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Monitoring Failure Behaviour of Pultruded CFRP Composites by Electrical Resistance Measurement
Mao, Yaqin,Yu, Yunhua,Wu, Dezhen,Yang, Xiaoping Korean Carbon Society 2004 Carbon Letters Vol.5 No.1
The failure behaviours of unidirectional pultruded carbon fiber reinforced polymer (CFRP) composites were monitored by the electrical resistance measurement during tensile loading, three-point-bending, interlaminar shear loading. The tensile failure behaviour of carbon fiber tows was also investigated by the electrical resistance measurement. Infrared thermography non-destructive evaluation was performed in real time during tensile test of CFRP composites to validate the change of microdamage in the materials. Experiment results demonstrated that the CFRP composites and carbon fiber tows were damaged by different damage mechinsms during tensile loading, for the CFRP composites, mainly being in the forms of matrix damage and the debonding between matrix and fibers, while for the carbon fiber tows, mainly being in the forms of fiber fracture. The correlation between the infrared thermographs and the change in the electrical resistance could be regarded as an evidence of the damage mechanisms of the CFRP composites. During three-point-bending loading, the main damage forms were the simultaneity fracture of matrix and fibers firstly, then matrix cracking and the debonding between matrix and fiber were carried out. This results can be shown in Fig. 9(a) and (b). During interlaminar shear loading, the change in the electrical resistance was related to the damage degree of interlaminar structure. Electrical resistance measurement was more sensitive to the damage behaviour of the CFRP composites than the stress/time curve.
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Monitoring Failure Behaviour of Pultruded CFRP Composites by Electrical Resistance Measurement
Yaqin Mao,Yunhua Yu,Dezhen Wu,Xiaoping Yang 한국탄소학회 2004 Carbon Letters Vol.5 No.1
The failure behaviours of unidirectional pultruded carbon fiber reinforced polymer (CFRP) composites were monitored by the electrical resistance measurement during tensile loading, three-point-bending, interlaminar shear loading. The tensile failure behaviour of carbon fiber tows was also investigated by the electrical resistance measurement. Infrared thermography non-destructive evaluation was performed in real time during tensile test of CFRP composites to validate the change of microdamage in the materials. Experiment results demonstrated that the CFRP composites and carbon fiber tows were damaged by different damage mechinsms during tensile loading, for the CFRP composites, mainly being in the forms of matrix damage and the debonding between matrix and fibers, while for the carbon fiber tows, mainly being in the forms of fiber fracture. The correlation between the infrared thermographs and the change in the electrical resistance could be regarded as an evidence of the damage mechanisms of the CFRP composites. During three-point-bending loading, the main damage forms were the simultaneity fracture of matrix and fibers firstly, then matrix cracking and the debonding between matrix and fiber were carried out. This results can be shown in Fig. 9(a) and (b). During interlaminar shear loading, the change in the electrical resistance was related to the damage degree of interlaminar structure. Electrical resistance measurement was more sensitive to the damage behaviour of the CFRP composites than the stress/time curve.
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Nan Feng,Xiaodong Wang,Dezhen Wu 한국물리학회 2013 Current Applied Physics Vol.13 No.9
Recycled carbon fiber (RCF) was employed as a reinforcement material for preparation of nylon 6-basedthermoplastic composites. An effective approach was developed to clean and modify the surface conditionof RCF with nitric acid and then with an epoxy macromolecular coupling agent. The interfacialadhesion between RCF and nylon 6 matrix was improved significantly as a result of such a surfacemodification. Consequently, the reinforcing potential of the RCF was enhanced substantially, and thus,the mechanical properties and thermal stabilities of nylon 6 composites were improved remarkably. Themorphologies of fracture surfaces indicated that RCF achieved a homogeneous dispersion in nylon 6matrix due to good interfacial boding between fibers and matrix. The studies of non-isothermal andisothermal crystallization behaviors showed that RCF acted as a nucleation agent for the crystallization ofnylon 6; therefore, the crystallization rate and nucleation density increased notably due to the heterogeneousnucleating effect of RCF in the matrix. These crystallization features may be advantageous forthe enhancement of mechanical performance and processability of nylon 6-based composites. This studymay provide a design guide for RCF-reinforced nylon 6 composites with a great potential as well as a lowcost for industrial and civil applications.
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Preparation and Microstructure Control of PMDA/ODA Polyimide Hollow Fibers
Meifeng Xiao,Jianhua Li,Huanyu Lei,Mengying Zhang,Hongqing Niu,Dezhen Wu,Xiaodong Wang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.5
Poly(4,4'-oxydiphenylene pyromellitimide) (PMDA/ODA) hollow fiber membranes with regular morphologieshave been successfully prepared through a two-step dry-jet wet spinning method. The morphologies of polyimide (PI) hollowfibers were regulated via adjusting the major spinning parameters, including dope/bore flow rate ratio, bore fluidcomposition, coagulation bath temperature and air gap distance. SEM results show that the morphologies of PI hollow fibersstrongly depended on the spinning conditions, and fibers with regular asymmetric structures were finally obtained. The fiberwall thickened with the increase of dope/bore flow rate ratio, and the fibers could well self-support when the dope/bore flowrate ratio ranged from 3:1 to 4:1. While higher DMAc content in the bore fluid was conducive to the formation of finger-likevoids, reduced amount of DMAc would result in smaller finger-like voids and thereby lower overall porosities as well asbetter mechanical properties. Moreover, the finger-like voids and surface defects could be effectively prevented by loweringthe coagulation bath temperature or extending the air gap distance. Gas separation and mechanical properties of the hollowfibers were found closely related to these morphological changes. On such basis, regular PI hollow fibers with differentmicrostructures and Young’s modulus up to 1040 MPa were successfully fabricated. The prepared polyimide hollow fibersare promising candidates for fine separation under high temperature and high pressure or can be employed as the support ofcomposite membranes.
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