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Zeitschrift Kunststofftechnik
Journal of Plastics Technology
© 2011 Carl Hanser Verlag, München
www.kunststofftech.com
archival, peer-reviewed online Journal of the Scientific Alliance of Polymer Technology
archivierte, peer-rezensierte Internetzeitschrift des Wissenschaftlichen Arbeitskreises Kunststofftechnik (WAK)
www.plasticseng.com, www.kunststofftech.com
handed in/eingereicht:
accepted/angenommen:
06.10.2010
29.03.2011
Dipl.-Ing. Andreas Nau, Prof. Dr.-Ing. habil. Berthold Scholtes,
IfW Institute of Materials Engineering - Metallic Materials, University of Kassel
Dipl.-Ing. Martin Rohleder, IfW Institute of Materials Engineering –
Plastics Technology, University of Kassel
PH.D João Nobre, CEMDRX, Department of Mechanical Engineering,
University of Coimbra, Portugal
Application of the Hole Drilling Method for
Residual Stress Analyses in Components
made of Polycarbonate
The incremental hole drilling method is widely used and a cost-effective procedure to analyse residual
stress depth distribution states in metallic components. By disturbance of the mechanical equilibrium
due to a stepwise introduced hole, it is possible to calculate residual stress depth distributions due to
the relaxed strains recorded by special strain gages. The calculation is based on modified elasticity
assumptions and implemented calibration functions. In this publication, using polycarbonate as model
material, important process conditions are outlined which have to be fulfilled to achieve reliable results
in case of residual stress analyses in components made of plastics.
Anwendung des Bohrlochverfahrens für
Eigenspannungsanalysen in Proben aus
Polycarbonat
Die inkrementelle Bohrlochmethode ist ein weit verbreitetes und wirtschaftliches Verfahren zur
Bestimmung von Eigenspannungstiefenverläufen. Durch Störung des vorhandenen mechanischen
Gleichgewichtes in Form eines stufenweise erzeugten Loches können mittels der mit einer speziellen
Dehnungsmessstreifenrosette registrierten relaxierten Dehnungen Eigenspannungstiefenverläufe
berechnet werden. Hierfür kommen modifizierte elastizitätstheoretische Ansätze zur Anwendung, die
üblicherweise auf Kalibrierfunktionen basieren. Die in dieser Arbeit beschriebenen Untersuchungen
geben am Beispiel des Werkstoffs Polycarbonat den Rahmen für die wichtigsten Prozessparameter
vor, die für die reproduzierbare Bestimmung von Eigenspannungen in Bauteilkomponenten aus
Kunststoffen eingehalten werden sollten.
© Carl Hanser Verlag
Zeitschrift Kunststofftechnik / Journal of Plastics Technology 7 (2011) 3
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Nau, Scholtes et al.
Hole Drilling Method for Stress Analyses in PC
Application of the hole drilling method for
residual stress analyses in components made of
polycarbonate
A. Nau, B. Scholtes, M. Rohleder, J. Nobre
1
INTRODUCTION
It is generally accepted that the manufacturing and processing of components
made of metallic as well as non-metallic materials e.g. thermoplastic polymers
is accompanied by the formation of characteristic residual stress states [1, 2],
which may have a decisive influence on strength, lifetime and applicability.
Therefore, a great interest exists in reliable methods of their analysis.
In thermoplastic polymers based on the highly dynamic processes during the
production, shear forces create characteristic inhomogeneous stresses in the
skin layer of the products, which are especially highly influenced by the injection
speed and the mold temperature [3]. The high thermal expansion coefficient
causes shrinkage of the material during the cooling process and leads to
warpage or rather residual stresses in immobile areas [4, 5].
Residual stresses can be reduced or even prevented by lower cooling rates,
special processing technologies like variothermic processing (fast heating and
cooling of the mould), injection compression moulding or foaming [6, 7] and also
by thermal annealing of the products afterwards. However, all of these methods
except foaming increase the cycle time as well as investment and production
costs.
