Methods of test for plywood

IS 1734 (Parts 1-20) — Scope & Key Specifications Summary

1. Scope (General)

• Covers methods for testing plywood and veneer-based panels.
• Includes specimen preparation, test procedures, and reporting.
• Applies to different wood density groups (High, Medium, Low).

2. Plywood Panel Shear Test (Clause 1.6 & Table 1)

• Specimen dimensions vary by plywood thickness and wood density group.
• Key dimensions (all in mm):

(Refer to full Table 1 for all thickness ranges and wood groups)

3. Test Calculations (Clause 2.4)

• Fibre stress at proportional limit:
  [ \sigma = \frac{3PL}{2bh^2} ]
• Modulus of rupture (MOR):
  [ MOR = \frac{3PL}{2bh^2} ]
• Modulus of elasticity (E):
  [ E = \frac{PL^3}{4bh^3 \Delta} ]
• Work to proportional limit (energy absorption):
  [ W = \frac{L \times b \times h \times A}{\text{volume}} ]
• **St

IS 1734 Part 1-20: Test Specimen Preparation & Dimensions

Key Specifications:

• Thickness: Full thickness of the material.

• Width & Length:

  • Standard specimen: 75 mm wide × 150 mm long (±0.3% accuracy).
  • For materials > 6 mm thick:
    • Width ≥ 25 mm and ≥ thickness
    • Length ≤ 7 × least cross-sectional dimension
  • For materials ≤ 6 mm thick:
    • Width = 25 mm
    • Length = 100 mm (10 cm)
    • Specimen supported laterally during test.

• Plywood Specimens (IS 1734 Part 10):

  • Width: 25 mm if thickness < 6 mm; 50 mm if thickness ≥ 6 mm
  • Length = (48 × thickness) + 50 mm
  • Grain direction parallel to length
  • Conditioned at 65 ± 5% RH and 27 ± 2°C
  • Dimensional accuracy: 0.1 mm; mass accuracy: 0.01 g

Summary Table:

Measurement Accuracy:

• Dimensional accuracy: ±0.3% (general), 0.1 mm (plywood)
• Mass accuracy: 0.01 g (plywood)

flowchart LR
    A[Material Thickness] -->|>6 mm| B[Width ≥ 25 mm & ≥ thickness]
    A -->|≤6 mm| C[Width = 25 mm]
    B --> D[Length ≤ 7 × least cross-sectional dimension]
    C --> E[Length = 100 mm]
    F[Plywood] -->

Determination of Glue Shear Strength - IS 1734 (Part 4)

Key Specifications:

• Specimen Dimensions: As per Clause 3.1, use dimensions detailed in IS 1734 (Part 4)-1983, Section 3.
• Moisture & Density: After testing, measure moisture content and density from a cut section (Clause 3.2.4).

Calculation of Glue Shear Strength:

The glue shear strength (panel shear stress) is calculated by:

[ \text{Panel Shear Stress} , (\text{N/mm}^2) = \frac{0.707 \times P}{L \times t} ]

Where:

Notes:

• The factor 0.707 accounts for shear stress distribution in the specimen.
• Specimen is square with side (L).
• Thickness (t) is measured as per Fig. 1 in the code.

flowchart LR
    A[Test Specimen] --> B[Apply Load (P)]
    B --> C[Measure Load at Failure]
    C --> D[Calculate Shear Stress]
    D --> E[Panel Shear Stress = 0.707 * P / (L * t)]

This method ensures consistent evaluation of glue shear strength in plywood panels.

IS 1734 Part 9: Tensile Strength Test Key Points

• Specimens: Types A, B, C, D, or E (see Fig. 1 in the code) with grain direction parallel or perpendicular to specimen length.
• Conditioning: Precondition specimens to constant mass at 65 ± 5% RH and 27 ± 2°C.
• Recorded Data:
  • Maximum tensile stress (ultimate tensile strength)
  • Modulus of elasticity (E)
  • Tensile stress at proportional limit (if required)
  • Moisture content and temperature at test time

Key Formula for Tensile Strength (σ_t):

[ \sigma_t = \frac{P}{A} ]

• (P) = Maximum load at failure (N)
• (A) = Cross-sectional area of specimen (mm²)

Modulus of Elasticity (E):

[ E = \frac{\Delta \sigma}{\Delta \varepsilon} = \frac{\text{Stress change}}{\text{Strain change}} = \frac{\sigma_2 - \sigma_1}{\varepsilon_2 - \varepsilon_1} ]

• Calculated from linear portion of stress-strain curve.

Typical Test Setup Diagram (Simplified):

graph LR
A[Specimen Clamped] --> B[Tensile Testing Machine]
B --> C[Load Application]
C --> D[Measure Load & Elongation]

Remember: Accurate moisture content and temperature recording are crucial for valid results per IS 1734.

