Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 53) Show all publications
Hallander, P., Sjölander, J., Petersson, M., Andersson, T. & Åkermo, M. (2019). Fast forming of multistacked UD prepreg using a high-pressure process. Polymer Composites, 40(9), 3550-3561
Open this publication in new window or tab >>Fast forming of multistacked UD prepreg using a high-pressure process
Show others...
2019 (English)In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 40, no 9, p. 3550-3561Article in journal (Refereed) Published
Abstract [en]

In this article, the opportunities of fast forming of multistacked UD prepreg when using high-pressure forming were examined in an experimental study. Forming is often considered a bottleneck in manufacturing of composite aircraft parts and speeding up the process is, therefore, of great interest. A Quintus Flexform fluid cell press was used to create pressure of 100 to 400 bars. In the study, different lay-up sequences and thicknesses were tested for manufacturing of c-shaped coupons. Tests were performed at different temperatures and some of the samples were sandwiched with mild steel sheets referred to as a steel sheet dummy. A case study was also performed on a double-curved spar geometry. It was found that forming at a relatively high overall pressure level combined with an elevated temperature, created squeeze flow-related wrinkle formations, and radius thinning. With high pressure forming, material compression/compaction mechanisms showed to have great influence on the forming result. This differs to low pressure vacuum forming, where intraply shear, interply shear, and ply bending are the dominant forming mechanisms. The steel sheet dummy minimized the squeeze flow related wrinkle in the web and flanges. Instead the forming temperature was found to exert the greatest influence on radius thinning. When forming at room temperature, radius thinning was almost eliminated and instead bending-related wrinkles in the flange below the radii appeared. POLYM. COMPOS., 40:3550-3561, 2019.

Place, publisher, year, edition, pages
WILEY, 2019
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-260174 (URN)10.1002/pc.25217 (DOI)000483701100019 ()2-s2.0-85060547654 (Scopus ID)
Note

QC 20190930

Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2019-09-30Bibliographically approved
Grankall, T., Hallander, P. & Åkermo, M. (2019). Geometric compensation of convex forming tools for successful final processing in concave cure tools - An experimental study. Composites. Part A, Applied science and manufacturing, 116, 187-196
Open this publication in new window or tab >>Geometric compensation of convex forming tools for successful final processing in concave cure tools - An experimental study
2019 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 116, p. 187-196Article in journal (Refereed) Published
Abstract [en]

To enable shimless composite part assembly it is desired to manufacture composite spars in concave, female tools. However, due to restricted access this process is often associated with a high degree of manual operations or expensive highly specialized production equipment. This study investigates a sequential manufacturing operation where the material is automatically laid up flat and hot formed onto a convex forming tool. Thereafter it is placed in the concave tool for curing. The study investigates four different ways to geometrically compensate the forming tool to simplify seating and enhance part quality. All compensations require material movement in-between forming and curing; this movement was tracked using Micro-CT. Micrographing and optical shape measurements show that a correct compensation provides high quality parts without adding labour intensive manufacturing steps.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2019
Keywords
Prepreg, CT analysis, Automation, Tooling
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-240344 (URN)10.1016/j.compositesa.2018.10.030 (DOI)000451491700020 ()2-s2.0-85056199790 (Scopus ID)
Note

QC 20181217

Available from: 2018-12-17 Created: 2018-12-17 Last updated: 2018-12-17Bibliographically approved
Jerpdal, L., Schuette, P., Stahlberg, D. & Åkermo, M. (2019). Influence of temperature during overmolding on the tensile modulus of self-reinforced poly(ethylene terephthalate) insert. Journal of Applied Polymer Science, Article ID 48334.
Open this publication in new window or tab >>Influence of temperature during overmolding on the tensile modulus of self-reinforced poly(ethylene terephthalate) insert
2019 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, article id 48334Article in journal (Refereed) Published
Abstract [en]

Self-reinforced polymer composites are thermoplastic materials for design of recyclable lightweight components. The combination of sheet forming and subsequent overmolding from these materials allows an efficient manufacturing process with function integration. This article investigates how temperature exposure during an overmolding cycle influences the tensile modulus, shrinkage, and warpage for an insert made from self-reinforced poly(ethylene terephthalate) (PET) when it is overmolded with polycarbonate (PC)/PET material. The temperature gradient that is induced by overmolding is simulated, and the results are validated through experiments. The results show that the insert reaches a temperature above the glass-transition temperature for the matrix material in the main part of the insert, which leads to relaxation of residual stresses and thereby a reduction of the tensile modulus up to 18% for the insert after overmolding. Even though overmolding is an efficient process, it requires thorough knowledge of how temperature influences the material when applied to self-reinforced composite materials. The study shows very interesting results, which can lead to new areas of applications for self-reinforced PET. 

