Lightweight microwave-absorbing epoxy–reticulated vitreous carbon foam composites manufactured by vacuum-assisted resin transfer moulding for structural application

Lightweight and mechanically strong sandwich panels are extensively used in the aerospace, defence and energy sectors. In this context, the present study aims to develop high-strength lightweight multifunctional composites using epoxy and reticulated vitreous carbon (RVC) foam. For this, epoxy-infiltrated RVC foams were prepared by the scalable vacuum-assisted resin transfer moulding (VARTM) technique. The complex porous structure of RVC foam, owing to its local variations in the density as well as open-cell content, entails variations in the compressive strength of the composite, making it a function of density and porosity. To rationalize the statistical variations in composites, the Weibull distribution was used to predict compressive properties, measured on a large number of specimens. The Weibull analysis revealed a regression coefficient of 0.98 and a characteristic strength of ~75.1 MPa. The average compressive strength and modulus of the epoxy–RVC foam composite were found to be 68.52 ± 16.03 and 1303.7 ± 141.63 MPa, respectively. Moreover, the flexural strength and modulus of these composites were found to be 33.6 ± 6.6 and 4.73 ± 2.6 GPa, respectively. In addition, the composites showed electromagnetic interference shielding effectiveness of >20 dB with absorption domination in X-band frequency. On account of its lightweight, promising microwave absorption and mechanical properties, epoxy–RVC foam composites are potential candidates as multifunctional core materials in sandwich panels.