Educational Administration in the University of Bristol School of Education

Hybrid auxetic foam and perforated plate composites for human body support

“…). The Poisson's ratio values were previously measured and ranged between −0.7 and −0.2 , in agreement with the figures calculated by Grima and Gatt . The working pressure for the water‐jet cutting was 55 000 psi, with a jet size of ±1.15 mm, accuracy of ±0.127 mm per 1 m and speed of 101.6 mm min −1 .…”

“…The analysis was done with a 95% confidence level, hence a P‐ value less or equal to 0.05 (5%) means that factor has a significant effect on K . The perforation dimensions affect the stiffness response of the curved plates on their own . This phenomenon was confirmed by the DoE analysis, with a resulting P‐ value of 0.000.…”

“…Four sets of plates were manufactured with ABS plastics and water‐cutting techniques (Flow Mach 1) with the geometry parameters listed in Table . The separation distances s (10–15 mm) and perforation dimensions a (15–35 mm) were chosen based on an initial exploration of the design envelope based on manufacturing constraints and overall size of the plates (Fig. ).…”

“…Auxetic materials have improved indentation resistance, enhanced bending stiffness in structural elements and shear compliance in comparison to their conventional counterparts . Auxetic behaviour has also been shown to exist with a number of materials; silicates and zeolites, metals, foams and polymers , whilst utilising a range of different mechanisms; re‐entrant units , rotating square models , chiral systems , auxetic composites , perforated systems with void filled/unfilled with another phase and auxetic behaviour induced by an elastic instability . Foams in particular have provided experimental evidence of high energy absorption under cyclic and impact loading, all characteristics that combined with the sinclastic curvature deformation make negative Poisson's ratio foams appealing materials for sport and biomedical applications .…”