Users:General FEM Analysis/Elements Reference/Shell9 Composite

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The element formulation is based on the Shell8. It contains further developments for layered composite shells.

Contents

Input Parameters

Parameter Description

Compulsory Parameters
Parameter Values, Default(*) Description
MAT EL-MAT int Linking to a material input block
INT_TYPE_SHELL9 FULL Control of integration type
ANS NONE, Q, T, QT, TQ Assumed Natural Strains (ANS) method:
  • NONE: ANS is not activated
  • Q: ANS against shear locking is activated. It works for 4-noded and 9-noded elements. It causes a constant-linear (linear-quadratic, respectively) interpolation of the transverse shear strains and thus avoids transverse shear locking. The approach for the 4-noded element represents the well-known Bathe-Dvorkin-Element (MITC-4).
  • T: ANS against curvature thickness locking
EAS M,B,T,Q,S Enhances Assumed Strains (EAS) method
  • M: Number of enhanced membrane modes. M = {1,(2),4,5,7} for 4-noded Elements, M = {(7),9,11} for 8- or 9-noded Elements
  • B: Number of enhanced bending modes. B = {4,5,(6),7} for 4-noded Elements, B = {9,11} for 8- or 9-noded Elements
  • T: Number of enhanced modes in thickness direction. T = {1,3,4,6,8,9} for all Elements. Recommended: 1 (3-noded), 4 (4-, 8- and 9-noded), 3 (6-nonded)
  • Q: Number of const. transverse shear modes. Q = {2,4} for 4-noded Elements, Q = {2,4,6} for 8- or 9-noded Elements
  • S: Number of lin. transverse shear modes. S = {2,4} for 4-noded Elements, S = {2,4,6} for 8- or 9-noded Elements
FORCE XYZ, RST_ORTHO, RST, MAT_DIRECTION Output control for stress constraints
  • XYZ:
  • RST_ORTHO:
  • RST:
  • MAT_DIRECTION:
SDC real condition factor for director length, recommended value: 1.0
MATERIAL_ANGLE real Fiber orientation angle. The angle is determined with respect to the element's edge from Node 1 to Node 2.
ROTATORIC_DOFS DIR_DIFF, GLOB_6 Switch between director and rotational degrees of freedom.
STRESS_OUTPUT PRIN_VM, SIG_EPS Stress output type
  • PRIN_VM: Von Mises Stresses
  • SIG_EPS: Stress and strains
STRESS_EVAL GP, SURF Stress evaluation location.
  • Gauss Point
  • Surface
Optional Parameters
Parameter Values, Default(*) Description
THICKNESS real Element thickness. This parameter is not compulsory, as the thickness can also be described via nodal values.
MATERIAL_DIRECTION real,real,real Fiber orientation with respect to the global Cartesian coordinate system. The value should be given as vector components.
PROJECTION DIRECTOR, X-AXIS, Y-AXIS, Z-AXIS Used projection method to calculate the material direction which is defined by the variable "MATERIAL_DIRECTION"
FAIL_ID int Failure criterion ID

In addition it is possible to define layer properties individually. Below is a sample input deck for this element.

Example of a Complete Input Block

EL-PROP 1: SHELL9_COMPOSITE
INT_TYPE_SHELL9 = FULL
SDC = 1.0
EAS = 4,4,4,4,4     !4,4,4,4,4    !LIN:4,4,4,4,4	NLN:0,0,0,0,0
ANS = NONE
FORCE = MAT_DIRECTION		!RST  !XYZ  !RST_ORTHO  !MAT_DIRECTION
!  MATERIAL_ANGLE = 0		! orientated wrt edge 1-2
MATERIAL_DIRECTION = 0, 0, 1  	! global cartesian 
PROJECTION = DIRECTOR  !  Y-AXIS   Z-AXIS   
FAIL_ID = 1,2
!-------------------
ROTATORIC_DOFS = DIR_DIFF ! GLOB_6
STRESS_OUTPUT = PRIN_VM 	!PRIN_VM SIG_EPS
STRESS_EVAL   = GP		!GP SURF
!-------------------
  MAT=EL-MAT 1  THICK=0.5  THETA=0		!  PLY 1        bottom
  MAT=EL-MAT 1  THICK=0.5  THETA=90		!  PLY 2          ||
  MAT=EL-MAT 1  THICK=0.5  THETA=90		!  PLY 3          \/
  MAT=EL-MAT 1  THICK=0.5  THETA=0		!  PLY 4         top

Benchmarks

The main benchmark files in the Carat++-repository are

'../examples/benchmark_examples/elements/shell9composite_canti_temperature/cbm_SHELL9comp_temperature.dat'

'../examples/benchmark_examples/elements/shell9composite_canti_temperature_GLOB6/cbm_SHELL9comp_temperature.dat'

'../examples/benchmark_examples/elements/shell9composite_globrot_nln/cbm_SHELL9_NLN.dat'

'../examples/benchmark_examples/elements/shell9composite_globrot_tensile/cbm_TENSILE_SHELL9.dat'

'../examples/benchmark_examples/elements/shell9composite_squareplate_ortho/cbm_shell9comp_plate.dat'

'../examples/benchmark_examples/elements/shell9composite_stress_nln/cbm_shell9comp_plate.dat'

'../examples/benchmark_examples/elements/shell9_GlobRot_moment_load/cbm_shell9_momentload.dat'

'../examples/benchmark_examples/elements/shell9_nln_composite/cbm_composite_nln.dat'

Known Issues

Eigenvalue analysis with DIR_DIFF gives wrong results (AE, SSH;2017)





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