Laminate Roof R1.

Research record

The detail behind
the study.

Source-linked work for this revision. Reported checks describe the stated model or test; physical qualification and applicability to the current retrofit remain separate.

Preliminary laminate and roof stiffness comparison

Design development only. No production layup or burial rating is released.

All candidate walls remain 3 mm thick. Each uses twelve nominal 0.25 mm plies. The candidate combines a mirror-symmetric axial-biased cap layup with either the same layup or a shear-biased web layup. Posts retain the axial-biased layup.

Longitudinal rule-of-mixtures estimate: E1 = 134.63 GPa at assumed 55% fiber volume. E2 = 8 GPa, G12 = 4 GPa and Poisson ratio 0.30 are assumptions. These are not measured properties of the selected fiber/resin pair. Mixture density = 1513 kg/m³, using assumed cured-matrix density of 1150 kg/m³. The half-stiffness case is a sensitivity, not a verified environmental knockdown.

Loads retain 101.44 kPa over the full projected roof, including the access closure. The actual closure panel is still missing from CAD. These results replace neither the mass ledger nor structural qualification. They establish how explicit elastic layup assumptions change the existing frame calculation.

Retain separate cap/web properties when sizing integrated members. Before thinning or selecting a layup, include local wall buckling, compression/shear interaction, joint behavior and the missing roof/sidewall panels.

- Constituent values are published typical material-selection data, not qualified laminate allowables. - E1 is a longitudinal rule-of-mixtures estimate; E2, G12, Poisson ratio, Vf, matrix density and cured ply thickness are explicitly assumed. - Neither proposed sequence specifies an available textile, qualified laminate, protection layer or corner architecture. - No strength, buckling, creep, fatigue, bond or environmental acceptance follows from elastic stiffness. - The 0.5 stiffness factor is a sensitivity only; it is not a validated long-term lower bound. - Roof wrap stiffness and all lower-frame flexibility except post axial springs remain excluded. - Membrane-equivalent wall moduli omit local bending-twisting and corner warping effects. - All roof members share one section; wrap stiffness and support fork flexibility are omitted. - Changing fiber orientation has not changed CAD wall thickness or selected a fabrication layup. - No local-buckling or strength screen is included; a stiffer candidate is not necessarily stronger.

- method - fiber - resin - product_material_scope

- Full CAD Python test suite: 47 passed in 25.47 seconds during this revision. - New elastic checks include isotropic rotation invariance, 0/90 axis interchange, known 45-degree transformed stiffness, thickness scaling, symmetric/balanced behavior and the homogeneous box-section limit. - Explicit section properties reproduce the previous roof solution when supplied its original values. - Five integrated checks passed: two uniform-stiffness scaling checks, two reaction-distribution checks and one mesh-refinement check. - NASA RP-1351 equations 45-49 were inspected on printed page 21 (PDF page 29). They define the A, B and D thickness integrals used here. - Existing tank geometry was not changed by this revision. No fabrication, physical load testing, material qualification or production approval is implied.

To reproduce, extract current-cad-source.zip, enter its cad directory, install the pinned environment using uv sync --locked, and run: