Issue link: http://cp.revolio.com/i/399448
The growing complexity of the global distribution environment and the need for environmentally responsible packaging solutions have led to increasing pressure on packaging engineers to design optimal protective packages. Leveraging the necessary protection of fragile products against minimizing the amount of packaging materials is paramount in today's market. Existing design tools for packaging engineers do not account for the nonlinear and viseoelastic properties of EPS foam, and current design approaches rely heavily on costly trial- and-error testing methods. But the push for sustainable packaging has opened the door for the development of new tools that enable designers to understand the complex behavior of expanded polymer foams. Crucial to developing these tools is the connection between the material behavior and the dynamic responses of packaging systems. The impact of these new tools and techniques on the use of expanded polymer foams are multifaceted: • They provide designers and material developers with a comprehensive physics-based understanding of the materials and their dynamic behavior; • They develop a link between the constitutive behavior of the material and the desired dynamic behavior; • They reduce the number of expensive and time consuming design iterations previously necessary for product development. The work resulting in these findings was conducted at Clemson University in Clemson, South Carolina and Clarkson University in Potsdam, New York. Dynamic Behavior Polymer foams can exhibit complex dynamic responses depending on the level of static stress, foam thickness and the level and frequency of input. Figures 1 a) and b) illustrate examples of the linear and nonlinear frequency responses of a simplified packaging system. The linear response shows the typical amplitude amplification at resonance. However, in the nonlinear response the amplitude amplification is dependent on the excitation and static stress level 1 and softening behavior characterized by a "bend" where two amplitudes of vibration can exist depending on the initial condition of the foam. 7 1 It should be noted that in the linear case the amplitude is also dependent on the static stress level, however, the "bending" behavior of the frequency response is not present in the linear case. By Gregory Batt, Ph.D., Clemson University & James Gibert, Ph.D., Clarkson University Recent Developments in the Modelling, Identification and Evaluation of Expanded Polymer Foams