Go Matsubara

Suppression of interfacial crack for foam core sandwich panel with crack arrester

Since delamination often propagates at the interfacial layer between a surface skin and a foam core, a crack arrester is proposed for the suppression of the delamination. The arrester has a semi-cylindrical shape and is arranged in the foam core and is attached to the surface skin. Here, energy release rates and complex stress intensity factors are calculated using finite element analysis. Effects of the arrester size and its elastic moduli on the crack suppressing capability are investigated. Considerable reductions of the energy release rates at the crack tip are achieved as the crack tip approached the leading edge of the crack arrester. Thus, this new concept of a crack arrester may become a promising device to suppress crack initiation and propagation of the foam core sandwich panels.

Evaluation of New Crack Suppression Method for Foam Core Sandwich Panel Via Fracture Toughness Tests and Analyses Under Mode-I Type Loading

A new crack arrester was proposed, in which a different material with higher stiffness is installed on the crack propagation path. The effect of this crack arrester was experimentally evaluated for interfacial crack propagation between a carbon fiber reinforced plastic surface skin and a foam core. The experimental results indicated that the crack arrester increased the critical load of the crack growth, and approximately five times larger apparent fracture toughness was obtained near the leading edge of the arrester by considering the energy release rate. It was also confirmed that the fabrication of the crack arrester had no detrimental effect on the intrinsic properties of the sandwich panel structures.

Development of the Advanced Combustor Liner Composed of CMC/GMC Hybrid Composite Material

Research Institute of Advanced Materials Gas-Generator (AMG), a joint effort by the Japan Key Technology Center and 14 companies in Japan, has, since 1993, been conducting technological studies on an innovative gas generator that will use 20% less fuel, weigh 50% less, and emit 70% less NOx than the conventional gas generator through the use of advanced materials[1].In the course of R&D, the feasibility of applying a gradient composite material with ceramic matrix composite (CMC) and glass matrix composite (GMC), which is expected to reduce the thermal stress of actual parts with temperature distribution, was evaluated based on its mechanical and thermal properties, productivity and stress analysis for an actual part as a combustor liner with 500 mm diameter, and non-cooled combustion tests for the liner outlet temperature of 1873 K.Through our studies we have confirmed the applicability of the selected CMC/GMC hybrid composite as a combustor liner.© 2001 ASME

Effect of Fiber Bridging on Growth Behavior of Mode I Interlaminar Fatigue Cracks in High Strength GFRP

高強度GFRPの モー ドI層 間は く離疲 労 き裂進展 におよぼす 繊維架橋の影響* 松 原 剛*1,尾 野 英 夫*2,田 中 啓 介*3 Effect of Fiber Bridging on Growth Behavior of Mode I Interlaminar Fatigue Cracks in High Strength GFRP Go MATSUBARA*4, Hideo ONO and Keisuke TANAKA *4 KAWAJU TECHNO SERVICE CORP., 3-1 Kawasaki-cho, Akashi-shi, Hyogo, 673-0014 Japan The mode I crack growth behavior from delamination was investigated with two kinds of laminates, UD laminates (made of unidirectional laminates) and C laminates (made of unidirectional laminates and cloth laminates), of high strength glass fiber reinforced plastics (GFRP). Crack growth tests were carried out by double cantilever beam specimens under cyclic and monotonic loadings. The fracture toughness at the onset of crack propagation, C.c., was not influenced by the lot of laminates and nearly equal for UD laminates and C laminates. On the other hand, the increase of the fracture toughness with crack extension, GIR, was very much dependent on the lot, and the value for C maminates was much higher than that of UD laminates. Under cyclic loading with a stress ratio of R=0.1, the fatigue crack propagation rate expressed in terms of a power function of the maximum crack-tip value, GI tipmax, of the energy release rate was nearly identical in UD and C laminates. The increase of the bridging component of the energy release rate, GIbridgemax /GImax, with crack extension was dependent on the lot and the kind of laminates. Fractographic observation of UD laminates showed mode II crack propagation on the surface of fibers, while mode I crack propagation in resin. In C laminates, crack propagation path was on the interface of cloth laminates and fiber bridging caused by fibers of cloth laminates.