IDB-MAT-026
Materials · metals · plastics · properties · selection
Engineering materials datasheet
Typical mechanical properties of the metals and engineering plastics used in product development — density, stiffness, strength, thermal expansion and service temperature — with quick selection guidance.
Abstract
A working reference of typical mechanical properties for the materials that show up most in electromechanical products: structural and sheet metals, and engineering plastics. Use it to size parts, compare candidates and sanity-check a supplier datasheet — then design to the supplier's certified values for the exact grade and temper.
Section 1 defines the properties and how to read them. Section 2 is metals. Section 3 is engineering plastics. Section 4 covers selection trade-offs (strength- and stiffness-to-weight, cost, CTE, temperature). Section 5 is quick "which material" guidance.
1.Reading the tables
The values below are typical room-temperature properties for a common grade/temper of each material. Real values vary with grade, temper, processing, fillers, moisture and temperature — always confirm against the supplier's certified datasheet for the exact material before final sizing.
1.1Properties
2.Metals
| Metal | ρ (g/cm³) | E (GPa) | Yield (MPa) | UTS (MPa) | CTE (µm/m·K) | Max °C | Notes |
|---|---|---|---|---|---|---|---|
| Steel, low-carbon (1018) | 7.87 | 200 | 350 | 440 | 12 | ~400 | Cheap, weldable, rusts — the structural default |
| Steel, alloy (4140 Q&T) | 7.85 | 205 | 655 | 1020 | 12 | ~425 | Shafts, high-strength parts; heat-treatable |
| Stainless 304 | 8.00 | 193 | 215 | 505 | 17 | ~600 | Corrosion resistant, non-magnetic, formable |
| Stainless 316 | 8.00 | 193 | 240 | 580 | 16 | ~600 | Marine / chemical grade (Mo added) |
| Aluminium 6061-T6 | 2.70 | 69 | 276 | 310 | 23 | ~150 | Machines & extrudes well; the all-rounder |
| Aluminium 7075-T6 | 2.81 | 72 | 503 | 572 | 23 | ~120 | Aircraft-grade strength; poor weldability |
| Aluminium A380 (die-cast) | 2.74 | 71 | 160 | 320 | 21 | ~150 | High-volume cast housings |
| Titanium Ti-6Al-4V | 4.43 | 114 | 880 | 950 | 8.6 | ~400 | Best strength-to-weight; expensive, hard to machine |
| Magnesium AZ91D | 1.81 | 45 | 160 | 230 | 26 | ~120 | Lightest structural metal; die-cast |
| Brass C360 | 8.50 | 97 | 125 | 340 | 20 | ~200 | Free-machining; connectors, fittings |
3.Engineering plastics
| Plastic | ρ (g/cm³) | E (GPa) | Tensile (MPa) | Max °C | Notes |
|---|---|---|---|---|---|
| ABS | 1.05 | 2.3 | 40 | ~80 | Tough, cheap, easy to mould; not UV/chemical |
| PC (polycarbonate) | 1.20 | 2.4 | 65 | ~120 | High impact, transparent; scratches, notch-sensitive |
| PC/ABS | 1.15 | 2.4 | 55 | ~110 | Balance of impact + processability; enclosures |
| PA6 / PA66 (nylon) | 1.14 | 2.7–3.0 | 80–85 | ~100–120 | Tough, wear-resistant; absorbs water (dims shift) |
| POM (acetal) | 1.41 | 2.8 | 65 | ~100 | Low friction, stiff, dimensionally stable; gears |
| PP (polypropylene) | 0.905 | 1.3 | 33 | ~100 | Chemical resistant, living hinges; low stiffness |
| PE (HDPE) | 0.95 | 1.0 | 28 | ~80 | Chemical resistant, low cost; hard to bond |
| PET | 1.38 | 3.0 | 75 | ~100 | Stiff, good barrier; bottles, structural |
| PMMA (acrylic) | 1.18 | 3.0 | 70 | ~80 | Optically clear, rigid; brittle |
| PEEK | 1.32 | 3.7 | 100 | ~250 | High temp + chemical + wear; expensive |
| TPU (elastomer) | 1.20 | 0.05–0.7 | 35 | ~80 | Flexible, abrasion resistant; seals, bumpers |
Glass-fibre fill (e.g. PA66-GF30) roughly doubles modulus, raises strength and service temperature, and lowers CTE — at the cost of toughness, surface finish and tool wear.
4.Selection trade-offs
- Stiffness-to-weight (E/ρ) is similar for steel, aluminium and magnesiumso for a stiffness-limited part, the lighter metal usually wins on weight at equal stiffness. Composites (CFRP) beat all metals here.
- Strength-to-weight favours titanium and 7075 aluminium; titanium also keeps it at temperature.
- Cost ranking (rough): mild steel < aluminium < stainless < titanium; commodity plastics (PP, ABS, PE) < engineering (PC, PA, POM) < high-performance (PEEK).
- CTE mismatch matters in mixed-material assemblies and press-fitsplastics expand 5–10× more than steel, so clearances and interference change a lot with temperature.
- Temperature quietly caps plastics: most commodity plastics soften by 80–120 °C; reach for PEEK, PPS or metal above that.
- Corrosion / environmentstainless, aluminium (anodised) and most plastics resist corrosion; plain steel needs coating or plating.
5.Which material — quick guidance
Pair this with the Mass from volume tool to turn a CAD volume into part weight across these materials, and design to certified supplier data for the final grade.