Research

14 pages, 3536 KiB

Open AccessArticle

Sensitivity of the Viscous Damping Coefficient of Carbon Fiber in Carbon-Fiber-Reinforced Plastic with Respect to the Fiber Angle

by Chan-Jung Kim

Crystals 2021, 11(7), 781; https://doi.org/10.3390/cryst11070781 - 04 Jul 2021

Cited by 3 | Viewed by 2322

Abstract

The variation in the viscous damping coefficient with the carbon fiber angle can be evaluated using the partial derivatives of the viscous damping coefficient with respect to the resonance frequency and modal damping ratio. However, the direct derivatives of the viscous damping coefficient [...] Read more.

The variation in the viscous damping coefficient with the carbon fiber angle can be evaluated using the partial derivatives of the viscous damping coefficient with respect to the resonance frequency and modal damping ratio. However, the direct derivatives of the viscous damping coefficient were not effective solutions to the sensitivity analysis of carbon-fiber-reinforced plastic (CFRP) structures because the viscous damping from the binding matrix was not changed over the carbon fiber angle. If the identified viscous damping coefficients were assumed to be equivalent values from the parallel relationship between the binding matrix and carbon fiber, the relative error of the viscous damping coefficient of carbon fiber between the increased carbon fiber angle and reference angle could be used as the sensitivity index for the viscous damping coefficient of carbon fiber only. The modal parameters, resonance frequency, and modal damping ratio were identified from the experimental modal test of rectangular CFRP specimens for five different carbon fiber angles between 0° and 90°. The sensitivity of the viscous damping coefficient of carbon fiber was determined for two sensitivity indices: the direct derivative of the mass-normalized equivalent viscous damping coefficient and the relative error of the viscous damping coefficient of carbon fiber. The sensitivity results were discussed using the five mode shapes of the CFRP specimen, that is, three bending modes and two twisting modes. Full article

(This article belongs to the Special Issue Dynamic Behavior of Carbon Fiber Related Materials)

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11 pages, 4399 KiB

Open AccessArticle

Comparison of Mode Shapes of Carbon-Fiber-Reinforced Plastic Material Considering Carbon Fiber Direction

by Chan-Jung Kim

Crystals 2021, 11(3), 311; https://doi.org/10.3390/cryst11030311 - 22 Mar 2021

Cited by 10 | Viewed by 2181

Abstract

Previous studies have demonstrated the sensitivity of the dynamic behavior of carbon-fiber-reinforced plastic (CFRP) material over the carbon fiber direction by performing uniaxial excitation tests on a simple specimen. However, the variations in modal parameters (damping coefficient and resonance frequency) over the direction [...] Read more.

Previous studies have demonstrated the sensitivity of the dynamic behavior of carbon-fiber-reinforced plastic (CFRP) material over the carbon fiber direction by performing uniaxial excitation tests on a simple specimen. However, the variations in modal parameters (damping coefficient and resonance frequency) over the direction of carbon fiber have been partially explained in previous studies because all modal parameters have only been calculated using the representative summed frequency response function without modal analysis. In this study, the dynamic behavior of CFRP specimens was identified from experimental modal analysis and compared five CFRP specimens (carbon fiber direction: 0°, 30°, 45°, 60°, and 90°) and an isotropic SCS13A specimen using the modal assurance criterion. The first four modes were derived from the SCS13A specimen; they were used as reference modes after verifying with the analysis results from a finite element model. Most of the four mode shapes were found in all CFRP specimens, and the similarity increased when the carbon fiber direction was more than 45°. The anisotropic nature was dominant in three cases of carbon fiber, from 0° to 45°, and the most sensitive case was found in Specimen #3. Full article

(This article belongs to the Special Issue Dynamic Behavior of Carbon Fiber Related Materials)

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11 pages, 1857 KiB

Open AccessArticle

Characterization of Failure Strain In Fiber Reinforced Composites: Under On-Axis and Off-Axis Loading

by Muhammad Yasir Khalid, Ans Al Rashid, Zia Ullah Arif, Naveed Akram, Hassan Arshad and Fausto Pedro García Márquez

Crystals 2021, 11(2), 216; https://doi.org/10.3390/cryst11020216 - 22 Feb 2021

Cited by 36 | Viewed by 4578

Abstract

Metals are known for high ductility and have, been used to design and fabricate structural components for many years. However, composite materials are taking over traditional materials owing to their significant mechanical properties. Fiber-reinforced composites exhibit lower ductility and failure strain, resulting in [...] Read more.

Metals are known for high ductility and have, been used to design and fabricate structural components for many years. However, composite materials are taking over traditional materials owing to their significant mechanical properties. Fiber-reinforced composites exhibit lower ductility and failure strain, resulting in brittle failure, limiting their application where high ductility is desired. In this study, an effort has been made to design, fabricate, and test continuous fiber-reinforced composites with improved ductility. A comparative analysis was performed for optimizing the failure strain of different woven fiber-reinforced composite materials under both on-axis (0°/90°) and off-axis (±45°) loading. The materials include carbon/epoxy, E-glass/epoxy, and jute/epoxy composite. The tests were performed according to ASTM D3039 standard. The strength of all tested composites in on-axis and off-axis loading was obtained from tensile test results. But failure strain was limited in on-axis loading. Interestingly, glass/epoxy composite showed improved failure strain, by 90%, without much loss in tensile strength in off-axis loading than on-axis loading. The jute fiber revealed limited tensile strength and failure strain in both loading conditions. Full article

(This article belongs to the Special Issue Dynamic Behavior of Carbon Fiber Related Materials)

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