JEC COMPOSITES MAGAZINE - Issue #96 - April 2015 - 29

In brief
A composite structure may be weightefficient, but it is rarely cost-efficient.
If a cost-efficient design is to be
found, it is important to study the
trade-off between weight and production cost as early as the conceptual
stage of a product development process. This paper briefly describes the
methodology of a composite cost estimation tool developed by the authors
within LOCOMACHS, under grant number no.314003. The tool is intended to
be used within the LOCOMACHS project
to reflect the cost benefits of the
design solutions developed.

most cost-efficient one for a certain
component. Furthermore, the production cost is a function of part size
and complexity (see figure 2). The
influences of both are incorporated
in the developed cost estimation
tool, and directly affect the production cost through cycle lead times
and dimensioned equipment.

Part size and complexity
The effect of part size and complexity can be understood by considering
the composite material of choice;
carbon prepreg parts are exemplified
here. These parts are manufactured
by placing prepregs of different

Tab.1: Influence of part size and complexity

HLU

ATL

AFP

Part size

Any

Large

Medium-large

Complexity

High

Low

Medium-high

Layup rate

1-2 kg/h

10-100 kg/h

2-100 kg/h

widths on a tool of suitable shape,
usually by hand layup (HLU), automatic tape layup (ATL) or automatic
fibre placement (AFP). The manufacturing difficulty is the placement
of the prepregs, which depends on
the response of the material relative
to component geometry, and on the
equipment used. In the case of hand
layup, the limitations are simply that
of the material's response while the
limitations for ATL and AFP are also
a result of the equipment's rotation
and steering capabilities. ATL allows
for the lowest level of complexity as
wide strips of material are placed,
which can quickly give rise to wrinkling of the applied tape if too complex geometries are attempted. AFP,
on the other hand, places thinner
strips of pre-impregnated fibre bundles that can be individually started
and dropped. These thin strips will
not be bent to the same degree as
the outer radii of a wider tape and

thus wrinkling will not occur as early,
which allows placement on geometries of increased complexity.

Manufacturability
and process time
To correctly use the effect of part
size and complexity, two measurements must be used: manufacturability and its influence on process time.
A measurement of manufacturability
records the limitations of a manufacturing method and the material
system used while its influence on
process time describes the effect of
complexity and part size within the
manufacturability borders. Examples
of the two measurements are given in
Table 1 for the discussed manufacturing methods. The effect of process
time is described using layup rates,
as the processing time directly results
from the weight of a part and the
possible layup rate.

More information:
www.locomachs.eu/

Fig. 2. Part cost calculated for a generic structure using its geometry and complexity

No96 April 2015 / jec

Feature Aeronautics

To summarize, this paper described
and motivated the methodology
used by the authors to develop a cost
estimation tool for general composite
structures. The authors underline the
importance of studying the trade-off
between potential weight savings and
production cost when designing with
composite materials. Future work
will focus on the transition from part
to structure by implementing cost
estimations with regards to assembly. Such a cost model allows for the
study of further issues related to the
benefits of integration through cocuring rather than assembly. n

composites magazine 29

http://www.locomachs.eu

JEC COMPOSITES MAGAZINE - Issue #96 - April 2015

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