# Spruce-Pine-Fir (SPF) Softwood

Spruce-pine-fir is a wood-based material. It has the highest tensile strength and a moderately low heat capacity among wood-based materials. The graph bars on the material properties cards below compare spruce-pine-fir to other wood-based materials (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

## Mechanical Properties

Compressive (Crushing) Strength

50 *MPa* 7.3 *x 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

16 *GPa* 2.3 *x 10 ^{6} psi*

Elongation at Break

1.5 *%*

Poisson's Ratio

0.38

Shear Modulus

1.2 *GPa* 0.17 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

85 *MPa* 12 *x 10 ^{3} psi*

## Thermal Properties

Maximum Temperature: Mechanical

130 *°C* 270 *°F*

Specific Heat Capacity

1380 *J/kg-K* 0.33 *BTU/lb-°F*

Thermal Conductivity

0.12 *W/m-K* 0.069 *BTU/h-ft-°F*

Thermal Expansion

6.5 *µm/m-K*

## Other Material Properties

Density

0.5 *g/cm ^{3}* 31

*lb/ft*

^{3}Dielectric Strength (Breakdown Potential)

0.5 *kV/mm* 0.020 *V/mil*

Limiting Oxygen Index (LOI)

24 *%*

## Common Calculations

Stiffness to Weight: Axial

18 *points*

Strength to Weight: Axial

47 *points*

Strength to Weight: Bending

86 *points*

Thermal Diffusivity

0.17 *mm ^{2}/s*

Thermal Shock Resistance

58 *points*

## Followup Questions

## Further Reading

Wood Handbook: Wood as an Engineering Material, Forest Products Laboratory, USDA Forest Service, 1999

CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015