Novel high performance polymeric composite materials for additive manufacturing of multifunctional components

Lead Research Organisation: University of Exeter
Department Name: Engineering

Abstract

The aim of this proposal is to develop novel high performance, nanocomposite feed materials for Additive Manufacturing (AM). The field of AM, also known also as 3D Printing, has expanded significantly over the last couple of decades across virtually all-industrial sectors due a number of key advantages that traditional manufacturing just cannot offer. These include mass customisation, geometrical complexity, tool-less manufacture and sustainable manufacturing. Among the companies using AM are GE (medical devices, and home appliance parts), Lockheed Martin and Boeing (aerospace and defense), Invisalign (dental devices) and LUXeXcel (lenses for light-emitting diodes, or LEDs). The worldwide revenue from 3D printing is expected to grow from $3.07 billion in 2013 to $12.8 billion by 2018, and exceed $21 billion by 2020, and has a potential of generating an economic impact of $230 billion to $550 billion per year by 2025.

While the forecast for AM products is huge this will only be achieved if we can actually manufacture parts with the desired properties. The majority of polymeric AM research is however focused on low glass transition temperature (Tg) polymers such as Polyamide 11, 12 , Polycarbonate and Poly Lactic acid (PLA), due to their good processing characteristics (rheological, thermal and crystallization). For advanced, high value applications in aerospace, telecommunication and defense where harsh environmental conditions often exist (and in some key biomedical application) these low Tg polymers for AM are not acceptable so there is a real need to develop materials for these applications. Whilst a sufficiently high Tg polymer could offer the required high performance, nanocomposites with increased functionalities and potential combinations of properties such as high stiffness, strength, wear and specific thermal, electrical and microwave response can really transform the performance of AM components. The ability to manipulate other properties, such as rheological and thermal performance, by the addition of nanoparticles offers further potential advantages in terms of processing characteristics.

This proposal will examine the potential of inorganic fullerene-like (IF) tungsten disulfide (WS2) or IF-WS2 as nanofillers for high value, PAEK (Poly Aryl Ether Ketone) based products made via the AM processes of Selective Laser Sintering (SLS) and Fused Deposition Modelling (FDM). The incorporation of IF particles has been shown to be efficient for improving thermal, mechanical and tribological properties of various thermoplastic polymers, such as polypropylene, nylon-6, poly(phenylene sulfide), poly(ether ether ketone). These nanocomposites were fabricated by simple melt-processing routes without the need for modifiers or surfactants . IF-WS2 have been proven to exhibit extremely high tribological performance in composites to reduce wear and coefficient of friction .These characteristics will also have important processability benefits for AM processes as will their dispersion characteristics which are superior to 1D and 2D nanoparticles. They are also the best shock absorbing cage structures known to mankind. Importantly, they are non-toxic, and thermally stable.

We will examine the two main AM processes for producing parts with engineering properties, Selective Laser Sintering (SLS) in which a laser is used to melt and sinter powdered polymer into the final part and Fused Deposition Modelling (FDM) in which a polymer filament is melted in a heated nozzle and deposited in the required pattern to form the part.

Planned Impact

The following new knowledge will be generated: knowledge of (i) the material modifications and processing techniques required to make high performance PAEK nanocomposite materials (ii) the processes required to produce high performance materials for the additive manufacturing process of selective laser sintering and fused deposition modelling (iii) the additive manufacturing processing conditions required to manufacture demonstrator parts for an aerospace application

People: In addition to the standard academic training delivered in PDRA/PhD posts the PDRAs and PhD students involved in this project will develop skills in polymer nanocomposite development, processing and characterisation. They will gain an understanding of the industrial requirements for additive manufacturing materials and how processing influences part properties. They will also gain an understanding of the stringent requirements placed on product performance for the aerospace sector. Through the dissemination and outreach activities in the proposal they will improve communication skills and increase personal networks. Secondary school students will benefit from the proposed outreach activities. Additive manufacturing provides an exciting and interesting topic for promoting STEM. The applications envisaged in this proposal in the aerospace and biomedical sectors should also prove to be attractive to the students and help further engage them with STEM and with industry.