The mechanical properties of thermoplastic polymers are highly influenced by
their residual stress state, especially in near surface volumes [4, 5]. A simple
method to characterize the residual stress state is the environmental stress
crack resistance (ESCR) test [8]. A disadvantage of this method is that the
determination of residual stress can only be done in areas close to the surface
and results are only qualitative and not quantitative. A further influencing factor
is the corrosion medium used, which necessitates a comparison with a
reference residual stress free material to relate the stress crack resistance to
the existing residual stress state.
The hole drilling method, unlike diffraction methods, which are restricted to
crystalline materials, is a widely used procedure to quantitatively analyse
residual stress states in metallic and plastic components. It is based on the
determination of strains relaxed by the disturbance of the mechanical
equilibrium in the component as a consequence of a stepwise introduced small
hole, Fig. 1. In general 6-blade face cutters are used to introduce an
Journal of Plastics Technology 7 (2011) 3
67
Hole Drilling Method for Stress Analyses in PC
approximately ideal cylindrical hole with a flat bottom. This is essential because
calibration functions based on numerical simulations assume an ideal drilling
process excluding geometrical deviations from an ideal cylindrical hole. For the
calculation of the initial residual stresses the theory of elasticity is used. The
most important influencing factors with respect to strain sensitivity of the applied
strain gage can be summarized as follows, see Fig.1:



The lower the stress state in the component, the lower are the measured
strains on the components surface.
The deeper the position of the removed material increment, the lower are
the measured strains on the components surface.
The larger the distance between the drilled hole and the applied strain gage,
the lower are the measured strains on the components surface.
Because of the marginal mechanical disturbance the hole drilling method is
classified by ASTM as semi-destructive [9].
In general, relaxed strains are measured by special strain gage rosettes. Other
contactless techniques based on optical analyses, e.g. speckle interferometry
[10], are available but more expensive as well as not fully developed for general
practical application.
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Nau, Scholtes et al.
Fig. 1:
Principle of the hole drilling method
left:
right:
introduction of a hole by incremental drilling with an end mill
strain sensitivity dependent on stress state and geometrical
parameters
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Hole Drilling Method for Stress Analyses in PC
If strain relaxation is analysed by strain gages, a careful surface preparation
and the use of appropriate adhesives is necessary to ensure an excellent
bonding between the strain gages and the components under investigation.
Different solvents e.g. acetone, propanol as well as acid are used to obtain a
high quality surface finish to apply strain gages in case of metallic materials
[11]. In order to ensure the direct transmission of the released strains to the
strain gages the layer thickness of the adhesive should be as thin as possible.
To get high-resolution output signals of the measurement amplifier, feeding
voltages between 3 V up to 5 V are used. This results in a high current density
due to the small diameter of the conducting paths of the strain gages [11], which
may generate a non-negligible temperature rise in materials with low thermal
conductivity.
Due to the notch effect of the drilled hole [12 - 15] measured residual stresses
are only reliable if they are below 60 % of the materials’ yield stress [14]. A
further important issue is the introduction of a hole into the specimen with a
minimum amount of plastic deformation. For metallic materials the recommended and most practical technique is the application of high speed drilling (HSD)
[16] by air turbines with a speed of rotation up to 400000 rpm. In general, end
mills with 6-blades are preferred in order to obtain a cylindrical hole with a flat
bottom. In this way, only negligible microstructural alterations are generated in
the vicinity of the drilled hole and elastic effects are by far prevailing.