Place, publisher, year, edition, pages
WILEY, 2019
Keywords
composites, mechanical properties, molding, thermoplastics
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-257553 (URN)10.1002/app.48334 (DOI)000478979500001 ()2-s2.0-85070676583 (Scopus ID)
Note

QC 20190925

Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2019-09-25Bibliographically approved
Karlsson Hagnell, M. & Åkermo, M. (2019). The economic and mechanical potential of closed loop material usage and recycling of fibre-reinforced composite materials. Journal of Cleaner Production, 223, 957-968
Open this publication in new window or tab >>The economic and mechanical potential of closed loop material usage and recycling of fibre-reinforced composite materials
2019 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 223, p. 957-968Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel recyclate value model derived from the retained mechanical performance of retrieved fibres in fibre-reinforced composites. The proposed recyclate value model was used to perform an economic analysis for establishing the future closed-loop material usage of fibre-reinforced composite materials. State-of-the-art recycling of carbon and glass-reinforced thermosets was adopted and resulted in a proposed recycling hierarchy in order to achieve a more sustainable environment and raw material cost reduction. The recyclate value model showed that approximately 50% material cost reductions can be achieved at comparable mechanical performance by using recycled fibre instead of virgin fibre in appropriate applications. From the aspect of lightweight design this cost reduction provides the designer with new material choices, appropriate for lower cost and diverse stiffness designs. The proposed closed-loop hierarchy documents the importance of further improvement of fibrous material recycling, including sorting according to mechanical performance, in order to identify application areas previously not utilised and to maximise material sustainability and value throughout the material's lifetime.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2019
Keywords
Closed loop recycling, Fiber-reinforced composites, Material cost reductions, Recycling cost, Lightweight design
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-252364 (URN)10.1016/j.jclepro.2019.03.156 (DOI)000466253100078 ()2-s2.0-85063283594 (Scopus ID)
Note

QC 20190613

Available from: 2019-06-13 Created: 2019-06-13 Last updated: 2019-06-13Bibliographically approved
Horberg, E., Nyman, T., Åkermo, M. & Hallström, S. (2019). Thickness effect on spring-in of prepreg composite L-profiles - An experimental study. Composite structures, 209, 499-507
Open this publication in new window or tab >>Thickness effect on spring-in of prepreg composite L-profiles - An experimental study
2019 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 209, p. 499-507Article in journal (Refereed) Published
Abstract [en]

This paper presents the results and analysis of an experimental study of laminate thickness effects on the spring-in and shape distortion of thermoset composite L profiles. The primary objective is to achieve a broader understanding of how shape distortion is affected by laminate bending stiffness and part thickness of L-shaped laminates whose thickness varies between 1 and 12 mm. The larger thicknesses in particular have not received much attention in previous research. This work further aims at distinguishing the pure (geometrical) thickness effect from that of the coupled laminate bending stiffness by comparing laminates with different lay-ups. The work is performed on test specimens subjected to both a standard cure cycle and post-cure heat treatment at elevated temperatures. In parallel, finite element (FE) analysis is performed to evaluate if variation in the bending stiffness or the laminate thickness affects the predicted spring-in angle. The results clearly show spring-in dependence on laminate thickness and bending stiffness, whereas this dependence is not well predicted by the FE approaches. It is concluded that both effects exist and that shape distortions are more strongly related to bending stiffness than to laminate thickness.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2019
Keywords
Process simulation, Cure behaviour, Prepreg, Thermal properties
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:kth:diva-241304 (URN)10.1016/j.compstruct.2018.10.090 (DOI)000454690700043 ()2-s2.0-85056208383 (Scopus ID)
Note

