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%.

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.

Assessment and propagation of mechanical property uncertainties in fatigue life prediction of composite laminates

2018 ◽  
Vol 52 (24) ◽  
pp. 3381-3398 ◽  
Author(s):  
Oscar Castro ◽  
Kim Branner ◽  
Nikolay Dimitrov
Keyword(s):  
Fatigue Life ◽  
Composite Laminates ◽  
Fatigue Behavior ◽  
Limit State ◽  
Turbine Blades ◽  
Laminated Composite ◽  
Load Level ◽  
Wind Turbine Blades ◽  
Laminated Composite Materials ◽  
Fatigue Limit State

A probabilistic model for estimating the fatigue life of laminated composite materials considering the uncertainty in their mechanical properties is developed. The uncertainty in the material properties is determined from fatigue coupon tests. Based on this uncertainty, probabilistic constant life diagrams are developed which can efficiently estimate probabilistic ɛ-N curves at any load level and stress ratio. The probabilistic ɛ-N curve information is used in a reliability analysis for fatigue limit state proposed for estimating the probability of failure of composite laminates under variable amplitude loading cycles. Fatigue life predictions of unidirectional and multi-directional glass/epoxy laminates are carried out to validate the proposed model against experimental data. The probabilistic fatigue behavior of laminates is analyzed under constant amplitude loading conditions as well as under both repeated block tests and spectral fatigue using the WISPER, WISPERX, and NEW WISPER load sequences for wind turbine 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.

Monitoring of Multidirectional and Cure-Induced Strain in CFRP Laminates Using FBG Sensors

2019 ◽  
Vol 953 ◽  
pp. 72-79 ◽  
Author(s):  
Cheng Biao Jiang ◽  
Li Hua Zhan ◽  
Xiao Bo Yang ◽  
Xiao Ping Chen ◽  
Zi Jun Lin ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Strain ◽  
Composite Laminates ◽  
Compressive Strain ◽  
Fibre Bragg Grating ◽  
Cfrp Laminates ◽  
Reinforced Plastics ◽  
Fiber Reinforced Plastics ◽  
Fbg Sensors ◽  
Curing Cycle

During the curing cycle, the residual stress has influence on cure-induced deformation for carbon fiber reinforced plastics (CFRP) laminates, which is highly susceptible to the ply design. Therefore, the change laws of strain and the effect of residual stress in CFRP laminates after curing, which is of great significance to ply design, were cleared by using the combining pattern of thermocouple and fibre Bragg grating (FBG) sensors. For the FBG sensors embedded with different directions in lay-up CFRP laminates, the temperature and strain in different directions of composite laminates were obtained in real-time. Monitoring results show that compared with strain in 45° direction, the carbon fibers (CF) act stronger to inhibit strain in 0° direction and weaker to inhibit strain in 90° direction of resin. After curing, the residual strain in 0° direction is tensile strain, and the residual strain in 45° direction and 90° direction are compressive strain. Meanwhile the value of residual strain in 90° direction is greater than that in 45° direction.

scholarly journals A cuckoo search based neural network to predict fatigue life in rotor blade composites

2020 ◽  
Vol 14 (1) ◽  
pp. 6430-6442
Author(s):  
Khaled Ziane ◽  
Adrian Ilinca ◽  
Abdullah Khan ◽  
Soraya Zebirate
Keyword(s):  
Neural Network ◽  
Fatigue Life ◽  
Wind Turbine ◽  
Composite Laminates ◽  
Turbine Blades ◽  
Cuckoo Search ◽  
Wind Turbine Blades ◽  
Target Values ◽  
Predicted Values ◽  
The Cost

In modern wind turbine blades industry, fiber-reinforced composites are mostly used for their good mechanical characteristics: high stiffness, low density and long fatigue life. Wind turbine blades are constructed in different structural elements from a variety of composite laminates, often including Unidirectional (UD) material in spars and multiple forms of Multidirectional (MD) in skins and webs.  The purpose of this paper is to identify materials that have appropriate fiber orientations to improve fatigue life. By using Cuckoo Search-based Neural Network (CSNN), we have developed a model to predict fatigue life under tension-tension charges for five composite materials, with different fiber stacking sequences embedded in three types of resin matrices (epoxy, polyester and vinylester), which are all appropriate for the design of wind turbine blades. In the CSNN approach used in this work, the cost function was assessed using the Mean Square Error (MSE) computed as the squared difference between the predicted values and the target values for a number of training set samples, obtained from an experimental fatigue database. The results illustrate that the CSNN can provide accurate fatigue life prediction for different MD/UD composite laminates, under different angles of fiber orientation.

