Impact Testing of Flexible Polyurethane Foams

Methods of obtaining information on dynamic properties of flexible foams from a limited number of impact tests are considered. The test procedure is based on measuring acceleration and displacement during the entire impact (not only maximum values as required in current standards). Interpretation of the results uses two theoretical approaches: stress-strain relationships and similarity considerations. Each approach has its own advantages. The developed algorithm, applied presently to four commercial packaging foams, allows the plotting of cushioning diagrams and predicts the shape of time-impact dependence for an arbitrary drop height and foam thickness. Properties of composite cushioning structures can be calculated.