Characterization of three-point bending properties of metal–resin interpenetrating phase composites

Metal-resin composites provide improved combinations of mechanical properties of raw materials. A novel metal-resin interpenetrating phase composite (IPCs) has been fabricated by spontaneously infiltrating unsaturated polyester resin into porous short-fiber preforms under vacuum conditions. In this study, three-point bending experiments are performed to characterize the bending properties of the IPCs. The fractographs after bending are examined to distinguish their characteristics. The flexural strength increases almost linearly from 42 ± 4 MPa to 119 ± 5 MPa in the in-plane direction and 59 ± 4 MPa to 151 ± 8 MPa in the through-thickness direction with an increasing fiber fraction ranging from 16.78 vol% to 32.11 vol%. The structures and bending properties of the IPCs exhibit significant anisotropy. Compared with the in-plane direction, higher bending strength and flexural modulus with smaller displacement at maximum bending force are observed in the through-thickness direction. The finer fibers contribute to improving the flexural strength (from 76 ± 6 MPa to 98 ± 5 MPa for the IPCs with about 23 vol% fiber fraction from 160 μm to 90 μm fiber diameters in the in-plane directions) and modulus. The fracture of the IPC after bending presents different appearances in different directions and the anisotropy becomes less severe with decreasing fiber fraction. Resin fracture, fiber necking and fracture, and debonding are the main fracture mechanisms.