corresponding to the type of loadings in the numerators (tension or compression). Safety factor:Let a<1 the Hill-Tsai expression found for a state of stress o,o,Te.One can then increase the load by means of a multiplication coefficient k to reach the limit as: (ka (ke)(o(ko)()=d=1 o 01 o rupture rupture rupture rupture The margin of safety can then be defined as the expression: (ko)-g!=k-1 O which can also be written as: safety factor 14.3 VARIATION OF RESISTANCE OF A UNIDIRECTIONAL PLY WITH RESPECT TO THE DIRECTION OF LOADING 14.3.1 Tension and Compression Resistance We propose to evaluate the maximum stress ox that one can apply on a ply in the direction x in Figure 14.3.The stresses 0 o,ta in the orthotropic axes are given by Equation 11.4 as: 「c2 s2 -2cs 6￥ c2 2cs 0 -cs (c2-3) 0 Figure 14.3 Direction of Loading Distinct from Orthotropic Axes 2003 by CRC Press LLCcorresponding to the type of loadings in the numerators (tension or compression).
Safety factor: Let a2 < 1 the Hill–Tsai expression found for a state of stress s
, st , t
t. One can then increase the load by means of a multiplication coefficient k to reach the limit as: The margin of safety can then be defined as the expression: which can also be written as: 14.3 VARIATION OF RESISTANCE OF A UNIDIRECTIONAL PLY WITH RESPECT TO THE DIRECTION OF LOADING 14.3.1 Tension and Compression Resistance We propose to evaluate the maximum stress sx that one can apply on a ply in the direction x in Figure 14.3. The stresses s
, st , t
t in the orthotropic axes are given by Equation 11.4 as: Figure 14.3 Direction of Loading Distinct from Orthotropic Axes ks
( )2 s
2 --------------- kst ( )2 s t 2 -------------- ks
( ) kst ( ) s
2 -------------------------- kt
t ( )2 t
t 2 + – + --------------- k2 a2 = = 1 rupture rupture rupture rupture ks
( ) – s
s
------------------------- = k – 1 safety factor 1 a = --- – 1 s
st Ót
t˛ Ô Ô Ì ˝ Ô Ô Ï ¸ c 2 s2 2– cs s 2 c2 2cs cs cs – c 2 s 2 ( ) – sx 0 0 Ó ˛ Ô Ô Ì ˝ Ô Ô Ï ¸ = TX846_Frame_C14 Page 280 Monday, November 18, 2002 12:30 PM © 2003 by CRC Press LLC