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Vacuum-Assisted Hot-Forming Using Tailored Laminate Temperature
KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.ORCID iD: 0000-0001-5567-1037
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0003-0613-2680
KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics.ORCID iD: 0000-0002-6616-2964
2021 (English)In: Applied Composite Materials, ISSN 0929-189X, E-ISSN 1573-4897, Vol. 28, no 2, p. 247-269Article in journal (Refereed) Published
Abstract [en]

A non-isothermal vacuum assisted hot-forming process using tailored laminate temperature is introduced. By using process simulation and manufacturing experiments, improved laminate quality is achieved compared to the standard hot-forming process. Furthermore, it is also shown that the manufacturing time in the clean room can be reduced to one tenth of the standard process time. In this study 8.4 mm thick quasi-isotropic laminates from unidirectional prepreg were laid up flat with an automatic tape laying machine and hot-formed to a U-shaped laminate. The laminates were then cured in a concave mould with standard bag on the inside. A complete tailored temperature hot-forming cycle of 7.5 min produced a very good final laminate quality with a total thickness variation as low as 4.0% and without wrinkles or indications of porosity. With a 4 min hot-forming cycle the thickness variation was also acceptable at 8%.

Place, publisher, year, edition, pages
Springer Nature , 2021. Vol. 28, no 2, p. 247-269
Keywords [en]
Forming, Prepreg, Simulation, Thickness variation, Wrinkles, Ceramic materials, Composite materials, Hot forming process, Laminate quality, Laying machines, Manufacturing time, Process simulations, Quasiisotropic laminates, Total thickness variations, Hot stamping
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
URN: urn:nbn:se:kth:diva-304439DOI: 10.1007/s10443-020-09858-8ISI: 000609050600001Scopus ID: 2-s2.0-85099543034OAI: oai:DiVA.org:kth-304439DiVA, id: diva2:1609507
Note

QC 20220503

Available from: 2021-11-08 Created: 2021-11-08 Last updated: 2022-06-25Bibliographically approved
In thesis
1. Tooling and processing for efficient and high tolerance prepreg composite manufacturing
Open this publication in new window or tab >>Tooling and processing for efficient and high tolerance prepreg composite manufacturing
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Composite use is normally motivated in aircraft design by improved weight-specific mechanical properties as compared to metals. However, fatigue and dielectric properties may also be critical for material selection. In the modern world the environmental footprint, with reduced emissions in focus, will be lighter with the successful use of composites. Flight safety is the most important requirement for the aerospace industry. In order to benefit from the important properties which ensure the necessary performance of the aircraft, part materials must be according to material specification. This is not unique to the composite materials. However, since the composite material is often created simultaneously with the composite part, the manufacturing processes used are even more critical for a composite part than for a metal part. Tooling is required for most of the process steps in composite part manufacturing. The large number of tools required to complete a composite part and the relatively small series involved in most composite applications render tooling cost a major contributor to final part cost. This is especially true in the aeronautical field considering the high-quality requirements as concerns shape accuracy and laminate quality, as well as low production rates with annual production ranging from a few dozen to the rare thousands of parts. Since tooling adds a substantial contribution to the part cost, it is imperative to be aware of the different options available for each process step and how these affect process stability and cost. Göte Strindberg, a former technical director at Saab, often said “Ninety-nine per cent right can be one hundred per cent wrong in a composite manufacturing process”. Finding the correct parameters for the last per cent is key to composite part success. This has been the overall goal of this project. The beginning of the project focused on both process and tooling related improvements for hot-forming of prepreg laminates enabling new opportunities and improved ergonomics. The research results in improvements in laminate quality, for example, reduced thickness variation, and a significant increase in process efficiency. One conclusion is that an 80% reduction of cycle time can be achieved with maintained, or even improved, laminate quality. A novel method for compensation of forming tools is also presented. Research then continued with cure tool related issues. Shape fidelity and durability for composite cure tools was studied with the combined outcome of an in-depth understanding of composite cure tool performance at the elevated temperature and moisture conditions present during the use of the tools.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022. p. 161
Series
TRITA-SCI-FOU ; 2022:10
Keywords
Tooling, Composite Manufacturing, Mould, Cure tool, Hot-forming, Compensation, Moisture, Shape distortion
National Category
Composite Science and Engineering
Research subject
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-312115 (URN)978-91-8040-246-0 (ISBN)
Public defence
2022-06-08, https://kth-se.zoom.us/j/61052452396, F3, Lindstedtsvägen 26, Stockholm, 09:00 (English)
Opponent
Supervisors
Funder
Swedish Foundation for Strategic Research, ID15-0042
Note

QC 220512

Available from: 2022-05-12 Created: 2022-05-11 Last updated: 2022-06-25Bibliographically approved

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Grankäll, TommyHallander, PerÅkermo, Malin

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