What is the coefficient of thermal expansion?
We know that thermal expansion and contraction are a natural phenomenon, but we have not studied its principles in depth. The phenomenon of expansion and contraction of objects due to temperature changes is called thermal expansion and contraction. The most critical factor of change is temperature. Under the same atmospheric pressure, the volume change of an object caused by a unit temperature change is called the thermal expansion coefficient. The thermal expansion coefficient is also divided into linear expansion coefficient and volume expansion coefficient. The former is a one-dimensional space perspective, and the latter is a three-dimensional space perspective.
1. Linear expansion coefficient: For an object that can be approximately regarded as one-dimensional, length is the decisive factor in measuring its volume. The definition of thermal expansion coefficient at this time can be simplified as: the ratio of the increase in length under a unit temperature change to the original length.
2. Volume expansion coefficient: For three-dimensional anisotropic substances, there are linear expansion coefficients and volume expansion coefficients. For example, the graphite structure has significant anisotropy, so the linear expansion coefficient of graphite fiber also shows anisotropy, which is manifested in that the thermal expansion coefficient parallel to the layer direction is much smaller than the direction perpendicular to the layer layer.
Comparison of thermal expansion coefficients between steel and carbon fiber
The coefficient of thermal expansion refers to any change in linearity, width, thickness or diameter of a solid when it is heated, and is represented by the symbol R, which is the relative change in length when the temperature changes by IK, and its unit is 1/K.
1. The expansion coefficient of steel is: 1.2*10^-5/K
2. The thermal expansion coefficient of T300 carbon fiber is -0.74×10^6/K
3. The thermal expansion coefficient of M40 carbon fiber is -1.23×10^6/K.
Before discussing the thermal expansion coefficient of steel and carbon fiber, one issue needs to be clarified. The thermal expansion coefficient is defined within a certain range. Below or above this temperature range, the coefficient of thermal expansion can change dramatically.
After comparing the thermal expansion coefficients of steel and carbon fiber, we found that they are not on the same level. Steel is more than 16 times that of T300 carbon fiber. In actual use, this huge gap can cause huge consequences.
