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Due to its superior mechanical properties, graphene (Gr) has the potential to achieve high performance polymer-based nanocomposites. Previous studies have proved that defects in the Gr sheets could greatly reduce the mechanical properties of Gr, while the Stone-Wales (SW) defect was found to enhance the interfacial mechanical strength between Gr and epoxy. However, the combined effects of defects on the overall mechanical properties of Gr/epoxy nanocomposites have not been well understood. In this paper, the effect of the SW defect on the mechanical properties of Gr/epoxy nanocomposites was systematically investigated by using molecular dynamic simulations. The simulation results showed that the SW defect would degrade the mechanical properties of nanocomposites, including the Young’s modulus and in-plane shear modulus. Surprisingly, the transverse shear modulus could be remarkably enhanced with the existence of SW. The reinforcing mechanisms were mainly due to two aspects: (1) the SW defect could increase the surface roughness of the Gr, preventing the slippage between Gr and epoxy during the transverse shea; and (2) the nanocomposite with defective Gr enables a higher interaction energy than that with perfect graphene. Additionally, the effects of temperature, the dispersion and volume fraction of Gr were also investigated.
Maoyuan Li; Peng Chen; Bing Zheng; Tianzhengxiong Deng; Yun Zhang; Yonggui Liao; Huamin Zhou. Effect of Stone-Wales Defect on Mechanical Properties of Gr/epoxy Nanocomposites. Polymers 2019, 11, 1116 .
AMA StyleMaoyuan Li, Peng Chen, Bing Zheng, Tianzhengxiong Deng, Yun Zhang, Yonggui Liao, Huamin Zhou. Effect of Stone-Wales Defect on Mechanical Properties of Gr/epoxy Nanocomposites. Polymers. 2019; 11 (7):1116.
Chicago/Turabian StyleMaoyuan Li; Peng Chen; Bing Zheng; Tianzhengxiong Deng; Yun Zhang; Yonggui Liao; Huamin Zhou. 2019. "Effect of Stone-Wales Defect on Mechanical Properties of Gr/epoxy Nanocomposites." Polymers 11, no. 7: 1116.
In this study, the formability of woven carbon-fiber (CF)-reinforced polyether-ether-ketone (PEEK) composite sheets in the solid-state thermoforming process were investigated, and the failure mechanisms were discussed. The formability of the woven CF/PEEK sheets were analyzed using flexural tests, Erichsen test, and microscopic observation. The results show that the formability of CF/PEEK sheets significantly increases as the temperature rises from 165 to 325 °C, and slightly decreases as the deformation speed rises from 2 to 120 mm/min. The deformation of the sheets is caused by plastic deformation, shear deformation and squeeze deformation, without plastic thinning and fiber slippage, which is due to the restriction of the solid matrix and locked fibers. Moreover, the wrinkles will cause fiber fracture at lower temperatures and delamination at higher temperatures. At higher temperatures, the wrinkles mainly occur at the position with [0°/90°] fibers due to the squeezing of the matrix and fibers.
Bing Zheng; Xiping Gao; Maoyuan Li; Tianzhengxiong Deng; Zhigao Huang; Huamin Zhou; Dequn Li. Formability and Failure Mechanisms of Woven CF/PEEK Composite Sheet in Solid-State Thermoforming. Polymers 2019, 11, 966 .
AMA StyleBing Zheng, Xiping Gao, Maoyuan Li, Tianzhengxiong Deng, Zhigao Huang, Huamin Zhou, Dequn Li. Formability and Failure Mechanisms of Woven CF/PEEK Composite Sheet in Solid-State Thermoforming. Polymers. 2019; 11 (6):966.
Chicago/Turabian StyleBing Zheng; Xiping Gao; Maoyuan Li; Tianzhengxiong Deng; Zhigao Huang; Huamin Zhou; Dequn Li. 2019. "Formability and Failure Mechanisms of Woven CF/PEEK Composite Sheet in Solid-State Thermoforming." Polymers 11, no. 6: 966.
In this study, the mechanical and thermal properties of graphene were systematically investigated using molecular dynamic simulations. The effects of temperature, strain rate and defect on the mechanical properties, including Young’s modulus, fracture strength and fracture strain, were studied. The results indicate that the Young’s modulus, fracture strength and fracture strain of graphene decreased with the increase of temperature, while the fracture strength of graphene along the zigzag direction was more sensitive to the strain rate than that along armchair direction by calculating the strain rate sensitive index. The mechanical properties were significantly reduced with the existence of defect, which was due to more cracks and local stress concentration points. Besides, the thermal conductivity of graphene followed a power law of λ~L0.28, and decreased monotonously with the increase of defect concentration. Compared with the pristine graphene, the thermal conductivity of defective graphene showed a low temperature-dependent behavior since the phonon scattering caused by defect dominated the thermal properties. In addition, the corresponding underlying mechanisms were analyzed by the stress distribution, fracture structure during the deformation and phonon vibration power spectrum.