QC 20190125

Available from: 2019-01-25 Created: 2019-01-25 Last updated: 2019-01-25Bibliographically approved
Jerpdal, L., Åkermo, M., Ståhlberg, D. & Herzig, A. (2018). Process induced shape distortions of self-reinforced poly(ethylene terephthalate) composites. Composite structures, 193, 29-34
Open this publication in new window or tab >>Process induced shape distortions of self-reinforced poly(ethylene terephthalate) composites
2018 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 193, p. 29-34Article in journal (Refereed) Published
Abstract [en]

This paper investigates shape distortion and tensile properties of hot consolidated Self-reinforced poly(ethylene terephthalate) (SrPET) by evaluating the influence from stretching before consolidation and annealing after consolidation. Spring-in angle and warpage is measured from V-shaped samples that are hot consolidated from a woven fabric that is stretched to different degrees during forming. Following the same process conditions, tensile stiffness is measured from plane laminates. This study confirms that stretching the SrPET-material during forming enhances the tensile modulus but introduces shape distortions with negative spring-in and increases warpage. However also non-stretched SrPET components experience spring-back in the same level as glass- or carbon reinforced PET composite, which is unexpected. The tensile modulus is reduced and spring-in angle further influenced when the SrPET-samples are exposed to higher temperature after consolidation. This study shows how easily the characteristics of a component made from SrPET-material are influenced by stresses developed during material forming and further by release of these stresses when exposed to higher temperatures as in post processes or even in the use phase of the component.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-227562 (URN)10.1016/j.compstruct.2018.03.038 (DOI)000429903300004 ()2-s2.0-85044141269 (Scopus ID)
Funder
VINNOVASwedish Energy AgencySwedish Research Council Formas
Note

QC 20180515

Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-05-15Bibliographically approved
Sjölander, J., Hallander, P. & Åkermo, M. (2016). Forming induced wrinkling of composite laminates: A numerical study on wrinkling mechanisms. Composites. Part A, Applied science and manufacturing, 81, 41-51
Open this publication in new window or tab >>Forming induced wrinkling of composite laminates: A numerical study on wrinkling mechanisms
2016 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 81, p. 41-51Article in journal (Refereed) Published
Abstract [en]

When manufacturing composite aircraft components consisting of uni-directional prepreg laminates, Hot Drape Forming (HDF) is sometimes used. One issue with HDF is that, in contrast to hand lay-up where normally only one ply is laid up at a time, multiple plies are formed together. This limits the in-plane deformability of the stack, thus increasing the risk of out-of-plane wrinkling during forming. In this paper mechanisms responsible for creating different types of wrinkles are explained. It is shown through simulations how the wrinkles are created as a result of interaction between two layers with specific fibre directions or due to compression of the entire stack. The simulations are compared to experimental results with good agreement.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
A. Prepreg, C. Process simulation, E. Forming
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-181434 (URN)10.1016/j.compositesa.2015.10.012 (DOI)000369214600005 ()2-s2.0-84946781893 (Scopus ID)
Funder
XPRES - Initiative for excellence in production research
Note

QC 20160205

Available from: 2016-02-05 Created: 2016-02-02 Last updated: 2018-08-03Bibliographically approved
Hallander, P., Sjölander, J. & Åkermo, M. (2016). Forming of composite spars including interlayers of aligned, multiwall, carbon nanotubes: an experimental study. Polymer Composites
Open this publication in new window or tab >>Forming of composite spars including interlayers of aligned, multiwall, carbon nanotubes: an experimental study
2016 (English)In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569Article in journal (Refereed) Published
Abstract [en]

Carbon nanotubes offer the potential for improved or changed matrix properties, thereby enabling the creation of novel, multifunctional composite materials. By using highly-aligned, multiwall, carbon nanotubes (MWCNT) with thermoset resins, good dispersion and distribution of nanotubes is obtained. To date, research has mainly focused on improving the growth process of the aligned MWCNTs, however little has been done on the processing of composites that include MWCNTs as interlayers in the stack.  The aim of this work is to study how the aligned MWCNTs are affected within composite part forming. The study shows that MWCNTs are influenced by the shearing that occurs during forming, but still maintain their integrity. To some extent, the shear pattern observed in the MWCNTs after deformation provides an indication of deformation modes. However, the presence of MWCNTs also significantly influences the forming characteristics of the prepreg stack.

