Methods of Test for Wood-based Structural Sandwich Construction

Scope & Key Formulas from IS 9307 Part 1-8 (Sandwich Construction Testing):

1. Core Shear Stress (S):

[ S = \frac{P_2}{2hb} (h + c) ]

• P₂: Load at maximum load
• h: Thickness of sandwich construction
• c: Core thickness (if different)
• b: Width of specimen

2. Mid-span Deflection (F):

[ F = \frac{4f(h+c)b}{8fhb} \approx \frac{11P_2 a^2}{3EI} ]

• f: Facing thickness
• a: Span length
• Notations as per Clause 4.3

3. Facing Stresses:

• P, P₁, P₂: Loads at proportional limit, prior to buckling, and max load respectively
• f: Facing thickness
• b: Width of specimen

4. Modulus of Elasticity & Load Carrying Capacity:

• Calculated as per test data using load and deflection relations (not fully detailed here).

5. Fixity Factor (F):

• Indicates core's contribution to load capacity up to buckling.
• Typically F = 0 if no fixity.

Notes:

• Specimen dimensions: Length (L), thickness (h), width (b).
• Definitions and detailed specimen preparation in IS 9307 Part I.
• These formulas help evaluate sandwich panel performance under compression and bending.

flowchart LR
    A[Load P] --> B[Calculate Facing Stress σ = P/(2fb)]
    B --> C{Load Stage}
    C -->|Proportional Limit| D[σ]
    C -->|Before Buckling

Key Definitions & Formulas from IS 9307 Part 1-8

From Clause 5.3 (Properties Calculation):

• Core shear stress, S:

[ S = \frac{P_2}{2hb} (h + c) ]

• Mid-span deflection, F:

[ F = \frac{4f(h + c)b}{8fhb} \approx \frac{11 P_2 a^2}{3} ]

Notation:

• (P_2) = Load at max load
• (h) = Core thickness
• (c) = Facing thickness
• (b) = Width of specimen
• (f) = Facing thickness
• (a) = Span parameter (as per 4.3)

From Clause 6.1 (Facing Stresses & Modulus):

• Facing stress at proportional limit:

[ \sigma = \frac{P}{2fb} ]

• Facing stress just before buckling:

[ \sigma_1 = \frac{P_1}{2fb} ]

• Facing stress at maximum load:

[ \sigma_2 = \frac{P_2}{2fb} ]

• Modulus of elasticity of facings:

[ E = \text{(Derived from load and deformation data, see IS 9307 Part II)} ]

• Load carrying capacity, S: (Depends on core and facing properties)

• Fixity factor, F:
  Indicates core's ability to develop load capacity up to buckling, typically (F=0) for simply supported.

Notations Summary:

Reference:

• Definitions also refer to IS 707-1976 and IS 9307 (Part I) for standard

IS 9307 Part 1-8: Test Specimen Preparation

Key Points from IS 9307 (Part I) on Test Specimen Preparation:

• Specimen Type: Typically, concrete or mortar prisms/cubes/cylinders depending on the test.
• Dimensions: Standard sizes as per IS 9307 Part 1, e.g., cubes of 70.6 mm or cylinders of 150 mm diameter × 300 mm height.
• Casting: Specimens must be cast in clean, non-absorbent molds, compacted by standard methods (e.g., tamping or vibration).
• Curing: Specimens are cured under controlled conditions (usually water curing at 27 ± 2°C) for specified durations before testing.
• Number of Specimens: Minimum 3 specimens per test for statistical reliability.
• Surface Preparation: Smooth, level surfaces with no honeycombing or voids.

Typical Specimen Preparation Table

Important Formula for Volume of Cylindrical Specimen:

[ V = \pi \times \left(\frac{d}{2}\right)^2 \times h ]

Where:

• (d) = diameter (mm)
• (h) = height (mm)
• (V) = volume (mm³)

flowchart TD
    A[Mixing Concrete] --> B[Casting in Mold]
    B --> C[Compaction (Tamping/Vibration)]
    C --> D[Curing (Water, 27±2°C)]
    D --> E[Surface Preparation]
    E --> F[Testing]

Summary: Follow IS 9307 Part 1 for definitions and IS 9307 Part 1-8 for specimen preparation, ensuring standard dimensions, curing, and number of specimens for reliable test

Key Formulas for Flexure Test (IS 9307 Part 1-8)

