PhD Studentship in Mechanics of Materials at University College London

Detection and Identification of Damage in Composite Fibre/Metal Laminate Structures Using Guided Ultrasonic Waves

Description:

Leading manufacturers in the aerospace industry are working towards the introduction of new composite materials for the next generation of aircraft structures. The design requirements are often to reduce weight while maintaining strength, damage tolerance, and structural integrity. Guided by nature inspired design for the engineering of such lightweight materials, the research group is involved in the development and testing of layered composite fibre/metal systems. These composite materials can combine the high ductility and toughness of metals with the high stiffness and resilience of fibre reinforced composites, achieving better properties than the individual components, leading to ultra-ductile precursors for stretch-forming and stamping processes of car and aircraft parts.

A critical need for the design of such materials is monitoring and modelling damage initiation during manufacturing and service. During manufacturing, delamination in the metal/composite interface, voids in the matrix, and fibre pull-out are the main mechanisms that limit ductility. In service, composite materials are especially susceptible to barely visible impact damage (BVID), limiting structural performance. Therefore, a requirement exists for the non-destructive inspection of these materials to characterize the internal structure, and to detect and monitor damage severity and extent before they have reached a critical size.

Guided waves are low-frequency ultrasonic waves that propagate along the structure, allowing for the rapid inspection of large structures with limited access requirements. This is a promising, novel technology for the efficient structural health monitoring (SHM) of smart structures. Signal analysis allows damage localization and sizing, with high detection efficiency for surface and internal defects. The multi-modal characteristics of guided waves provide abundant damage information but increase the signal processing complexity to classify damage type and severity of BVID in composite materials, especially for practical and industrial engineering applications.

The overarching aim of this PhD project is to develop structurally efficient layered composite systems by investigating and improving the detection and characterisation of damage, through the use of guided ultrasonic waves. The main objectives include:

-       Testing the mechanical response of the developed composite materials during typical manufacturing processes (e.g. stretch-forming and stamping processes) and service cyclic loading, supported by surface strain measurements through digital image correlation.

-       Finite Element Analysis (FEA) modelling of the response of the materials in the above processes, developing appropriate homogenisation and plasticity models.

-       Development of non-destructive damage detection techniques, based on guided ultrasonic waves.

-       Improvement of guided wave experimental procedures and signal analysis for increased sensitivity to small defects in anisotropic composite structures.

-       Development of a synergistic damage mechanics (SDM) based model to predict the remaining life of the composite structures.

-       Finite Element Analysis (FEA) modeling of guided wave scattering, damage initiation and evolution, considering the different length scales at which different damage modes are observed to nucleate and progress.

The academic group at UCL has an internationally leading profile and an exceptional publication record, and this project will provide numerous opportunities for high-profile publications and conference presentations. The project involves considerable interaction with other members of the research group, which has a very open, co-operative and friendly culture. The UCL laboratories are very well resourced with equipment, computers, consumables and all that is needed to perform research at the highest standard. The aim is to provide the best conditions for world-leading research.

Person Specification: Applicants must have a UK-equivalent first degree in Mechanical/Structural/Materials Engineering, or an equivalent discipline with a high technical content. Experience with Finite Element software (ABAQUS) is a significant advantage.

Closing Date and Start Date: Applications will be accepted until 15 July 2020. The start date of the studentship is 01 October 2020, or by mutual agreement.

Value of award: Full tuition fees and stipend (£17,285 in 2020/2021, rising with inflation) for 4 years. Funding is provided through an EPSRC DTA studentship.

Eligibility:  Funding requirements dictate that only students with UK nationality, or any EU passport holders who have lived in the UK for more than 3 years can receive the full value of the award. All other applicants are only eligible for fees-only funding.

Application Procedure:  Applicants should write to Dr Eral Bele (e.bele@ucl.ac.uk) and Dr Paul Fromme  (p.fromme@ucl.ac.uk) with a recent CV, letter of interest, and a full transcript of exam results.