HDF5 Composite CAE Specification#

This document describes the HDF5 Composite CAE file format specification. This format is used to exchange composite layup information between different CAE tools. The specification document is quite detailed. The most important items are:

  • The mesh is a set of nodes and elements on which you store the geometrical information of the layup

  • A component represents a layer in the layup. It always references a data_map and a mesh. The data_map contains the actual geometrical information for each element or node in the mesh. In the simplest case this is just the thickness and the reference direction/fiber direction.

Since hdf5 is a binary format you need a viewer to look at the file which you can find here:

https://www.hdfgroup.org/download-hdfview/

There are several libraries available to write hd5 files, for example:

Python: https://docs.h5py.org/en/stable/

Tree overview#

HDF5 Composite CAE Specification Tree

Click to view full size#

General information#

Node Types in HDF5 Tree#

Container Node#

Group node which contains a list of object nodes of the same type.

Examples: fabrics, meshes, rosettes

Named Object Node#

Node to specify an object. To avoid naming restrictions of HDF5 nodes, the external object name should be stored in the title attribute of the node.

The associated data of an object is stored in attributes of the object node or attached data nodes.

Examples: fabric, mesh, rosette

Data Node#

Data nodes can either contain array data or scalar data in attributes.

Specification of Node Names#

To provide smooth interoperability with most high-level HDF5 interfaces (for example PyTables), the HDF node names must match the (perl regexp) pattern '^[a-zA-Z_][a-zA-Z0-9_]*$'. The names on the Nodes must be unique within each group.

General Comments#

The encoding of String attributes is UTF8.

Root level nodes#

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”

All properties are optional, if no unit system is specified the unit system of the importer is used. The different *_unit attributes have higher priority than the unit_system attribute. E.g if unit_system is SI and length_unit is mm, mm is used as a length unit.

composite_cae->global_coord_sys#

4 by 3 array of double

[origin x]   [origin y]   [origin z]
[dir1 x]     [dir1 y]     [dir1 z]
[dir2 x]     [dir2 y]     [dir2 z]
[dir3 x]     [dir3 y]     [dir3 z]

Defines the origin and directions of the origin for the entire model. Currently not supported by ansys.

Material Data#

material_data->fabrics->fabric(named)#

material_data->fabrics->fabric(named)->orientations (Obsolete)#

Array of double

[0, 45, -45]

Note

This property is not written or read by ansys. It will be removed in the future.

material_data->fabrics->fabric(named)->mechanical#

Attribute

Type

Description

architecture

string (optional)

uni, woven

weight_per_area

double

cured_thickness

double

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)

material_data->fabrics->fabric(named)->cost#

Attribute

Type

Description

currency

string

EUR, USD, etc

cost_per_area

double

material_data->stackups->stackup(named)->cost#

Attribute

Type

Description

currency

string

EUR, USD, etc

cost_per_area

double

material_data->stackups->stackup(named)->fabric#

Attribute

Type

Description

number

unsigned

Determines order of fabrics within stackup

angle

double

Angle of fabric within stackup

Meshes#

meshes->mesh(named)->node_labels#

n by 1 array of int

[unique node id]

meshes->mesh(named)->nodes#

n by 3 array of doubles

[node x]  [node y]  [node z]

meshes->mesh(named)->element_labels#

n by 1 array of int

[unique element id]

meshes->mesh(named)->element_types#

n by 1 array of int

[element type]

Currently the following element types are defined:

  • 3: 3 node shell

  • 4: 4 node shell

  • 6: 6 node shell

  • 8: 8 node shell

The list of element types might be expanded in the future, for example using 108 and 120 for 8 and 20 node bricks.

meshes->mesh(named)->element_nodes#

n by m VLArray of int

[node 1] [node 2] … [node m]

Defines nodes of elements with node INDICES pointing directly to entries in the nodes/node_labels arrays.

The order of the nodes must correspond to the following indices:

  • 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

Here a VLArray data set is used since the mesh can contain element of different types (refer to meshes->mesh(named)->element_types)

meshes->mesh(named)->edge_sets->edge_set(named)#

Array of unsigned

Array with node INDICES referencing the nodes in this set.

meshes->mesh(named)->element_sets->element_set(named)#

Array of unsigned

Array with element INDICES referencing the elements in this set.

Components#

components->component(named)#

Attributes:

Attribute

Type

Description

type

string

ply, core, etc.

layer_id

integer

aka step value. Global identifier. Determines the order of the plies (increasing from bottom to top)

orientation

double

nominal orientation angle relative to the reference direction

mapping_type

string

Note

The mapping_type is optional and will be detailed later. Since ACP allows to use multiple rosettes to define the reference direction within a ply, different mapping types (interpolation algorithms) are defined, such as “minimum distance”, “minimum angle”, etc.

components->component(named)->placement_coord_sys#

4 by 3 array of double

[origin x]   [origin y]   [origin z]
[dir1 x]     [dir1 y]     [dir1 z]
[dir2 x]     [dir2 y]     [dir2 z]
[normal x]   [normal y]   [normal z]

The placement_coord_sys is used for two things:

  • The normal of the placement coordinate system is used to define the default offset direction of the layup.

