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形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: PA2120068000

形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: PA2110071000

形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: PA1710056000

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: AA0062291015, レポート番号: JAXA-SP-13-014

第21回宇宙構造・材料シンポジウム（2005年12月5日. 宇宙航空研究開発機構宇宙科学研究本部 (JAXA)(ISAS)）, 相模原市, 神奈川県, 21st Symposium on Aerospace Structure and Materials (December 5, 2005. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000020007

International audience; To detect indentation or low-velocity impact induced damage in foam-core sandwich structures, a fiber-optic distributed strain monitoring system is applied to the structures. An optical fiber is embedded into the sandwich structures and the strains are measured using a Rayleigh scattering based monitoring system which offers high resolution. Indentation loading tests with sandwich beam and panel structures are conducted to verify the monitoring ability of the system and compared with numerical analysis predictions. The monitoring system could measure the strain distribution with very high spatial resolution and allowed for observation of the strain formation throughout the whole indentation event. The detectability of the damage in panel structures with regards to the location and density of the optical fiber sensor network is also discussed. The used system could accurately detect slightest changes in residual strains indicating barely visible damage and thus allowed for good estimation of the location and size of damage in the core of the sandwich structures.

This study investigates the numerical simulation and theoretical modeling of longitudinal compressive failure in fiber reinforced composite materials. Firstly the numerical simulation of longitudinal compressive failure is conducted. The simulated results show that at one moment of the loading, the localized deformation catastrophically appears in the material, and in this initiation of the localized deformation, the reduction of tangent shear stiffness plays an important role. Secondly the theoretical modeling of longitudinal compressive failure is implemented. A set of mathematical equations is obtained for the deformation of composite materials, and the mathematical solution of the equations is considered. There exists a state where arbitrariness appears in the solution of equations expressing deformation of composite materials, and it is indicated that the onset of arbitrariness in solution of equations expressing deformation of composite materials is closely related with the initiation of longitudinal compressive failure, and also related with the initiation of narrow localized band in the materials. Finally the numerical simulation is conducted for compressive failure in quasi-isotropic laminate. The localized deformation also appears in the laminate, and the simulated deformation of the material agrees with the microscope picture of the experimental result. compressive strength in the materials are related to the fundamental compressive strength of the materials, and improvement of compressive strength would be related with the increase of the light weight potential of the materials. This study investigates the numerical simulation and theoretical modeling of longitudinal compressive failure in fiber reinforced composite materials.

International audience; Applying secondary bonding to places where carbon fiber reinforced plastic (CFRP) structures are conventionally bolted leads to significant cost and weight saving. However, it has yet to be utilized due to difficulties in quality control. Lack of local pressure in bonding process has detrimental influence on the quality of the cured adhesive layer. Pressure detection is hence a key for controlling bonding quality, and a new quality assurance technique is urgently needed. This study established a fiber-optic-based pressure detection and quality assurance technique for secondary bonding process. Fiber Bragg grating (FBG) optical sensors were embedded in the adhesive layer and the reflected spectrum changes were monitored during the pressurizing stage to detect the applied pressure. Thermal residual strain after curing was also evaluated for further quality assurance. Good correlation was observed between the cure pressure, the CFRP quality and the FBG sensor response, confirming the validity of the proposed technique.

International audience; Airframe structures, especially composite structures, are prone to damage by tool drops, bird strikes, hailstones, etc. The authors have developed an optical fiber based impact damage detection system for composite airframe structure since 1998. In this method, impact locations are measured with the signals of multiple Fiber Bragg Grating (FBG) sensors. In case of aircraft implementation, impact information should be detected under the actual vibration condition, and both detection capability for impact localization and damage level should be improved. This paper presents the detectability assessment result from the impact tests under a simulated vibration condition. In addition, study of optimal FBG sensor direction for localization and review of damage level detection method are conducted to enhance the accuracy of detection.

The objective of this study is evaluating the effect of stretching on the angular orientation of carbon nanotubes (CNT) and the mechanical properties of aligned CNT/epoxy composites. Stretching tests were conducted by tensile testing after fabricating prepregs with stretch rations of 0%, 2%, 5%, 10% and 18%, respectively. Microscopic observations by scanning electron microscope (SEM) were carried out for quantitative evaluation of the CNT angular distribution. Young's modulie and tensile strengths were evaluated using monotonic tensile testing at room temperature after molding prepreg into composites and resultant values were compared with theoretical estimations (Eshelby/Mori-Tanaka theory). Numbers of CNT in the composites orientation exceed 30 degree were relatively low, which were significantly improved with a small stretching ratio, however the misorientation at higher angle still remain, which means that stretching prepregs are effective for CNTs with small angle. Resultant Young's modulie of composites increased with stretching the prepreg. Young's modulie estimated results by Eshelby/Mori-Tanaka theory were in good agreement with experimental ones, for small stretching ratio, however disagreed for over 10% stretching ratio., 形態: 図版あり, Physical characteristics: Original contains illustrations, 資料番号: PA1520016000

繊維強化複合材料を実際に構造部材料として用いる場合,静的な荷重ばかりでなく動的な荷重を受けることが少なくない.特に,繊維強化方向に垂直方向の衝撃力に対する応答が最も重要であるが,未だこの分野の研究は少ない.そこで,本報告ではまず,応力波伝播の一次元理論を用いて,異種材料から成る材料の境界面での反射,伝達を扱った.次にそれを基礎として,様々な一方向繊維強化複合材料の簡単なモデルについてその繊維垂直方向の衝撃応答を計算した.モデルI,IIは無限体中に薄い帯状部分が存在する場合であり,モデルIII,IVはそれぞれ2層または3層から成る材料の場合である.以上のモデルについて,衝撃荷重下では静的荷重下より境界面において大きな引張応力が生じ,境界面での引張破壊が生じやすいことがわかった., Fiber-reinforced composite materials receive not only a static force but a dynamic force when they are used in practical structures. Especially, the impact response in the direction perpendicular to fibers is the most important, but tardy in research. In this report, first we treat wave reflection and transmission at the interface of different element materials, by using the one-dimensional theory of stress waves. Secondly, those results are applied to some simple models of unidirectional fiber-reinforced composite materials and impact responses in the direction perpendicular to fibers are calculated. Model I and II are composite structures in which two semi-infinite elastic solids are bonded with a thin layer made of a different material. Model III and IV are composed of two and three bonded layers, respectively. These models subjected to impact loading receive a larger tensile stress at the interface than those subjected to static loading, and it is predicted that the tensile fracture at the interface easily occurs., 資料番号: SA0125656000

For the simulation of the injection stage of the manufacturing process of composite materials, the permeability value of the textile preform is an important input parameter. The permeability of textiles can be determined experimentally, however, that is a time and resource consuming process. In this paper we present two methods to compute the permeability tensor of textile models. One is a full CFD method based on the finite difference discretisation of the Stokes equations. The second method reduces the 3D problem to a 2D problem, which leads to a reduction of the computational cost. We compare the results obtained with both methods with each other, and with experimental data and theoretical predictions. ispartof: pages:220-221 ispartof: Book of abstracts of the papers presented at the Sixteenth International Conference on Composite Materials, July 8-13, 2007: Kyoto Japan pages:220-221 ispartof: International Conference on Composite Materials location:Kyoto, Japan date:8 Jul - 13 Jul 2007 status: published