Transverse characterization of carbon fibers is essential to predict the properties of fiber reinforced composites. The transverse and longitudinal coefficients of thermal expansion are evaluated at cryogenic (~ -180°C) and high temperatures (~ 1100°C), by measuring the contraction or expansion of the fiber, from the images taken in a transmission electron microscope equipped with a cooling as well as heating stage. The specimen is rotated about its axis so as to take images of different cross sections along the same fiber for analyzing the orthotropy in transverse properties. Tests conducted reveal that the transverse and longitudinal CTE’s of PAN based IM7 fibers are 6 x 10^-06 /°C and -4.17 x 10^-07 /°C respectively. We also plan to study the influence of the transverse structure of the fiber on the CTE. The generated data will be used as an input to a finite element model for predicting the residual stresses in a composite. 

• "Transverse and Longitudinal CTE Measurements in TEM at Cryogenic and High Temperatures"
  R. Kulkarni, O. Ochoa and Z. Luo
  28th Annual Conference on Composites, Materials and Structures
  Cocoa Beach, Florida [January 2004]