SAMPE Journal - September/October 2016 - 48

Feature Article
Manufacturing of Hybrid Profiles: Continuous Fiber Reinforced
Thermoset Profiles with a Thermoplastic Top Layer
C. Hopmann, P. Schneider, A. Boettcher
Institute of Plastics Processing at RWTH Aachen University (IKV)
Aachen, Germany
Email: Peter.Schneider@ikv.rwth-aachen.de
Abstract
Pultruded continuous fiber reinforced thermoset profiles are widely applied as semi-finished products for example in load-bearing parts of
bridges or as claddings in vehicles. At the Institute of Plastics Processing at RWTH Aachen University (IKV), an enhancement of the pultrusion
process is investigated to functionalize the thermoset pultruded profile inline by coating with a thermoplastic top layer. On the one hand, this
offers process advantages such as an economic one-step manufacturing of hybrid profile. On the other hand, the product properties, e.g. surface
qualities and impact resistance, are improved. At the same time the welding of load transfer elements can be realized.
In order to achieve these advantages, a combined pultrusion and extrusion process has been developed. Based on the identified challenges
related to the combination of two continuous processes with a thermoset and a thermoplastic material, a suitable process layout and die technology
was developed to establish an optimal process. The process must realize an intrinsic joining between the pre-cured, however still reactive pultruded
thermoset profile and the extruded thermoplastic melt. This paper describes the developed process and the results of the research that has been
conducted to optimize both the process parameters and the product properties.
Introduction
Fiber Reinforced Plastic Profiles
Fiber reinforced plastics (FRP or composites) are an
attractive alternative material choice to conventional,
mostly metal materials, due to their lightweight design
potential and adjustable properties1-2. However, for many
applications conventional materials are chosen over
FRP because of uncertainties regarding the structural
behavior of FRP and drawbacks regarding processing
and material efficiency3. Here, the continuous pultrusion
process is an economic, highly automated manufacturing
process for profiles of FRP and is thus an ideal base for
further process improvements.
Applications and Properties of Pultruded FRP Profiles
Pultruded, mostly thermoset FRP profiles are applied
as versatile structural parts with highly oriented,
unidirectional fibers or semi-finished products in
various applications. Figure 1 (left) shows typical profile
geometries of pultruded profiles and two exemplary
applications (Figure 1 right). Bridges made of pultruded
profiles are lightweight and thus can be erected fast
and easily in remote places with low effort. A secondary

advantage of the fast construction is that traffic routes
are only blocked for a very short construction time.
Furthermore, the superior corrosion performance
accounts for a long life at low service costs. The second
exemplary application is a vehicle bumper structure that
features a pultruded beam. Here, besides lightweight
design and low corrosion, the highly adjustable
properties of FRP are of particular interest. By the
kind and the ratio of fiber and matrix, the crash energy
absorption and damping properties can be adjusted to
the application, which means that in this case a good
crash behavior could be achieved.1-5
However, disadvantages of pultruded profiles (see
Figure 2 left) encompass medium surface qualities due
to fiber sign-off that often require painting5. Furthermore,
thermoset FRP usually have a low impact resistance,
which is particularly bad for automotive applications1,5.
Due to the continuous nature of the pultrusion process,
it is fairly impossible to integrate load transfer elements
like inserts into the profile during the process. Thus, in
many applications load transfer is achieved using screws
and bolts, which weakens the profile because the load-

Figure 1. Geometries and applications of pultruded FRP profiles6-8.
48

SAMPE Journal, Volume 52, No. 5, September/October 2016

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