Flexure Testing of Glass Fibers
in Materials Testing Laboratory at the University of Missouri-Rolla
Photos by Jeff Thomas, January 18, 2000.

 

Click on value for raw data and load-deflection curve.

		Flexure Modulus (GPa)
		NAP-3	Silica	Silica McDo	F43	Silica K Old
Sample	1	45.69*	71.60*	72.99	77.07	87.45
	2	68.50	77.23	75.74	79.89	88.71
	3	56.41	79.13	74.99	65.52	88.69
	4	67.22	78.35	75.80	68.71	91.15
	5	62.97	79.35	73.88	70.19	91.00
	6	58.75	79.52		73.55	91.89
	7				65.72	88.98
	8				67.27
	9
	10
Average		62.77	78.72	74.68	70.99	89.70
STD		4.68	0.84	1.09	5.00	1.52

* Eliminated from average due to improper span measurement

Click on image to enlarge.

Derivation of E

From beam deflection theory for 3-point bending,

y = x(3L² - 4x²)P / 48EI_NA

where

y = deflection of middle of beam (read by Instron 4469 UTM)
x  = L / 2
L = span
P = load (read in grams using gram-scale)
E = flexure modulus
I_NA = moment of inertia about the neutral axis = pr⁴ / 4 (for cylindrical samples)

Rearranging,

E = (P/y)L³  / 12pr⁴