Enhancing the Fracture Resistance and Impact Toughness of Mechanically Frothed Epoxy Foams with Hollow Elastomeric Microspheres

Nonporous elastomeric particles are often employed to improve the toughness of brittle epoxy foams but this also decreases their compressive strength and stiffness. Herein, a novel strategy utilizing hollow elastomeric microspheres as toughening agent for epoxy foams is presented. The addition of 0.5 wt.% hollow elastomeric microspheres into epoxy foam leads to a 15% increase in critical stress intensity factor (K 1c) to 0.38 MPa m0.5 and 33% increase in Charpy impact strength (acU ) to 1.05 kJ m−2, respectively, compared to unfilled epoxy foam (K 1c = 0.33 MPa m0.5 and acU = 0.79 kJ m−2). However, a further increase in the hollow elastomeric microsphere concentration to 1.0 wt.% leads to microsphere agglomeration, which reduces both K 1c and acU to 0.35 MPa m0.5 and 0.93 kJ m−2, respectively. Nevertheless, the added hollow elastomeric microspheres do not lead to a reduction in the quasi‐static compressive properties of the epoxy foams. Toughening epoxy foam without sacrificing its compressive properties? In this work, a method to enhance the fracture resistance and impact toughness of brittle epoxy foam without sacrificing its quasi‐static compressive properties using porous elastomeric microspheres is presented. The fracture toughness and Charpy impact strength of hollow elastomeric microsphere‐filled epoxy foams improves by 15% and 33%, respectively, compared neat epoxy foams.