There are many kind of "local axes" for shells.
 
Element coordinate system, element direction and material direction can be
relatively complicated and confusing. I will try to explain how things
works for shell elements in LS-PrePost:
 
The local x-axis is by definition from N1 to N2, see Figure 14.8 in the 971
manual. Element local y- and z-axis is obtained from the cross product of
local x axis and the element normal direction. The element x-axis direction
can be displayed in LS-PrePost By toggle the ident-Element-Elem Dir toggle
button and then select elements. I call this the ELEMENT COORDINATE SYSTEM.
 
Then you also have a reference material direction which can be set on the
*ELEMENT_SHELL card using the _BETA option, see remark 6 on *ELEMENT_SHELL
in v971 manual. I call this ELEMENT REFERENCE SYSTEM Note that this
direction still is an element property. No material card is needed to
define this direction. This element direction can be displayed, set and/or
modified in ElEdit-Direction. This is the direction which defines the base
orientation when AOPT=0 is used on the material card. This is a very
convenient way of applying the reference material direction to the elements.
I would recommend this way of setting the material direction in most
situations.
 
The MATERIAL DIRECTION for each ply or integration point is defined from
the base direction adding a layer offset angle, beta_i, see remark 6 on
*ELEMENT_SHELL in v971 manual. This material direction can be displayed in
LS-PrePost by set the toggle Ident-Element-Mat Dir and then select elements.
 
Finally, to create, view and/or modify element directions for
*element_shell_composite elements, I recommend to use "Element Tools" -
"Element Editing" - "Composite" in v4.1. This defines a element reference
system per layer in the composite and is designed to be used in combination
with AOPT=0, which makes it equivalent to material system.
 
Easy? ;)
 
regards,
Anders
anders.jernberg@dynamore.se
1/8/14 (in LS-PrePost User Group)