Read the given statements (S1,S2) pertaining to structural plywood as per IS: 10701-2012 and select the most appropriate option with respect to the correctness of the statements.
S1: The moisture content of finished plywood boards shall be in the range 5% to 15%.
S2: The tensile strength and compressive strength across the grain shall be greater than that along the grain.
📖 Understanding Structural Plywood Standards (IS: 10701)
Structural plywood is an engineered wood product designed for use in load-bearing applications. To ensure safety and reliability, its properties are strictly defined by standards like IS: 10701-2012. These standards specify requirements for moisture content, strength, and other physical properties.
📝 Detailed Analysis of the Statements
Statement S1: The moisture content of finished plywood boards shall be in the range 5% to 15%.
This statement is TRUE. According to IS: 10701, the moisture content of finished structural plywood must be within the range of 5% to 15%. This range ensures the dimensional stability of the board and prevents issues like warping or delamination that can occur if the wood is too wet or too dry.
Statement S2: The tensile strength and compressive strength across the grain shall be greater than that along the grain.
This statement is FALSE. While the cross-graining of plywood makes it strong in both directions, it is still strongest "along the grain" of its outer face veneers. The long, continuous wood fibers of the outer layers provide the highest resistance to both tension and compression in that direction. The strength "across the grain" is substantial but lower. The standard values confirm this.
Conclusion
Since Statement S1 is true and Statement S2 is false, the correct option is (c).
📊 Required Minimum Strength of Structural Plywood (IS: 10701)
| Property | Direction | Strength Requirement (N/mm²) |
|---|---|---|
| Tensile Strength | Along the grain | 55 |
| Across the grain | 35 | |
| Compressive Strength | Along the grain | 35 |
| Across the grain | 30 |
💡 Study Tips
- Moisture Content (5-15%): Memorize this standard range for structural plywood. It's a common specification.
- Along > Across: For plywood strength, the rule is always "Along the grain is greater than Across the grain". The outer veneers' continuous fibers dictate the primary strength direction.
- Check the Numbers: The table clearly shows that for both tensile (55 > 35) and compressive (35 > 30) strength, the value along the grain is higher.
- Know the Code: Associate these properties with IS: 10701 for structural plywood.