However, plastics have quite different and strongly temperature dependent
materials properties. As a consequence, it has to be expected that different
tools and process parameters have to be applied in order to produce holes of
the required quality. Otherwise, detrimental effects on the residual stress
measurements cannot be excluded. It is well known that reliable stress analyses by the hole drilling method are based on special requirements concerning
the drilling as well as the strain measuring procedure. Basically, it is of
importance that only elastic deformations are relaxed by the drilling process. In
practice, that means that plasticity effects due to the chip forming drilling
operation have to be minimized as far as possible. In addition, the hole
geometry should be as close as possible cylindrical with a flat bottom and the
position of the strain gages relative to the hole should be exactly known. Finally,
any additional fictitious strains not due to the drilling procedure and time
dependent effects should be strictly avoided. There are several publications in
literature using hole drilling experiments for residual stress analyses in plastics
(see e. g. [2, 17 - 19]). However, clear recommendations about the necessary
boundary conditions for the application of the hole drilling method in such
materials are still lacking.
As a consequence, in a systematic experimental study important process
conditions were identified which have to be fulfilled to achieve reliable results in
case of residual stress analyses in plastic components and results are
presented in this publication.
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2
Hole Drilling Method for Stress Analyses in PC
MATERIAL INVESTIGATED AND EXPERIMENTAL
DETAILS
The material investigated was polycarbonate (Makrolon 2805 - Bayer
MaterialScience) with medium viscosity and an MVR of 9.5cm³/10 min (300 °C;
1.2 kg). It is a transparent general purpose grade with release additive
produced intended for a mould. Important material parameters are given in
Table 1. Most remarkable is the thermal conductivity of 0.2 W/(m K), which is
considerably smaller in comparison to metallic materials (>15 W/(m K)). As a
consequence, all process steps producing heat, e.g. manufacturing of the
soldering connections of the strain gages, have to be carried out very carefully
in order to avoid detrimental temperature effects.
Residual stresses are highly influenced by the production process of the
specimens. Main influencing parameters are the mould, the melt temperature
and injection velocity.
tensile
modulus
yield
stress
poisson
ratio
glas
thermal
transition t. conductivity
in MPa
in MPa
-
in °C
in W/(mK)
2373
66
0.35*
148**
0.20**
*assumption, **Bayer AG
Table 1:
Material properties of polycarbonate (Makrolon 2805)
The higher the mould temperature, the lower the residual stress of the produced
sample, based on the lower cooling rate and the possibility to relax emerging
stresses by a creep process. Furthermore a low mould temperature generates
high shear forces by freezing the melt on the surface of the mould which leads
to residual stress in these areas of the sample. This can be intensified by an
increase of the injection velocity.
The mould used in this study had a plate geometry with a size of (160 x 60 x
4) mm³. The melt was injected through a film gate which should lead to a
homogeneous residual stress value in flow direction over most of the specimen.
Specimens were manufactured according to DIN EN ISO 294-1 and one batch
of the specimens was additionally tempered at 128°C for 72 hours in order to
obtain a residual stress free starting condition.
Further specimens were manufactured with two different manufacturing
conditions. These specimens were produced by an injection moulding process
(Engel E-Motion 100 – clamp force 100 to, screw diameter 35 mm) with different
processing parameters. Condition “l” was produced according to DIN EN ISO
294-1 [20] and DIN EN ISO 7391-2 [21]. To achieve higher residual stress
amounts condition “h” was produced with a higher injection velocity and lower
melt and mould temperatures, Table 2.
Journal of Plastics Technology 7 (2011) 3
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Hole Drilling Method for Stress Analyses in PC
process
mould
temperature temperature
injection
velocity
basic process
conditions
in °C
in °C
in mm/s
condition l
300
80
200
DIN EN ISO 294-1
DIN EN ISO 7391-2
condition h
280
40
300
DIN EN ISO 294-1
Table 2:
Injection moulding processing parameters
The test equipment used for hole drilling measurements, Fig. 2, consists of the
milling guide RS-200 (Vishay Measurements Group), the measurement
amplifier Picas (Peekel Instruments GmbH), strain gage rosettes of the type
CAE-13-062UM-120 (Vishay Micro-Measurements) and the evaluation software
BOP (MPA Stuttgart).
