A Study of Friction in Composite Materials Forming
Lead Research Organisation:
University of Glasgow
Department Name: School of Engineering
Abstract
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Organisations
Publications
P. Harrison
(2020)
Induction melt thermoforming of advanced multi-axial thermoplastic composite laminates
in Journal of Manufacturing Processes
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509668/1 | 30/09/2016 | 29/09/2021 | |||
| 1937718 | Studentship | EP/N509668/1 | 01/10/2017 | 01/11/2021 | Iain Campbell |
| NE/W503058/1 | 31/03/2021 | 30/03/2022 | |||
| 1937718 | Studentship | NE/W503058/1 | 01/10/2017 | 01/11/2021 | Iain Campbell |
| Description | Investigation was carried out into the use of interlayers to reduce friction between composite plys in high temperature press forming Composite materials consist of a (usually) polymer matrix reinforced by a woven fiber sheets(glass fiber, carbon fiber etc). When press formed into complex shapes these woven fiber sheets must be able to slide and rotate relative to each other. If they cannot do this then there is a tendency wrinkles to appear in the final part. These wrinkles reduce the strength of the final part. The ability for these to slide and rotate is governed by the frictional forces between two sheets. Normally this is carried out in a molten polymer (eg nylon) which has a high viscosity much like honey and limits the ability to slide and rotate. The use of a low viscosity inter layer was proposed to lower friction and allow for more complex shapes to be formed. In this investigation Carbon Fiber Reinforced Nylon has been paired with interlayers of tin due to their similar melt points (~230 Celcius). Use of a metallic interlayer also led to other novel points which are discussed below (1) Induction Heating- -Press forming conventionally uses radiant heaters and a shuttle system to heat and move the sheets into place. - The use of a metallic interlayer allows for heat to be generated directly into the sample allowing for in situ heating (no shuttle) and reduced temperature requirements of the surrounding apparatus - Equipment was rented and due to time limitations we were not able to fully optimise the heating process which limited control over forming temperature. Trial and error and user expertise was used and a "feedback loop" involving infrared cameras was set up (2) Multi step press forming tool - This was driven by a desire to remove tin interlayer from final part during forming - A multi step tool of interlocking concentric tubes was used to form from the center out - Forming from the center out produced a pressure gradient which removed the tin - Multi stage forming also allows for improved forming of multi cavity parts which can be an issue in single step forming. (3) Results of the experiments - We were able to produce a number of succesful samples (both flat and with a multi cavity ripple shape). However we have not had enough time with the testing apparatus to identify best practices - To date we have quantified the levels of residual tin which can be brought down to ~2-5% of part volume. This was quantified using a combination of Computed Tomography Scans, Conventional X rays and microscope analysis of polished cross sections. - We have not yet confirmed the effects of the residual tin on the mechanical properties, however mechanical testing will soon be carried out in order to quantify this. - We have not carried out a comparison with samples containing no interlayer. This is also planned for future works. |
| Exploitation Route | Academically the department is applying for a core project through the EPSRC Future Composites Manufacturing Research Hub with the following objectives 1. Take methods to improve the process (develop control system to manage heating of larger parts, analysis of parameters such as speed of press forming, pressure applied, thickness of interlayer, temperature of forming) 2. Extend the investigation to other material combinations 3. Extend investigation into the multi step forming tool In industry This is a much more long term project which deliberately attempting a step change. Long term, if proven effective, this could be used in composites manufacturing which is rapidly expanding. Potential benefits include Increased energy efficiency through being able to heat the sample directly and without shuttling the sample. Ability to form more complex shapes with less wrinkling or other defects |
| Sectors | Aerospace Defence and Marine Manufacturing including Industrial Biotechology |