IS 1734 Part 6: Water Resistance Test for Plywood - Key Points

• Test Specimen Size:

  • Approximately 125 x 125 mm (Clause 3.1) or 100 x 12.5 mm (Clause 5.1) depending on test method.
  • Full thickness of the plywood.

• Preconditioning:

  • Specimens conditioned at 65 ± 5% relative humidity and 27 ± 2°C until constant mass is achieved.

• Test Objective:

  • To determine the water resistance of plywood by subjecting specimens to water exposure and evaluating physical changes (e.g., swelling, delamination).

Typical Test Procedure (from IS 1734 Part 6):

1. Precondition specimen to constant mass.

2. Immerse specimen in water at specified temperature (usually room temp or boiling water depending on test).

3. Duration: Usually 24 hours or as per specific test.

4. Post-test evaluation:

   • Measure thickness swelling (%) using:
     [ \text{Thickness Swelling (%)} = \frac{T_w - T_d}{T_d} \times 100 ] where,
     (T_w) = thickness after water exposure,
     (T_d) = thickness before water exposure.

5. Visual inspection for delamination, surface checking.

Summary Table of Specimen Dimensions and Conditioning

flowchart TD
    A[Start: Prepare Specimen] --> B[Precondition at 65±5% RH, 27±2°C]
    B --> C[Measure initial thickness (T_d)]
    C --> D[Immerse in water (duration as per test)]
    D --> E[Remove and dry surface]
    E --> F[Measure thickness after test (T_w)]
    F --> G[Calculate Thickness Swelling %]
    G --> H[Visual Inspection for

IS 1734 Part 3: Fire Resistance Test for Plywood — Key Points

Fire Resistance Tests (Clause 2.1)

• a) Flammability Test
• b) Flame Penetration Test
• c) Rate of Burning Test

Flammability Test Procedure (Clause 5.2)

• Specimen Setup: Suspended inside a fire tube, 30 mm above burner flame.
• Ignition: Using a blue flame.
• Measurement: Record time for every 10% mass loss.
• Comparison Metric: Time taken for mass loss from 30% to 70%.

Key Specifications

Interpretation (Clause 1.1)

• Fire resistance determined by time taken for specified mass loss.
• Longer time indicates better fire-proofing efficacy.

flowchart LR
    A[Specimen Suspended 30mm above flame] --> B[Ignite with blue flame]
    B --> C[Measure mass loss every 10%]
    C --> D[Record time from 30% to 70% mass loss]
    D --> E[Evaluate fire resistance]

Summary: The fire resistance test evaluates plywood's fire-proofing by measuring mass loss rate under controlled flame exposure. The key metric is the time taken for 30-70% mass loss.

IS 1734 Part 18 (1983) — Impact Resistance Test for Plywood

Key Specifications:

• Test Setup: A mass is dropped on the plywood specimen from a specified height.
• Initial Test: Use a 5 kg mass dropped from heights up to 1000 mm.
• If No Failure: Increase mass to 10 kg and drop from 500 mm height.
• Failure Criteria: Cracking, tearing, or indentation on the surface.
• Report: Maximum indentation depth and any damage (cracking, tearing) must be recorded.

Test Procedure Summary:

Notes:

• "Failure" means visible damage or permanent indentation.
• Use apparatus as per Fig. 1 (impact test hammer with specified mass and drop height).

flowchart TD
    A[Start: Select 5 kg mass] --> B[Drop from up to 1000 mm]
    B --> C{Failure?}
    C -- Yes --> D[Record indentation & damage]
    C -- No --> E[Select 10 kg mass]
    E --> F[Drop from 500 mm]
    F --> G[Record indentation & damage]

This ensures consistent evaluation of plywood panel impact resistance per IS 1734 Part 18.

IS 1734 Part 1-20: Scarf Joint Strength Test Key Points

1. Test Types:

• Mandrel Test: For plywood ≤ 3 mm thickness (bending test).
• Tensile Strength Test (Longitudinal Test): For plywood > 3 mm thickness.

2. Test Procedure (Clause 4.2):

• Specimens with scarf joint tested for tensile strength as per IS 1734 Part 9 (Tensile strength test).
• Repeat test with identical specimen without scarf joint.
• Report ratio of wood failure percentages between specimens with and without scarf joints (Clause 3.3.1).

3. Strength Evaluation:

• Scarf Joint Strength (%) = (Tensile strength of specimen with scarf joint / Tensile strength of specimen without scarf joint) × 100

4. Mandrel Test (Clause 2.1):

• Bending test to assess scarf joint strength for plywood up to 3 mm.
• Specimen bent over a mandrel; failure indicates joint quality.

