Periodic Reporting for period 1 - TEMPEST (Towards Carbon-Neutral Composite Crashworthiness)
Reporting period: 2021-10-18 to 2023-10-17
The transport sector is currently facing global economic uncertainty, tough market competition, stringent EU emission and efficiency targets, increased vehicle occupant safety requirements, and pollution and safety scandals which have damaged its reputation. These factors require engineers to increasingly adopt the use of composite materials, to come up with cheaper, safer, and more environmentally friendly solutions. However, even if these materials enable the production of light energy-efficient vehicles, most carbon fibre composites are expensive, and thus the majority of their current applications are limited to the aerospace and motorsport industries. Furthermore, conventional composites have a high manufacturing carbon footprint, and they are typically non-recyclable at the end of life of the components. Natural fibre composites (NFCs) are now being used in the automotive industry, as a cheaper and more environmentally friendly option to conventional carbon fibre composites, albeit limited to non-safety critical components, due to their poorer mechanical performance. The TEMPEST research programme explored the possibility of using a novel NFC material offering improved mechanical performance (developed by partner organisation Bcomp) in safety-critical structural components. Furthermore, by collaborating with McLaren Racing, who have been developing composite crash structures for over two decades, the project aimed to advance on the current state-of-the-art in the fields of experimental and numerical crashworthiness, all the while trying to reduce the carbon footprint of such structures. The project also drew on the resources and experience of Instron's drop tower R&D department in the development of improved dynamic crush testing for composite materials. Furthermore, the FIA also contributed to the project, overseeing and guiding the development of the experimental and numerical work, with the aim of providing the motorsport and automotive industries with new data and proven methodologies for improving the design of composite crash structures.
The main project objectives were: a) to develop and standardise experimental characterisation techniques for obtaining the energy absorption of composite materials; b) to explore the use of sustainable flax fibre composite materials in crashworthiness applications; and c) to improve the accuracy and robustness of macro-scale numerical modelling tools for the design of better composite crash structures.
At the end of the project, the main outcomes were: a) significantly improved experimental setups for dynamic crush testing of various coupon geometries; b) a successful demonstration of the potential use of flax fibre composites in crash structures; and c) an objective geometry-dependent discretisation methodology that improves the accuracy and robustness of numerical predictions from Finite Element crash structure models.
The main project objectives were: a) to develop and standardise experimental characterisation techniques for obtaining the energy absorption of composite materials; b) to explore the use of sustainable flax fibre composite materials in crashworthiness applications; and c) to improve the accuracy and robustness of macro-scale numerical modelling tools for the design of better composite crash structures.
At the end of the project, the main outcomes were: a) significantly improved experimental setups for dynamic crush testing of various coupon geometries; b) a successful demonstration of the potential use of flax fibre composites in crash structures; and c) an objective geometry-dependent discretisation methodology that improves the accuracy and robustness of numerical predictions from Finite Element crash structure models.
The project involved research and development activities in both experimental and numerical fields related to sustainable composite crashworthiness.
The focus of the experimental research work was on advancing the characterisation methods for various energy absorption parameters, including the ply-level fracture toughness and the laminate-level ‘crush stress’. Numerous experimental campaigns were undertaken. These included quasi-static and dynamic testing of notched coupons, as well as flat, tubular, and conical crush coupons with machined triggers. These tests were conducted for both conventional carbon fibre composites as well as the more sustainable flax fibre alternatives. Hybrid carbon/flax coupons were also manufactured and tested in a bid to understand their overall potential for use in crashworthy structures. The numerical advances were centred around the development of a new objective discretisation methodology. Using the energy absorption parameters acquired from the experimental tests, a customised macro was developed to discretise the energy absorption potential of complex 3D structures based on their local curvature and inclination, resulting in more accurate numerical predictions of the behaviour of such structures compared to predictions made using previous discretisation techniques.
The main project results include: an improved experimental methodology and data reduction technique for quasi-static and dynamic ply-level fracture toughness characterisation; novel experimental fixtures for dynamic crush coupon testing offering a significantly more accurate and reliable way of measuring composite energy absorption; and a novel numerical modelling methodology that enables improved accuracy in predicting the progressive crushing behaviour of geometrically-complex crash structures through a more objective discretisation of its localised energy absorption potential.
