Format specification#

This document defines the specification for the HDF5 composite CAE format. Use this format to exchange composite layup data between computer-aided engineering (CAE) tools.

Use the following concepts in this format:

Mesh: A mesh stores geometric information consisting of nodes and elements.
Component: A component represents a layer in the composite structure. Each component references a mesh and data map.
Data map: A data map stores data for each element or node in a mesh, including thickness, reference direction, and fiber direction.

Note

HDF5 is a binary format. Use a viewer such as HDFView to inspect file contents.

Tree overview#

HDF5 composite CAE specification tree — Click to view full size.#

General information#

This section describes general information about the HDF5 composite CAE format.

Node types in HDF5 tree#

Node type	Definition	Examples
Container node	A group node that contains object nodes of the same type.	fabrics, meshes, rosettes
Named object node	Represents a single object. To avoid HDF5 naming restrictions, store the external object name in the `title` attribute. Store object data in attributes or attached data nodes.	fabric, mesh, rosette
Link node	A link node stores dependencies between nodes in the tree.
Data node	A data node stores array or scalar values in its attributes.

Important

To support interoperability with high-level interfaces such as PyTables, use HDF5 node names that match the Perl-compatible regular expression:

^[a-zA-Z_][a-zA-Z0-9_]*$

Node names must be unique within a group.

General rule: all string attributes use UTF-8 encoding.

Root-level nodes#

composite_cae#

Path: composite_cae

All attributes are optional.

Attribute	Type	Values
`format_version`	string	1.0
`last_modified`	datestring	“2010-08-23 13:31:13Z”
`vendor`	string	“ansys, inc.”
`unit_system`	string	“SI”, “Imperial”
`length_unit`	string	“m”, “cm”, “mm”, “um”, “in”
`mass_unit`	string	“kg”, “t”, “g”, “lbf”, “lbm”
`time_unit`	string	“s”
`temp_unit`	string	“C”, “K”, “F”
`angles`	string	“deg”, “rad”

If unit_system is not specified, the importer uses its default unit system. The *_unit attributes override unit_system.

For example, if unit_system is “SI” and length_unit is “mm”, the length unit is “mm”.

Global coordinate system#

Path: composite_cae → global_coord_sys

Field	Type	Description
`global_coord_sys`	4×3 double array	Defines origin and directions for the entire model: `[origin]`, `[dir1]`, `[dir2]`, and `[dir3]` with x/y/z components.

Ansys does not currently support this attribute.

Material data#

Fabric (named)#

Path: material_data → fabrics → fabric(named)

Orientations (obsolete)#

Path: material_data → fabrics → fabric(named) → orientations (obsolete)

Array of doubles.

[0, 45, -45]

Note

Ansys does not read or write this property. This property may be removed in a future release.

Mechanical#

Path: material_data → fabrics → fabric(named) → mechanical

Attribute	Type	Description
`architecture`	string (optional)	uni, woven
`weight_per_area`	double	Weight per area
`cured_thickness`	double	Cured thickness
`E1`	double (optional)
`E2`	double (optional)
`E3`	double (optional)
`G12`	double (optional)
`G23`	double (optional)
`G31`	double (optional)
`v12`	double (optional)
`v13`	double (optional)
`v23`	double (optional)
`alpha1`	double (optional)
`alpha2`	double (optional)
`alpha_ref_temp`	double (optional)

Cost#

Path: material_data → fabrics → fabric(named) → cost

Attribute	Type	Description
`currency`	string	EUR, USD, etc.
`cost_per_area`	double

Stackup (named)#

Path: material_data → stackups → stackup(named)

Cost#

Path: material_data → stackups → stackup(named) → cost

Attribute	Type	Description
`currency`	string	EUR, USD, etc.
`cost_per_area`	double

Fabric#

Path: material_data → stackups → stackup(named) → fabric

Attribute	Type	Description
`number`	unsigned	Defines the order of fabrics within the stackup.
`angle`	double	Angle of the fabric within the stackup.

