Enhanced anti-impact performance of composite sandwich panels with modified polyurethane foams, exploiting phase transition occurrence of non-newtonian polymer.

Lightweight, flexible and low-cost materials which possess great energy absorption properties are in great demand in composite sandwich panels, and in body protective equipment used in sports and military. One of the most widely used materials in these applications is polyurethane foam (PUF), showing good energy absorption and shape restorability under low-rate dynamic loading conditions. However, their response to high-rate dynamic loading conditions can lead to cell wall damage significantly hindering their performance. In this work, a non-Newtonian polymer with high energy dissipation efficiency was selected as an excellent candidate for the enhancement of the mechanical properties of PUFs. Low Velocity Impact tests were employed directly on foams, composite sandwich panels and post-impact for the evaluation of their residual properties. Results indicated that the presence of the non-Newtonian polymer led to an improvement of the energy dissipation of the modified foams, averting cell wall damage, constituting these as ideal core structure candidates.