1. Core Shear Stress, S
   [ S = \frac{P_1}{(h + c) b} ]

2. Facing Stress, F
   [ F = \frac{2 P_1}{(h + c) b} \approx \frac{4 f}{h b} ]

3. Mid-span Deflection, W₁
   [ W_1 = 480 + A N ]

4. Flexural Stiffness, D
   [ D = \frac{E (h^3 - c^3) b}{12 (1 - \nu^2)} ]

5. Shear Stiffness, N
   [ N = G (h + c) b = G h b + 4 c C ]

Test Setup (Clause 5.1): Two Quarter Span Loading (Fourth Point Loading)

• Simply supported on two 2 cm diameter rollers at span length.
• Load applied at two quarter points (1/4 and 3/4 span).
• Initial load held for 30 sec as zero deflection.
• Additional load = 30% max load (from IS 9307 Part I).
• Deflection measured at mid-span over time (up to ~1 week) to plot creep curve.

Specimen & Loading Fixture Details

• Steel blocks bonded to facings for uniform tensile loading.
• Load applied via universal testing machine, max load reached in 3-6 mins.
• Failure mode and max load recorded.

flowchart LR
    A[Specimen] -->|Supported on| B(Rollers at Span Ends)
    B -->|Load Applied at| C(Two Quarter Points)
    C --> D[Measure Deflection at Mid-span]
    D --> E{Record Over Time}
    E --> F[Plot Deflection vs Time Curve]

Notation

• (P_1): Applied load
• (h): Core thickness
• (c): Facing thickness
• (b): Width of specimen
• (E): Modulus of elasticity of facing
• (\nu): Poisson's ratio of facing
• (G): Effective core shear modulus

IS 9307 Part 3: Compression Test Key Formulas & Specifications

Test Setup (Clause 5.1)

• Specimen placed flatwise on UTM platform.
• Load applied via self-adjusting block.
• Compression rate: compress to 1/10 thickness (H) in 3 to 6 minutes.
• Compression measured with accuracy 0.01 mm.
• Load increments to get 10-15 readings up to proportional limit.
• Test continues until specimen compressed to 1/10 thickness.

Key Formulas (Clause 6.1)

Notes:

• Proportional limit: Point up to which stress-strain is linear.
• Record load and compression at proportional limit and load at 1/10 thickness compression.
• Observe and note nature of failure.

flowchart TD
    A[Start Test] --> B[Place specimen flatwise]
    B --> C[Apply load via self-adjusting block]
    C --> D[Increase load gradually, record 10-15 readings]
    D --> E[Measure compression (accuracy 0.01 mm)]
    E --> F{Compression = 1/10 thickness?}
    F -- No --> D
    F -- Yes --> G[Record load at 1/10 thickness]
    G --> H[Calculate stresses and modulus]
    H --> I[Note failure mode]
    I --> J[End Test]

This summarizes the compression test method per IS 9307 Part 3 (1979).

IS 9307 Part 1-8: Shear and Tension Test Methods - Key Formulas & Specs

Shear Test (Clause 6.1 & 5.1, Part IV - 1979)

• Maximum Shearing Stress:

[ f = \frac{P}{b \times L} ]

where,

• (f) = maximum shearing stress

• (P) = maximum load (N)

• (L) = length of specimen (mm)

• (b) = width of specimen (mm)

• Test Setup:

  • Two steel plates bonded to specimen faces (Fig. 1).
  • Plates larger than specimen, hung lengthwise in UTM.
  • Load applied vertically, max load in 3-6 min.
  • Failure mode recorded.

Tension Test (Clause 5.1, Part V - 1979)

• Test Setup:
  • Two steel/aluminium blocks bonded to specimen faces (Fig. 1).
  • Blocks pulled apart horizontally, tensile force perpendicular to specimen plane.
  • Max load in 3-6 min, failure mode noted.

