#### 2.1.9.6. Butt Joint Sequence

The Butt Joint Sequence allows you to define butt joints between Modeling Plies. A butt joint consists of sequences (master and slave plies) which specify the lay-up on both sides of a butt joint. The Butt Joint Sequence object automatically detects where the selected plies join and generates butt joints instead of drop-offs.

Figure : Drop-Off Elements and a Butt Joint Between Two Cores

The Butt Joint Sequence Properties window contains the following options:

- Active: Active plies are considered in an analysis, inactive plies are present but not considered.

- Global Ply Number: Defines the global ply order. By default, a new Sequence is added after the last one in the Modeling Group. The order of the Plies in the Modeling Groups is equal to this value.

- Master Plies: Sequences which pass their thickness on to the other plies of a Butt Joint Sequence. A Master Ply can be a Modeling Ply or a Modeling Group. The Level column specifies which sequence defines the thickness at a butt joint. The sequence with the lower level is dominant where the other sequence inherits the thickness. Potential differences in the thickness between the sequences are graduated over one element within the sequence with the higher level (the transition zone in the following image).

- Slave Plies: Slave plies inherit the thickness from Master Plies but do not pass it further. This means that drop-offs are generated where two slave plies join.

  In most cases, you can define a Butt Joint Sequence without the use of slave plies. An example where slave plies may be necessary would be a butt joint on a cylinder where you need drop-offs:

##### 2.1.9.6.1. Butt Joint Sequence Notes and Limitations

The following is a list of notes limitations of the Butt Joint Sequence:

- A Modeling Ply can only be used in one Butt Joint Sequence

- Butt Joint Sequences do not affect shell models. They are only considered in Section Cuts

- Solid model extrusion does not consider butt joints

- A Butt Joint Sequence can only be linked to Modeling Plies with a lower Global Ply Number.

- The butt joint can not be updated if a ply sequenced between the first and last ply of the butt joint covers the node where the plies join, shown in the following diagram:

- Modeling groups may be easier to work with if a butt joint consists of a large number of plies

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