Composite Structural Analysis

Deflection, stress, and buckling analysis for composite beams, sandwich panels, plates, and cylinders using CLT stiffness data.

Overview

The structural analysis tools take your laminate's CLT stiffness properties (from the ABD matrix) and apply them to common structural elements. Each tool calculates deflections, stresses, and buckling loads for a specific geometry under your chosen loading and boundary conditions, and each has its own reference page with the formulas, validity limits, and design guidance: beam, sandwich panel, plate, and cylinder.

All structural tools share the same workflow:

1. Select a laminate from your saved laminates, or define a quick custom layup directly on the page.
2. Enter geometry: dimensions specific to the structural element (length, width, radius, etc.).
3. Define loading: choose boundary conditions, load type, and magnitude.
4. Read results: deflections, stresses, safety factors, and buckling loads update in real time.

The beam, plate, and cylinder tools use CLT stiffness data only and do not perform strength-based ply failure checks; for ply-level strength assessment, use the First Ply Failure tool alongside the structural analysis. The sandwich panel tool additionally checks facesheet first ply failure (Maximum Stress criterion) when the facesheet laminate carries strength data.

Beam / Column

Analyses a rectangular composite beam under transverse loading and provides Euler column buckling capacity as a reference. Bending stiffness comes from the laminate's D₁₁ term, four boundary conditions and three load types cover the common cases, and deflection, bending stress, and the critical buckling load are reported side by side. See the full beam analysis reference for the formulas and the boundary condition coefficients.

The beam tool, with bending and Euler buckling results for one laminate.

Sandwich Panel

Analyses a rectangular sandwich panel with composite facesheets bonded to a lightweight core under uniform transverse pressure. Bending and shear deflection are reported separately, and every sandwich failure mode (facesheet stress, core shear, face wrinkling, core crushing, general buckling, shear crimping) gets its own safety factor so the governing one is visible at a glance. Core materials (honeycomb, structural foam, balsa) live in your material library with presets to start from. See the full sandwich panel analysis reference for the formulas, the failure modes, and core selection.

The sandwich panel tool, with a safety factor per failure mode.

Plate

Analyses a rectangular composite plate for bending deflection under uniform pressure or buckling under uniaxial compression, straight from the laminate's D-matrix. The tool checks whether the laminate is orthotropic enough for the closed-form solutions and flags it when not, and a reduced bending stiffness option extends the analysis to unsymmetric laminates. See the full plate analysis reference for the Navier solution, the orthotropy check, and the D-matrix treatment.

The plate tool on a symmetric quasi-isotropic laminate, with the bend-twist coupling chip green.

Tube / Cylinder

Analyses a thin-walled composite cylinder for membrane stresses, torsional properties, and buckling under five load cases: internal and external pressure, axial compression, torsion, and bending. Buckling results always pair the classical value with an empirical knock-down factor (NASA SP-8007 for axial compression and bending), because classical shell theory overestimates capacity by 2 to 5 times. See the full tube and cylinder analysis reference for the formulas, the load cases, and the knock-down factors.

The cylinder tool under external pressure, knock-down factor visible.

Safety Factors

The plate, cylinder, and sandwich panel tools report safety factors using the same color-coded scheme as the failure criteria tools (the beam tool reports deflection, stress, and buckling values directly, without a safety factor):

• Green (SF ≥ 1.5): comfortable margin above failure or buckling.
• Amber (1.0 ≤ SF < 1.5): safe but with limited margin. Review loading assumptions.
• Red (SF < 1.0): the applied load exceeds the predicted failure or buckling load.

Assumptions & Limitations

The structural analysis tools are intended for preliminary sizing and trade studies. Key assumptions to keep in mind:

• Linear elastic analysis. All tools assume small deformations and linear material behavior. Nonlinear effects (large deflections, material degradation) are not captured.
• CLT-based stiffness. Laminate properties come from Classical Lamination Theory, which assumes thin plies with perfect bonding (no delamination).
• Simplified geometry. Beams are rectangular, plates are flat and rectangular, cylinders are circular. Complex shapes require FEA.
• Closed-form solutions. Results come from analytical formulas, not numerical simulation. They are most accurate for simple loading and boundary conditions.

Author: Rick Schrijver

References

1. Gere, J.M. & Timoshenko, S.P. (1997). Mechanics of Materials, 4th ed. PWS Publishing. ISBN: 978-0534934293. (Euler-Bernoulli beam theory and column buckling)
2. Zenkert, D. (1995). An Introduction to Sandwich Construction. EMAS Publishing. ISBN: 978-0947817760. (Sandwich panel theory, wrinkling, and failure modes)
3. Reddy, J.N. (2004). Mechanics of Laminated Composite Plates and Shells: Theory and Analysis, 2nd ed. CRC Press. ISBN: 978-0849315923. (Plate theory and Navier solutions for composite plates) doi:10.1201/b12409
4. NASA. (1968). Buckling of Thin-Walled Circular Cylinders. NASA Space Vehicle Design Criteria (Structure), NASA SP-8007. ntrs.nasa.gov
5. US Department of Defense. (1968). Structural Sandwich Composites, MIL-HDBK-23A. (Core material properties, honeycomb and foam core design data, face wrinkling and core crushing)
6. Barbero, E.J. (2018). Introduction to Composite Materials Design, 3rd ed. CRC Press. Chapter 10. (Sandwich panel design and core selection) doi:10.1201/9781315296494

Frequently Asked Questions