Improving the delamination bridging behaviour of z-pins through material solutions

Lead Research Organisation: University of Bristol
Department Name: Aerospace Engineering

Abstract

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Planned Impact

The chief impacts are twofold:

1. Supply of doctoral level engineers trained to the very highest standards in advanced composites. They will take up positions in industry as well as academia.
2. Development of next generation advanced composite materials and applications for wealth creation in the UK.

Other important impacts are:

3. Enhanced UK reputation as a world leading centre in advanced composites that attracts inward investment and export opportunity.
4. Attracting elite overseas students, enhancing the UK's global reputation for excellence in Advanced Composite materials and their applications and widening the pool of highly skilled labour for UK industry.
5. Engaging with local schools and media, to disseminate, enthuse and raise the profile of Engineering to school children and to the wider public.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
NE/W503174/1 31/03/2021 30/03/2022
2096017 Studentship NE/W503174/1 23/09/2018 30/03/2023 Eduardo Santana De Vega
 
Description The project aim was to develop composite-based Z-pins that exhibit excellent interlaminar toughening regardless of the mode mixity of the interlaminar crack. Additionally, it was key to understand the effect of altering the individual material properties of the Z-pin components on their interlaminar bridging effectiveness.

Through materials selection, manufacturing and experimental mechanics, the aim of the project together with a number of individual achievements were met:
- Several novel Z-pins were manufactured in-house through pultrusion and braiding, including hybrid fibre composites Z-pins.
- A method of testing individual Z-pins whilst being able to observe the failure mechanism during the test was developed.
- The effect of increasing the ductility of the Z-pin matrix was evaluated. The use of a ductile matrix resulted in a significant improvement in the delamination bridging behaviour of carbon fibre Z-pins, pushing the mode-mixity at which the pins are effective closer to mode II.
- The effect of employing tougher and stronger fibrous reinforcement was evaluated, creating novel pseudo-ductile composite Z-pins. These novel pins are able to pull out of the laminate under mode II delamination. Their development were the key outcome of the project, as they satisfied the aim of creating a Z-pin with a balanced delamination toughening behaviour and led to the filing of a patent with the industrial sponsor (Rolls Royce plc).

A number of new important research questions can been derived from this work:
- How effective are these novel pseudo-ductile Z-pins under more complex loading conditions such compression after impact (CAI)?.
- What is the effect of environmental degradation on the performance of the new Z-pin materials?
- How will the interlaminar toughening effect seen in the coupon-sized samples be translated into larger structures which more representative of real applications?
Exploitation Route The research outcomes will help design composite structures more efficiently, with lower risk of catastrophic interlaminar failure. Sectors which rely on pre-impregnated lamination will benefit the most, as Z-pinning is a well established method of through-thickness reinforcement used in combination with it. The use of the novel Z-pins can be introduced into the manufacturing processes already in place.
Preventing interlaminar failure of composite laminates is essential to the successful use of composites in large structures in the aerospace and automotive industries. The outcomes of the project will help engineers make the correct decision with regards to what material to employ as a method of through-thickness reinforcement.
Sectors Aerospace

Defence and Marine

Energy

Transport

 
Description Industrial Sponsorship 
Organisation Rolls Royce Group Plc
Country United Kingdom 
Sector Private 
PI Contribution The collaboration was founded through the well established Composites University Technology Centre (UTC) at the University of Bristol. The key contributions made towards the collaboration are monthly reports about the work carried out, frequent update meetings with an industrial supervisor and attendance to Rolls Royce led conferences.
Collaborator Contribution As the UTC has been well established for over 15 years, the contribution goes beyond that specific to this project. They have provided us with a network of expertise and intellectual input as well as access to data, monetary contribution towards equipment and intellectual property support.
Impact Research Paper: 10.1016/j.compositesa.2022.107241 Conference Paper: Improving the mode II delamination bridging performance of fibrous composite Z-pins (ECCM20, Lausanne), 10.5075/epfl-298799_978-2-9701614-0-0 Patent application: GB 2118257.1
Start Year 2018