Place, publisher, year, edition, pages
John Wiley & Sons, 2016
Keywords
Carbon Fibre, Prepreg, Forming, Multi wall carbon nanotubes
National Category
Aerospace Engineering
Research subject
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-185696 (URN)10.1002/pc.23918 (DOI)000419819800019 ()2-s2.0-84957836987 (Scopus ID)
Funder
VINNOVA, GF Demo 2012-01031VINNOVA, GF Demo 2013-04667
Note

QC 20180129

Available from: 2016-04-25 Created: 2016-04-25 Last updated: 2018-08-03Bibliographically approved
Hallander, P., Sjölander, J., Petersson, M. & Åkermo, M. (2016). Interface manipulation towards wrinkle-free forming of stacked UD prepreg layers. Composites. Part A, Applied science and manufacturing, 90, 340-348
Open this publication in new window or tab >>Interface manipulation towards wrinkle-free forming of stacked UD prepreg layers
2016 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 90, p. 340-348Article in journal (Refereed) Published
Abstract [en]

The aim of this paper is to experimentally study how forming behaviour can be changed by local manipulation of prepreg interfacial characteristics. Different methods for surface modification are examined, however all were aimed at enabling significantly increased interply friction. The paper shows that by using increased friction in between layers, these neighbouring pairs will act together during forming, thereby either improving or exacerbating the forming outcome. For the geometry utilized, wrinkle free forming was obtained when the cross-plied layers were paired to deform mainly through intraply shear during forming. The method is supported by the appended numerical analysis and interaction between forming mechanisms and radius thinning is instigated as part of the experimental outcome.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
A. Carbon fibre, A. Prepreg, E. Forming, Carbon, Carbon fibers, Friction, Surface treatment, Forming mechanism, Interfacial characteristics, Intraply, Prepregs, Numerical methods
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-195224 (URN)10.1016/j.compositesa.2016.07.013 (DOI)000384853500034 ()2-s2.0-84980410659 (Scopus ID)
Funder
VINNOVA
Note

QC 20161117

Available from: 2016-11-17 Created: 2016-11-02 Last updated: 2017-11-29Bibliographically approved
Mellin, P., Jönsson, C., Åkermo, M., Fernberg, P., Nordenberg, E., Brodin, H. & Strondl, A. (2016). Nano-sized by-products from metal 3D printing, composite manufacturing and fabric production. Journal of Cleaner Production, 139, 1224-1233
Open this publication in new window or tab >>Nano-sized by-products from metal 3D printing, composite manufacturing and fabric production
Show others...
2016 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 139, p. 1224-1233Article in journal (Refereed) Published
Abstract [en]

Recently, the health and environmental perspective of nano-materials has gained attention. Most previous work focused on Engineered Nanoparticles (ENP). This paper examines some recently introduced production routes in terms of generated nano-sized by-products. A discussion on the hazards of emitting such particles and fibers is included. Fine by-products were found in recycled metal powder after 3D printing by Selective Laser Melting (SLM). The process somehow generated small round metal particles (~1e2 mm) that are possibly carcinogenic and respirable, but not small enough to enter by skin-absorption. With preventive measures like closed handling and masks, any health related effects can be prevented. The composite manufacturing in particular generated ceramic and carbonaceous particles that are very small and respirable but do not appear to be intrinsically toxic. The smallest features in agglomerates were about 30 nm. Small particles and fibers that were not attached in agglomerates were found in a wide range of sizes, from 1 μm and upwards. Preventive measures like closed handling and masks are strongly recommended. In contrast, the more traditional production route of fabric production is investigated. Here, brushing residue and recycled wool from fabric production contained few nano-sized by-products.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Ultrafine particles; Nano-emissions; Nanoparticles; Additive manufacturing; Composite manufacturing; Fabric production
National Category
Metallurgy and Metallic Materials Composite Science and Engineering Textile, Rubber and Polymeric Materials Production Engineering, Human Work Science and Ergonomics Nano Technology
Research subject
Industrial Ecology; Production Engineering
Identifiers
urn:nbn:se:kth:diva-196849 (URN)10.1016/j.jclepro.2016.08.141 (DOI)000386991600112 ()2-s2.0-84995543561 (Scopus ID)
Projects
XPRES – Initiative for excellence in production research
Funder
XPRES - Initiative for excellence in production research
Note

QC 20170109

Available from: 2016-11-23 Created: 2016-11-23 Last updated: 2017-11-29Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6616-2964

Search in DiVA

Show all publications