Fatigue behaviour of carbon fibre reinforced plastic under spectrum loading

Sudha, J.; Kumar, Shakti; Srinivasan, Prabha; Vijayaraju, K.

doi:10.1016/j.msea.2008.09.032

Cited by 5 publications

(4 citation statements)

References 19 publications

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“…They found that spectrum loading does have an effect on the material properties and failure of the composite. 7 This result is supported by further work by Reis, Ferreira, Costa, and Richardson regarding fatigue life of carbon/epoxy laminates subject to constant and variable block loading. They found that the fatigue life does agree with the Palmgren-Miner's law.…”

Section: A Backgroundsupporting

confidence: 54%

Time to Flutter of a Viscoelastic Goland Wing

Merrett

2015

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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A number of aircraft are manufactured from high-polymer composite materials, for example the Predator drone, micro-aerial vehicles, and larger aircraft contain a significant amount of composite material such as the Boeing 787. The increasing use of polymer composite materials adds a time dimension to existing analyses for flutter of an aircraft lifting surface because polymer composites exhibit a viscoelastic material behaviour, in particular energy dissipation and a memory effect. The derivation of the time to flutter theory uses Lyapunov stability principles to provide a set of conditions for stability of a viscoelastic structure. The conditions contain a time parameter that may be isolated, and represents the time to flutter. A generalization of this theory has a number of ramifications including the existence of a finite time to instability for a viscoelastic structure that is a function of the applied loads and material properties. The theory may be applied in practice using a simplified set of bending-torsion equations and will correctly predict the flutter speed of an elastic Goland wing in subsonic, incompressible flow. The equations also predict the time to flutter at other flight speeds for a viscoelastic Goland wing. Nomenclature t Time u(t) General displacement function H Hilbert spacē A Unbounded, non-commuting, scalar type operator B Unbounded, non-commuting operator A Operator B Operator B * Adjoint of B A 1 Goland wing inertia operator B 1 Goland wing damping operator C 1 Goland wing elastic stiffness operator D 1 Goland wing viscoelastic stiffness operator U Bounded linear operator S Symmetric component of an operator Ω Skew-symmetric component of an operator Q(t) Relaxation measure R(t) Relaxation function E Elastic modulus at t = 0 Q 0 Q(t)/E R 0 Long time relaxation function µ 1 Eigenvalue t max Maximum time to instability χ Material viscosity T Relaxation time T n Relaxation time bound γ Characteristic rate of relaxation H Norm of operator product * Copyright© Downloaded by PURDUE UNIVERSITY on July 26, 2015 | http://arc.aiaa.org |

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Section: A Backgroundsupporting

confidence: 54%

Time to Flutter of a Viscoelastic Goland Wing

Merrett

2015

56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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“…With the rising cost of energy, the push for lighter and more efficient aircraft has been a key issue for manufacturers. One method of achieving this has been the adoption of lightweight polymer matrix composite (PMC) materials which can provide high specific strength or specific stiffness [5,6]. In addition to the weight saving, these materials tend to be more corrosion and fatigue resistant when compared to traditional materials like aluminium [7].…”

Section: Review Of Composite Materials Use the Aviation Industrymentioning

confidence: 99%

“…Due to the extensive use of metals in modern society, mathematical models to represent fatigue's effect on metals has been the focus of ongoing research as direct testing of every structure is uneconomic and time consuming for an accurate life prediction. Since the use of composite materials are is relatively new compared to the use of metals, there are limited theories to properly represent its effects on composites as many mechanisms the tend to be more complex [6,7,14,16]. Figure 2.5 is a illustration comparing the difference in results between a metal and a composite fatigue test on a notched specimen.…”

Section: Fatigue and Its Effect On Service Lifementioning

confidence: 99%

“…Current methods of characterizing fatigue in composite structures are through direct modulus degradation, determination of a fatigue modulus, residual strength, fatigue damage accumulation or through energy methods. Each of these methods have advantages and disadvantages and are typically selected based on the load type and frequency [6,16].…”

Section: Fatigue and Its Effect On Service Lifementioning

confidence: 99%

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The Effect of Viscoelasticity on the Life Expectancy of Light Composite Aircraft

Goudie¹

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In modern aircraft, polymer matrix composites (PMC) are becoming more prevalent in both primary and secondary structures due to their high strength and stiffness to weight ratios. Due to the molecular composition of polymers, these materials exhibit viscoelastic phenomena such as creep, recovery and relaxation. The scope of this thesis is to predict the service life of the Diamond DA-20 Katana based on the viscoelastic properties of the MSG L285/H287 epoxy matrix. The prediction methodology is applied to the composite wing spar because the spar bears the majority of the load during flight. The methodology requires the experimental characterization of the epoxy matrix, which was achieved by retrofitting a decommissioned undergraduate laboratory furnace. The retrofit created a novel creep and relaxation measurement apparatus. Using elevated temperature, the long term response of the epoxy matrix was determined using the time-temperature superposition principle. The results were then applied to the spar to determine its long term response using the Classical Lamination Theory applied to complex geometries. Failure was determined based on the Tsai-Hill and maximum strain failure theory or if the compressive flange buckles under the applied load.Based on the analysis, it was determined that the MSG L285/H287 epoxy system adheres to the Time-Temperature Superposition principal and master curves were generated using a limited data set. Composite analysis was performed on the wing spar using the viscoelastic properties of the epoxy. Based on the analysis presented in this thesis, it is concluded that Diamond's claim's of unlimited service life is possible based on the assumptions made with respect to viscoelastic phenomena.ii

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Time to flutter theory for viscoelastic composite aircraft wings

Merrett

2016

Composite Structures

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Fatigue behaviour of carbon fibre reinforced plastic under spectrum loading

Cited by 5 publications

References 19 publications

Time to Flutter of a Viscoelastic Goland Wing

Time to Flutter of a Viscoelastic Goland Wing

The Effect of Viscoelasticity on the Life Expectancy of Light Composite Aircraft

Time to flutter theory for viscoelastic composite aircraft wings

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