Geometrically exact, intrinsic mixed variational formulation for smart, slender multilink composite structures

2021 ◽  
pp. 1045389X2110322
Author(s):  
P M G Bashir Asdaque ◽  
Sitikantha Roy
Keyword(s):  
Composite Structures ◽  
Turbine Blades ◽  
Space Structures ◽  
Wind Turbine Blades ◽  
Weak Formulation ◽  
Helicopter Blades ◽  
Static Mechanical ◽  
Computational Platform ◽  
Swept Wings ◽  
Variational Statement

Flexible links are often part of massive aerospace structures like helicopter or wind turbine blades, satellite bae, airplane wings, and space stations. In the present work, a mixed variational statement based on intrinsic variables is derived for multilinked smart slender structures. Equations involved in the derivation do not involve approximations of kinematical variables to describe the deformation of the reference line or the rotation of the deformed cross-section of the slender links resulting in a geometrically exact formulation. Finite element equations are derived from weak formulation, which can analyze large geometrically non-linear problems. The weakest possible variational statement provides greater flexibility in the choice of shape functions, therefore reducing the associated numerical complexities. The present work focuses on developing a single integrated computational platform which can study multibody, multilink, lightweight composite, structural system built with both embedded actuations, sensing, as well as passive links. Validation of static mechanical and electrical outputs from 3D FE simulation and literature proves the efficacy of the computational platform. Dynamic results will be communicated in future correspondence. The computational platform developed here can be applied for monitoring and active control applications of flexible smart multilink structures like swept wings, multi-bae space structures, and helicopter blades.

Automated Damage Detection in Composite Components Using Acoustic Emission

2013 ◽  
Vol 569-570 ◽  
pp. 80-87 ◽  
Author(s):  
Rhys Pullin ◽  
Matthew R. Pearson ◽  
Mark J. Eaton ◽  
Carol A. Featherston ◽  
Karen M. Holford ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Health Monitoring ◽  
Composite Structures ◽  
Impact Damage ◽  
Turbine Blades ◽  
Fatigue Loading ◽  
Potential Method ◽  
Base Line ◽  
Wind Turbine Blades ◽  
Ae Signals

The ability of a Structural Health Monitoring (SHM) system to automatically identify damage in a composite structure is a vital requirement demanded by end-users of such systems. This paper presents the demonstration of a potential method. A composite fatigue specimen was manufactured and initially tested at 1Hz for 1000 cycles. Acoustic emission (AE) signals were recorded for complete fatigue cycles periodically in order to establish a base-line associated with undamaged specimens. The specimen was then subjected to impact damage to create barely-visible impact damage (BVID) and subjected to further fatigue cycles with acoustic emission recorded until failure. The data was subsequently analysed using a range of techniques including basic RMS signal levels and frequency-based analysis. At various stages during the test, C-scanning was used to validate the results obtained. Results demonstrated that AE is capable of detecting BVID in composite materials under fatigue loading. The proposed method has wide applicability to composite structures which are subjected to cyclic loading, such as wind turbine blades.

scholarly journals Multiscale Toughening of Composites with Carbon Nanotubes—Continuous Multiscale Reinforcement New Concept

2021 ◽  
Vol 5 (5) ◽  
pp. 135
Author(s):  
Monssef DRISSI-HABTI ◽  
Yassine El ASSAMI ◽  
Venkadesh RAMAN
Keyword(s):  
Carbon Nanotubes ◽  
Composite Materials ◽  
Composite Structures ◽  
Numerical Study ◽  
Glass Fibers ◽  
Turbine Blades ◽  
Offshore Wind ◽  
Wind Turbine Blades ◽  
Structural Composite ◽  
Offshore Industry

