Setting Stresses in Polymer Composites with Multiple‐Size Particles

Abstract

The effect of size gradation and geometric arrangement of multiplesize reinforcing particles on setting stresses in polymer composites was investigated using three‐dimensional finite element analysis. The composites were modeled by systems containing spherical reinforcing particles packed in orderly arrangements within the polymer matrix. Two groups of models were assembled by placing the largest particles in simple or face‐centered cubic arrangements. Within each model group the placement of successively smaller particles in the interstices of the larger particles produces specific composites with different aggregate‐to‐resin volume ratios and different shapes of the resin domains. The maximum setting stresses occur at the particle‐resin interface, underlining the importance of resin/aggregate adhesion in these composites. This is usually achieved in practice by the use of chemical additives that act as coupling agents between resin and aggregate. Setting stresses decrease in systems with efficient packing, achieved with proper size gradation and close‐packed geometry. Reduction in setting stresses by a factor of two is possible in these systems. These results are supported by experiments.