scholarly journals Fatigue Damage Evaluation of Short Carbon Fiber Reinforced Plastics Based on Thermoelastic Temperature Change and Second Harmonic Components of Thermal Signal

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4941
Author(s):  
Daiki Shiozawa ◽  
Takahide Sakagami ◽  
Yu Nakamura ◽  
Takato Tamashiro ◽  
Shinichi Nonaka ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Temperature Change ◽  
Stress Level ◽  
Second Harmonic ◽  
Fiber Reinforced ◽  
Carbon Fiber Reinforced Plastics ◽  
Reinforced Plastics ◽  
Thermal Signal ◽  
Fiber Reinforced Plastics ◽  
Short Carbon

Short fiber reinforced plastics (SFRPs) have excellent moldability and productivity compared to continuous fiber composites. In this study, thermoelastic stress analysis (TSA) was applied to detect delamination defects in short carbon fiber reinforced plastics (SCFRPs). The thermoelastic temperature change ΔTE, phase of thermal signal θE, and second harmonic temperature component ΔTD were measured. In the fatigue test of SCFRP, it was confirmed that changes in ΔTE, θE, and ΔTD appeared in the damaged regions. A staircase-like stress level test for a SCFRP specimen was conducted to investigate the generation mechanism of the ΔTD. The distortion of the temperature change appeared at the maximum tension stress of the sinusoidal load—and when the stress level decreased, the temperature change returned to the original sinusoidal waveform. ΔTD changed according to the change in the maximum stress during the staircase-like stress level test, and a large value of ΔTD was observed in the final ruptured region. A distortion of the temperature change and ΔTD was considered to be caused by the change in stress sharing condition between the fiber and resin due to delamination damage. Therefore, ΔTD can be applied to the detection of delamination defects and the evaluation of damage propagation.

Long-Term Durability of Pitch-Based High Modulus Carbon Fiber Reinforced Plastics

2020 ◽  
Author(s):  
Satoshi Kobayashi ◽  
Toshiko Osada
Keyword(s):  
Acoustic Emission ◽  
Carbon Fiber ◽  
Stress Level ◽  
Residual Strength ◽  
Fatigue Loading ◽  
High Modulus ◽  
Fiber Reinforced ◽  
Carbon Fiber Reinforced Plastics ◽  
Reinforced Plastics ◽  
Fiber Reinforced Plastics

Abstract Static tensile and tensile-tensile fatigue were conducted on PITCH-based high modulus carbon fiber reinforced plastics (CFRP). PAN-based intermediate and high modulus CFRP were also tested for comparison.. Unidirectional laminates were prepared with wet panel method. The damage mode for high modulus CFRP was fiber breakage for both static and fatigue loading, whereas splitting was dominant for intermediate modulus CFRP. The slope of the S-N curve was larger for the intermediate modulus CFRP than that for the high modulus CFRP. This is attributed to the lower failure strain of the high modulus carbon fibers. That is, the larger strain on intermediate modulus CFRP at lower stress level comparing with high modulus CFRP caused severer matrix damages during fatigue loading. This results indicated the higher durability of high modulus CFRP. Residual strength measurement were conducted on the un-broken PITCH-based CFRP up to 1,000,000 cycles with acoustic emission measurements. The Kaiser effect was not satisfied for the specimen with lower residual strength at the stress level of the fatigue test. In addition, gradual acoustic emissions with longer duration and rise time were measured before final fracture in the static tests. These results indicated the possibility to detect the microscopic damage monitoring for the CFRP with acoustic emission measurement focusing on the duration of the acoustic wave.

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