Summary Table:

flowchart LR
    A[Specimen Preparation] --> B{Thickness ≤ 3 mm?}
    B -- Yes --> C[Mandrel Bending Test]
    B -- No --> D[Tensile Strength Test (Longitudinal)]
    C --> E[Evaluate joint failure]
    D --> F[Compare strength with no-joint specimen]
    E --> G[Report scarf joint quality]
    F --> G

Note: Refer IS 1734 Part 9 for detailed tensile test setup and Part 12 for scarf joint strength determination procedures.

IS 1734 Part 19: Nail and Screw Holding Power Test

Purpose

• To determine the holding capacity of nails and screws in plywood.

Test Setup (Clause 5.1)

• Specimen is fixed in the testing machine.
• Nail or screw is withdrawn at a uniform rate of 2 mm/min.
• Measure the maximum load (force) required to pull out the nail or screw completely.

Key Parameters

• Withdrawal Rate: 2 mm/min
• Maximum Load: Recorded at complete withdrawal (in Newtons or kgf).

Typical Formula

Holding Power, ( P ) = Maximum Load at Withdrawal (N)

Important Notes

• Test is performed one nail/screw at a time.
• Results help assess plywood quality for fastener retention.

Summary Table (Example format)

flowchart LR
    A[Specimen Mounted] --> B[Nail/Screw Inserted]
    B --> C[Withdraw at 2 mm/min]
    C --> D[Record Max Load at Pullout]
    D --> E[Calculate Holding Power]

This test quantifies the resistance of plywood to fastener pullout, critical for structural and furniture applications.

IS 1734 Part 20: Acidity and Alkalinity Resistance Test - Key Points

• Purpose: Assess plywood surface resistance to mild acid/alkali, simulating conditions in chemical containers (Clause 2.1).

• Specimens: 4 pieces placed horizontally on separate tables (Clause 5.1).

• Test Procedure (Clause 5.1):

  • Drop 2 ml acid solution on 2 specimens.
  • Drop 2 ml alkaline solution on other 2 specimens.
  • Cover wet area with watch-glass for 6 hours.
  • Wash specimens, dry at room temperature for 24 hours.
  • Examine surface under oblique light for:
    • Blistering
    • Delamination
    • Cracks
    • Softening
    • Color or lustre changes

• Note: Wood resists acids with pH ≥ 2 but is vulnerable to alkalis with pH > 11; protective treatment needed for such use.

Typical Solutions Preparation (Clause 3 - summarized)

Summary Diagram

flowchart LR
    A[Specimens (4)] --> B[2 with Acid Solution (2 ml)]
    A --> C[2 with Alkaline Solution (2 ml)]
    B & C --> D[Cover with watch-glass (6 hrs)]
    D --> E[Wash & Dry (24 hrs)]
    E --> F[Examine Surface]
    F --> G{Surface Condition?}
    G -->|No Damage| H[Pass]
    G -->|Damage| I[Fail]

This test ensures plywood durability against mild acidic/alkaline exposure per IS 1734 Part 20.

IS 1734 Part 7: Mycological Test for Plywood - Key Points

• Purpose:
  Evaluate the resistance of the glue line (adhesive) in plywood against microbial attack, not the wood species durability.

• Test Specimen:
  Prepared plywood samples with exposed glue lines as per clause 3 (details in the standard).

• Test Method Overview:

  • Incubate specimens in a controlled environment with known fungal cultures.
  • Maintain specified temperature and humidity to promote fungal growth.
  • Observe and record fungal growth on glue lines over a fixed period (usually 4 weeks).

• Evaluation:

  • Degree of fungal attack is rated visually on a scale (e.g., 0 to 5) indicating no attack to severe attack.
  • Adhesive resistance is acceptable if fungal growth is minimal or absent.

Typical Rating Scale (Example)

Important Notes:

• Use standard fungal cultures as per IS 1734 Part 7.
• Maintain temperature ~27±2°C and relative humidity >90% during incubation.
• The test duration is typically 28 days.

flowchart LR
    A[Prepare Plywood Specimens] --> B[Expose Glue Lines]
    B --> C[Inoculate with Fungal Cultures]
    C --> D[Incubate at 27±2°C, RH >90% for 28 days]
    D --> E[Visual Inspection & Rating]
    E --> F{Fungal Growth Level}
    F -->|Low| G[Adhesive Resistant]
    F -->|High| H[Adhesive Not Resistant]

For detailed procedures, refer to IS 1734 Part 7 full text.

