a fiber the assumptions were as follows calculations were based on ambient conditions in air the load was the pressure drop acting directly towards the fiber the load was uniform over the fiber length there was no fiber overlapping the load was calculated from the applied pressure for example 70 gram force square millimeter 100 psi and the fiber surface area exposed to that pressure from the preceding equations one may derive an expression for calculating u201c stiffness u201d these equations may be applied to fibers of regular or irregular cross sectional shape an example of stiffness calculations for fibers having circular cross sections is given below the deflection is proportional to 1 stiffness and the w and i in eq 1 were kept constant for all the fibers and the stiffness was thus calculated table 1 presents u201c stiffness factors u201d defined as the ratio of the stiffness of a given fiber to the stiffness of a glass fiber gl used in experiments that will be described later in the examples section the glass fibers had a young 39 s modulus of 65 gpa a 20 micron diameter and were 12 mm long the nature of the polypropylene fm nylon nl and crosslinked polyvinyl alcohol r1 and r2 fibers will also be described later in more detail the calculation of the stiffness or stiffness factor for the.