Kazuhisa Harakawa

Analysis of the Thermal Expansion Coefficients of Particle-Filled Polymers

An attempt has been made to predict the thermal expansion coefficients of particle-filled polymers in which particles have various types of orienta tion distributions. The calculation is based on Eshelbys theory and a kind of self-consistent method is introduced to estimate the effect of the orien tation distribution together with the interaction among particles. The ex pression for the space random orientation of disk-shaped particles with infinitesimal aspect ratio, which is derived here, agrees with lower bound of isotropic composites predicted by Schapery. The calculated results are also compared with existing experimental data for glass particle-epoxy resin composites, and these are almost in good agreement.

A Study of Throstle-spun-silk/Raw-silk Core-spun Yarn Part III: Yarn Appearance

Using different spinning systems, the experimental core-spun yarns are made from the same fiber material under the same yarn conditions, namely, yarn count, twist factor, and fiber composition. The shape factor is adopted to evaluate the core eccentricity expressed as the position of the continuous-filament core yarn in the cross section of the core-spun yarn. The bispectrum is applied to consider the yarn irregularity in spectral analysis. The characteristic-appearance of the throstle-spun yarn is discussed and compared with that of the ring-spun yarn.

A Study of Throstle-spun-silk/Raw-silk Core-spun Yarn Part II: Stuffer-tube Motion

The importance of stuffer-tube dimensions and motion on yarn regularity when a throstle-spinning system is used is demonstrated. A description is given of some attempts to produce longer yarn without piecing and to improve yarn quality. Yarn properties are discussed in relation to the vertical motion of the stuffer tube.

A Study of Throstle-spun-silk/Raw-silk Core-spun Yarn Part I: Yarn Properties

Throstle spinning, or ‘Gara-bo’ spinning, is one of the simplest spinning methods, and the method of operation is explained. A mechanism for producing throstle-spun-silk/raw-silk core-spun yarn is described. Yarn properties are discussed in relation to three mechanical factors of the machine.

Thermal expansion coefficients of unidirectional carbon fiber/PEEK composite made of commingled yarns

Unidirectional carbon fiber (CF)/poly(ether‐ether‐ketone) (PEEK) composite was manufactured from the commingled yarns composed of CF and PEEK filaments (this composite is named ‘‘commingled composite’’). The thermal expansion coefficient (TEC) of the commingled composite was measured and compared with that of CF/PEEK unidirectional composite made of prepreg sheets (this composite is named ‘‘prepreg composite’’). The minimum value of TEC’s parallel to the fiber direction was observed at around 150 °C for both specimens which were not thermally treated. This minimum disappeared after the thermal treatment at 230 °C for 30 min or the repeating measurements (0 °C→230 °C, 0 °C→230 °C,...). While the TEC of the prepreg composite was almost independent of temperature, that of the commingled composite showed a remarkable decrease at temperatures above the glass transition temperature (Tg) of PEEK. This could be interpreted in terms of the orientation distribution of carbon fibers in the commingled composite. The ...