JEC COMPOSITES MAGAZINE - Issue #110 - January/February 2017 - 54

TECHNOLOGY braiding

Temperature-sensitive joints
for water-soluble braiding mandrels

DIPL.-ING. TOBIAS FORSSBOHM,
German Aerospace Center, Institute of
Composite Structures and Adaptive Systems
DR.-ING. MAKSIM DANILOV
ZAL Center of Applied Aeronautical
Research GmbH

A braiding mandrel and its support structure based on a temperature-sensitive autonomous slip- and backlash-free coupling are investigated in
this paper. In combination with water-soluble moulding materials, temporarily stable mandrels are created, which can be used for the braiding
of multiple-curved hollow CFRP profiles.

T

he braiding of profiles is a well-known technology that allows
higher production rates than hand lay-up. It starts with the automated placement of dry fibres on a rigid mandrel (braiding).
The resulting dry preform, which has a web-like structure, is then infiltrated with liquid resin. The composite material is cured in a subsequent step. The main drawback of this technology is the limited variety
of shapes, since the solid mandrel has to be removed from the profile
at the end of the manufacturing process. Creating complex shapes and
multiple curves is a cost- and time-intensive process.
A recently developed approach uses mandrels made of water-soluble
moulding materials such as Aquacore. However, the manufacturing
process has several limitations in this case. During the braiding process, high local forces appear at the braiding point due to friction effects between the fibre rovings and the mandrel. These local forces act
on the core and need to be directed to the machine's clamping system.
To avoid destruction, the mandrels are reinforced with a metallic rod.
The variety of possible shapes and radii of curvature is limited by the
shape of the reinforcing rod.

Objectives and requirements
For the production of filigree, multiple-curved hollow profiles, the
use of a multi-part reinforcement is advisable. Only such a support

Fig. 1: Activated and deactivated (disassembled) state of the reinforcement

54

structure can be disassembled and removed from the complex-shaped
hollow CFRP profile once cured. This type of reinforcement has to
exhibit the following characteristics:
- Switching capacity: The reinforcement should not be permanently
stiff, but switchable between the rigid and the disassembled state.
While "activated" (before and during the braiding process), the reinforcement has a high rigidity. In the "disabled" state (after the end
of the polymerization process), the reinforcement may be separated
into multiple pieces (see Figure 1).
- Autonomy: Since the reinforcement is fully embedded into the mandrel, it cannot be activated externally and therefore has to operate
autonomously.

Reinforcement concept
Based on the requirements stated above, the approach was to develop
a multi-part reinforcement which consists of sequentially arranged,
stiff and short segments and autonomously switchable joints.
The operation mechanism of the joint described here is based on the
reversible thermal expansion of bodies. In case of a shaft-hub connection this results in a temperature-dependent force-fit. The developed
joint basically consists of three hollow cylinder-like elements: shaft,
pulling hub and releasing hub and a prestressed spring. Three hollow
elements are coaxially aligned with each other, wherein the releasing
hub and the pulling hub are frontally in contact with each other. The
shaft is arranged coaxially with both hubs and is in contact with them
via its surface area (Figure 2 left).
In order to ensure the required thermal dependency of the fit, both

Fig. 2: Joint concept of interference (left) and reconfigured clearance fit (right)

jec composites magazine / No110 January-February 2017



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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