ASTM C272 Standard Test Method for Water Absorption of Core Materials for Sandwich Constructions

Get Certified ASTM C272 Water Absorption Testing

ASTM C272 is a standard test method for obtaining standardized moisture-absorption information for sandwich core materials. Results are used in design properties, material specification, research and development, and quality assurance. According to ASTM, absorbed water can also impact the electrical and mechanical characteristics of core materials used in sandwich structures and can also influence the behavior of the sandwich structures. The technicians prepare and treat specimens following the procedure chosen and measure their mass and dimensions accurately. Engineers and analysts use the resulting water-absorption data to compare core materials and evaluate their suitability for applications where moisture exposure is important.

• Material Type: Sandwich construction core materials, including balsa wood, foams, and honeycomb.
• Purpose: Determination of the relative amount of water absorbed by the core material.
• Property Measured: Water absorption or moisture-related mass increase.
• Method: Exposure of core specimens to water immersion or a high-relative-humidity environment followed by mass measurement.
• Result: Water absorption expressed as the change in specimen mass.
• Test Limitations: Water absorption is influenced by core material, fabrication method, geometry, specimen preparation, conditioning, and moisture content during measurement.
• Environmental Conditions: Specimens are exposed to specified water or humidity conditions and controlled temperature conditions.
• Applications: Design properties, material specifications, research and development, and quality assurance.

What are the uses of ASTM C272 testing?

The ASTM C272 standard specifies the amount of water absorbed by a sandwich core material under certain moisture conditions. The absorbed water can influence properties like dielectric constant, loss tangent, electrical resistance, strength, and modulus. Also, the absorbed water may influence the behavior of sandwich structures. Manufacturers can use the results to compare core materials and evaluate moisture sensitivity. Engineers can use water-absorption data when developing sandwich structures and establishing material specifications. The test helps to:

• Water Absorption Evaluation: Determines the relative amount of water absorbed by the core material.
• Material Comparison: Compares moisture absorption among different core materials.
• Design Evaluation: Provides moisture-absorption information for sandwich construction design.
• Quality Assurance: Supports verification of core material performance.
• Material Specifications: Provides data for applicable material requirements.
• Research and Development: Supports development and evaluation of sandwich core materials.
• Moisture Performance Assessment: Helps evaluate core behavior under specified moisture exposure.

Which Materials Can Be Tested According to ASTM C272?

ASTM C272 applies to various types of sandwich construction core materials. The standard permits core forms having continuous bonding surfaces as well as discontinuous bonding surfaces. Technicians select representative specimens based on material type, geometry, and test conditions. The method applies to:

• Foam Cores: Sandwich construction core materials with continuous bonding surfaces.
• Balsa Wood Cores: Core materials commonly used in sandwich constructions.
• Honeycomb Cores: Core materials with discontinuous bonding surfaces.
• Other Sandwich Core Materials: Applicable core forms covered by the standard.
• Structural Core Materials: Core materials evaluated for moisture absorption in sandwich construction applications.

Why is ASTM C272 Testing Important?

Water absorbed by a sandwich core can change important electrical and mechanical characteristics. ASTM C272 establishes a series of standardized procedures for presentation of data on water absorption that can be used for design properties, material specification, research and development, and quality assurance. The standard also identifies core material, fabrication method, core geometry, specimen geometry, specimen preparation, measurement methods, conditioning, and moisture content as factors that influence the reported results.

ASTM C272 Testing Process and Data Collection

Technicians prepare the core specimens and measure their length, width, and thickness. They dry and condition the specimens as required, allow them to reach the appropriate measurement condition, and determine their initial mass. The specimens are then exposed to the selected moisture-conditioning procedure. For the 24-hour immersion procedure, technicians completely immerse the specimens in water maintained at 23 ± 3 °C for 24 +1/−0 h. For materials that float, technicians hold them below the water surface without substantially affecting the exposed surface area. After conditioning, technicians remove the specimens, remove surface water, and immediately determine their mass. Analysts compare the post-conditioning mass with the pre-conditioning mass and calculate the relative increase in mass attributable to absorbed water. The standard also specifies the type of specimen (geometry), preparation of the specimen, core geometry, fabrication process, mass measurement methods, dimensional measurement methods, conditioning, and moisture content, which may affect water-absorption readings.

Common Challenges and Troubleshooting

Variations in specimen geometry, core density or structure, fabrication method, conditioning, surface water removal, and mass measurement can influence ASTM C272 results. The technicians must ensure that the specimens they are preparing are consistent and properly record the dimensions and the mass of each specimen before and after they are exposed to moisture. Excess surface water will result in an overestimation of water absorption and lead to an erroneous water-absorption value. In addition, the analyst should keep the specified conditioning temperature and conditioning time and report any deviations from the prescribed procedure. 

• The laboratory reports the initial and final specimen mass in g and records the calculated water-absorption result as a percentage increase in mass, according to the applicable procedure.
• The technician records specimen length, width, and thickness in mm, specimen geometry, core material, conditioning method, test temperature in °C, and exposure time in h.
• The analyst documents the observed change in specimen mass and records relevant specimen condition, surface-water removal, moisture exposure, and other characteristics that may influence the water-absorption result.
• Analysts record specimen identification, material fabrication details, core geometry, specimen preparation, conditioning procedure, mass and dimensional measurement methods, moisture content, and other required test information.
• Engineers compare the observed or calculated water-absorption results among sandwich core materials to support material selection, design properties, material specifications, research and development, and quality assurance.

Link to ASTM C272