Recent progresses in materials science are described from the viewpoint of cluster-based materials. Solids constructed from carbon clusters are reviewed and unique properties are summarized with their crystal structural features. Future perspectives in cluster science are also briefly discussed.
High-glass-content glass fiber-reinforced plastics (GFRPs) have been developed, a commercially available GFRP with a 72vol% woven E-glass content and another with 74vol%. The thermal contraction in the laminated direction down to liquid nitrogen temperature was 0.27 and 0.25%, respectively. Compressive modulus at room temperature was 23.6 and 24.8GPa, respectively. When the glass content of GFRP made of commercially available glass cloth and produced by hot pressing was increased to more than 75vol%, thermal contraction and Young's modulus were not improved.
Unidirectional hybrid composites reinforced with high-strength polyethylene fiber and glass fiber were prepared to develop a spacer having a low thermal expansion coefficient for cryogenic use. The thermal expansion coefficient and compressive strength of the hybrid composites were measured together with the effect of thermal cycling between room and cryogenic temperatures. Though the hybrid composites showed anisotropy in the thermal expansion coefficient, the coefficient could be calculated by the law of mixtures. The thermal expansion coefficient became zero when the ratio between polyethylene and glass fiber volume was 3/7. The compressive strength and thermal expansion coefficient did not change after 5 heat cyclings. The compressive modules of the hybrid composite was approximately 50GPa at small strain and then decreased slightly. The breaking energy and strain of the hybrid composite were larger than those of the composites reinforced by polyethylene or glass fiber. The compressive strength of hybrid the composite can be expressed by the law of mixtures.
We propose a new method for measuring flux flow resistivity, and name it the “pulse-excited vibration method, ” This method is capable of evaluating effective flux flow resistivity, which is important to analyze the properties of superconducting bulk materials in a transient mode. In this paper, we describe the pulse-excited vibration method in detail, and estimate the flux flow resistivity of a superconducting bulk sample based on our model. Furthermore, the validity of this method was verified successfully by applying the measurement process to a superconducting tape.