The development of armour systems with higher ballistic resistance and light weight has gained considerable attention as an increasing number of countries are recognising the need to build up advanced self-defence system to deter potential military conflicts and threats. Graphene is a two dimensional one-atom thick nanomaterial which possesses excellent tensile strength (130 GPa) and specific penetration energy (10 times higher than steel). It is also lightweight, tough and stiff and is expected to replace the current aramid fibre-based polymer composites. Currently, insights derived from the study of the nacre (natural armour system) are finding applications on the development of artificial nacre structures using graphene-based materials that can achieve high toughness and energy dissipation. The aim of this review is to discuss the potential of graphene-based nanomaterials with regard to the penetration energy, toughness and ballistic limit for personal body armour applications. This review addresses the cutting-edge research in the ballistic performance of graphene-based materials through theoretical, experimentation as well as simulations. The influence of fabrication techniques and interfacial interactions of graphene-based bioinspired polymer composites for ballistic application are also discussed. This review also covers the artificial nacre which is shown to exhibit superior mechanical and toughness behaviours.
Adequate awareness of sustainable materials and eco-legislation have inspired researchers to identify alternative sustainable and green composites for synthetic fiber-reinforced polymer composites in the automotive and aircraft industries. This research focused on investigating the physical, mechanical, and morphological properties of different hybrid Cyrtostachys renda (CR)/kenaf fiber (K) (10C:0K, 7C:3K, 5C:5K, 3C:7K, 0C:10K) reinforced with 0.5 wt% MWCNT-phenolic composites. We incorporated 0.5 wt% of MWCNT into phenolic resin (powder) using a ball milling process for 25 h to achieve homogeneous distribution. The results revealed that CR fiber composites showed higher voids content (12.23%) than pure kenaf fiber composites (6.57%). CR fiber phenolic composite was more stable to the swelling tendency, resulting in the lowest percentage of swelling rate (4.11%) compared to kenaf composite (5.29%). The addition of kenaf fiber into CR composites had improved the tensile, flexural, and impact properties. The highest tensile and flexural properties were found for weight fraction of CR and kenaf fiber at 5C:5K (47.96 MPa) and 3C:7K (90.89 MPa) composites, respectively. In contrast, the highest impact properties were obtained for 0C:10K composites (9.56 kJ/m2). Based on the FE-SEM image, the CR fiber lumen was larger in comparison to kenaf fiber. The lumen of CR fiber was attributed to higher void and water absorption, lower mechanical properties compared to kenaf fiber. 5C:5K composite was selected as an optimal hybrid composite, based on the TOPSIS method. This hybrid composite can be used as an interior component (non-load-bearing structures) in the aviation and automotive sectors.
Natural fibers have emerged as a potential alternate to synthetic fibers, because of their excellent performance, biodegradability, renewability and sustainability. This research has focused on investigating the thermal, visco-elastic and fire-retardant properties of different hybrid Cytostachys Renda (CR)/kenaf fiber (K) (50/0; 35/ 15, 25/25, 15/ 35, 0/50)-reinforced MWCNT (multi-walled carbon nanotubes)-modified phenolic composites. The mass% of MWCNT-modified phenolic resin was maintained 50 mass% including 0.5 mass% of MWCNT. In order to achieve homogeneous dispersion ball milling process was employed to incorporate the MWCNT into phenolic resin (powder). Thermal results from thermogravimetric analysis and differential scanning calorimetric analysis revealed that the hybrid composites (35/15; 35 mass% CR and 15 mass% K) showed higher thermal stability among the composite samples. Visco-elastic results revealed that kenaf fiber-based MWCNT-modified composites (0/50; 0 mass% CR and 50 mass% K) exhibited higher storage and loss modulus due to high modulus kenaf fiber. Fire-retardant analysis (UL-94) showed that all the composite samples met H-B self-extinguishing rating and exhibited slow burning rate according to limiting oxygen index (LOI) test. However, (15/35; 15 mass% CR and 35 mass% K) hybrid composites showed the highest time to ignition, highest fire performance index, lowest total heat release rate, average mass loss rate, average fire growth rate index and maximum average rate of heat emission. Moreover, the smoke density of all hybrid composites was found to be less than 200 which meets the federal aviation regulations (FAR) 25.853d standard. Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was carried out to select an optimal composite sample considering the thermal, visco-elastic and fire-retardant behaviors. Through TOPSIS analysis, the hybrid (15/35; 15 mass% CR and 35 mass% K) composite sample has been selected as an optimal composite which can be used for high-temperature aircraft and automotive applications.