The results of this project have resulted in the publication of 5 peer-reviewed journal articles, and to the contribution of 6 international conference presentations. More scientific publications are anticipated in the near future, all of which will be made accessible on the official project website. The project results were openly shared amongst all the industrial partners, as well as the wider academic community through a number of invited presentations, and with the public through a seminar organised and hosted at the beneficiary. Presentations/lectures on the project results and sustainable engineering were also given to both aspiring STEM students and current undergraduates.
Both experimental and numerical developments are being exploited by the beneficiary and the project partners through joint ventures. The experimental fixtures developed for dynamic crush coupon testing are being further refined with the aim of establishing novel industry-wide standards for the characterisation of composite energy absorption. The numerical modelling strategy which was created during the project is now being further assessed in the advanced design phase of a novel prototypic hybrid laminate crash structure manufactured from sustainable flax fibre composites.
The focus of the experimental research work was on advancing the characterisation methods for various energy absorption parameters, including the ply-level fracture toughness and the laminate-level ‘crush stress’. Numerous experimental campaigns were undertaken. These included quasi-static and dynamic testing of notched coupons, as well as flat, tubular, and conical crush coupons with machined triggers. These tests were conducted for both conventional carbon fibre composites as well as the more sustainable flax fibre alternatives. Hybrid carbon/flax coupons were also manufactured and tested in a bid to understand their overall potential for use in crashworthy structures. The numerical advances were centred around the development of a new objective discretisation methodology. Using the energy absorption parameters acquired from the experimental tests, a customised macro was developed to discretise the energy absorption potential of complex 3D structures based on their local curvature and inclination, resulting in more accurate numerical predictions of the behaviour of such structures compared to predictions made using previous discretisation techniques.
The main project results include: an improved experimental methodology and data reduction technique for quasi-static and dynamic ply-level fracture toughness characterisation; novel experimental fixtures for dynamic crush coupon testing offering a significantly more accurate and reliable way of measuring composite energy absorption; and a novel numerical modelling methodology that enables improved accuracy in predicting the progressive crushing behaviour of geometrically-complex crash structures through a more objective discretisation of its localised energy absorption potential.
The results of this project have resulted in the publication of 5 peer-reviewed journal articles, and to the contribution of 6 international conference presentations. More scientific publications are anticipated in the near future, all of which will be made accessible on the official project website. The project results were openly shared amongst all the industrial partners, as well as the wider academic community through a number of invited presentations, and with the public through a seminar organised and hosted at the beneficiary. Presentations/lectures on the project results and sustainable engineering were also given to both aspiring STEM students and current undergraduates.
Both experimental and numerical developments are being exploited by the beneficiary and the project partners through joint ventures. The experimental fixtures developed for dynamic crush coupon testing are being further refined with the aim of establishing novel industry-wide standards for the characterisation of composite energy absorption. The numerical modelling strategy which was created during the project is now being further assessed in the advanced design phase of a novel prototypic hybrid laminate crash structure manufactured from sustainable flax fibre composites.
The main project results which push beyond the state-of-the-art include:
• A better understanding of the energy absorption mechanisms and overall potential of sustainable flax fibre composites.
• Improved characterisation methodologies for energy absorption that will provide a solid basis for future industry-wide standardisation.
• A more accurate and reliable methodology for predictive numerical modelling of the overall behaviour and performance of geometrically-complex composite crash structures.
• Significant advances which will lead to more sustainable crash structure designs that will benefit the wider society in driving towards carbon-neutrality and improved overall safety in transportation.
• A better understanding of the energy absorption mechanisms and overall potential of sustainable flax fibre composites.
• Improved characterisation methodologies for energy absorption that will provide a solid basis for future industry-wide standardisation.
• A more accurate and reliable methodology for predictive numerical modelling of the overall behaviour and performance of geometrically-complex composite crash structures.
• Significant advances which will lead to more sustainable crash structure designs that will benefit the wider society in driving towards carbon-neutrality and improved overall safety in transportation.