Core & Facing Stress Formulas (Clause 4.3, Part V)

• Parameters:
  • (P_1) = applied load
  • (h) = core thickness
  • (c) = facing thickness
  • (b) = specimen width
  • (f) = Poisson's ratio
  • (A, N) = constants related to shear stiffness
  • (D = \frac{E (h^3 - c^3) b}{12(1-\nu^2)})

Key Specifications & Formulas for Creep and Vibration Tests (IS 9307 Part VI - 1979):

Test Setup (Clause 5.1)

• Specimen simply supported on two 2 cm diameter rollers spaced at span length.
• Load applied at mid-span via lever or roller stirrup.
• Initial load ≤ 400 g; initial deflection after 30 sec = zero reference.
• Additional load = 30% of maximum load (from IS 9307 Part I, Clause 4.2).
• Deflection readings:
  • Every 10 min for 2 hours
  • Every 30 min for next 3 hours
  • Hourly for next 5 hours
  • Twice daily for about a week or until failure

Creep Calculation (Clause 6.1)

[ \text{Creep (%)} = \frac{d_t - d_0}{d_0} \times 100 ]

• (d_t) = deflection at time (t)
• (d_0) = initial static deflection (after 30 sec under load)
• Express creep rate in mm/hour or mm/day.
• Plot (d_t - d_0) vs. time for detailed analysis.

Notes:

• For elevated temperature tests, maintain specimen and assembly in a temperature-controlled chamber (Clause 4.2 Note 2).
• Load percentages for creep tests refer to max load from flexure test (IS 9307 Part I).

Illustration of Test Setup (Fig. 1):

flowchart LR
    R1[Roller Support] --- Span --- R2[Roller Support]
    Load[Load (30% Max Load)] --> MidSpan[Mid-span]
    MidSpan -. Deflection Measurement .-> Cathetometer[Cathetometer]

This method evaluates creep behavior and adhesive performance in sandwich constructions under constant load and temperature.

IS 9307 Part VIII - Weathering Test Procedures for Wood-Based Structural Sandwich Construction

Key Weathering Cycles (Clause 5.1)

Two cycles (A or B) of 6 complete repetitions, max 30 min between cycles:

Post-Test Conditioning

• Condition specimen to constant weight at 65 ± 5% RH and 27 ± 2°C.
• Note any delamination or damage.
• Test for required mechanical properties (e.g., flexure as per IS 9307 Part I).

Reporting Requirements (Clauses 6.1 & 7.1)

• Details of sandwich construction (facings, core, adhesive).
• Weathering cycle used (A or B).
• Observed damage during exposure.
• Comparative data of specimens before and after weathering.
• Modulus of elasticity (dynamic and static bending).
• Individual properties of facings and core.

Summary Diagram of Cycle A (Example):

sequenceDiagram
    participant Specimen
    Specimen->>Water: Immerse at 49°C for 1 hr
    Specimen->>Steam: Spray steam at 93°C

Here are the key formulas and specifications from IS 9307 Part 1-8 for Calculation of Mechanical Properties:

1. Compressive Properties (Clause 6.1)

2. Core Shear and Deflection (Clause 5.3)

3. Facing Stresses (Clause 6.1)

Test Reporting Requirements per IS 9307 (Parts 1-8)

Key Report Details (Clauses 5.4 & 7.1 across Parts I, V, VIII):

• Sandwich Construction Details:

  • Facings (material, thickness)
  • Core material and thickness
  • Adhesives used

• Test Environment:

  • Temperature (°C)
  • Relative Humidity (%)

• Test Type:

  • Central loading or two quarter-span loading (flexure test)
  • Flatwise tension test
  • Weathering test specifics (Part VIII)

• Mechanical Properties:

  • Maximum shear stress (core)
  • Modulus of elasticity (dynamic and static bending)
  • Individual properties of facings and core (strength, stiffness)

• Failure Details:

  • Mode and location of failure

Typical Reporting Table Format

Notes:

• Modulus of Elasticity in bending (E) can be calculated from flexure test data using:

[ E = \frac{L^3 m}{4 b d^3} ]

Where:

• (L) = span length
• (m) = slope of load-deflection curve
• (b) = specimen width
• (d) = specimen thickness

flowchart TD
    A[Start Test] --> B[Record Sandwich Construction Details]
    B --> C[Conduct Test at Specified Temp & RH]
    C -->

IS 9307 (Part I-VIII) — Failure Analysis & Observations

Key Formulas (Clause 6.1, Part I)

Failure Observations (Part II, Clause 4.3)

• Failure location: Facings or core.
• Order of failure: Sequence during test.
• Individual strength & stiffness: For facings and core if available.
• Stress details: Facings and core stresses as per Part I.
• Failure details: Type, mode, and location.
• Material properties: Facings and core.

Reporting Requirements (Part VII, Clause 6.1)

• Sandwich construction details (facings, core, adhesive).
• Weathering procedure & cycles.
• Damage observations during exposure.
• Comparative figures (with/without weathering).
• Observations on comparative data.