Effect of Hybridization on Flexural Performance of Unidirectional and Bidirectional Composite Laminates under Ambient Temperature

2021 ◽  
Vol 56 ◽  
pp. 16-33
Author(s):  
Getahun Aklilu ◽  
Sarp Adali ◽  
Glen Bright
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Carbon Fibre ◽  
Composite Laminates ◽  
Hybrid Composites ◽  
Flexural Modulus ◽  
Turbine Blades ◽  
Carbon Fibres ◽  
Wind Turbine Blades ◽  
Flexural Performance

Abstract. Fibre Reinforced Plastic (FRP) materials are widely used in several key engineering applications such as ships, aircraft, wind turbine blades, helicopter blade, automobiles, and other transportation vehicles because of their mechanical properties and tailoring capabilities.Carbon and glass fibres are the most popular fibre reinforcements used for composite components. In the present study, two different stacking sequences, (0 degrees) and (0/90 degrees), are selected to study effect of fibre hybridization on flexural performance using three-point bending tests. Materials used are E-glass and T-300 carbon fibres in an epoxy matrix and the laminates were produced by resin transfer moulding methods. Fracture surfaces of composite laminates were examined using a scanning electron microscope. The results showed that the flexural strength, modulus and strain at failure of unidirectional and bidirectional composite laminates were strongly influenced by stacking sequences, fibre orientation and the hybrid ratio of the fibres. A higher flexural modulus was achieved when carbon fibres were placed on the compressive side. Hybrid specimens showed higher flexural strength and modulus by 21.08% and 145.39%, respectively, compared to the pure glass fibre reinforced laminates. On the other hand, flexural strength and modulus of hybrid specimen were less by 6.50% and 8.20%, respectively, as compared to carbon fibre reinforced specimens. Stacking sequences and hybrid ratio of glass/carbon fibre reinforced specimens were investigated with a view towards improving the mechanical properties of hybrid composites.

High Strain Monitoring during Fatigue Loading of Thermoplastic Composites Using Imbedded Draw Tower Fibre Bragg Grating Sensors

2008 ◽  
Vol 56 ◽  
pp. 441-446 ◽  
Author(s):  
Eli Voet ◽  
Geert Luyckx ◽  
Ives De Baere ◽  
Joris Degrieck ◽  
J. Vlekken ◽  
...  
Keyword(s):  
Composite Laminates ◽  
High Strength ◽  
Fatigue Loading ◽  
Strain Sensors ◽  
Thermoplastic Composites ◽  
Bragg Grating ◽  
Fibre Bragg Grating ◽  
Strain Measurements ◽  
Strain Monitoring

This paper presents the experimental study of fibre Bragg grating sensors for measuring strain inside composite laminates during fatigue loading. The optical fibres are imbedded inside thermoplastic CFRP test-coupons which have an ultimate strain of about 1.1%. Tension – tension fatigue cycling at a rate of 5Hz is been carried out at 314MPa with a maximum strain of 0.51%. At such extreme strain levels the use of high strength sensors becomes inevitable. Neither the sensor nor the composite test-coupons showed any significant degradation even after more than 500000 cycles. Fibre optic Bragg grating sensors are known to be very accurate strain sensors but one should be very careful interpreting their response once they are imbedded inside composite materials. In this study high strength fibre Bragg grating sensors with coating are imbedded in composite test coupons and a pretty good correlation was found between the strain measurements of an electrical extensometer and the imbedded sensor during the complete cycling. The high strength sensor show to be very feasible for extreme and long term strain measurements.

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.

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