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Chopped carbon fibers with different dispersion types (colony type and uniform type) and area densities were inserted at sandwich beams, consisting of a PVC foam core covered with two glass fiber/epoxy composite face sheets. The effects of this reinforcement on the interfacial bonding between PVC foam core and glass fiber face sheets were evaluated. Their mechanical properties were measured by three‐point‐bending and Charpy impact tests. Their structures after mechanical failure were observed by scanning electron microscopy. Compared with the beam without interfacial reinforcement, the bending strength, energy absorption, and impact strength after interfacial reinforcement using 20 g/m2 uniform chopped fibers increased by up to 109%, 184%, and 47%, respectively, surpassing those of other chopped fiber mats. The weight percentage of carbon fibers/sandwich structure was less than 1%, so the chopped carbon fiber interleave had both cost effectiveness and outstanding structural performance. The improvement of interlayer toughness can mainly be attributed to the fiber bridging structure and the interlayer strength. POLYM. COMPOS., 40:E449–E455, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Sandwich beams were prepared by vacuum-assisted resin transfer molding, containing a PVC foam core covered with two glass fiber/epoxy composite face sheets. Their mechanical properties were measured by impact test and three-point bending (3 PB) test. To improve the interfacial bonding between the PVC foam core and glass fiber face sheets as well as the mechanical properties of the sandwich structure, different chopped fibers (aramid fiber, carbon fiber and glass fiber) with the same lengths and densities were inserted at the face-core interface during fabrication. Compared with the beam without interfacial reinforcement, the bending strength and energy absorption were increased by up to 100% and close to 161% respectively under 3 PB condition, and the impact strength after interfacial reinforcement using chopped glass fiber was augmented by nearly 45%, surpassing those of other two kinds of chopped fibers. The interfacial distribution characteristics of different chopped fibers were tested using scanning electron microscopy. The toughening and strengthening mechanisms for mechanical properties were analyzed based on the interfacial crack-bridging and wettability between chopped fiber and resin. [ABSTRACT FROM AUTHOR]