JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 39

manufacturing process, in particular
milling, without a noteworthy benefit
for the final part shape. In other words,
unnecessary costs are induced. Thus,
there is a need for "pragmatic" tool compensation measures in order to compensate the most relevant distortions but
also to consider milling efforts and other tool manufacturing processes. This
was adopted for the -stiffener at hand.
Only the flange-to-web angles were
modified, while compensation measures
were obtained from the P-approach
simulation. The flanges and the web
itself remained flat in the CAD model of
the tool. Even though the complexity increase of the tool geometry would have
been limited for the -stiffener, the
concept of "pragmatic compensation
measures" for more complex geometries
needs further attention in the future in
order to improve the parts' dimensional
fidelity while keeping tooling costs low.

Verification and validation

Conclusions
An autoclave injection manufacturing
concept for composite -stiffeners
was developed and validated as part
of a common project conducted by
Embraer, Toho Tenax and DLR. The
project addressed the challenges of manufacturing aerospace-grade composite
structures at reasonable cost with excellent dimensional fidelity. Therefore,
the process-induced distortions, which
are inevitable for composite structures,
were compensated in the tool using
numerical predictions derived from the
semi-numerical P-approach simulation strategy developed by DLR. The
laminate thickness evaluation revealed
that aerospace-specific tolerances were
met for all manufactured frames. The
evaluations of the cross-section shapes

Fig. 4: Cross-section evaluation of the four manufactured composite profiles

underlined that the developed manufacturing concept is suited for the production of parts with excellent dimensional
fidelity. Stiffener tolerances of ±0.1° for
the flange-to-web angles were met for all
the manufactured frames. This is significantly below the prescribed baseline tolerance of ±0.5° that is representative for
many composite structures used today.
This result indicates that assembly bottlenecks due to severe shimming issues
can be avoided in the future. However,
designers and engineers need to be
aware of the inevitable process-induced
distortions of composite structures and
the corresponding prediction-based tool
compensations, which can be derived
using the P-approach, for example. n
More information:
www.dlr.de
References
[1] Kappel E., Liebers N., Buggisch M.,
Hilmer P., Kleineberg M., Hühne C. Holistic quality approach for autoclave-injection composite manufacturing. JEC
Composites Magazine no. 96 - Feature
Aeronautics, 2015
[2] Kappel E., Reinhard B., Roser T. Highrate, spring-in compensated, net-shape
manufacturing of RTM made composite
frames within the EU project MAAXIMUS. ECCM17 conference, München, 2016
[3] Kappel E., Stefaniak D., Holzhüter
D., Hühne C., Sinapius M. Manufacturing
distortions of a CFRP box-structure - A
semi-numerical prediction approach.
Composites: Part A 2013;51:89-98
[4] Kappel E., Stefaniak D., Fernlund
G. Predicting process-induced distortions in composite manufacturing - A
pheno-numerical simulation strategy.
Composites Structures, 2015;120:98-106
[5] Liebers N. Effective and flexible ultrasound sensors for cure monitoring for
industrial composite production. German
Aerospace Congress, Berlin, Germany,
2012
[6] Kappel E., Stefaniak D., Hühne C.
Process distortions in prepreg manufacturing - An experimental study on
CFRP L-profiles. Composites Structures,
2013;106:615-625

No106 July 2016 / jec

FEATURE AERONAUTICS

Two sets of stiffeners were produced
using the established autoclave injection process. A fibre-volume fraction
of 59% was targeted. The shape of the
stiffeners was evaluated using a full-field
GOM ATOS metrology system. The
cross-section evaluations and laminate
thickness measurements showed that
the prescribed tolerances were met. The
results of the cross-section evaluation
demonstrated that the developed autoclave injection process made it possible
to manufacture parts with a high degree
of reproducibility. They also proved the
suitability of the applied prediction and

the corresponding "pragmatic" compensation measures realized in the tool.
A comparison between the weight of
the manufactured part and the preform
showed that the intended fibre-volume
fraction of 59% was achieved with the
developed manufacturing concept.
Figure 4 shows the flange-to-web angle
measurement results of the four manufactured frames. The illustrated angles
refer to Figure 1, while the nominal
angle is 111.03°. The prescribed angle
tolerance of ±0.5° is fully met. As can be
seen, all the measured angles are below
a tolerance threshold of ±0.1°. This
result is convincing as it is in the range
of typical part-to-part scattering observed in recent studies on prepreg-based
L-profiles [6].

composites magazine 39


http://www.dlr.de

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #106 - July 2016

Cover
Edito
Point of view: Europe
Contents
COMPANY & BUSINESS
Development
Agenda of Events
APPLICATIONS
Thermoplastics
Automotive
MARKET
Aircraft engine
FEATURE AERONAUTICS
Aerostructures
Characterisation
Thermoplastics
Aero-engines
Process
CFRP
Semi-product
RESEARCH & DEVELOPMENT
Review
Core material
TECHNOLOGY & INNOVATIONS
NDT
Marine
Index
In the world
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Ad1
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Cover
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 2
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Edito
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Point of view: Europe
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 5
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Contents
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 7
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - COMPANY & BUSINESS
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 9
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Development
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 11
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Agenda of Events
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 13
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - AdHEC
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - AdCro
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Thermoplastics
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 15
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 16
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Automotive
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Aircraft engine
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 19
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 20
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 21
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 22
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Aerostructures
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 24
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 25
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Characterisation
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 27
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 28
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 29
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 30
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Thermoplastics
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 32
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Aero-engines
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 34
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 35
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 36
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Process
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 38
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 39
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - CFRP
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 41
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 42
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Semi-product
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 44
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 45
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Review
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 47
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 48
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 49
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Core material
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 51
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 52
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - NDT
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 54
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Marine
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 56
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - Index
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - In the world
JEC COMPOSITES MAGAZINE - Issue #106 - July 2016 - 59
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