Papers by Keyword: Carbon Fiber Reinforced Polymer/Plastic (CFRP)

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Authors: Sang Kyo Lee, Mohd. Zahid Ansari, Na Wang, Chong Du Cho
Abstract: The present study investigates numerically the compressive residual strength of indented sandwich composite panel. The composite is made of carbon fiber reinforced plastic (CFRP) face sheets and aluminum honeycomb core. The sandwich is loaded under quasi-static condition and along out-of-plane direction. A commercial finite element analysis software ABAQUS is used. The results show that the indented composite retains significant amount of strength after indentation. And, the post-indentation strength of the composite is about 65% its pre-indentation strength under compression.
Authors: Hui Cheng, Yuan Li, Kai Fu Zhang, Jun Zhang
Abstract: Thrust force is the most important element which will cause delamination in the drilling of CFRP. This paper developed a dynamic thrust force prediction model for CFRP drilling, by firstly, representing the drilling process into a three-step model. Secondly, the dynamic thrust force is decomposed into two parts. Thirdly, the thrust force components on both tool major cutting edge and chisel edge is developed according to the analysis on infinitesimal cutting unit. Lastly, several experiments are performed to compare the result of thrust force analyzed, which proves that the purposed model can analyze the dynamic thrust force in drilling of CFRP well.
Authors: Masamichi Kawai
Abstract: The full shape of constant fatigue life (CFL) diagram has been identified for three kinds of carbon fiber-reinforced plastic (CFRP) laminates of [45/90/-45/0]2s, [0/60/-60]2s and [0/90]3s lay-ups, respectively. First, the effects of mean stress on fatigue behavior are observed for the quasi-isotropic [45/90/-45/0]2s CFRP laminate. It is clearly observed that the CFL diagram turns out asymmetric and the peak of the CFL diagram is slightly offset to the right of the alternating stress axis. The CFL plots indicate that the alternating stress component of fatigue load becomes maximal at a critical stress ratio closely equal to the compressive strength to tensile one (i.e. a C/T strength ratio). It is also demonstrated that CFL curves for different constant values of life are linear in the range of a short life, but they turn quadratic in the range of a longer life. Similar features are observed for the other kinds of CFRP laminates. Then, to construct the asymmetric dissimilar shape of CFL diagrams, a new methodology is developed on the basis of the static strengths in tension and compression and the reference S-N relationship for the critical stress ratio. An efficient procedure for determining the reference S-N relationship for the critical stress ratio by using fatigue data for another stress ratio is also developed.
Authors: Masamichi Kawai, Jian Qi Zhang
Abstract: A macromechanics constitutive model to describe the anisotropic creep behavior of unidirectional composites under off-axis loading conditions is developed with a particular emphasis on accurate prediction of temporal creep softening due to stress variation. A viscoplasticity model that takes account of a combined isotropic and kinematic hardening is adopted as a base for this formulation, and the evolution equation of the kinematic hardening variable is elaborated to enhance the accuracy of prediction of the transient creep softening due to stress variation. Validity of the modified kinematic-hardening viscoplasticity model is evaluated by comparing with the experimental results on unidirectional T800H/3631 carbon/epoxy composites. It is demonstrated that the proposed model can adequately describe the off-axis creep behavior of the unidirectional CFRP laminate under constant and variable stress conditions.
Authors: Qiang Hu, Song Lin Jia, Jin Biao Chen, Jun Zhang
Abstract: This paper explores the issue how to improve utilization ratio of CFRP strengthening steel structure in allusion to the diseconomy of steel structure strengthened with CFRP. An experiment including six single axisymmetric steel beams was carried out to study ultimate capacity of single axisymmetric steel beam strengthened with CFRP sheets. These samples were divided into three groups, and each group included two samples strengthened with one and two layers of CFRP sheets respectively. The experimental results show that single axisymmetric steel beam strengthened with CFRP is advantageous over biaxial symmetrical steel beam because the former has superior material utilization ratio. On the basis of the experimental results, a simplified analytical model is put forward for prediction of capacity and material utilization ratio. In the proposed approach, ultimate capacity formula is established and an index named material utilization ratio is suggested to study how to enhance CFRP utilization ratio. The analytical calculation results state clearly that steel beam strengthened with enough CFRP is favorable in improving capacity and material utilization and owns optimal utilization ratio. Above all, the proposed approach is convenient and accurate enough for practical application in material utilization assessmetn and capacity design.