Society will benefit through (i) the ability to replace metal parts with lighter polymer nanocomposite parts in aerospace and other transport applications (ii) the potential of these new materials to reduce wear in biomedical implants such as hip joints (iii) better product design enabled by the additive manufacturing of complex products in high performance materials

The economy will benefit via the availability of a new range of high performance materials for the additive manufacturing industry. Aerospace and biomedical sectors requiring better performing, lightweight, multifunctional materials in relatively small quantities or in customised designs will also benefit. The worldwide revenue from additive manufacturing is expected to grow from $3.07 billion in 2013 to $12.8 billion by 2018, and to exceed $21 billion by 2020. These new materials will contribute to this projected growth.
 
Description We have successfully developed two new techniques for making composite particles for use in additive manufacturing. Two scienctific papers have been published to demonstrate the detailed process, to benefit the wider community of 3D printing. The scale up of these new composite powders for 3D printing would make a significant contribution to the 3D printing industry by supplying advanced raw powders which restricts its current wide applications.
Exploitation Route It is on public domain, with open access.
Sectors Aerospace, Defence and Marine,Construction,Electronics,Energy,Healthcare,Manufacturing, including Industrial Biotechology,Transport

URL https://www.sciencedirect.com/science/article/pii/S0266353818313915
 
Description Bombardier 
Organisation Short Brothers Plc
Country United Kingdom 
Sector Private 
PI Contribution Bushing component using new composite materials
Collaborator Contribution Guide on design, performance assessment etc on prototype component.
Impact New project and new collaboration just started.
Start Year 2016
 
Description Daido 
Organisation Daido Steel Co., Ltd.
Department Daido Metal
Country United Kingdom 
Sector Private 
PI Contribution Testing new polymeric nanocomposites for their new bearings.
Collaborator Contribution Helping to evaluate new composite properties, both mechnical properties and tribological properties.
Impact We are in the process of joint publication and patent.
Start Year 2016
 
Description LPE 
Organisation Laser Prototype European Ltd
Country United Kingdom 
Sector Private 
PI Contribution We will provide new materials for LPE to test on their facilities, to establish new protocol for manufacturing.
Collaborator Contribution Support with the SLS process, including training our researchers and accessing their facilities.
Impact New collaboration on new project, to be updated later.
Start Year 2016
 
Description Victrex 
Organisation Victrex
Country United Kingdom 
Sector Private 
PI Contribution Develop new composite to enhance their production line.
Collaborator Contribution Provide expensive PEEK raw materials for experiments in our project.
Impact Not yet available because of new project.
Start Year 2016
 
Description European Strategy for High Temperature AM polymers (event - September 2016) 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact As high temperature polymer additive manufacturing moves from development to production, material understanding remains essential, explains Oana Ghita, academic lead at the University of Exeter's Centre for Additive Layer Manufacturing (CALM).

The rapid advances in additive manufacturing (AM) and the use of high temperature polymers to create viable, cost-effective parts for demanding applications in the aerospace industry has meant that interest in this field has never been stronger. But how is this technology really developing?

To examine the latest developments and technical challenges, CALM has once again brought together the leading experts in the AM industry from the UK, Europe and the USA. Its second European Strategy for AM with High Performance Polymers Conference, supported by Victrex and the University of Exeter, included presentations from polymer manufacturers, right through to end-users and companies involved in post-manufacturing processing, as well as updates on latest academic research.

As a leading research centre, CALM collaborates with a wide range of organisations and academia to develop the next generation of high temperature polymers and composites used in AM processes. It is the only independent centre worldwide researching laser sintering of high temperature polymers using the EOS P800 platform.

In 2014, when CALM hosted its first European event, the challenges were easy to identify as the technology was still in its infancy. There was a need for more specific high temperature materials, lower material costs, better reprocessing rates, improved multi-functionality and greater knowledge of material properties.

Government backing

As a result of the first event, many of these issues are being addressed. With funding from Innovate UK, CALM and a consortium of seven other organisations led by Victrex, are exploring ways to create affordable, new high performance polymers and composite materials.

Victrex, a leading global provider of polymer solutions, is developing ground-breaking new grades of high performance polyaryletherketone (PAEK) polymers specifically designed for AM for use in the aerospace industry. The new Victrex PAEK materials will be tailored for laser sintering, filament fusion and new technologies. such as the Airbus patented AM process 'ThermoMELT.'

PEEK and PEEK-CNT micro-gears
PEEK and PEEK-CNT micro-gears
High performance adaptable plastics such as those in the PAEK family and their engineered composites are of particular interest to airframe makers as metal replacements, being up to 70% lighter than steel, titanium or aluminium resulting in fuel efficiency and lower CO2 emissions. They are also chemically resistant and have excellent flame retardancy. The additive manufacture of PAEK polymers and composites is expected to become a standard fabrication route throughout the aero industry with defence, oil and gas and automotive industries also benefiting significantly from these developments.

