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Cryogenic technologies group
Material Properties: Kevlar 49 Composite
 Data Available:
 Thermal Conductivity

Material Description: Kevlar 49 Composite

Kevlar 49 aramid fiber (65-70% by volume)
Epoxy (30-35% by volume)
Along fiber direction


Thermal Conductivity

a -2.65
b 1.986637
c 1.24851
d 0.57
e -8
data range
equation range
curve fit standard
error relative to data


Has equation of the form:
Therefore k Solves as:

Coefficients a f are summarized in the appropriate table and

  T is the temperature in K (x-axis), and y is Thermal Conductivity, k to solve for.
  "erf(x)" is the Gauss error function and "exp()" is the exponential.
NOTE: The error function (sigmoid shape) is used to blend fits over separate temperature ranges.

The error function ‘erf(x)’ (also known as the Gauss error function) is defined as:

(When x is negative, the integral is interpreted as the negative of the integral from x to zero.)

In Excel the error function may be calculated by employing the following format ‘ERF( lower_limit, upper_limit)‘ or simply ‘ERF(value of x)‘. For example ERF(0, 1.5) = ERF(1.5) which results in the integral of error function between 0 and 1.5. Excel 2010 and later evaluate correctly for both possitive and negative values of x. Whereas earlier versions can only evaluate for positive values of x (ie x > 0). Thus one must employ –ERF(x) = ERF(-x) to evaluate negative values of x properly in earlier versions of Excel (prior to 2010).

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