Meshes#

Mesh (named)#

Path: meshes → mesh(named)

Node labels#

Path: meshes → mesh(named) → node_labels

Field	Type	Description
`node_labels`	n×1 integer array	Unique node identifiers.

Nodes#

Path: meshes → mesh(named) → nodes

Field	Type	Description
`nodes`	n×3 double array	Node coordinates `(x, y, z)`.

Element labels#

Path: meshes → mesh(named) → element_labels

Field	Type	Description
`element_labels`	n×1 integer array	Unique element identifiers.

Element types#

Path: meshes → mesh(named) → element_types

Field	Type	Description
`element_types`	n×1 integer array	Element type identifier for each element.

Supported element types:

3-node shell
4-node shell
6-node shell
8-node shell

The list of element types may expand in future releases, for example with 108 and 120 for 8-node and 20-node bricks.

Element nodes#

Path: meshes → mesh(named) → element_nodes

Field	Type	Description
`element_nodes`	n×m variable-length integer array (VLArray)	Node indices for each element.

Defines element nodes. Node indices point directly to entries in the nodes and node_labels arrays.

Node order must follow the indices shown below:

3 nodes (linear triangle): I, J, K
4 nodes (linear rectangle): I, J, K, L
6 nodes (quadratic triangle): I, J, K, M, N, P
8 nodes (quadratic rectangle): I, J, K, L, M, N, O, P

Note

A VLArray (variable length array) is used to support different element types (see meshes → mesh(named) → element_types).

Edge set (named)#

Path: meshes → mesh(named) → edge_sets → edge_set(named)

Field	Type	Description
`edge_set`	n×1 unsigned integer array	Node indices that reference nodes in this set.

Element set (named)#

Path: meshes → mesh(named) → element_sets → element_set(named)

Field	Type	Description
`element_set`	n×1 unsigned integer array	Element indices that reference elements in this set.

Components#

Component (named)#

Path: components → component(named)

Attributes:

Attribute	Type	Description
`type`	string	ply, core, etc.
`layer_id`	integer	The step value and global identifier. It defines ply order from bottom to top.
`orientation`	double	The nominal orientation angle relative to the reference direction.
`mapping_type`	string

Note

The mapping_type attribute is optional and is detailed later. Because ACP can use multiple rosettes to define a ply’s reference direction, several mapping types are defined, including interpolation algorithms such as “minimum distance” and “minimum angle.”

Placement coordinate system#

Path: components → component(named) → placement_coord_sys

Field	Type	Description
`placement_coord_sys`	4×3 double array	Placement coordinate system rows: `[origin]`, `[dir1]`, `[dir2]`, and `[normal]` with x/y/z components.

The placement_coord_sys has two purposes:

Its normal defines the default offset direction of the layup.
Its origin and dir1 define the starting point and initial direction of the draping calculation.

Material#

Path: components → component(named) → material

Softlink

Defines the ply material and refers to an object in material_data → fabrics or material_data → stackups.

Element set#

Path: components → component(named) → element_set

Softlink

Defines a link to an element set of a mesh and specifies the ply extent.

Data map#

Path: components → component(named) → data_map

Softlink

Defines a link to the data map of this component.

The following rules apply:

If the data map contains a thickness, a material of type material_data → stackups is not supported.
If data_map → thickness is not defined, thickness is computed from cured_thickness when the material is a fabric, or from the sum of all cured_thickness values when material_data → stackups.
If matorient_1_angles is not present, it is set equal to component → orientation.
If matorient_2_angles is not present, it is computed as: matorient_2_angles = matorient_1_angles + 90°.

Rosette (named)#

Path: components → component(named) → rosettes → rosette(named)

Softlink (Optional)

Defines a link to the rosettes of this component.

Rosettes#

Rosette (named)#

Path: rosettes → rosette(named)

Attributes:

Attribute	Type	Description
`mapping_type`	string

Note

The possible values of the rosette mapping_type are not yet specified. FiberSIM defines the mapping types as “translational”, “standard”, or “rotational”. ACP defines the standard rosette types as “parallel”, “radial”, “cylindrical”, or “spherical”. The exact definition of this attribute has been postponed because this information is optional and is not required to map the ply orientation field correctly.

