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

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 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.

Relationship between Structural Stiffness and Viscous Damping Coefficient in Reinforced Carbon Structure under Varying Carbon Fiber Angles

“…Moreover, unexpected additional resonance frequencies could be found as the carbon fiber angle increased from the reference value. Because the mode trace was conducted using only the MAC value, the variation of each mode could not be clearly explained in that study [22]. The variation of the four resonance frequencies generally decreased with an increase in the carbon fiber angle.…”

“…The direct variation of both equivalent parameters-structural stiffness and viscous damping coefficient-can be analyzed with sensitivity indices in Equations ( 21) and (22), respectively, and the variation of both parameters relating to the carbon fiber only can be analyzed with the proposed sensitivity indices in Equations ( 23) and ( 24…”

“…Under the same uniaxial excitation condition, the dynamic behavior of the CFRP structure was investigated for different spectral loading patterns, random and harmonic, and the sensitivity difference was determined by comparing the normalized sensitivity indices [21]. A modal analysis using an impact hammer was used for the simple CFRP specimen, and the variation of four mode shapes, two bending modes, and two twisting modes was compared using the modal assurance criterion (MAC) [22]. The four traced modes indicated unique trends for each mode over five different carbon fiber angles.…”

Changes in Frequency and Mode Shapes Due to Damage in Steel–Concrete Composite Beam

“…Table 5 shows the MAC values for vectors of the mode shapes obtained from the experiment Q A and the model Q B . The model can be assumed as reliable when the MAC value is higher than 0.8 [ 43 , 44 ]. As it can be seen, for the first four modes of vibrations, MAC > 0.8 was obtained.…”

Modal Parameter Tracking in a Carbon Fiber-Reinforced Structure over Different Carbon Fiber Angles

“…Both the resonance frequency and modal damping ratio were obtained from the representative frequency response functions (FRFs), and the variations in the two modal parameters were discussed based on the different carbon fiber angles. In a recent study, the modal parameters of CFRP specimens were more reliably obtained through a modal analysis of clamped simple CFRP specimens at room temperature [25]. A modal analysis was applied to an isotropic material specimen, SCS13A, and five CFRP specimens with different carbon fiber angles: 0 • , 30 • , 45 • , 60 • , and 90 • .…”