Evaluating Interfacial Foam Compression Set Effects on Module Stress Distribution Profiles
Foam compression set collapses baseline clamping force, shifting planar pressure to rigid edges, elevating thermal impedance, and risking tab fatigue.
ISO 1856
Meaning
The evaluation of polymeric materials for set deformation after long-term compression lies at the center of international standards for cellular structures. This standard, known as ISO 1856, dictates how to measure the recovery of flexible polyurethane or rubber foams after being held under constant strain. It establishes a uniform way to evaluate the long-term elastic resilience of the foam pads that isolate adjacent cells.
Testing Protocol
Foam specimens are compressed to a fraction of their initial thickness using parallel plates and held at a specified temperature for a set duration. The procedure defined in ISO 1856 measures the recovery of the material after the compressive force is removed and the sample has been allowed to rest. This test is repeated at several temperatures to simulate the environmental conditions the battery pack will experience over its service life.
This systematic approach ensures that the resulting measurements are highly reproducible across different test centers.
Compression Set
Permanent thinning occurs when the foam has a high compression set under ISO 1856 testing, leading to cell movement. If a foam suffers permanent thinning when installed in a module, it creates gaps that allow cells to move, which worsens the risk of physical damage and thermal interface degradation. Consequently, battery designers rely on low-set materials to keep components locked in place.
Sourcing Standard
Sourcing teams specify compliance with this international standard when purchasing elastomeric compression pads from global foam manufacturers. The test reports allow engineering groups to compare raw materials and select foam grades that maintain their cushioning action over the vehicle lifetime. Selecting certified materials minimizes the likelihood of recall campaigns due to structural foam failure.