Passive load alleviation on wind turbine blades from aeroelastically driven selectively compliant morphing

Cavens, Wolf D. K.; Chopra, Abhishek; Arrieta, Andres F.

doi:10.1002/we.2555

Cited by 13 publications

(6 citation statements)

References 49 publications

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“…Selective stiffness in compliant structures has previously been proposed as an alternative to bridge the gap between the trade-offs faced when designing morphing systems. 33,34 This type of stiffness variability can be achieved by exploiting local changes in compliant topologies. Several approaches to achieve local bistability within compliant structures have been explored in the literature, including leveraging thermally prestressed composite laminates, 19,[35][36][37] employing thin shells, 38,39 and utilizing bistable compliant mechanisms.…”

Section: Selective Stiffness and Shape Lock-in Effects From Geometric...mentioning

confidence: 99%

Aero-structural optimization and actuation analysis of a morphing wing section with embedded selectively stiff bistable elements

Rivas-Padilla

Boston

Boddapati

et al. 2023

Journal of Composite Materials

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Morphing wings provide a potential avenue to improve aerodynamic performance of aircraft operating at multiple design conditions. Nevertheless, morphing wing design is constrained by the mutually exclusive goals of high load-carrying capacity, low weight, and sufficient aerodynamic control authority via conformal shape adaptation. This trade-off can be addressed by exploiting the stiffness selectivity and shape “lock-in” properties enabled by using bistable beam-like elements within compliant structures. In this paper, we present an aero-structural optimization method to realize morphing structures with selective stiffness and shape “lock-in” capability from embedded bistable elements. We leverage an embeddable beam element with an invertible curved arch that provides stiffness selectivity and camber variation to the proposed rib geometry. Optimization objectives and constraints are designed to maximize the structure’s stiffness change and camber morphing “lock-in” effect when operating at two distinct flight conditions. Using the optimization results, we manufacture a wing section demonstrator with selective stiffness and “lock-in” morphing featuring two optimized ribs, a load-carrying skin made of a carbon reinforced laminate, Macro-Fiber Composite (MFC) actuators, and a servo-controlled mechanism for switching the bistable elements’ states. The power and energy requirements of actuating and holding a target deflection are experimentally measured and compared. The results show that the bistable elements can assist in holding a target deflection at a reduced energy cost. Finally, we test the experimental demonstrator in a low-speed wind tunnel demonstrating the load carrying capability and lift variation achieved from switching states.

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Section: Selective Stiffness and Shape Lock-in Effects From Geometric...mentioning

confidence: 99%

Aero-structural optimization and actuation analysis of a morphing wing section with embedded selectively stiff bistable elements

Rivas-Padilla

Boston

Boddapati

et al. 2023

Journal of Composite Materials

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“…Recent studies have shown that natural design strategies can be used to develop adaptive structures that automatically respond to external stimuli. These include but are not limited to dragonfly‐inspired flapping kites that adapt their stiffness in response to the wind speed, [ 16 ] Passive load alleviation of morphing structures for wind turbine blades, [ 17,18 ] passive morphing of a solar powered flying wing aircraft to enhance solar energy absorbency, [ 19 ] plant‐inspired composites that reconfigure upon immersion in water or change in the ambient humidity, [ 20,4 ] pollen‐inspired drug delivery capsules that collapse under pressure, [ 21,22 ] insect‐inspired artificial fliers that reversibly buckle upon collisions. [ 23–25 ] These studies have opened a new avenue to the design of a new generation of adaptive systems, which can emerge as an independent research area to be called as Mechanical Intelligence (MI).…”

Section: Figurementioning

confidence: 99%

Mechanical Intelligence (MI): A Bioinspired Concept for Transforming Engineering Design

Khaheshi

Rajabi

2022

Advanced Science

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Despite significant scientific advances in the past decades, most structures around us are static and ironically outdated from a technological perspective. Static structures have limited efficiency and durability and typically perform only a single task. Adaptive structures, in contrast, adjust to different conditions, tasks, and functions. They not only offer multi-functionality but also enhanced efficiency and durability. Despite their obvious advantages over conventional structures, adaptive structures have only been limitedly used in everyday life applications. This is because adaptive structures often require sophisticated sensing, feedback, and controls, which make them costly, heavy, and complicated. To overcome this problem, here the concept of Mechanical Intelligence (MI) is introduced to promote the development of engineering systems that adapt to circumstances in a passive-automatic way. MI will offer a new paradigm for designing structural components with superior capabilities. As adaptability has been rewarded throughout evolution, nature provides one of the richest sources of inspiration for developing adaptive structures. MI explores nature-inspired mechanisms for automatic adaptability and translates them into a new generation of mechanically intelligent components. MI structures, presenting widely accessible bioinspired solutions for adaptability, will facilitate more inclusive and sustainable industrial development, reflective of Goal 9 of the 2030 Agenda for Sustainable Development."The wings are in effect "smart" aerofoils, combining remote and automatic shape control in ways which seem to occur nowhere else in nature or in technology" -Robin J Wootton [1] Imagine a dynamic world, where structures change their shape and properties to adapt to different needs; buildings that expand to allow more people in, bridges that morph to open

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“…However, this narrative has been challenged more recently, and instabilities have been exploited for novel functionalities. This has led to the creation of well-behaved nonlinear structures [5] such as shape-adaptive structures [6][7][8][9], deployable structures [10][11][12], zero or negative stiffness structures [13,14], energy harvesters [15], as well as non-destructive testing techniques [16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Structural function from sequential, interacting elastic instabilities

et al. 2023

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Elastic instabilities have traditionally been considered a failure mechanism; however, recent years have seen numerous studies exploiting instabilities as a means to achieve structural functionality. By contrast, interacting instabilities and compound buckling are still largely viewed as a failure mechanism. In this paper, we show that interacting instabilities can also be exploited to achieve bespoke functionality. We focus on ‘sequential instabilities’, whose associated critical points cannot both lie on a fundamental equilibrium path. We obtain sequential instabilities by combining canonical bifurcations, (e.g. limit point, pitchfork) as building-blocks. Initially, this concept is explored through simple bar-and-spring models that are found to have several properties not exhibited by the building blocks from which they are constructed. Further, the utility of the building block approach, and that of sequential, interacting instabilities, is demonstrated through the development of a morphing structure which must rapidly deploy after a critical input displacement is attained, and meet specific post-deployment stiffness requirements. Two design concepts are proposed, each comprising building blocks to mirror the fundamental working principles identified through the bar-and-spring models. Finite-element models of the design solutions are presented, demonstrating how the designs positively use sequential, interacting instabilities in order to meet the challenging requirements of the application. This work extends the contextual framework of instabilities that can be used to create structures with novel functionality.

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Passive load alleviation on wind turbine blades from aeroelastically driven selectively compliant morphing

Cited by 13 publications

References 49 publications

Aero-structural optimization and actuation analysis of a morphing wing section with embedded selectively stiff bistable elements

Aero-structural optimization and actuation analysis of a morphing wing section with embedded selectively stiff bistable elements

Mechanical Intelligence (MI): A Bioinspired Concept for Transforming Engineering Design

Structural function from sequential, interacting elastic instabilities

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