IS 1734 Part 16 - Vibration Test of Plywood Plates: Key Points

Test Setup (Clause 3.2)

• Attach a thin soft iron piece at the specimen center using glue/lac.
• Hold specimen rigidly in a frame.
• Place an electromagnetic driver below the iron piece.
• Adjust distance for free vibration.
• Energize driver with a calibrated oscillator.
• Detect vibrations with electromagnetic/piezoelectric pickup.
• Use cathode ray oscillograph or AC millivoltmeter to find resonance frequency by varying oscillator frequency.

Recorded Details (Clause 5.2)

• Manufacturer/source, plywood type & grade
• Ply thickness ratio, species, adhesive
• Specimen size, mass at 65±5% RH & 27±2℃
• Loading rate, elastic limit load (P), deflection (d)
• Maximum load (P_max), stiffness factor ( \frac{P a^2}{d} ) for simply supported/clamped edges

Important Formula

• Stiffness factor:
  [ \text{Stiffness factor} = \frac{P a^2}{d} ] where
  • (P) = Load at elastic limit (N)
  • (a) = Length of plate side (m)
  • (d) = Deflection at elastic limit (m)

Schematic Diagram Summary (Fig.1)

flowchart LR
    A[Electromagnetic Driver] --> B[Soft Iron Piece on Plywood Plate]
    B --> C[Plywood Plate in Frame]
    C --> D[Electromagnetic/Piezoelectric Pickup]
    D --> E[Cathode Ray Oscillograph / AC Millivoltmeter]

This setup helps determine the resonance frequency and dynamic stiffness of plywood plates per IS 1734 Part 16.

IS 1734 Part 1-20: Panel Shear Strength Test - Key Points

1. Purpose (Clause 2.1)

• To evaluate the panel shear strength of plywood panels.

2. Test Specimen

• Square panel with side length L (mm) and thickness t (mm).

3. Calculation of Panel Shear Stress (Clause 3.3)

[ \text{Panel shear stress } (\tau) = \frac{0.707 \times P}{L \times t} \quad \text{(N/mm}^2\text{)} ]

• P = Total applied load (N)
• L = Side length of square panel (mm)
• t = Thickness of specimen (mm)
• Factor 0.707 accounts for shear on the diagonal.

4. Moisture and Density (Clause 3.2.4)

• After testing, cut a section to determine:
  • Moisture content (%)
  • Density (kg/m³)

Summary Table

flowchart LR
    A[Apply Load P] --> B[Panel Shear Stress Calculation]
    B --> C[τ = 0.707 * P / (L * t)]
    C --> D[Evaluate Shear Strength]
    D --> E[Cut Section]
    E --> F[Determine Moisture & Density]

This formula and procedure ensure accurate evaluation of plywood panel shear strength per IS 1734 Part 1-20.

Key Formulas & Specifications from IS 1734 (Part 1-20) for Load-Deflection & Elastic Properties

1. Test Setup & Measurement

• Deflection measured at specimen center to nearest 0.02 mm (dial gauge).
• Minimum 12-15 load-deflection readings up to proportional limit.
• Record moisture content and temperature during test.

2. Important Parameters

3. Formulas

• Fibre stress at proportional limit
  [ \sigma_p = \frac{3PL}{2bh^2} \quad \text{(N/mm}^2) ]

• Modulus of rupture
  [ f_r = \frac{3P_{max}L}{2bh^2} \quad \text{(N/mm}^2) ]

• Modulus of elasticity
  [ E = \frac{PL^3}{4bh^3 \Delta} \quad \text{(N/mm}^2) ]
  where (\Delta) = deflection at load P (elastic limit)

• Work to proportional limit
  [ W_p = \frac{L \times b \times h}{A} \quad \text{(N·mm/mm}^3) ]

• Work to maximum load
  [ W_{max} = C \times A' \quad \text{(N·mm/mm}^3) ]

• Total work
  [ W_{total} = C \times A'' \quad

Reporting & Interpretation of Test Results (IS 1734 Parts 1-20)

1. Rounding Off:

• Follow IS : 2-1960 for rounding final test values.

2. Load-Deflection Data (Clause 2.4):

• Deflection readings: Nearest 0.02 mm
• Minimum 12-15 readings up to proportional limit
• Record moisture content & temperature

Key formulas:

Where:

• (P) = Load (N)
• (L) = Span (mm)
• (b) = Width (mm)
• (h) = Thickness (mm)
• (\Delta) = Deflection at load (P) (mm)
• (A, A', A'') = Areas under load-deflection curve (mm²)

3. Additional Reporting Requirements:

• Percentage of wood failure (Clause 3.3)
• Panel shear stress, moisture content, density (Clause 4.3)
• Manufacturer, plywood type/grade, construction details, species, adhesive, specimen details, loading rate, max load, etc.

flowchart