Authors: Xiao Qiang Chen, Bin Jia, Hua Chuan Yao, Yu Zhang
Abstract: This paper compares the flexural bearing capacity, rigidity, and ductility of the reinforced RC beams after comparative tests of reinforcing RC beams by three different ways: directly bonding CFRP, bonding CFRP after replacing concrete and bonding CFRP after replacing concrete and planting bar. The results show that the method of replacing concrete can sufficiently avoid the debonding between CFRP and concrete, improve the flexural bearing capacity, and further strengthen the rigidity and ductility; whereas the method of planting bar can well guarantee the bond of Young and old concretes, let the replacing concrete together with CFRP work better, and carry capacity increase in reinforcement.
Authors: Hee Jae Shin, Lee Ku Kwac, Sun Ho Ko, Tae Hoon Kim, Hong Gun Kim
Abstract: Of the advanced composite materials for aerospace structures such as aircrafts and space devices, the carbon fiber reinforced plastics (CFRP) is applied to many sectors that require lightweight materials for its high strength and stiffness. One of the disadvantages of the CFRP, however, is that it is weak against impact. In this study, impact test specimens were manufactured with five fiber stacking angles (0°/0°, 0°/15°, 0°/30°, 0°/45°, 0°/90°) according to ASTM D7136[15], and a falling weight test was performed to analyze the correlation between their mechanical and thermal characteristics. As a result, the impact energy applied to the five test specimens with different fiber stacking angles was almost constant at 30.63 J - 30.78 J. The absorbed energy increased with the increase in the fiber stacking angle, and decreased after 0°/45°. The average temperature on the fractured surface increased with the increase in the fiber stacking angle in all specimens other than the 0°/0° specimen.
Authors: Ju Ho Choi, In Young Yang, Woo Chae Hwang
Abstract: Vehicle structure must be lightweight in order to improve fuel-efficiency and reducing exhaust fumes. The most important goals in designing automobile are safety and environment-friendliness. There are lots of studies on the crushing absorption energy of a structural members in automobile. The crashworthy behavior of circular composite material tubes subjected to axial compression under same conditions is reported in this paper. Energy absorption of CFRP circular member is affected by lamination conditions. Test was executed in order to compare the results to the energy absorption and collapse shape.
Authors: Kyung Min Hong, Young June Kang, Nak Kyu Park, Weon Jae Ryu
Abstract: The ESPI (Electronic Speckle Pattern Interferometry) is a real-time, full-field, non-destructive optical measurement technique. In this study, ESPI was proposed for the purpose of vibration analysis for new and composite materials. Composite materials have various complicated characteristics according to the materials, orientations, stacking sequences of the ply and boundary conditions. Therefore, it was difficult to analyze composite materials. For efficient use of composite materials in engineering applications the dynamic behavior (i.e., natural frequencies and nodal patterns) should be informed. With the use of Time-Average ESPI, one could analyze vibration characteristics of composite material by real time easily. We manufactured two kinds of laminated composites (i.e., symmetry and asymmetry) which were consisted of CFRP (Carbon Fiber Reinforced Plastics) and the shape of the test piece was of rectangular form.
Authors: Yun Ping Pan, Wen Juan Yang, Yi Min Mo
Abstract: Short pulse lasers, including picosecond laser and femtosecond laser are involved to investigate the ablation characteristics of processing carbon fiber reinforced plastics (CFRPs). The ablation threshold of the femtosecond laser, 0.453 J/cm2, is twice higher than that of the picosecond laser 0.867 J/cm2, since the former generates an intense and shorter pulse and the atoms excitation and multi-photon absorption may occur as short as 10 ps or less. The ablation test also describes the processing qualities, where the femtosecond laser has processing abilities without visible thermal defects or charring over the picosecond laser.
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