforced braiding cores, other applications can be considered, especially in fields where a temperature gradient exists or can be imprinted
and high mechanical loads apply on the overall system. Applications
in hostile atmospheres where load-bearing, but removable and therefore reusable, structures are required are also possible.
More information:
www.dlr.de/fa/en/
Acknowledgments
This research project was supported by the German Federal
Ministry for Economic Affairs and Energy as part of the joint project
"Development and validation of hybrid, partially resolvable form core
elements" (FKZ 20W1121B) and the project executing organisation
within the German Aerospace Center (PT-DLR).
References
[1] Danilov M.; AZ.: 10 2014 114 734.0,
Deutsches Patent und Markenamt

No110 January-February 2017

/ jec composites magazine

55


http://www.dlr.de/fa/en/

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017

Cover
Edito
Opinion: Mobility
Contents
NEWS
In brief
Startup competition
Construction & public transport
Investment
Agenda
BUSINESS
Trend
Startup booster
China
MANUFACTURING
RTM
WPC
Sandwich
Feature Automotive - El dorado, or a lure
3D printing
Cycle time
Raw materials
Reinforcements
Compression moulding
Compression moulding
Lightweighting
Interior part
SOLUTIONS
Marine
Motorcycle
Medical
In the world
TECHNOLOGY
OPLC
Draping
Damping
Index
Advertisers
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 60
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Cover
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 2
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Edito
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Opinion: Mobility
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 5
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Contents
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 7
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - In brief
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 9
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Startup competition
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 11
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Construction & public transport
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 13
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Investment
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 15
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Agenda
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 17
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Trend
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 19
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Startup booster
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - China
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 22
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - RTM
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 24
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - WPC
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Sandwich
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 27
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 3D printing
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 29
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Cycle time
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 31
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Raw materials
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 33
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 34
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 35
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Reinforcements
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 37
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Compression moulding
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Compression moulding
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Lightweighting
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 41
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Interior part
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Marine
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 44
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Motorcycle
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Medical
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - In the world
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - OPLC
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 49
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 50
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 51
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 52
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 53
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Draping
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 55
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Damping
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 57
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - Advertisers
JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 59
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