scholarly journals Effects of Starter Defect on Energy Release Rate of Three-Point End-Notch Flexure Tested Unidirectional Carbon Fiber Reinforced Polymer Composite

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 904 ◽  
Author(s):  
Fethma M. Nor ◽  
Joong Yeon Lim ◽  
Mohd Nasir Tamin ◽  
Ho Yong Lee ◽  
D. Kurniawan

The mechanics of damage and fracture process in unidirectional carbon fiber reinforced polymer (CFRP) composites subjected to shear loading (Mode II) were examined using the experimental method of the three-point end-notch flexure (3ENF) test. The CFRP composite consists of [0o]16 with an insert film in the middle plane for a starter defect. A 3ENF test sample with a span of 50 mm and interface delamination crack length of 12.5 mm was tested to yield the load vs. deformation response. A sudden load drop observed at maximum force value indicates the onset of delamination crack propagation. The results are used to extract the energy release rate, GIIC, of the laminates with an insert film starter defect. The effect of the starter defect on the magnitude of GIIC was examined using the CFRP composite sample with a Mode II delamination pre-crack. The higher magnitude of GIIC for the sample with insert film starter defect was attributed to the initial straight geometry of the notch/interface crack and the toughness of the resin at the notch front of the fabricated film insert. The fractured sample was examined using a micro-computerized tomography scanner to establish the shape of the internal delamination crack front. Results revealed that the interface delamination propagated in a non-uniform manner, leaving a curved-shaped crack profile.

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3184
Author(s):  
Yaonan Yu ◽  
Fumio Narita

Wireless sensor networks are the future development direction for realizing an Internet of Things society and have been applied in bridges, buildings, spacecraft, and other areas. Nevertheless, with application expansion, the requirements for material performance also increase. Although the development of carbon-fiber-reinforced polymer (CFRP) to achieve these functions is challenging, it has attracted attention because of its excellent performance. This study combined the CFRP electrode with epoxy resin containing potassium sodium niobate piezoelectric nanoparticles and successfully polarized the composite sample. Furthermore, a three-point bending method was applied to compare the bending behavior of the samples. The peak output voltage produced by the maximum bending stress of 98.4 MPa was estimated to be 0.51 mV. Additionally, a conversion efficiency of 0.01546% was obtained. The results showed that the piezoelectric resin with CFRPs as the electrode exhibited stress self-inductance characteristics. This study is expected to be applied in manufacturing self-sensing piezoelectric resin/CFRP composite materials, paving the way for developing stable and efficient self-sensing structures and applications.


2019 ◽  
Vol 8 (4) ◽  
pp. 6836-6841

The present work investigates the wear properties of nanoclay-modified carbon fiber reinforced polymer (CFRP) composites when sliding under adhesive and abrasive wear. The specimens were fabricated using epoxy resin, short carbon fiber, and nanoclay filler of 1.0wt%, 3.0wt%, and 5.0wt% content. The wear tests were conducted using pin-on-disc and abrasion resistance test rig for adhesive and abrasive wear condition, respectively. Operating parameters were fixed at 30N load, 300rpm speed and 10km distance for both tests. Pure CFRP composite exhibited lower wear performance compared to pure epoxy in both test conditions. However, with nanoclay incorporation, the wear properties of CFRP composite have improved up to 56% and 44% under adhesive and abrasive wear, respectively. Therefore, the composite reinforced polymer of carbon fiber and nanoclay filler in epoxy matrix provides a synergistic effect under adhesive and abrasive wear conditions. The experimental findings suggest that the CFRP composite has the potential for tribological components and application such as sliding-contact and rolling-contact bearings.


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