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Types of wood; strength along grain

Short answer

Wood types: hardwood (deciduous, strong) and softwood (coniferous, light), plus engineered wood like plywood. Along the grain, compression, tension and bending strengths are high due to aligned fibres; across the grain, strengths are very low (1/5 to 1/20 of parallel) because fibres separate easily.

What are the different types of wood? Explain in brief strength along and perpendicular to the grain of wood.

Types of wood

  1. Hardwood: from deciduous broad-leaved trees (sal, teak, shisham, oak); dark, heavy, strong, durable; for beams, doors, furniture.
  2. Softwood: from coniferous trees (pine, deodar, fir, cedar); light, easily worked, less durable; for roof frames, shuttering, packing.
  3. Also by processing: natural timber (sawn), and manufactured or modified wood (plywood, particleboard, fibreboard).
  4. By structure: exogenous (outward growing, used as timber) and endogenous (inward growing like bamboo and palm).

Strength along and across the grain

Wood is an anisotropic (direction-dependent) material because its fibres run along the trunk.

StrengthAlong grain (parallel)Across grain (perpendicular)
CompressionHigh (for example 30-60 MPa in sal)Low (about 1/5 to 1/10 of parallel)
TensionVery high (50-100 MPa)Very low (about 1/20)
ShearLow (fibres slide on each other), 5-12 MPaHigher
BendingGood (load applied across grain, fibres in tension and compression along the length)-
  • Along the grain the fibres act like bundles of tubes and carry load axially, so strength is high.
  • Across the grain the fibres are held only by weak lignin bonds and tend to crush or split, so strength is low.
  • Hence timber members are placed so that main stresses act along the grain.

✓ Answer checked by Claude Opus 5.5 (high effort)

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