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Material definitions for origami simulation.
Provides dataclass-based material properties and preset materials
for paper, mylar, aluminum, and nitinol.
"""
from dataclasses import dataclass
@dataclass
class Material:
name: str
thickness_mm: float # mm
youngs_modulus_gpa: float # GPa
max_strain: float # fraction (e.g. 0.03 = 3%)
poissons_ratio: float = 0.3 # dimensionless
@property
def thickness_m(self) -> float:
"""Thickness in meters."""
return self.thickness_mm / 1000.0
@property
def youngs_modulus_pa(self) -> float:
"""Young's modulus in Pascals."""
return self.youngs_modulus_gpa * 1e9
# ── Preset materials ────────────────────────────────────────────────
MATERIAL_PRESETS: dict[str, Material] = {
"paper": Material(
name="paper",
thickness_mm=0.1,
youngs_modulus_gpa=2.0,
max_strain=0.03,
poissons_ratio=0.3,
),
"mylar": Material(
name="mylar",
thickness_mm=0.05,
youngs_modulus_gpa=4.0,
max_strain=0.03,
poissons_ratio=0.38,
),
"aluminum": Material(
name="aluminum",
thickness_mm=0.1,
youngs_modulus_gpa=69.0,
max_strain=0.01,
poissons_ratio=0.33,
),
"nitinol": Material(
name="nitinol",
thickness_mm=0.1,
youngs_modulus_gpa=75.0,
max_strain=0.08,
poissons_ratio=0.33,
),
}
def get_material(name: str) -> Material:
"""Return a copy of a preset material by name.
Raises KeyError if name is not in MATERIAL_PRESETS.
"""
if name not in MATERIAL_PRESETS:
available = ", ".join(sorted(MATERIAL_PRESETS))
raise KeyError(f"Unknown material '{name}'. Available: {available}")
preset = MATERIAL_PRESETS[name]
return Material(
name=preset.name,
thickness_mm=preset.thickness_mm,
youngs_modulus_gpa=preset.youngs_modulus_gpa,
max_strain=preset.max_strain,
poissons_ratio=preset.poissons_ratio,
)
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