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Fig. 2:
Experimental equipment and investigated drilling techniques
RS-200 is a high-precision device for analysing residual stresses by the hole
drilling method, but without any automatic functions for in depth feed rate or
circular direction. The parameters have to be adjusted manually by the
operator. It is possible to assemble the RS-200 with an air turbine or with a
milling rod. The latter can be connected to an electrical drilling machine or be
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Hole Drilling Method for Stress Analyses in PC
operated manually. In this study the air turbine and manual drilling were applied.
The drilling process can be carried out in a conventional manner by advancing
the rapidly rotating end mill into the specimen as well as in an orbital manner
with an additional rotary motion around a radial offset relative to the axial center
line of the turbine assembly. Orbital drilling unlike conventional drilling has
advantages in chip removal, reduction of overheating and results in increasing
tool lifetime [22].
To connect the strain gage rosette with the amplifier, a 3-wire technique is the
best choice to compensate cable resistance of the back wire. A quarter
Wheatstone bridge circuit without an additional strain gage for temperature
compensation was selected due to laboratory conditions as well as stable
temperature conditions of the specimen.
To assess the influence of the different drilling techniques on the materials
damage in the vicinity of the hole, specimens were investigated in a first step by
means of photoelasticity with linear polarized light in the dark field to get a
qualitative information about the drilling induced plastic deformation.
Micrographs of the cross sectional area of the drilled hole were prepared to
obtain information about the hole geometry. For this purpose, the polycarbonate
plates were cut close to he holes by a low speed saw using diamond coated
saw blades and water cooling. Subsequently, the prepared pieces were cold
embedded with epoxid resin and grinded as well as polished to the center of the
cross sectional area of the hole. For polishing a special polishing plate
appropriate for plastic materials was used.
To investigate the thermal influence on the material induced only by a single
strain gage, measurements were carried out with a thermal sensor applied
directly on the strain gage grid as well as 1 mm below the strain gage in the
material, as a function of different feeding voltages. For the latter thermal
sensor, a small hole was drilled into the specimen filled with heat transfer paste.
Additional measurements were carried out by a thermography camera in order
to obtain a temperature distribution field. The required emission coefficient for
the applied strain gage on polycarbonate was identified using the two thermal
sensors, mentioned above and set to 1 for a black body.
For all experimental steps, a relaxation time after drilling of about 5 min was
taken into account before strain values were recorded.
To assess the selected experimental parameters based on previous investigations, residual stresses were simulated by applied external uniaxial loading
stresses using a tensile testing machine, Fig. 3. To avoid any effects that might
arise due to unknown residual stress states, two different stresses max and
min were applied and according to the equation below, the calibration stress
cal was determined (Eq. 1). The applied loads were controlled by an
additional calibration strain gage. An appropriate specimen for the tensile
machine was milled out of a polycarbonate plate and was subsequently
tempered.
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Hole Drilling Method for Stress Analyses in PC
 cal   max   RS    min   RS 
Fig. 3:
(1)
Working with calibration stresses by means of a tensile machine
To calculate residual stresses from the measured strain distributions, software
BOP with the evaluation algorithm MPA II developed by Kockelmann and
Schwarz [23] was used which has calibration functions implemented for a
component geometry of a thick wide plate. However the calibration functions
are also appropriate for other geometries within well defined geometrical
boundary conditions, if the restrictions listed in Table 2 are fulfilled [24, 25].
Table 2:
Geometrical boundary conditions for the MPA II standard [24]
3
EXPERIMENTAL RESULTS AND DISCUSSION
3.1.
Drilling operation
For metallic materials, HSD using appropriate end mills, e.g. 6-blade face
cutters, is recommended. However, polymer materials have a lower thermal
conductivity and a low glass transition temperature. Thus, thermal effects due to
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Hole Drilling Method for Stress Analyses in PC
frictional heating cannot be neglected. In order to demonstrate qualitatively the
influence of different drilling techniques, only photoelasticity was used in a first
step. Fig. 4 shows the tempered polycarbonate plate before as well as after
drilling, grouped for HSD (Pos. 1-10) and for manual drilling (Pos. 13-15). It is
quite obvious that in all cases HSD introduces coupled thermal / mechanical
effects into the specimen. In this way, unintentional strains are produced. On
the other hand, manual drilling results in the smallest effects. Additionally, Fig. 4
highlights the reproducibility of the manual technique, which was carried out
three times under the same testing conditions.
Fig. 4:
Specimen before and after drilling with different conditions
A detailed investigation of the effects of the different drilling techniques is
illustrated in Fig. 5. It is quite obvious that, the higher the turbine air pressure
and, hence, the rotational speed, the more pronounced are deformations due to
the drilling procedure on the material. Additionally, the hole diameter increases
with higher air pressure of the turbine due to higher radial vibrations of the end
mill which results in an expanding of the holes. However, there is a difference
among the three HSD-techniques. The orbital unlike the conventional one
seems to have less detrimental effects on the materials state near the hole. In
[17] this technique is preferred because air can circulate in the hole and is able
to cool the drill and to prevent chips from being trapped between the drill bit and
the edges of the hole. Because the theory of the hole drilling method and
existing evaluation standards require an ideal geometry of a cylindrical hole with
a flat bottom, the resulting hole geometries dependent on the different drilling
processes have to be investigated, too.
Journal of Plastics Technology 7 (2011) 3
74
Fig. 5:
Hole Drilling Method for Stress Analyses in PC
Photoelastic analysis of different drilling techniques for PC
For this purpose, cross sections of the drilled holes were prepared and
analysed which is shown in Fig. 6. The differences of the geometries are
marginal. The best cylindrical geometry can be achieved with the conventional
HSD and a high turbine air pressure. But manually drilling also results in
appropriate cylindrical geometries with even sharper vertices at the bottom of
the hole.
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Fig. 6:
Hole geometries dependent on different drilling techniques
Journal of Plastics Technology 7 (2011) 3
75
3.2.
Hole Drilling Method for Stress Analyses in PC
Effect of the strain gage feeding voltage
Besides the drilling technique there is still another more important aspect as far
as thermal effects are concerned. If the strain measurement is carried out with
electrical resistance strain gages, the feeding voltage has a non negligible effect
due to the low thermal conductivity of the material. Working with a feeding
voltage of 5 V, which is commonly used in case of metallic materials, results in
a current density of 46 A/mm² for a 120  strain gage in a symmetric bridge
circuit. The generated Joule heat cannot be adequately dissipated in the
material itself, see Fig. 7. The mean temperature of the two thermal sensors
(dotted line), one directly on the grid (MP1) and the other one inside the
material below the grid (MP2), increases up to 50 °C, working with a maximum
feeding voltage of 5 V. The investigation with the thermography camera yields
maximum values up to nearly 80°C (see upper part of Fig. 7).
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Fig. 7:
Influence of feeding voltage of a strain gage rosette applied on PC
Fig. 8 highlights the thermal strain output signal of the grid of the applied strain
gage rosette when the feeding voltage is stepwise activated and switched off
from 0.5 V up to 5 V The strain values were recorded, when the strain signal
reached a constant state. A holding time of about 10 min was required. It is
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Hole Drilling Method for Stress Analyses in PC
clearly shown that due to the heat produced, a remarkable thermal strain
develops. Moreover, after voltage switch off, the strain signal does not
disappear and, obviously, a permanent strain has been produced. Only for a
feeding voltage of 0.5 V, the strain signal behaviour is acceptable. To ensure
that no thermal influences affect the strain analyses by temperature induced
thermal strains, it is recommended that a low feeding voltages of about 0.5 V is
used in order to get reliable results.
Fig. 8:
Influence of feeding voltage on the output signal of a strain gage
rosette applied on PC, displayed for grid 2.
3.3.
