Characterstic curves of tensile stress versus displacement(σ-δ curve)for loosely packed powder beds (high void fraction) containing fibrous materials have been measured to evaluate the mixing and unraveling states of fibers as a filler for composite materials by using a separable cell type tensile tester. The values of energy consumption calculated from the σ-δ curves were used to discuss the relationships among unraveling and/or formation of the fiber network state in the bulk powders and

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... imental conditions. As a result, it has been shown that the unraveled degree of fibers could be evaluated by the calculated energy consumption for pulling out a single fiber from the powder bed.