Shock-absorption properties of functionally graded EVA laminates for footwear design

The shock-absorbing performance of single ethylene-vinyl acetate (EVA) foams and functionally graded laminates of these foams were evaluated with simulated gait experiments. Mechanical properties such as the hardness and density were measured, along with the viscoelastic behavior. The shock-absorbing performance was found to be dependent on the cellular structure, namely the density, elastic modulus, and loss tangent of the single EVA foams. However, for the laminated samples, there were slight variations in the shock-absorption efficiency for samples with the same density. The graded materials showed higher shock-absorption efficiency compared with non-graded single materials with the same density. In addition, laminates with elastic modulus values slightly higher than those of the single EVA samples showed higher shock-absorption efficiency. Finally, since laminates with varied properties were produced, a design concept for a suitable functionally graded material is presented for footwear applications.