LS-DYNA复合材料建模教程

Modeling of Composites in LS-DYNA LSSome Characteristics of Composites Orthotropic Material Coordinate System UserUser-defined Integration Rule for Shells Output for Composites Some Characteristics of Several Composite Material Models in LS-DYNA LSClosing Recommendations

Two General Classes of CompositesAdvanced composites have stiff, high strength fibers bound in a matrix material. Each layer/lamina/ply is orthotropic by nature as the fibers run in a single direction. Usually, an advanced composite section will have multiple layers and each lamina within the stack will have the fibers running in a different direction than in the adjacent lamina.

A sandwich composite section has laminae which may be individually isotropic but the material properties and thickness may vary from lamina to lamina. A foam core composite is a particular type of sandwich composite where a thick, soft layer of foam is sandwiched between two thin, stiff plies.

Orthotropic Materials in LS-DYNA LSOrthotropic material constants are defined in the material coordinate system. system. The material coordinate system must be initially established for each orthotropic element and, in the case of shells, for each through-thickness integration throughpoint as well. This orientation comes from three sources. In the material definition (*mat) See description of “AOPT” in User’s Manual under *mat_2 (orthotropic_elastic) (orthotropic_elastic) In the section definition (*section_shell) (*section_shell) A “beta” angle is given for each integration point Optionally, in the element definition (*element_shell_beta, (*element_shell_beta, *element_solid_ortho) element_solid_ortho)

Orthotropic Materials in LS-DYNA LS-

As the solution progresses and the elements rotate and deform, the material coordinate system is automatically updated, following the rotation of the element coordinate system. system. The orientation of the material coordinate system and thus response of orthotropic shells can be very sensitive to ininplane shearing deformation and hourglass deformation, depending on how the element coordinate system is established. To minimize this sensitivity, “Invarient Node Numbering”, “Invarient invoked by setting INN = 2 (shells) or 3 (solids) in *control_accuracy is highly recommended.

UserUser-Defined (Through-Thickness) Integration (Through-

Gaussian or Lobatto integration rules have prepreestablished integration point locations and weights (NIP <= 10). Lobatto includes integration points on the outside surfaces

Trapezoidal integration has equally spaced integration points. For composites, the user may need to define his/her own integration point locations and weights (corresponding to ply thicknesses) and may need to reference a different set of material constants for each integration point.

UserUser-Defined Integration (970)*PART material 1 1 1 11 *PART material 2 2 1 12 $---+----1----+----2----+----3----+--

--4----+----5----+----6*SECTION_SHELL 1 2 -20 18.000000 18.000000 18.000000 18.000000 *mat_layered_linear_plasticity 11, 2.7e-6, 73.4, 0.32, 1e9 Negative value indicates user integration rule

*mat_layered_linear_plasticity 12, 6.3e-7, 0.286, 0.3, 1e9

*INTEGRATION_SHELL 20,8,0 -.9722, .02778, 1 -.9167, .02778, 1 -.6667, .22222, 2 -.2222, .22222, 2 .2222, .22222, 2 .6667, .22222, 2 .9167, .02778, 1 .9722, .02778, 1 *ELEMENT_SHELL 1 1 2 1

1 2

2 3

33 34

32 33

UserUser-Defined Integration (971)$ no *section command needed $ thickness is sum of thick values given in *PART_COMPOSITE $ no need for multiple *PART commands $ *PART_COMPOSITE $ pid, elform 1, 2 $ mid, thick, beta,,mid,thick,beta 11, 0.5,,, 11, 0.5 12, 4.0,,, 12, 4.0 12, 4.0,,, 12, 4.0 11, 0.5,,, 11, 0.5 *mat_layered_linear_plasticity 11, 2.7e-6, 73.4, 0.32, 1e9

$ NOTE: foam core could use a different $ material model (971) *mat_layered_linear_plasticity 12, 6.3e-7, 0.286, 0.3, 1e9

*ELEMENT_SHELL 1 1 2 1

1 2

2 3

33 34

32 33

Output for CompositesFor composite material models, stresses (and strains) will be written in the material coordinate system rather than the global coordinate system if CMPFLG (and STRFLG) is set to 1 in *database_extent_binary. Useful option for postprocessing of fiber and matrix stresses.

Set MAXINT in *database_extent_binary to the total number of through-thickness integration points in throughyour composite shell. By default, stresses only at the top, bottom, and middle integration points are written.

Output for Composites

Some composite material models have “extra history variables” that help to track modes of failure in each integration point. (See material documentation in the User’s Manual for details.) NEIPS (shells) or NEIPH (solids) in *database_extent_binary should be set to the number of extra history variables needed. For example, if you want to track the damage parameter (6th extra history variable) in mat_054, set NEIPS to 6.

Composite Material Models*mat_2 (elastic_orthotropic) 9 elastic constants (solids); 6 elastic constants (shells). Total Lagrangian formulation (okay for large elastic deformations). No failure criteria. Each of the following orthotropic materials offer a particular brand of fiber/matrix damage and failure criteria. Up to 5 strength values are given (XT, XC, YT, YC, SC). *mat_22 (composite_damage) *mat_54,55 (enhanced_composite_damage) *mat_58 (laminated_composite_fabric) *mat_158 like 58 but includes strain rate effects *mat_59 (composite_failure(_shell, _solid)_model) Mats 22 and 59 can be used with shells and solids

Composite Material Models

The paper "Crashworthiness Analysis with Enhanced Composite Material Models in LS-DYNA - Merits and LSLimits", Schweizerhof et al, 5th International LS-DYNA LSUser's Conference (1998) provides some insight into several co …… 此处隐藏：4679字，全部文档内容请下载后查看。喜欢就下载吧 ……