Strengthening composite structures for advanced industries such as offshore wind generation is a real issue. Due to the huge dimensions expected for next generation wind-blades, composites based on glass fibers can no longer be used due to the lack of stiffness, whereas composites based on carbon fibers are expensive. Therefore, switching to alternative structural solutions is highly needed. This might be achieved by appropriate use of carbon nanotubes (CNTs) either as fillers of epoxy matrices, especially in inter-plies, or as fillers of epoxy glues used in structural bonding joints. As an example, trailing edges of offshore wind-blades are addressed in the current article, where monolithic bonding holds together the two structural halves and where the risk of sudden and brittle separation of edges while wind-turbines are in service is quite high. This can lead to tedious and very expensive maintenance, especially when keeping in mind the huge dimensions of new generation wind turbine blades that exceed lengths of 100 m. Bond joints and composites inter-plies of the final CNT-reinforced structures will exhibit stiffness and toughness high enough to face the severe offshore environment. In this article, multiscale Finite Element (FE) modeling is carried out to evaluate mechanical properties following the addition of CNTs. To achieve an optimal reinforcement, the effect of inclination of CNTs vs. mechanical loading axis is studied. Two innovations are suggested through this numerical study: The first consists of using homogenization in order to evaluate the effects of CNT reinforcement macroscopically. The second innovation lies in this forward-looking idea to envisage how we can benefit from CNTs in continuous fiber composites, as part of a deep theoretical rethinking of the reinforcement mechanisms operating at different scales and their triggering kinetics. The presented work is purely numerical and should be viewed as a “scenario” of structural composite materials of the future, which can be used both in the offshore industry and in other advanced industries. More broadly and through what is proposed, we humbly wish to stimulate scientific discussions about how we can better improve the performances of structural composite materials.

Intelligent Resin Delivery System for Manufacturing Large Composite Structures

2014 ◽  
Author(s):  
Tolga Yuksel ◽  
Daniel Stockton ◽  
Paul Marshall ◽  
Dave Kim ◽  
Hakan Gurocak
Keyword(s):  
Delivery System ◽  
Optical Sensors ◽  
Composite Structures ◽  
Turbine Blades ◽  
Prototype System ◽  
Resin Flow ◽  
Production Environment ◽  
Wind Turbine Blades ◽  
Composite Manufacturing ◽  
Design Specifications

Fabrication of large composite structures, such as recreational yacht hulls and wind turbine blades, is a cost intensive and high-risk operation, which must be carefully controlled to meet demanding design specifications and reduce defects. In this study, the goal was to develop an intelligent resin delivery system that can easily be integrated into the existing traditional setup in production environment and without any modifications to the mold. A prototype system with two resin supply lines and 16 optical sensors was developed. The system automatically monitors and adjusts resin flow in the mold in real-time using a controller. The effect of process setup parameters on the resin flow was investigated with the design of experiments technique to identify the best settings. The results showed that the automatic system can successfully control the resin flow, hence can be a potential future option in composite manufacturing.

Guided wave–based approach for ice detection on wind turbine blades

2018 ◽  
Vol 42 (5) ◽  
pp. 483-495 ◽  
Author(s):  
Siavash Shoja ◽  
Viktor Berbyuk ◽  
Anders Boström
Keyword(s):  
Experimental Data ◽  
Wind Turbine ◽  
Composite Structures ◽  
Detection System ◽  
Turbine Blades ◽  
Guided Wave ◽  
Cold Climate ◽  
Wind Turbine Blades ◽  
Time Frequency ◽  
Ice Detection

An efficient ice detection system is an important tool to optimize the de-icing processes in wind turbines operating in cold climate regions. The aim of this work is to study the application of guided wave for ice detection on wind turbine blades. Computational model is developed to simulate guided wave propagation on composite structures. The model has been validated with experimental data obtained in cold climate laboratory. Effect of ice accretion on composite structures is studied in the time, frequency and wavenumber domains. In each case, post-processing algorithms as well as icing index are introduced which are sensitive to accumulated ice on the composite structure. The algorithms and icing index are applied to both simulation results and experimental data. Analysis of the obtained results has shown that the guided wave–based approach can be used for developing ice detection systems for wind turbine blades.

