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EPSRC DTP Studentship - Effects of pre-stress in morphing thin bilayers: from structural engineering to 4D printing


Slender structures are natural candidates for designing shape-changing systems: they undergo large deformations when subjected to moderate forces. Recent fabrication techniques combine active materials with structural design to create systems with properties tunable in time (termed 4D-printing). Potential applications range from mechanical meta-materials to sensors or actuators in soft robotics. This project is focussed on a class of morphing filaments generated by introducing geometrically incompatible pre-strains in rod-like bilayer structures: biological filaments subject to differential growth or engineered systems fabricated using e.g. materials with different thermal expansion coefficients, shape memory polymers or hydrogels subject to differential swelling.

To efficiently predict the mechanical response of such structures is challenging. Current approaches either rely on computationally expensive numerical simulations or on classical structural models that yield inaccurate results due to the high strains and geometric non-linearities generated in these structures. The aim of this project is to establish an accurate 1D structural model for pre-stressed morphing filaments, and thus provide a physical understanding of the non-linear effects triggering the complex 3-dimensional patterns observed in these thin structures (https://www.nsf.gov/news/mmg/mmgdisp.jsp?medid=77573&from=).

The project will involve a mix of theoretical and numerical approaches. We will use dimension reduction methods such as asymptotic two-scale expansions, starting from the full 3D description, combined with numerical approaches such as finite elements to discretise and solve 2D boundary value problems in the cross-sections of the filaments. Non-linear solutions of the resulting 1D model will eventually be obtained with the differential geometry-based open-source library for discrete framed curves developed within the Structures group.

EPSRC DTP studentships are fully-funded (fees and maintenance) for eligible UK students. International (including EU) students will be considered for partial funding (home-level fees and maintenance) from the DTP. We recommend that international students follow the instructions below and apply for admission to the PhD via the applicant portal by 3 December, in order to be put forward for funding from the Cambridge Trust for the home-overseas fee difference if selected.

Further details about eligibility and funding can be found at: https://epsrc.ukri.org/skills/students/help/eligibility/ https://www.postgraduate.study.cam.ac.uk/finance/fees
https://www.cambridgetrust.org/scholarships/

Applicants should have (or expect to obtain by the start date) at least a high 2:1, preferably a 1st class honours degree in Civil Engineering/Mechanical Engineering or Physics/Applied Mathematics.

To apply for this studentship, please send your two page CV, a transcript and a cover letter to Dr Claire Lestringant at casl4@cam.ac.uk, with subject "Prestressed Structures - PhD", to arrive no later than midnight on 31 January 2021. Queries about the post should be addressed to the same email address.

Please note that any offer of funding will be conditional on securing a place as a PhD student. Candidates will need to apply separately for admission through the University's Graduate Admissions application portal; this can be done before or after applying for this funding opportunity. Note that there is a £70 fee for PhD applications. The applicant portal can be accessed via: www.graduate.study.cam.ac.uk/courses/directory/egegpdpeg. The funding is conditional on submitting this application before 31 January 2021.

The University actively supports equality, diversity and inclusion and encourages applications from all sections of society.