Specimen preparation
First measurements were carried out by manual drilling technique and a feeding
voltage of 0.5 V on tempered, i. e. residual stress relieved PC. Hence, negligible
strain relaxation was expected due to the tempered state of the specimen on
the one hand and the selected sensitive drilling technique and the low feeding
voltage on the other hand. But in contrast to that, considerable strain relaxation
was observed. It turned out that the solvent used to provide an appropriate
clean surface condition for applying strain gages has an enormous consequence on the measurement because of its influence on the near surface region
of the specimen. Fig. 9 illustrates the measured strains for a tempered PCspecimen, prepared with different solvents for different drilling techniques.
Again, it is confirmed by several measurements that the strain values measured
if HSD is used are considerably distorted by the drilling process itself,
introducing undesirable machining strains, because the results are absolutely
unrealistic for a tempered PC-specimen. Additionally the investigation clearly
points out the consequences of different solvents for surface preparation. In
both cases the measured strains are clearly higher in the region close to the
surface of the specimen, where the solvent can affect the material properties, if
propanol is used compared to the use of ethanol. Cleaning with propanol leads
to considerable strain relaxation during the following drilling process, which is
not the case for ethanol. Propanol is known to damage the affected areas of
plastics [26] and this might be the reason for the observed effects. Therefore it
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Hole Drilling Method for Stress Analyses in PC
is recommended to clean the surface of PC with ethanol before applying strain
gages, because it does not affect the material [26].
Fig. 9:
Influence of the surface preparation on measured stress values
3.4.
Examples of stress analyses
To validate the measuring procedure developed in the foregoing sections, two
different kinds of stress analyses were carried out: Tests with calibration stress,
simulating residual stress by appling loading stress, and tests with specially
manufactured specimens where due to the individual manufacturing process
characteristic residual stress states were expected.
Results of the calibration stress experiments are plotted in Fig. 10. On the left
hand side, the applied strain gage on the specimen clamping in the tensile
testing machine and the directions of the three grids as well as the relaxed
strains under uniaxial tensile loads of cal, max = 15 MPa (solid lines) and
cal, min = 10 MPa (dotted lines) resp. are shown. The diagram on the right hand
side shows the calculated first principal stress (dashed line) compared with
theoretical expectations (solid lines). A good agreement between measured and
applied stress can be stated, which confirms the reliability of the measuring
procedure. There are only devations close to the surface and for the maximum
hole depth, which is commonly observed for the hole drilling method.
Journal of Plastics Technology 7 (2011) 3
78
Fig. 10:
Hole Drilling Method for Stress Analyses in PC
Residual stress analysis with applied calibration stress
Fig. 11 shows results of measurements of specimens with manufacturing
induced residual stress compared with a tempered condition.
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Fig. 11:
Residual stress analysis for different manufacturing conditions of PCspecimens in comparison to a tempered one
In condition “h” and “l”, small tensile residual stresses are measured at the
surface and in both cases max. compression residual stresses between -3 and -
Journal of Plastics Technology 7 (2011) 3
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Hole Drilling Method for Stress Analyses in PC
4 MPa at a surface distance of approximately 0.4 mm. By contrast, tempered
specimens are almost free of residual stresses in agreement with expectation.
4
SUMMARY
The presented experimental results clearly show that only a careful execution of
the drilling procedure and measurement of the relaxed strains by strain gages
results in reliable residual stress values. Established procedures and process
parameters valid for stress analyses in metallic materials cannot be applied
without appropriate adaptation. In the case of polycarbonate, the typical
elastoplastic materials behaviour of plastics as well as their characteristic
thermophysical properties are of importance. From the experimental results
gained in this work, guidelines and instructions are deduced for the application
of the hole drilling method, which can be transferred and generalized to other
components made of plastics. A comprehensive summary of the
recommendations is given in Fig. 12.
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Fig. 12:
Recommendations for residual stresses analysis in PC
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Hole Drilling Method for Stress Analyses in PC
ACKNOWLEDGEMENT
The work presented in this paper was carried out within the scope of TRR 30
funded by German Research foundation DFG, which is gratefully acknowleged.
