The transverse and longitudinal coefficients of thermal expansion (CTE) of carbon fibers are important parameters in C/C composites behaviour. In this study, the measurements of CTE are presented at very high temperatures (up to 2500 K). Experimental validations are first realised on isotropic metallic (tungsten) fiber. Then, measurements are performed on four carbon fibers (rayon-based, PAN-based and pitch-based). The results show that the mean transverse CTE varies from 5 x 10~(-6) K~(-1) to 10 x 10~(-6) K~(-1) and the longitudinal one from 1.6 x 10~(-6) K~(-1) to 2.1 x 10~(-6) K~(-1) depending on the fiber structural properties. For that, the relationships between the structural properties and the heat treatment temperature of the carbon fibers are discussed in relation to thermal expansion behaviour. A calculation of the ratio between the transverse and the longitudinal measured CTE as a function of the temperature allows us to classify fibers from the most isotropic to the most anisotropic in relation with the structural properties measured at room temperature.
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机译：碳纤维的横向和纵向热膨胀系数（CTE）是C/C复合材料性能的重要参数。在这项研究中，CTE的测量值是在非常高的温度（高达2500 K）下进行的。首先在各向同性金属（钨）纤维上实现了实验验证。然后，对四种碳纤维（人造丝基、PAN基和沥青基）进行测量。结果表明：根据纤维结构性质的不同，平均横向CTE在5 x 10~（-6） K~（-1）至10 x 10~（-6） K~（-1）之间变化，纵向CTE在1.6 x 10~（-6） K~（-1）至2.1 x 10~（-6） K~（-1）之间变化。为此，讨论了碳纤维的结构性能与热处理温度之间的关系与热膨胀行为的关系。通过计算横向和纵向测量的 CTE 之间的比率作为温度的函数，我们可以根据在室温下测量的结构特性，将纤维从各向同性到各向异性进行分类。
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