This paper reports the effects of epoxy when reinforced with graphite flakes (GFs) and was compared to epoxy reinforced by hybrid reinforcements consisted of graphite flakes (GFs) and graphene nanoplatelets (GNPs). DGEBA, the type of epoxy which has been used in this work was added with 2, 4 and 6 wt.% of reinforcement respectively, relative to the total weight of the mixture. Nanocomposites was prepared using mechanical stirrer, stirred at 2000 rpm for 30 minutes followed by curing in the oven. The flexural testing shows that the epoxy/GFs composites has higher modulus compared to epoxy/GFs+GNPs. At 4wt.% filler loading, epoxy containing GFs exhibited 132% enhancement of modulus relative to neat epoxy. At the same filler amount, epoxy containing GFs+GNPs demonstrated slightly lower magnitude than system containing GFs with only 27% increase in modulus. However, addition of higher filler loading to the epoxy resin caused the modulus to decrease in magnitude speculated due to agglomeration of particles within the host matrix. The Charpy impact testing indicated similar pattern with epoxy/GFs system exhibited higher capability in absorbing energy than epoxy/GFs+GNPs where the peak was obtained at 4wt.% filler loading. At this amount of filler, 18.36 J/m increase in energy absorbed was recorded for epoxy/GFs compared to 2.13 J/m increased for epoxy/GFs+GNPs composite. Higher amount of filler loading added into epoxy only deteriorate the impact energy absorb by the sample. The hardness test show similar pattern of result with epoxy/GFs shows higher resistance in scratching compared to epoxy/GFs+GNPs.

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Hexagonal honeycomb cores have found extensive applications particularly in the aerospace and naval industries. In view of the recent interest in novel strong and lightweight core architectures, square honeycomb cores were manufactured and tested under uniform lateral compression. A slotting technique has been used to manufacture the square honeycomb cores based on three different materials; glass fibre-reinforced plastic (GFRP), carbon fibre-reinforced plastic (CFRP) and self-reinforced polypropylene (SRPP). As semi-rigid polyvinyl chloride (PVC) foam was placed in each of unit cells to further stiffen the core structure. The core then was bonded to two skins to form a sandwich structure. The compressive responses of the sandwich structures were measured as a function of relative density. In this paper, particular focus is placed on examining the compression strength and energy absorption characteristics of the square honeycombs with and without the additional foam core. Comparisons in terms of specific strength and specific energy absorption have shown that the CFRP core offers excellent properties. The presence of the foam core significantly increases the energy absorption capability of overall structure and the SRPP core could potentially be used as an alternative lightweight core material in recyclable sandwich structures.