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Journal of Plastics Technology 7 (2011) 3
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Nau, Scholtes et al.
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Scholtes, B.
Use of the Hole-drilling Method for Measuring
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Procter E.
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www.kunststofftech.com
Nicht zur Verwendung in Intranet- und Internet-Angeboten sowie elektronischen Verteilern.
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Business
Developement–
Polycarbonate
Bayer
MaterialScience
AG (Hrsg.)
Hole Drilling Method for Stress Analyses in PC
Makrolon Chemische Beständigkeit, 2004
Keywords:
residual stresses, hole drilling method, polycarbonate, plastics
Stichworte:
Eigenspannungen, Bohrlochmethode, Polycarbonat, Kunststoffe
© 2011 Carl Hanser Verlag, München
www.kunststofftech.com
Nicht zur Verwendung in Intranet- und Internet-Angeboten sowie elektronischen Verteilern.
Nau, Scholtes et al.
Journal of Plastics Technology 7 (2011) 3
84
© 2011 Carl Hanser Verlag, München
www.kunststofftech.com
Nicht zur Verwendung in Intranet- und Internet-Angeboten sowie elektronischen Verteilern.
Nau, Scholtes et al.
Hole Drilling Method for Stress Analyses in PC
Author/Autor:
Dipl.-Ing. Andreas Nau
University of Kassel
IfW Institute of Materials Engineering - Metallic Materials
Mönchebergstr. 3
34125 Kassel
Prof. Dr.-Ing. habil. Berthold Scholtes
University of Kassel
IfW Institute of Materials Engineering - Metallic Materials
Mönchebergstr. 3
34125 Kassel
Dipl.-Ing. Martin Rohleder,
University of Kassel
IfW Institute of Materials Engineering – Plastics Technology
Mönchebergstr. 3
34125 Kassel
E-Mail: nau@uni-kassel.de
Website: uni-kassel.de
Phone.: +49(0)561/804-3697
Fax: +49(0)561/804-3699
E-Mail: scholtes@uni-kassel.de
Website: uni-kassel.de
Phone.: +49(0)561/804-3660
Fax: +49(0)561/804-3699
E-Mail: rohleder@uni-kassel.de
Website: kutech-kassel.de
Phone.: +49(0)561/804-3688
Fax: +49(0)561/804-3692
E-Mail: joao.nobre@dem.uc.pt
PH.D João Nobre
University of Coimbra, Portugal
CEMDRX, Department of Mechanical Engineering
Editor/Herausgeber:
Europe/Europa
Prof. Dr.-Ing. Dr. h.c. G. W. Ehrenstein, verantwortlich
Lehrstuhl für Kunststofftechnik
Universität Erlangen-Nürnberg
Am Weichselgarten 9
91058 Erlangen
Deutschland
Phone: +49/(0)9131/85 - 29703
Fax.:
+49/(0)9131/85 - 29709
E-Mail: ehrenstein@lkt.uni-erlangen.de
Publisher/Verlag:
Carl-Hanser-Verlag
Jürgen Harth
Ltg. Online-Services & E-Commerce,
Fachbuchanzeigen und Elektronische Lizenzen
Kolbergerstrasse 22
81679 Muenchen
Phone.: 089/99 830 - 300
Fax: 089/99 830 - 156
E-mail: harth@hanser.de
Journal of Plastics Technology 7 (2011) 3
The Americas/Amerikas
Prof. Dr. Tim A. Osswald,
responsible
Polymer Engineering Center,
Director
University of Wisconsin-Madison
1513 University Avenue
Madison, WI 53706
USA
Phone: +1/608 263 9538
Fax.:
+1/608 265 2316
E-Mail: osswald@engr.wisc.edu
Editorial Board/Beirat:
Professoren des Wissenschaftlichen
Arbeitskreises Kunststofftechnik/
Professors of the Scientific Alliance
of Polymer Technology
85