JEC COMPOSITES MAGAZINE - Issue #121 - May 2018 - 63

High-confidence performance predictions for hybrid thermoplastic composite applications

Fig. 1: Hybrid overmoulding technology for thermoplastic hybrid components: 1)
pick up of the composite blank; 2) IR heating; 3) blank fixation in the mould; 4) blank
thermoforming; 5) injection overmoulding; and 6) part demoulding

Fig. 2: Sabic's composite material portfolio

Sabic developed UD tapes using various resins and fibres, as
well as multiaxial or unidirectional laminates, and can offer a
wide range of fully-compatible overmoulding products.
One of these UD tape products, UDMAX™ GPP 45-70, is
based on glass fibre-reinforced polypropylene (see Figure 2).
The material is 45% glass fibres by volume, which corresponds to 70% fibres by weight. In addition, moulding and application development support can be provided, including the
expertise and capability needed to predict a part's mechanical behaviour [2]. Note that fabric-based materials were also
evaluated for use in specific applications not discussed here.
More details on material forms and application examples can
be found in literature published by Sabic [7, 8].
As can be observed through data published in [2], significant
weight savings are possible compared to the existing solutions, depending on the choice of carbon or glass fibres.
Looking at the $/kg weight saved value, glass fibre is the most
favourable alternative and compares very well against weight
saving alternatives considered by many OEMs such as magnesium or aluminium.

Validation test set-up
Although, as shown in [7], the cost and cycle time hurdles can
be overcome and hybrid thermoplastic composite components are quite cost effective, confidence in predictability still
needs to be gained. For this reason, a beam-like test component was designed that would tackle process variations and
validate predictions of actual in-part composite material performance. The test component is a four-point bending beam

Fig. 3: Four-point bending hybrid test component. Note the depression in the midtest section. Right: 3D cross section showing a highly asymmetric UD insert layout
(red colour)

with a hat-shaped or "omega" cross-section, see Figure 3.
As shown in the picture, the beam has reduced height in the midtest area. This is needed to have a well-controlled test region and to
make sure that the highest stresses do not occur very locally, just
underneath the load introduction points. However, this depression
in the height of the beam easily leads to buckling at the high failure
stresses, as typically seen for UD materials. For this reason, the final geometry design has an unusually large number of ribs. More
details about this beam can be obtained from Sabic's paper [9].

Establishing the predictive methodology
Predictive solutions include the use of CAE software packages,
combined with accurate material data, proper material
modelling, accounting for the influence of manufacturing
processes (heating, draping and overmoulding) and
experimental validation.
Material data is the input for simulations and needs to be
accurate to ensure overall prediction accuracy. Therefore,
significant effort was devoted to accurate material data
characterization.
Manufacturing processes also have a significant influence on
mechanical performance and are taken care of through an
integrated simulation approach.
More details on the influence of manufacturing parameters
can be found in Sabic's paper [10].
Material modelling consists of two parts: establishing material
modelling for the UD tape product and for the overmoulding
material.
N°121 May - June 2018

/ jec composites magazine

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #121 - May 2018