Coordinate system#

Path: rosettes → rosette(named) → coord_sys

Field	Type	Description
`coord_sys`	4×3 double array	Rosette coordinate system rows: `[origin]`, `[dir1]`, `[dir2]`, and `[normal]` with x/y/z components.

Data maps#

Data map (named)#

Path: data_maps → data_map(named)

Element/node set link#

Path: data_maps → data_map(named) → element_set/node/node_set

Field	Type	Description
`element_set` / `node_set`	softlink	Link to a mesh element set or edge set where orientations, thicknesses, and other values are defined.

Reference directions#

Path: data_maps → data_map(named) → reference_directions

Field	Type	Description
`reference_directions`	n×3 double array	Reference directions as absolute direction vectors.

Normals#

Path: data_maps → data_map(named) → normals

Field	Type	Description
`normals`	n×3 double array (optional)	Normal directions as absolute vectors used to project the reference direction onto the normal plane.

Matorient 1 angles#

Path: data_maps → data_map(named) → matorient_1_angles

Field	Type	Description
`matorient_1_angles`	n×1 double array (optional)	Material orientation 1 angles relative to the reference direction and given normal.

Matorient 2 angles#

Path: data_maps → data_map(named) → matorient_2_angles

Field	Type	Description
`matorient_2_angles`	n×1 double array (optional)	Material orientation 2 angles relative to the reference direction and given normal.

Thicknesses#

Path: data_maps → data_map(named) → thicknesses

Field	Type	Description
`thicknesses`	n×1 double array (optional)	Position-dependent thickness values.

Scalar user data (named)#

Path: data_maps → data_map(named) → scalar_user_data → scalar_user_data(named)

Field	Type	Description
`scalar_user_data`	n×1 double array (optional)	User-defined scalar data field. Only supported by Ansys.

Attribute	Type	Values
`unit_type`	string	“dimensionless”, “length”, “mass”, “time”, “temp” (default: “dimensionless”)

Component groups#

Component group (named)#

Path: component_groups → component_group(named)

Component groups are optional. You can define them to store grouping information of components.

Change log#

Date	Description
May 5, 2010	ACP–FiberSIM Interface Format Specification Rev 01
June 5, 2010	HDF5 Composite CAE Data File Specification Proposal version 1.1
Aug 10, 2010	HDF5 Composite CAE Data File Specification Release Candidate 1 for stable version 1.0.
Aug 11, 2010	Minor updates in “Open Questions”, added Section “Specification of Node Names”
Aug 30, 2010	Upgrade specification to match all issues recently discussed with Vistagy via emails
Mar 17, 2011	Cleanup the document a little
Oct 17, 2014	Adding component_groups and component_group nodes
June 28, 2019	Adding some additional information
January 24, 2020	Corrected name for matorient_angles: “mat_orient1_angles” to “matorient_1_angles” and “mat_orient2_angles” to “matorient_2_angles”. Defined which fields in data_map are optional and specify what happens if optional nodes are missing. Clarified use of placement_coord_sys
September 15, 2020	Mentioned that global_coord_sys is currently not supported. Correct what happens when matorient_1_angles are not present
January 26, 2022	Mark `material_data->fabrics->fabric(named)->orientations` as obsolete
February 4, 2022	Change Href to Softlink for items that have to be linked with a Softlink
February 8, 2022	Correct datatype for element_labels, element_nodes and element_types (now int), clarified layer id
February 17, 2022	Clarified units specification, Mark optional material properties as optional
May 12, 2022	Add optional scalar_user_data data_map property
May 31, 2022	Improved formatting, Removed outdated future plans section. Added missing rosettes in component
May 22, 2023	Improve documentation of node order
May 15, 2024	Complete supported units
June 21, 2024	Clarified orientation
April 14, 2024	Some clarifications