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Unformatted text preview: 06Ch06.qxd 9/24/08 5:32 AM Page 497 6
Stresses in Beams
(Advanced Topics) Composite Beams
When solving the problems for Section 6.2, assume that the
component parts of the beams are securely bonded by
adhesives or connected by fasteners. Also, be sure to use the
general theory for composite beams described in Sect. 6.2. y Problem 6.2-1 A composite beam consisting of fiberglass
faces and a core of particle board has the cross section
shown in the figure. The width of the beam is 2.0 in., the
thickness of the faces is 0.10 in., and the thickness of the
core is 0.50 in. The beam is subjected to a bending moment
of 250 lb-in. acting about the z axis.
Find the maximum bending stresses sface and score
in the faces and the core, respectively, if their respective
moduli of elasticity are 4 106 psi and 1.5 106 psi. 0.10 in.
z 0.50 in. C 0.10 in.
2.0 in. Solution 6.2-1 Composite beam
hc 2 in. h 0.5 in. E1 4 I1 b3
12 I2 bh3
12 0.7 in.
M 250 lb-in. 6 10 psi E1I1 + E2I2 h3)
c E2 1.5 106 psi 0.03633 in.4 0.02083 in.4
From Eq. (6-6b): score 176,600 lb-in.2 From Eq. (6-6a): sface ; M(h/2)E1
E1I1 + E2I2 ; 1980 psi ; M(hc / 2)E2
E1I1 + E2I2 ; 531psi ; ; 497 ...
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- Fall '11