抄録
Thermo-mechanical properties of three-dimensional (3D) fabric composites have been studied systematically. The fiber orientation distribution and the maximum volume fraction of various 3D-microtextures were at first examined. The fiber structures which could be fabricated are shown to be derived from the polyhedra which completely fill up the three dimensional space.
Then, analytical studies for the elastic moduli and thermal expansion coefficients were carried out to clarify the relationship between the fiber textures and the thermo-mechanical properties. Although the complete isotropy of the moduli was obtainable theoretically by adequately placing reinforcing fibers in 6 directions, it was difficult to fabricate the preform with high fiber volume fraction. Among practical preforms, those with 3, 4, and 7 reinforcing axes are suggested to be useful for tailoring the thermomechanical properties.
Next, the strength and fracture toughness were examined mainly for the tri-axial 3D composites. It was shown that the strength of the tri-axial 3D composites could be predicted by the rule of mixture but the fracture toughness was extraordinarily high compared with the laminate composite. The reason for this high toughness was suggested to be weak interface between the fiber and matrix caused by thermal mismatch between the constituents and 3D constraint by reinforcements.
Finally, the effectiveness of the use of 3D composites in an actual applications are exemplified by picking up a 3D-reinforced truss joint frequently used in space structures as an example.
