An active interface for rapid structural control

Lead Research Organisation: University of Surrey
Department Name: Mechanical Engineering Sciences

Abstract

Most natural organisms show fascinating mechanical versatility when interacting with their environments. Stiffness tuning in nature is used as a powerful tool to combine the load carrying functionality of rigid structures with compliance and adaptability. A remarkable example of stiffness tuning can be seen in echinoderms, such as sea cucumbers, where the mechanical stiffness can change by a factor of 10 in less than 1s. Human-made structures are normally designed to meet a specific load carrying requirement. To add other functionalities, additional components are often required; these increase the total weight and cost of the structure and consequently cause limitations in performance, efficiency and safety. Therefore, embedding sensing, actuation and control within a structure is highly desirable. Inspired by stiffness tuning in natural organisms, various synthetic materials have been developed in recent years for active structural control. However, achieving significant stiffness reduction in a short time frame with minimum power requirements but without undermining the load carrying capacity of the structure remain as some of main challenges.
In this proposal, we aim to tackle these challenges by exploiting recent advances in optoelectronics and nanotechnology to design, manufacture and evaluate a nano-structured interconnected metallic network embedded in a thermoplastic layer. This layer will be then employed, as an active interface, in a conventional multi-layered structure. Upon activation, it will provide rapid structural control and impact protection capabilities. We will use a combined experimental and numerical approach to investigate the electro-thermo-mechanical response of this interface. Understanding the main physical obstacles that limit the response time and the fundamental parameters controlling the stability and the failure of this interface under harsh electro-thermal loading will help us to better engineer this interface at the micro level to meet the fast response and low power requirements.
This new understanding will accelerate the technology readiness level of active structural control technology to be used in future multi-functional and smart structures. This technology has a wide range of application in robotics, morphing and deployable structures, active damping and active impact protection. As a potential representative technology, we aim to employ this active interlayer in laminated glass windscreens for automotive vehicles. Application of this transparent active interface in windscreens will help protect vulnerable road users against head-related injuries and is believed to be a step change toward designing more pedestrian/cyclist-friendly vehicles. To motivate the development of this technology, the University of Surrey is partnering with Pilkington, a member of the NSG group, which is one of the world's largest manufactures of glass and glazing products for architectural, automotive and technical glass sectors to manufacture and test this active transparent interlayer for application in automotive windscreens.

Planned Impact

Traditionally, structures have been designed to meet a specific load carrying requirement. This means that to introduce other functionalities, additional components are required that increase the total weight and cost of the structure. Therefore, encapsulating sensing, actuation and control within a structure is highly desirable especially in industries such as space, aerospace, automotive and defence where the weight has a significant impact on performance and cost. This project investigates an enabling technology to embed mechanical adaptability within the structure without compromising its load carrying capacity. The proposed technology can be integrated into many conventional multi-layered structures currently in use. Employing lightweight multi-functional structures results for example in greener transportation which has many environmental and economical impacts.
As a representative technology, in this proposal we aim to design and optimise an active interface to be employed in laminated glass windscreens for pedestrian impact protection. Application of this new multi-functional structure as an active safety system can change people's lives. Road traffic injuries are a global challenge and are amongst the top ten causes of death globally and the top cause of death for young people aged between 15-29 years. Annually 1.24 million deaths and 20-50 million non-fatal injuries have been recorded as a result of road traffic accidents. In 2010, the United Nations adopted a resolution for a decade of action for road safety with a goal of stabilising and then reducing the forecasted level of global road fatalities (estimated to reach about two million by 2020). In the UK, the importance of reducing the UK road casualties has been acknowledged in the Driver and Vehicle Standards Agency's five-year strategy document, which was published in April 2017. According to the Department for Transport's 2017 annual report, 51% of all fatalities (1,793) and 59% of all "clinically seriously injured casualties" (24,831) in the UK were related to pedestrians and cyclists. This new active safety technology is expected to help in reducing these casualties in the near future. According to the Department for Transport's statistics, road crashes cost the UK economy £35.6 billion annually, about 2% GDP. Long-term hospitalisation and rehabilitation also put an additional financial burden on the already stretched NHS. The injuries or deaths caused by road traffic accidents often have a profound social impact. The pain, grief and suffering of lost family members are indescribable. Not only fatalities but also long-term injuries can change the life of families forever. Injuries such as traumatic brain injury and neurological damage can cause permanent impairments and disabilities, which affects the quality of life of families. Around 50% of all traumatic brain and spinal cord injuries are the result of road accidents.
Introducing mechanical adaptability to a structures has other economical impacts as multi-functionality has become an important aspect in the manufacture of future materials. The knowledge generated in this project can give UK's companies such as Pilkington, the industrial partner in this project, a competitive edge in the manufacture of high value products. Pilkington has long been the leading manufacturer of glass and windscreens in automotive and aerospace industries. The proposed research helps to establish new manufacturing capabilities that can help Pilkington continue to be at the frontier of introducing novel and smart products. The market value of smart glass was $1.58 billion worldwide in 2013 and is predicted to grow by 20% by 2020.
Highly skilled engineers play a crucial role in the UK economy. During this project, a post doctoral research associate, requested for this project, and a PhD student provided by the department will gain a valuable skill set necessary for successful careers in the high-value manufacturing sector.

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