Page 22 - Mechanics Analysis Composite Materials

Chapter 1. Introduclion 7
Table 1.1 (Contd.)

Material Ultimate Modulus E Specific Maximum Maximum
tensile stress, (GPa) gravity specific specific
C (MPa) strength, modulus,
k, x lo3(m) kF: x IO3(m)
Polyethylene (20-40) 2600-3300 120-170 0.97 310 17500
Carbon (5-1 1)
High-strength 7000 300 1.75 400 17100
High-modulus 2700 850 1.78 150 47700
Boron (1O(r200) 2500-3700 39M20 2.5-2.6 150 16800
Alumina - A1203 (20-500) 240W100 470-530 3.96 100 13300
Silicon Carbide - Sic (1&I 5) 2700 185 2.4-2.7 110 7700
Titanium Carbide - Tic (280) 1500 450 4.9 30 9100
Boron Carbide - B& (50) 2 100-2500 480 2.5 100 10000
Boron Nitride - BN (7) 1400 90 1.9 70 4700

Fig. 1.4. Introduction of secant and tangent moduli.

Fig. 1.5. Stress-strain diagram for elastic-plastic material.

However, in application to particular problems, this model can be usually
substantially simplified. To show this, consider the bar in Fig. 1.1 and assume
that force F is applied at the moment t=O and is taken off at moment t = tl as
shown in Fig. 1.6(a). At the moment t =0, elastic and plastic strains that do not
depend on time appear, and while time is running, the creep strain is developed. At