Maoyuan Li; Tianzhengxiong Deng; Bing Zheng; Yun Zhang; Yonggui Liao; Huamin Zhou. Effect of Defects on the Mechanical and Thermal Properties of Graphene. Nanomaterials 2019, 9, 347 .
AMA StyleMaoyuan Li, Tianzhengxiong Deng, Bing Zheng, Yun Zhang, Yonggui Liao, Huamin Zhou. Effect of Defects on the Mechanical and Thermal Properties of Graphene. Nanomaterials. 2019; 9 (3):347.
Chicago/Turabian StyleMaoyuan Li; Tianzhengxiong Deng; Bing Zheng; Yun Zhang; Yonggui Liao; Huamin Zhou. 2019. "Effect of Defects on the Mechanical and Thermal Properties of Graphene." Nanomaterials 9, no. 3: 347.
In this study, the flexural behavior and fracture mechanisms of short carbon fiber reinforced polyether-ether-ketone (SCFR/PEEK) composites at various ambient temperatures were investigated. First, the crystallinity and glass transition temperature (Tg) of PEEK and SCFR/PEEK were analyzed by differential scanning calorimetry analysis and dynamic mechanical analysis tests, respectively. The addition of SCFs increases the Tg but does not change the crystallinity of the PEEK matrix. Then, the three-point flexural tests of PEEK and SCFR/PEEK were performed over the temperature range of 20 to 235 °C, and the temperature-dependencies of the flexural properties of PEEK and SCFR/PEEK were discussed in detail. Finally, the microstructure of SCFR/PEEK was observed using a digital microscope and scanning electron microscope. The results show that the tension crack occurs first, and the crack extends upward leading to the shear crack and compression crack at room temperature. The fracture of SCFR/PEEK is mainly due to the extraction and rupture of SCFs. At high temperatures (above Tg), the tension crack and compression crack both occur, and the strong ductility of the matrix prevents the generation of shear crack. The fracture of SCFR/PEEK is mainly due to the rotation and extraction of SCFs, while the SCFs rupture plays a minor role.
Bing Zheng; Tianzhengxiong Deng; Maoyuan Li; Zhigao Huang; Huamin Zhou; Dequn Li. Flexural Behavior and Fracture Mechanisms of Short Carbon Fiber Reinforced Polyether-Ether-Ketone Composites at Various Ambient Temperatures. Polymers 2018, 11, 18 .
AMA StyleBing Zheng, Tianzhengxiong Deng, Maoyuan Li, Zhigao Huang, Huamin Zhou, Dequn Li. Flexural Behavior and Fracture Mechanisms of Short Carbon Fiber Reinforced Polyether-Ether-Ketone Composites at Various Ambient Temperatures. Polymers. 2018; 11 (1):18.
Chicago/Turabian StyleBing Zheng; Tianzhengxiong Deng; Maoyuan Li; Zhigao Huang; Huamin Zhou; Dequn Li. 2018. "Flexural Behavior and Fracture Mechanisms of Short Carbon Fiber Reinforced Polyether-Ether-Ketone Composites at Various Ambient Temperatures." Polymers 11, no. 1: 18.
Carbon fiber fabric‐reinforced polycarbonate composites with different processing parameters were fabricated by thermoforming process. Effects of processing conditions on volume fraction, spatial distribution, geometrical shape and size of voids were investigated with the aid of X‐ray computed tomography and microscopy observation. Regardless of holding pressure or dwell time, voids exhibited similar shape and size and were mainly concentrated in interlaminar zone. Meanwhile, three‐point bending test and short‐beam strength test were performed to evaluate the effects of the void content on mechanical properties. The flexural strength and modulus significantly reduced with only a small amount of void content increase, which decreased by about 23 MPa and 2.17 GPa for each rise of 1% in void content, respectively. The relationship between the voids and interlaminar shear property was also established and a suitable processing window was gained. POLYM. COMPOS., 2018. © 2018 Society of Plastics Engineers
Wei Jiang; Zhigao Huang; Yunming Wang; Bing Zheng; Huamin Zhou. Voids formation and their effects on mechanical properties in thermoformed carbon fiber fabric‐reinforced composites. Polymer Composites 2018, 40, E1094 -E1102.
AMA StyleWei Jiang, Zhigao Huang, Yunming Wang, Bing Zheng, Huamin Zhou. Voids formation and their effects on mechanical properties in thermoformed carbon fiber fabric‐reinforced composites. Polymer Composites. 2018; 40 (S2):E1094-E1102.
Chicago/Turabian StyleWei Jiang; Zhigao Huang; Yunming Wang; Bing Zheng; Huamin Zhou. 2018. "Voids formation and their effects on mechanical properties in thermoformed carbon fiber fabric‐reinforced composites." Polymer Composites 40, no. S2: E1094-E1102.