Figure 2a [34] shows the fractional change in resistance for the as-received carbon fiber Nylon-6-matrix composite during heating, in which the temperature was raised from 25 to 350°C at a rate of 0.5°C min'. Two peaks were observed. The onset temperature of the first peak was 80°C and that of the second peak was 220°C. The first peak is attributed to matrix molecular movement above tg ; the second peak is attributed to matrix molecular movement above Tm. Because the molecular movement above Tg is less drastic than that above Tm, the first peak is much lower than the second one. As indicated before, the DSC curve of the as-received composite does not show a clear glass transition (Fig. 1a). Therefore, the resistance is more sensitive to the glass transition than DSC. The onset temperature (220°C) of the second peak (Fig. 2a) is higher than the onset temperature (T =200.9°C) of the DSC melting peak (Fig. 1a) and is close to the melting temperature (Tm218.5°C) indicated by DSC (Fig. 1a). The matrix molecular movement at T is less intense than that at Tm, thereby giving no effect on the resistance curve at T. Another reason may be a time lag between the matrix molecular movement and the resistance change.