Concrete vs. PCB Laminate FR-4

Compare Concrete vs. PCB Laminate FR-4 strength, stiffness, weight and thermal properties.

Mechanical	Concrete	PCB Laminate FR-4
Yield strength	none (brittle)	not given (tensile used)
Ultimate tensile strength	not sourced	246–385MPa1
Compressive strength	27.6MPa2	not sourced
Flexural strength	not sourced	531–621MPa1
Elongation at break	none (brittle)	not sourced
Young's modulus (stiffness)	design value25.1GPa3	21.9–25.8GPa1
Density	2,240–2,400kg/m³4	1,920kg/m³5
Strength to weight	not sourced	164kN·m/kg
Stiffness to weight	10.8MN·m/kg	12.4MN·m/kg15% higher
Poisson's ratio	0.15–0.26	0.171–0.1771
Shear modulus	10.7GPa5% stiffer in shear	10.2GPa
Bulk modulus	12.9GPa6% higher	12.2GPa
Speed of sound	3,289m/s	3,525m/s7% faster

Stiffness against densityHigher and further left: stiffer for its weight

Strength against densityHigher and further left: stronger for its weight

Thermal	Concrete	PCB Laminate FR-4
Thermal conductivity	0.9W/m·K72.25x more heat through a fin	0.4W/m·K1
Thermal expansion	8–12µm/m·K8	13–14µm/m·K1
100 mm part over a 50 °C swing	50µm growth35% less	67.5µm growth
Specific heat	900J/kg·K9	1,200–1,400J/kg·K5
Heats up and cools (diffusivity)	0.431mm²/s2.69x faster	0.16mm²/s
Thermal shock resistance	not sourced	324W/m
Glass transition	not sourced	180°C1
Max service temperature	65°C6	130°C165 °C hotter

Thermal conductivity against densityHigher and further left: spreads more heat for its weight

Thermal expansion against thermal conductivityLower and further right: warps less when heated

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Sources9 documents: Isola, National Ready Mixed Concrete Association, Federal Highway Administration, Park Electrochemical (Nelco), Oak Ridge National Laboratory, USDA Forest Products Laboratory, National Institute of Standards and Technology

Concrete: Normal-weight portland cement concrete, strength class f'c = 4000 psi (28 MPa) per NRMCA CIP 35; density NRMCA CIP 36; thermal conductivity USDA FPL Wood Handbook; service temperature ORNL/NRC review
PCB Laminate FR-4: Isola 370HR FR-4 laminate (Polyclad PCL-FR-370HR, 180 C Tg multifunctional epoxy, E-glass fabric), copper removed; Isola data sheet Revision C, last updated April 15, 2021. Woven-glass laminate: the sheet gives in-plane values per weave direction (length / cross) and the Z-axis CTE separately; the solver is isotropic per material.

1
370HR Laminate and Prepreg Data SheetIsolaarchived copyPCB Laminate FR-4 · Ultimate tensile strength: typical, in-plane: cross direction .. length direction (ASTM D3039)PCB Laminate FR-4 · Flexural strength: typical: cross direction .. length direction (IPC-TM-650 2.4.4B)PCB Laminate FR-4 · Young's modulus (stiffness): typical, in-plane: cross direction .. length direction (ASTM D790-15e2)PCB Laminate FR-4 · Poisson's ratio: typical, in-plane: cross direction .. length directionPCB Laminate FR-4 · Thermal conductivity: typical (ASTM E1952); direction not stated by the sheetPCB Laminate FR-4 · Thermal expansion: typical, in-plane X/Y-axis, below Tg (IPC-TM-650 2.4.24C)PCB Laminate FR-4 · Glass transition: typical, DSC (IPC-TM-650 2.4.25C)PCB Laminate FR-4 · Max service temperature: UL Relative Thermal Index (UL 796)
2
CIP 35: Testing Compressive Strength of ConcreteNational Ready Mixed Concrete Associationarchived copyConcrete · Compressive strength: specified compressive strength class (f'c), not a measured typical
3
LRFD Steel Girder Superstructure Bridge Design Example, Design Step 2: Concrete Deck DesignFederal Highway AdministrationConcrete · Young's modulus (stiffness): design value: AASHTO LRFD 5.4.2.4 applied by FHWA to f'c = 4.0 ksi normal-weight concrete
4
CIP 36: Structural Lightweight ConcreteNational Ready Mixed Concrete Associationarchived copyConcrete · Density: range for normalweight concrete
5
N4000-6 Laminate Data Sheet (2006)Park Electrochemical (Nelco)archived copyPCB Laminate FR-4 · Density: typical, 50% resin content; another FR-4 producer: Park Nelco N4000-6 (high-Tg multifunctional epoxy), not Isola 370HRPCB Laminate FR-4 · Specific heat: typical (ASTM E1461); another FR-4 producer: Park Nelco N4000-6 (high-Tg multifunctional epoxy), not Isola 370HR
6
The Effect of Elevated Temperature on Concrete Materials and Structures: A Literature Review (ORNL/TM-2005/553)Oak Ridge National Laboratoryarchived copyConcrete · Poisson's ratio: general range at normal ambient conditions (overall 0.11-0.32)Concrete · Max service temperature: code long-term temperature limit (ASME Code, concrete containments)
7
Wood Handbook (FPL-GTR-282), Chapter 4: Moisture Relations and Physical Properties of WoodUSDA Forest Products LaboratoryConcrete · Thermal conductivity: typical (comparative value)
8
Thermal Coefficient of Portland Cement ConcreteFederal Highway AdministrationConcrete · Thermal expansion: typical range for portland cement concrete (aggregate dependent)
9
Best Practice Guidelines for Structural Fire Resistance Design of Concrete and Steel Buildings (TN 1681)National Institute of Standards and Technologyarchived copyConcrete · Specific heat: typical (NIST guidance for thermal analysis)

Each number points to the document that states it, with the exact basis. Values without a number are computed from the sourced ones. "Not sourced" means no citable source states it (or only a specification minimum); figures computed from it are left out too.

Questions

Mechanical

Which is lighter, Concrete or PCB Laminate FR-4?

PCB Laminate FR-4 is lighter: 1,920 kg/m³ against 2,320 kg/m³ for Concrete.

Which is stiffer, Concrete or PCB Laminate FR-4?

Concrete is stiffer: Young's modulus 25.1 GPa against 23.9 GPa for PCB Laminate FR-4, so the same part in Concrete deflects less under the same load.

Which is lighter for the same job, Concrete or PCB Laminate FR-4?

For the same stiffness or strength: PCB Laminate FR-4 is lighter for a stiff rod or tie (tension), stiff beam (bending), stiff panel or plate.

Part that must be	Concrete	PCB Laminate FR-4
Stiff rod or tie (tension)	15% heavier	lighter
Stiff beam (bending)	18% heavier	lighter
Stiff panel or plate	19% heavier	lighter

For the same stiffness or strength, mass scales with density over stiffness (or strength) raised to a power set by how the part is loaded: 1 for a rod in tension, 1/2 for a beam in bending, 1/3 for a panel (the standard material-selection indices).

Thermal

Which handles higher temperatures, Concrete or PCB Laminate FR-4?

PCB Laminate FR-4 does: 130 °C against 65 °C for Concrete.

Which conducts heat better, Concrete or PCB Laminate FR-4?

Concrete conducts heat better: 0.9 W/m·K against 0.4 W/m·K for PCB Laminate FR-4.

Which expands less with temperature?

Concrete expands less: 10 µm/m·K against 13.5 µm/m·K for PCB Laminate FR-4.