Concepts for Adaptive Wind Turbine Blades

2002 ◽  
Author(s):  
Thomas D. Ashwill ◽  
Paul S. Veers ◽  
James Locke ◽  
Ivan Contreras ◽  
Dayton Griffin ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
State University ◽  
Braided Composites ◽  
Wind Turbine Blades ◽  
Widespread Implementation ◽  
Fiber Reinforced Materials ◽  
Critical Issues ◽  
Wichita State University ◽  
Swept Wings

Bend-twist coupling in wind turbine blades has been shown to reduce both fatigue and extreme operating loads, especially when applied in conjunction with a pitch-controlled rotor. This type of coupling has been used in other industries, implemented either through biased lay-ups of fiber-reinforced materials, or with swept wings. The critical issues restricting the widespread implementation of this technology to wind turbines lies in the detailed design, manufacturing, and durability of the bend-twist-coupled blades. A series of industry contracts were initiated to evaluate/study these issues. The results of three of these studies are summarized in this paper. Global Energy Concepts (GEC) studied design issues from the perspective of traditional wind turbine blade conceptual design. Wichita State University investigated the use of braided composites with a multi-cellular blade structure. Finally, MDZ Consulting studied the possibilities of using sweep alone to achieve the desired bend-twist coupling. A common result of all the studies is that a higher stiffness fiber, such as carbon, has tremendous benefits in this application.

Modeling Heat Flow Interaction With Defects in Composite Materials Using Virtual Heat Sources in Pulsed Thermography

2013 ◽  
Author(s):  
Arun Manohar ◽  
Francesco Lanza di Scalea
Keyword(s):  
Heat Conduction ◽  
Heat Flow ◽  
Composite Structures ◽  
Quantitative Estimation ◽  
Turbine Blades ◽  
Heat Sources ◽  
Wind Turbine Blades ◽  
Conduction Model ◽  
Transverse Thermal Conductivity ◽  
Different Depths

Quantitative defect detection in composite structures is an important problem as the aerospace and wind energy industries are increasingly using composites due to their attractive properties. Newer aircraft contain over 50% composites, while the wind turbine blades contain over 95% composites. Quantitative estimation of defect parameters is relevant to perform repairs and assess the integrity of these structures. Previous studies are based on simple 1D heat conduction models, which are inadequate in predicting heat flow around defects, especially in composites where the ratio of longitudinal to transverse thermal conductivity is about 100. In this study, a novel heat conduction model is proposed to model heat flow around defects accounting for 3D heat conduction in quasi-isotropic composites. The validity of the proposed methodology is established using experiments performed on a CFRP panel containing defects of different dimensions at different depths. The inverse problem could be used to quantitatively determine the defect depth and size.

scholarly journals Multi-Objective Optimisation of Curing Cycle of Thick Aramid Fibre/Epoxy Composite Laminates

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4070
Author(s):  
Guowei Zhang ◽  
Ling Luo ◽  
Ting Lin ◽  
Boming Zhang ◽  
He Wang ◽  
...  
Keyword(s):  
Composite Laminates ◽  
Composite Structures ◽  
Signal To Noise Ratio ◽  
Turbine Blades ◽  
High Strength ◽  
Curing Temperature ◽  
Aramid Fibre ◽  
Fibre Bragg Grating ◽  
Wind Turbine Blades ◽  
Curing Cycle

Aramid fibre-reinforced epoxy composites (AF/EP) are promising materials in the aerospace, transportation, and civil fields owing to their high strength, high modulus, and light weight. Thick composite laminates are gradually being applied to large composite structures such as wind turbine blades. During curing, temperature overheating is a common problem in thick composites, which leads to matrix degradation, thermal residual stresses, and uneven curing. This paper proposes a signal-to-noise ratio (SNR) method to optimise the curing cycle of thick AF/EP laminates and reduce the overheating temperature. During curing, the temperature and strain evolution in a thick AF/EP laminate were monitored using fibre Bragg grating sensors. The effects of the curing factors on the overheating temperature of the thick AF/EP laminate were evaluated using the Taguchi method and predicted via the SNR method and analysis of variance. The results indicate that the dwelling temperature is the main factor affecting the overheating temperature. The optimal curing cycle involves an overheating temperature of 192.72 °C, which constitutes an error of 2.58% compared to the SNR method predictions. Additionally, in comparison to the initial curing cycle, the overshoot temperature in the optimised curing cycle was reduced by 58.48 °C, representing a reduction ratio of 23.28%.

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