  • The origin and dir1 are used to define the starting point and the initial direction of the draping calculation, respectively.

components->component(named)->material#

Softlink

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

components->component(named)->element_set#

Softlink

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

components->component(named)->data_map#

Softlink

Defines a link to the data map of this component.

The following restrictions and 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 the thickness is computed from cured_thickness if material is a “fabric” or the sum of the cured_thickness for all the “fabric” if material is a material_data->stackup

  • If matorient_1_angles is not present it set equal to component->orientation

  • If matorient_2_angles is not present it is computed as: matorient_2_angles = matorient_1_angles + 90°

components->component(named)->rosettes->rosette(named)#

Softlink (Optional)

Defines a link to the rosettes of this component.

Rosettes#

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 “translational”, “standard”, and “rotational” mapping types. ACP defines “parallel”, “radial”, “cylindrical” and “spherical” as standard rosette types. The exact definition of this attribute has been postponed, because this is optional information to exchange, which it is not needed to map the orientation field of the plies correctly.

rosettes->rosette(named)->coord_sys#

4 by 3 array of double

[origin x]   [origin y]   [origin z]
[dir1 x]     [dir1 y]     [dir1 z]
[dir2 x]     [dir2 y]     [dir2 z]
[normal x]   [normal y]   [normal z]

Data Maps#

data_maps->data_map(named)->element_set/node/node_set#

Defines a link to an element set of a mesh or a link to an edge_set of a mesh. This defines the positions where the orientations, thicknesses etc are given.

data_maps->data_map(named)->reference_directions#

n by 3 array of double

Defines the reference directions absolutely with direction vectors.

data_maps->data_map(named)->normals#

n by 3 array of double (Optional)

Defines the normal directions absolutely with direction vectors. If present they can be used to project the reference direction onto the plane defined by the normal.

data_maps->data_map(named)->matorient_1_angles#

n by 1 array of double (Optional)

Defines the material orientation 1 angles with respect to the reference direction and the given normal.

data_maps->data_map(named)->matorient_2_angles#

n by 1 array of double (Optional)

Defines the material orientation 2 angles with respect to the reference direction and the given normal.

data_maps->data_map(named)->thicknesses#

n by 1 array of double (Optional)

Defines position dependent thickness values.

data_maps->data_map(named)->scalar_user_data->scalar_user_data(named)#

n by 1 array of double (Optional)

User defined scalar data fields. Only supported by ansys.

Attribute

Type

Values

unit_type

string

“dimensionless”, “length”, “mass”, “time”, “temp” (default: “dimensionless”)

Component Groups#

component_groups->component_group(named)#

Optional

Component groups can be defined to store grouping information of components.

Change Log#

Date

Description

Author

May 5, 2010

ACP–FiberSIM Interface Format Specification Rev 01

  1. Koenig, M. Wintermantel

June 5, 2010

HDF5 Composite CAE Data File Specification Proposal version 1.1

  1. Grape, J. Koenig

Aug 10, 2010

HDF5 Composite CAE Data File Specification Release Candidate 1 for stable version 1.0

Latest modifications from EVEN:

  • Modified stackup definition slightly to take into account that links cannot have attributes

  • Proposing element type IDs to be used within mesh/elements array

Latest modifications taken from Vistagy’s feedback of Aug 9 2010:

  • Added composite_cae/temp_unit attribute

  • Added the proposed thickness map data to the specification. This extension also leads to a name change of the “orientation_map” to the more general “data_map”. For consistency we also propose to change ‘material_thickness’ to ‘thicknesses’

  1. Koenig, U. Mennel, M. Wintermantel

Aug 11, 2010

Minor updates in “Open Questions”, added Section “Specification of Node Names”

  1. Koenig, U. Mennel

Aug 30, 2010

Upgrade specification to match all issues recently discussed with Vistagy via emails

  1. Koenig

Mar 17, 2011

Cleanup the document a little

  1. Koenig

Oct 17, 2014

Adding component_groups and component_group nodes

  1. Koenig

June 28, 2019

Adding some additional information

  1. Roos

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

  1. von Rickenbach

September 15, 2020

Mentioned that global_coord_sys is currently not supported. Correct what happens when matorient_1_angles are not present

  1. von Rickenbach

January 26, 2022

Mark material_data->fabrics->fabric(named)->orientations as obsolete

  1. von Rickenbach

February 4, 2022

Change Href to Softlink for items that have to be linked with a Softlink

  1. von Rickenbach

February 8, 2022

Correct datatype for element_labels, element_nodes and element_types (now int)

  • Clarified layer id

  1. von Rickenbach

February 17, 2022

Clarified units specification

  • Mark optional material properties as optional

  1. von Rickenbach

May 12, 2022

Add optional scalar_user_data data_map property

  1. von Rickenbach

May 31, 2022

Improved formatting, Removed outdated future plans section. Added missing rosettes in component

  1. von Rickenbach

May 22, 2023

Improve documentation of node order

  1. von Rickenbach

May 15, 2024

Complete supported units

    1. Rickenbach

June 21, 2024

Clarified orientation

Jan von Rickenbach

April 14, 2024

Some clarifications

  1. Roos
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