Overview of trends in advanced composite research and applications in Japan

Abstract

Recent research activities in advanced composites technologies conducted in Japan are reviewed and introduced. New research topics in reinforcing fibers described are low modulus pitch-based carbon fiber and PBO fiber. The second of these is very topical at the present time: nano-technology based composites use materials such as carbon nanotube, or carbon nano-fiber, or nanoclay. Because the Composites Technology Center in the Japan Aerospace Exploration Agency (JAXA) leads many new research fields in composites, the present review paper shows a slight bias towards the outputs of JAXA. The most remarkable outcome in this field at present is a compression strength improvement by loading cup-stack type carbon nano-fiber (CSCNF). Prepreg containing this CSCNF has been developed and has already been rerleased into the market. The third topic is related to newly developed high performance polymers including heat resistant polyimide, Tri A-PI and its family. The most recent product is a heat resistant polyimide that is highly soluble in some organic solvents; this material is suitable for preparation of imide wet prepreg. Composites fabricated through this prepreg route exhibit no voids and defects compared to the traditional amid-acid polyimide prepreg route. Another new topic in polymers is related to Japan's national project, radiation cure polymers and their processing. Electron beam cure, ultra-violet cure and visual light cure resins and their processing technologies have been developed in this national project. The next topic is a development of the low cost composites technology mainly for aircraft components. JAXA's activities related to this field are introduced first based on two new key technologies — Z-anchor® and stitching. New findings about the mechanism of interlaminar reinforcement by stitching are slightly focused. Finally, remarkable theoretical findings about composite mechanics in recent years are described. A clarification of mechanics of compression after impact behavior by using a newly developed cohesive zone element is reviewed first in this category. Matrix crack growth theories in the laminae adjacent to the initially cracked layer are introduced next where a motivation of this research is a cryogenic composite tank for future space transportation systems. The final topic is a development of the theory of structural health monitoring by using small diameter FBG sensor. By an evolution of these theories structural health monitoring has almost reached the level of practical applications.