Overview
EN ISO 4651:1995 (ISO 4651:1988) specifies a laboratory method for assessing the dynamic cushioning performance of cellular rubbers and cellular plastics used in packaging. The standard measures the peak deceleration of a mass (drop hammer) when it impacts a test piece. The procedure is intended primarily for quality assurance, while an informative annex provides notes for using the test to obtain design data. Typical apparatus arrangements (guided vertical drop tester and pendulum tester) are illustrated.
Key topics and requirements
- Test principle: measure peak deceleration of a drop hammer impacting a specimen to characterise cushioning behaviour (dynamic stress, strain, displacement curves).
- Test pieces: rectangular specimens, nominal 150 × 150 × 50 mm (thickness ±5 mm); cutting must not alter dynamic properties (no hot-wire cutting); set of at least ten specimens.
- Impacts and repeats: each specimen is impacted three times at fixed velocity and static stress; peak deceleration is recorded on first and third impacts; allow recovery and remeasure thickness.
- Impact velocities: two standard equivalent free-fall heights - 250 mm and 750 mm (1250 mm optional). Hammer velocity must be ≥95% of equivalent free-fall velocity.
- Static stress: choose several static stress values (typically five) distributed to identify minimum and ±10–20% response points; number of stresses may be reduced by agreement.
- Apparatus & recording: use a drop hammer with an anvil (anvil mass ≥100× hammer), transducer mounted centrally on the hammer, and recording electronics. Transducers may be piezoelectric or strain-gauge; frequency response and damping must be adequate to measure transient deceleration pulses within ±5% accuracy.
- Conditioning: specimens conditioned per referenced standards (e.g., ISO 291, ISO 471) - recommended 23 °C ±2 °C and 50% ±5% RH.
- Data and corrections: corrected peak deceleration accounts for deviations from the reference thickness (50 mm); displacement and dynamic compression diagrams can be derived (annex A).
Practical applications
- Quality control and acceptance testing of packaging foams and cushioning materials
- Comparative material evaluation for shock absorption and impact protection
- Input data for packaging design when combined with annex guidance (selection of cushioning for fragile goods)
- Research and development for cellular rubbers and plastics
Who uses this standard
- Packaging engineers and designers
- Manufacturers and suppliers of cellular rubbers and plastics
- Independent testing laboratories and QA departments
- Procurement/specification teams requiring objective cushioning performance data
Related standards
Normative references include ISO 291, ISO 471, ISO 845, ISO 1923, ISO 2231, and ISO 3205, which cover conditioning, dimensional measurement and density assessment relevant to EN ISO 4651 testing.