The journey so far

Two years on, with a greater understanding of materials and their properties, industry representatives at the second Conference heard from Victrex about its commitment to support this growing sector and to satisfy end user requirements. Victrex is engaged in focused research in this area and investing in the construction of a dedicated polymer innovation centre to increase capacity to turn lab concepts - engineers' dreams - into real-world solutions.

Airbus Group Innovations highlighted its advances in addressing recyclability and process reliability through its new ThermoMELT process, Versarien Advanced Composites presented its work with CALM on innovative new Graphene-PAEK nanocomposites, Indmatec, pioneers of extrusion deposition printers for PEEK, discussed its equipment manufacturing developments and CALM gave an update on recent research projects funded by EPSRC, Innovate UK and DSTL, demonstrating the rapidly growing knowledge now available about both materials and processes.

New research on encapsulated carbon fibre-reinforced high temperature polymers by laser sintering process specialist EOS, has shown significant improvement of mechanical properties and enhanced isotropy. The material was developed within a collaboration with Boeing, ALM and Stratasys and first parts were already used in Boeing's ecoDemonstrator programme. Boeing also talked about its learning journey and findings of developing engineering polymers, while Eurocoating and Oxford Advanced Surfaces introduced innovations for PAEK surfaces, including titanium coating and adhesive bonding solutions.

Brett Lyons, from Boeing Commercial Aircraft, product development, material integration commented: "This size of event is great for discussions and networking and was a chance for me to meet people outside of the USA, working in the same area. It showcased a variety of different applications as well as the value of academic research in this field."

The pace of material change

With new materials being developed, attention now is on tackling the remaining challenges and the events hosted by the University of Exeter have helped focus industry efforts.

A motorsport suspension mount manufactured from EOS PEK-HP3
A motorsport suspension mount manufactured from EOS PEK-HP3
Of these, robustness of the process is one of the major technical challenges still facing AM PAEK parts manufacture, with concerns around the variability of the process and quality of end product to meet the requirements for lightweight, stiffness, flammability and chemical resistance for aerospace applications. Delegates agreed that capturing data, further testing and research and the potential for real time process monitoring leading to a closed loop manufacturing process were essential next steps.

End users are also particularly interested in the long-term chemical, thermal and aging properties of high temperature AM components. Currently there is little data available on the stability of PAEK AM powders and parts. For many applications, a 30-years material performance forecast is desirable and more data and analysis is essential.

As Sybille Fischer, material & process developer at EOS observed: "I have come away with lots of new ideas, a big list of things to work on, and a better understanding of the future requirements of potential customers."

The lower mechanical performance in z direction (high anisotropy) of AM parts is another area needing more research to create the ultimate isotropic structures. The use of nanomaterials with high aspect ratio, such as graphene and carbon nanotubes may be a possible solution to opening up new applications.

Recognising the need for process and long-term performance testing, these areas are likely to be the focus of investigations in the short-term, coupled with research to create the 'tailored' new materials the industry needs.

But with clearly identified applications now available and good knowledge of the materials and processes, the next few years are set to provide significant advancement with the aerospace industry positioned to capitalise on the growth of high temperature polymers for AM.

This was summed up by Uwe Popp, head of research and development at Indmatec: "Now is the right time for growth in the use of industrially relevant polymers in Additive Manufacturing. People are realising the significant opportunities that exist from using PAEK and although there are still many steps to get it into the market, innovations and developments in the field are moving very fast."

At CALM, we are delighted with the outcome of the event. Engagement with industry is very important when working in the manufacturing research area. The ability to combine advanced materials knowledge with high temperature additive manufacturing capabilities places Exeter in a unique position within the UK manufacturing research landscape.

www.exeter.ac.uk
Year(s) Of Engagement Activity 2016
URL https://www.aero-mag.com/performance-polymers-performance-parts/
 
Description Event sponsored/organised and chaired by University of Exeter and Victrex Manufacturing Plc- "European Strategy for High Temperature Additive Manufacturing" - An industrial event at University of Exeter 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact The discussions are summarised in the article published in Aerospace Manufacturing magazine
https://www.aero-mag.com/performance-polymers-performance-parts/
Year(s) Of Engagement Activity 2016
URL https://www.aero-mag.com/performance-polymers-performance-parts/