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Moisture absorption and desorption by a matrix resin, and the resulting deformation, exert a critical adverse effect on the shape stability of carbon fiber reinforced plastic (CFRP) space structures. This study evaluates the effect of the moisture content of prepreg sheets on the life-cycle behavior of the prepreg-based CFRP. After evaluating the moisture absorption and desorption characteristics of the prepreg sheets, the cure-induced strain and moisture absorption and desorption deformations were measured, employing embedded optical fiber sensors. Furthermore, to investigate the relationship between the moisture absorption and desorption behaviors and the chemical structure of the matrix resin, its structure was analyzed by Fourier-transform infrared spectroscopy (FTIR). Since absorption and desorption are dependent on the matrix resin, two types of resins were evaluated: epoxy resin and a low moisture absorption cyanate resin. Finally, recommendations for the manufacture and operation of CFRP space structures are offered, with respect to maintaining their long-term shape stability. [ABSTRACT FROM AUTHOR]

Self-healing composites using microvascular channel networks have been intensively studied. Microvascular networks in composite in-plane directions are normally utilized to deliver healing agents to damaged areas. However, this channel configuration is not optimal to form robust networks and to infuse large damaged areas. This study proposes a self-healing system using multiple short microvascular channels in the through-thickness direction. First, the advantage of using this channel configuration was confirmed through delamination filling tests. Next, the feasibility of this channel configuration was evaluated by tensile tests and four-point bending tests. Double cantilever beam tests were then conducted to confirm its healing function. Finally, this system was applied to composite stiffened panels and the healing performance was evaluated using compression testing following panel indentation. The healing system almost fully recovered the original strength, confirming its high potential under practical conditions. Additionally, the weight reduction potential of the self-healing system was discussed through a strength comparison of specimens with different thicknesses. [ABSTRACT FROM AUTHOR]

CFRP pipes are used in spacecraft to support heavy optical instruments. CFRPs' low coefficients of thermal expansion and high stiffness improve the instrument performance. However, significant through-thickness strain arises in thick CFRP pipes in curing and operation at low temperature, resulting in delamination failure. In this study, we developed a fiber-optic-based life-cycle monitoring system to measure through-thickness strain development. First, we addressed the mechanism of strain development using a theoretical approach and finite element analysis (FEA). We confirmed that geometrical constraint arising from the cylindrical shapes causes significant out-of-plane stress in the through-thickness center, and the stress increases with increased thickness and stiffness. A fiber Bragg grating (FBG) sensor was then embedded at the through-thickness center of a pipe during lay-up. Non-axisymmetric strain change in the FBG sensor was continuously measured using the birefringence effect throughout the life cycle, including curing and simulated operation in a low temperature environment. Through comparison between pipe and plate specimens, it was clearly demonstrated that the system could sensitively capture through-thickness strain development and detect delamination failure in the pipe. In addition, FEA was conducted and the result agreed well with the experiment data, confirming the validity of the experiment results. [ABSTRACT FROM AUTHOR]

The Japanese Smart Materials and Structures System Project started in 1998 as a five-year program funded by the Ministry of Economy, Trade and Industry (METI) and supported by the New Energy and Industrial Technology Development Organization (NEDO). This project was primarily conducted by the Academic Institutions Centered Program, a collaborative research and development project among universities, industries, and national laboratories. Initially, this project consisted of four research groups: structural health monitoring, smart manufacturing, active/adaptive structures, and actuator material/devices. Two years later, two demonstrator programs were added in order to integrate the developed sensor and actuator elements into the smart structure system and to verify the research and development results of the four research groups. The application target of these demonstrators was the airplane, and two demonstrators whose shapes simulated the fuselage of a small commercial airplane (for example, Boeing B737) were established. The first demonstrator integrated the following six innovative techniques: (1) impact monitoring using embedded, small diameter optical fiber sensors newly developed in this program, (2) impact monitoring using integrated acoustic emission (AE) systems, (3) whole-field strain mapping using the BOTDR/FBG integrated system, (4) damage suppression using embedded shape memory alloy (SMA) films, (5) maximum and cyclic strain sensing using smart composite patches, and (6) smart manufacturing using the integrated sensing system. The second demonstrator was for suppressing vibration and acoustic noise generated in a composite cylindrical structure. In this program, high-performance PZT actuators/sensors (developed in this project) were also installed. All tests and evaluations were completed. This paper outlines the demonstrator programs. [ABSTRACT FROM AUTHOR]

Introduces several articles about smart materials and structures.