The Non-Linear Characteristics of Cushioning Materials

Abstract

Much of the mechanical damage to packages or products in shipment can be attributed to shocks and vibrations encountered during transportation. These vibrations, which are generally random in nature, can cause the shipment, or critical elements within, to resonate. This has the potential for damage to or failure of the product due to the repetitive application of stresses. It is therefore imperative that the design of protective cushioning systems takes into account the resonant frequencies of critical elements within the product. Conventionally, this is achieved by the measurement of the linear Frequency Response Function (FRF) or transmissibility of the product/ cushion system. However, commonly used cushioning materials can exhibit strong non-linear behaviour. This non-linear behaviour is exacerbated when the cushioning system is placed under high static loads. Large static loads are often a result of attempts to minimise the environmental impact (as well as the associated economical benefits) of packaging materials by reducing the amount of cushioning material used. Non-linear behaviour can have significant implications for the design and optimisation of protective packaging systems, especially when trying to evaluate the transmissibility of the system.