Summary Diagram of Failure Analysis Process

flowchart TD
    A[Test Setup] --> B[Load Application]
    B --> C[Measure Load & Compression]
    C --> D[Calculate Stresses & Modulus]
    D --> E{Failure Occurs?}
    E -- Yes --> F[Identify Failure Location]
    F --> G[Record Failure Mode & Order]
    G --> H[Analyze Material Properties]
    H --> I[Prepare Report

IS 9307 Part VIII (1979) - Specimen Conditioning & Exposure Cycles

Exposure Cycles (Clause 5.1)

Each specimen undergoes 6 complete cycles of one of the following two exposure sequences, with max 30 min interval between cycles:

Cycle Option 1:

Cycle Option 2:

Post-Exposure Conditioning (Clause 5.1 & 3.1)

• Condition specimens to constant weight at:
  • 65 ± 5% RH
  • 27 ± 2°C
• Observe and record any **delamination or damage

Here are the key formulas and specifications for Load Application and Rate of Loading from IS 9307 Part 1-8:

1. Core Shear Stress (S)

[ S = \frac{P_1 (h + c)}{b} ]

• (P_1) = applied load
• (h) = core thickness
• (c) = facing thickness
• (b) = specimen width

2. Facing Stress (F)

[ F = \frac{2 P_1 a_1 - 2 f (h + c) b}{4 f h b} ]

• (a_1), (f) = facing thickness parameters

3. Mid-span Deflection (W1)

[ W_1 = 480 + AN ]

• (A, N) = constants related to shear stiffness
• (N = G (h + c) b) where (G) = effective core shear modulus

4. Flexural Stiffness (D)

[ D = \frac{E (h^3 - c^3) b}{12 (1 - \nu^2)} ]

• (E) = modulus of elasticity of facings
• (\nu) = Poisson's ratio

5. Facing Stress at Various Stages

6. Fixity Factor (F)

• Indicates core's load capacity development before buckling
• Usually (F = 0) if no fixity

Notes on Load Application:

• Load expressed as % of max load (per IS 9307 Part 1, Clause 4.2)
• Creep measured as % of instantaneous deflection
• Rate of loading affects def

IS 9307 Part 1-8: Safety and Handling Precautions - Key Formulas & Specifications

Key Formulas (Clause 6.1 & 5.3)

Handling & Safety Highlights:

• Use proper PPE when testing sandwich specimens.
• Handle specimens carefully to avoid damage to facings and core.
• Ensure load application is gradual to prevent sudden failure.
• Follow standard test specimen dimensions as per Clause 4.
• Maintain calibration of testing equipment to ensure accurate load and deflection readings.

flowchart LR
    A[Load Application] --> B[Measure Load P, P1, P2]
    B --> C[Calculate Facing Stress σ, σ1, σ2]
    C --> D[Calculate Core Shear Stress S]
    D --> E[Evaluate Deflection F]
    E --> F[Assess Fixity Factor F]

Summary:

IS 9307 Part 1-8: References and Related Standards

• Primary Reference:
  IS 9307 Part 1 provides fundamental definitions and general requirements applicable across Parts 1 to 8.

• Key Related Standards:

  • IS 456: Code of Practice for Plain and Reinforced Concrete
  • IS 383: Specification for Coarse and Fine Aggregates for Concrete
  • IS 516: Methods of Tests for Strength of Concrete
  • IS 2386: Methods of Test for Aggregates for Concrete
  • IS 10262: Concrete Mix Proportioning
  • IS 1199: Methods of Sampling and Analysis of Concrete

• Test Specimen (Clause 4):
  Specimens for testing concrete properties (compressive, tensile strength) must conform to dimensions and curing conditions as per IS 516 and IS 9307 Part 1.

Typical Test Specimen Dimensions (IS 516 / IS 9307)

Key Formula: Compressive Strength

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

• (f_c) = Compressive strength (N/mm²)
• (P) = Load at failure (N)
• (A) = Cross-sectional area (mm²)

flowchart TD
    A[IS 9307 Part 1 Definitions] --> B[Test Specimen Preparation]
    B --> C[Specimen Dimensions as per IS 516]
    C --> D[Testing Procedures]
    D --> E[Strength Calculation]

Summary: IS 9307 Part 1-8 refers to Part 1 for definitions and aligns testing methods with IS 516 and related standards. Always ensure specimen dimensions and curing comply with these for valid results.