Laminate Properties
The laminate definition is the foundation of any BJSFM analysis. You can define your laminate in two ways:
Builder Mode — Ply-by-Ply Definition
The Builder tab lets you construct the laminate ply-by-ply. For each ply, you specify:
| Property | Units | Description |
|---|---|---|
| Material | — | Label for the ply material (informational only) |
| Angle | degrees | Fiber orientation angle relative to the loading (x) axis |
| ET1 | Msi | Longitudinal tensile modulus in the fiber (1) direction |
| EC1 | Msi | Longitudinal compressive modulus in the fiber (1) direction |
| ET2 | Msi | Transverse tensile modulus in the matrix (2) direction |
| EC2 | Msi | Transverse compressive modulus in the matrix (2) direction |
| G12 | Msi | In-plane shear modulus |
| ν12 | — | Major Poisson's ratio |
| t | in | Ply thickness |
| σ₁t | ksi | 1-direction tension allowable limit (stress) |
| σ₁c | ksi | 1-direction compression allowable limit (stress) |
| σ₂t | ksi | 2-direction tension allowable limit (stress) |
| σ₂c | ksi | 2-direction compression allowable limit (stress) |
| σ₁₂s | ksi | In-plane shear allowable limit (stress) |
| r_c,t | in | Characteristic Distance, Tension (distance from hole boundary at which tension margins are evaluated) |
| r_c,c | in | Characteristic Distance, Compression (distance from hole boundary at which compression margins are evaluated) |
| B_f,t | — | Bearing Factor, Tension (dimensionless bearing load scaling factor for the ply/angle under tension) |
| B_f,c | — | Bearing Factor, Compression (dimensionless bearing load scaling factor for the ply/angle under compression) |
The client computes the laminate [A] matrix from the ply stack in real-time using Classical Lamination Theory. Separate tension and compression moduli (ET1/EC1, ET2/EC2) are carried per ply to accurately convert between stress and strain allowables. Allowables are taken as the most critical (minimum tension, minimum compression, minimum shear) across all plies in both the 1- and 2-directions for each unique ply angle. Characteristic distances (r_c,t, r_c,c) are taken as the minimum for each angle, and Bearing Factors (B_f,t, B_f,c) are taken as the maximum for each angle to ensure conservative margin calculations.
Direct A-ij Mode — Manual Matrix Entry
The Direct A-ij tab allows you to enter the 3×3 extensional stiffness matrix directly if you already have it from another source (e.g., HyperSizer, NASTRAN, or hand calculation).
You also manually specify the total laminate thickness and the global stress allowables (σt, σc, σs). In this mode, margins are evaluated at the fixed set of ply angles [0°, 45°, −45°, 90°] using the single set of allowables you provide.
Material Presets
Several built-in material presets are provided for common aerospace composite systems:
- T300/977-14AC Fabric (70°F) — Balanced woven fabric, commonly used in secondary structure
- IM7/8552 UD Tape (70°F) — High-performance unidirectional tape for primary structure
- AS4/3501-6 UD Tape (70°F) — Legacy aerospace unidirectional tape
- IM7/8552 Plain Weave (70°F) — Balanced plain weave fabric
- Custom Material — User-defined properties
Preset properties can be edited in-place. Any changes are session-local and do not persist between page reloads.
Ply Stack Operations
- Quick Add — Adds a ply at 0°, 45°, −45°, or 90° using the currently selected preset’s properties.
- Bulk Add Plies — Quickly add multiple plies at a specific angle all at once.
- Custom Ply — Adds a ply at 0° that you can then edit to any angle.
- Symmetric — Mirrors the current stack to create a symmetric laminate (appends the reverse of the current plies).
- Repeat — Duplicates the entire current stack and appends it.
- Clear — Removes all plies from the stack.
- Move Up/Down — Reorders individual plies within the stack.
- Delete — Removes an individual ply.