PSI - Issue 48

Ilham Bagus Wiranto et al. / Procedia Structural Integrity 48 (2023) 65–72 Wiranto et al. / Structural Integrity Procedia 00 (2023) 000 – 000

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1. Introduction Composite materials are suitable for this implementation due to their high specific modulus and strength, as well as their own chemical stability [Wang et al., 2018]. Carbon-fiber-reinforced plastics (CFRP) have seen increased use in lightweight structures in recent years, particularly in aviation [Kühnel et al., 2014]. Composite sandwich structures are typically made up of thin panels with high strength and stiffness on the outside and a light thick core material on the inside, shown in Fig. 1. Sandwich structures, despite being many times lighter, can withstand similar heavy loads as solid structures. The CFRP honeycomb specimens were created using the corrugation technique, in which pre-preg CFRP sheets were corrugated into a specific shape using corrugated aluminium moulds under heat and pressure, and then the corrugated CFRP sheets were glued and stacked to create honeycomb specimens [Pehlivan et al., 2019]. Honeycomb structures are increasingly being used in a variety of industrial applications due to their low weight-to strength and weight-to-cost ratios, high energy absorption capacities, and good crashworthiness performances. Because of their high stiffness and strength-to-density ratio, phenolic resin-impregnated aramid paper honeycombs, also known as Nomex® honeycombs, are promising cores of stiffness-dominated sandwich structures in aerospace applications [Zhang et al., 2018]. Multi-cell sections and composite wrapping are two effective methods for improving the crashworthiness of thin walled tubes. The interaction effect of CFRP on energy absorption of various sections is also investigated, and the results show that the interaction effect decreases as the number of sectional cells increases, while it increases as the number of CFRP layers increases [Huang et al., 2019]. The cell wall thickness has a significant impact on the overall crushing response of CFRP honeycombs, whereas the honeycombs' out-of-plane compressive strength is generally independent of height [Pehlivan et al., 2019]. Due to their large double foil bonding surfaces, hexagonal specimen groups have generally superior crushing performance when compared to square and circular counterparts.

Fig. 1. CAD Model of sandwich panels with honeycomb core and CFRP skin.

The crashworthy design has attracted a lot of attention as the number of vehicles increases. Thin-walled energy absorbing structures' crashworthiness becomes a crucial safety standard for the automotive and aircraft industries. In order to protect passengers from serious injuries during a collision, a good structure must be able to absorb a significant quantity of kinetic energy in a controlled and irreversible manner [Abdullah et al., 2020; Alkateb et al., 2018]. Material selection and structural design are the keys to enhancing crashworthiness [Baroutaji et al., 2017]. In aircraft industries, it is critical to have a structure with a good capability of absorbing energy, especially in crash incident scenarios [Abosbaia et al., 2003; Chiaberge et al., 2011; Gowid et al., 2019; Laban et al., 2016]. Composite material has become one of the proven solutions to increase the energy absorption capability in automobile and aircraft industries. For example, composite structures can be used either as the outer skin of an aircraft or as the main structure of a fuselage. During aircraft crash incident scenarios, mostly the first impact will be subjected to skin and a structure behind it. However, it is crucial to investigate the structure's crashworthiness performance under drop weight impact events. Many researchers conducted a drop weight impact event to investigate the crashworthiness using specific mechanical parameters, such as drop height variation, weight or load carrying, and impactor shape. Furthermore, some researchers use a variety of measurement methods extensively, including load cells, accelerometers, strain gauges, and high-speed photography. For composite sandwich structure, many researchers also analyse composite through a variety of