JEC COMPOSITES MAGAZINE - Issue #99 - September 2015 - 31

Fig. 7: Sandwich structure design for a wind turbine blade

Fig. 5: Snapshots from the experiment and RTM
simulation results for the filling time at 980 sec.
and 2590 sec.

Fig. 6: Resin front evolution based on experimental data and RTM simulation data

Fabric

Core

1.24

K11 [m ]

1.80E-11

0.44E-10

K22 [m2]

1.23E-11

1.47E-10

K33 [m2]

1.11E-12

1.47E-10

0.44

0.11

Thickness [mm]
2

and the simulation results at different time steps. Figure 6 compares
the simulation results of the resin
front evolution with the results of the
experiment. It can be concluded that
the simulation results have good agreement with the experiment results.

Traditional 2D simulation only considers flow behaviour in the in-plane
direction. The geometric values for
curvature cannot be accurately captured and reflected in the computation
of 2D simulation. The flow behaviour
variables in the thickness direction are
treated as being the same in 2D/2.5D
simulation, which ultimately creates a
great discrepancy in the results compared with the actual moulding scenario, since the influence of different
material permeabilities and porosities
is not considered.
Figures 8 and 9 show Moldex3D's 3D
simulation results for the sandwich
structure design for a wind turbine

blade. Figure 8 shows a non-isothermal 3D flow simulation that includes
the different curvature geometric values and material parameters. Figure 9
shows the 3D flow analysis of a sliced
section of the part in the thickness
direction. It is observed that the resin
flows faster in the core region than
in the fabric region due to the higher
permeability and lower porosity of the
core material, resulting in a faster flow
phenomenon in the core region.
The results are relatively similar to
those shown in Figure 2 but, in Figure
9, the differences in the model's
geometric curvature and the flow's interchange mechanisms in the different
regions are factored into Moldex3D's
3D simulation.
Figure 10 shows a comparison of the
flow front results in the thickness
direction between uniform and anisotropic flow conditions. The impact of
the different material properties and
characteristics in the thickness direction on the actual flow behaviour can
be clearly understood. As a result, it
can be concluded that 3D simulation
is the only simulation technology that
can fully capture a complex geometric
design and truly reflect the intricate,
interchangeable material mechanisms
in a multilayer fibre design structure in
the RTM process.

Conclusions
This study proves that the Moldex3D
RTM module is capable of predicting
filling behaviour accurately. Moldex3D
simulation for the RTM process not

No99 September 2015 /

Feature Wind Energy

Tab. 3: Fabric and core material parameters used in
the simulation of the sandwich structure design [2]

RTM simulation: sandwich structure
design for a wind turbine blade
The sandwich structure design used
for a wind turbine blade is shown in
Figure 7 and the corresponding material parameters are listed in Table 3.
This sandwich structure is a multilayer fibre mat design with a core
material and a skin material. One of
the distinctive features of a sandwich
structure design is the variation in
material permeability and porosity in
the thickness direction across different materials. In this case, the fabric
(thickness 1.24mm) is placed on the
top and bottom of the core material.
An inlet is designed in the middle of
the structure, passing through the
whole blade. The resin will flow from
the inlet in the middle to both sides of
the blade. Swancor 2502-A/B epoxy is
used as the injected resin at a constant
pressure of 1 atm.

jec composites magazine 31

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #99 - September 2015