A Study of Time-dependent and Anisotropic Effects on the Deformation Response of Two Flywheel Designs

Saleeb, A. F.; Arnold, Steven M.; Al-Zoubi, N.R.

doi:10.1520/stp38406s

Cited by 4 publications

(1 citation statement)

References 27 publications

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“…The values of the stress dependent tangent modulus for the IM7/8552 used was evaluated by Tsai and Sun (Jialin Tsai, 2004), and Saleeb, Arnold, and AI-Zoubi, N. R (Saleeb, 2003). Figure …”

Section: ̅ ̅mentioning

confidence: 99%

On Compressive Response of IM7/8552 Lamina- A Theoretical & Experimental Review

Hussien¹,

Moehring²,

Schwall³

et al. 2012

53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference

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Analytical models to predict the compressive strength of unidirectional composites along fiber direction are either based on microbuckling, kinking of fibers or fiber splitting. Experiments showed that all those mechanisms are together responsible for the failure. The present work evaluates and compares some of the existing models proposed for predicting the compressive strength of unidirectional composites. As an attempt to evaluate analytical models that can be used for the design purposes with a greater degree of confidence, and are easy to use and computationally simple. Experimentally, the determination of lamina compressive strength and modulus using simple fixture of Combined Loading Compression (CLC) test method was investigated. In this test method a tabbed, [0] 12 test coupons were tested in uniaxial compression to measure the longitudinal modulus and strength of IM7/8552 CFRP. Nomenclature F1c = ultimate compressive strength in fiber direction Vf = fiber volume fraction Em = matrix modulus of elasticity Ef = fiber modulus of elasticity Gm = matrix modulus of rigidity Gf = fiber modulus of rigidity k = bonding parameter rf = fiber radius  m = matrix Poisson's ratio  f  = fiber Poisson's ratio  = matrix slippage coefficient  = fiber-matrix bond condition E = effective axial stiffness of the lamina l = fiber length  = end condition coefficient  = misalignment angle Hp = stress dependent tangent modulus of the uniaxial stress/plastic strain curve = matrix elastic-plastic shear modulus by incremental theory of plasticity = matrix elastic-plastic shear modulus by deformation theory of plasticity = ultimate tensile yield strength = ultimate shear yield strength  = kink band angle n = hardening coefficient = ultimate shear yield strain t = specimen thickness w = specimen width = critical interfacial surface energy G12 = effective shear modulus of the lamina h = gage length E11 = effective Young's modulus of the lamina = effective bending flexural modulus of the lamina Gxz = effective transverse shear modulus of the lamina I = specimen cross-section second moment of area

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“…The values of the stress dependent tangent modulus for the IM7/8552 used was evaluated by Tsai and Sun (Jialin Tsai, 2004), and Saleeb, Arnold, and AI-Zoubi, N. R (Saleeb, 2003). Figure …”

Section: ̅ ̅mentioning
confidence: 99%

On Compressive Response of IM7/8552 Lamina- A Theoretical & Experimental Review
Hussien¹,
Moehring²,
Schwall³
et al. 2012
53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
2
0
0
0
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Durability of Polymer Composites in Power and Propulsion Applications
Thesken
¹
,
Bowman²,
Sutter³
2011
Long-Term Durability of Polymeric Matrix Composites
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Time-Temperature Dependent Response of Filament Wound Composites for Flywheel Rotors
Thesken¹,
Bowman
²
,
Arnold
³

et al. 2003
Composite Materials: Testing and Design, Fourteenth Volume
4
1
6
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Flywheel energy storage offers an attractive alternative to the electrochemical battery systems currently used for space applications such as the International Space Station. Rotor designs utilizing the load carrying capacity of carbon fibers wound in the hoop direction are capable of high operational speeds and specific energies. However, the long-term durability of such rotors may be limited by the time-temperature dependent behavior of the epoxy matrix, which controls the uniaxial properties transverse to the fiber and the shear properties. This proposition was investigated for the prototypical rotor material, IM7/8552. Flat filament wound panels were made using the same process as for composite rotors. Coupon specimens, sectioned normal and parallel to the winding axis, were tested in compression and tension, at room temperature (RT), 95 °C and 135 °C for strain rates from 5 × 10-6/s to 5× 10-3/s. Creep and stress relaxation testing ran 72 hrs followed by a 72 hr recovery. Time, temperature and load sign dependent effects were significant transverse to the fiber. Under a fixed deformation of -0.5% strain for 72 hrs, compressive stresses relaxed 16.4% at 135 °C and 13% at 95 °C. Tensile stresses relaxed only 7% in 72 hrs at 135 °C for 0.5% strain. The postulate of a linear hereditary material response and the application of Boltzmann's principle of superposition to describe the behavior observed here are problematic if not intractable. Undoubtedly microstuctural analysis including the influence of residual stresses due to processing will be needed to resolve the observed paradoxes. Within the scope of these experiments, uniaxial compressive stress relaxation data may be used to bound the amount of relaxation with time of radial pre-load stresses in flywheel rotors. A more detailed appraisal of the design implications of these results is made in the analysis by Saleeb and co-workers [1].

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A Study of Time-dependent and Anisotropic Effects on the Deformation Response of Two Flywheel Designs

Cited by 4 publications

References 27 publications

On Compressive Response of IM7/8552 Lamina- A Theoretical & Experimental Review

On Compressive Response of IM7/8552 Lamina- A Theoretical & Experimental Review

Durability of Polymer Composites in Power and Propulsion Applications

Time-Temperature Dependent Response of Filament Wound Composites for Flywheel Rotors

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