PSI - Issue 52

Satrio Wicaksono et al. / Procedia Structural Integrity 52 (2024) 438–454

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Satrio Wicaksono et al. / Structural Integrity Procedia 00 (2023) 000 – 000

materials presents several challenges due to their anisotropic nature and sensitivity to damage. Among the different types of joints, the T-joint configuration is one of the most commonly used in composite structures because of its simplicity and versatility. Mechanical fastening involves the use of fasteners such as bolts, screws, or rivets to hold the composite components together. This method provides a high level of mechanical strength and is relatively easy to implement. However, it can create stress concentrations and damage the composite material, reducing its strength and durability [1]. Furthermore, mechanical fastening can lead to weight penalties due to the additional weight of the fasteners. Adhesive bonding is a widely used technique for joining composite materials, and it involves the use of an adhesive material to bond two composite components together. The adhesive material can be a thermoplastic or thermosetting resin, and the bonding process can be achieved through various methods, including heat, pressure, or curing. One significant advantage of adhesive bonding is that it provides a continuous load transfer path, which results in a more efficient joint than other methods [2], [3]. In addition, adhesive bonding can provide an effective seal against moisture and other environmental factors that can cause degradation of the composite material. Moreover, the design of the T joint itself plays a crucial role in the joint's overall strength and durability. The joint geometry, the thickness and orientation of the composite plies, and the surface preparation are all critical factors that must be carefully considered. Recently, the T-joint method has been widely adopted in the construction of the float of amphibious aircraft [4]. This float is made of composite sandwich material and is composed of several bulkheads. One of the important components to connect the bulkhead to the hull is the T-joint. The T-joint is a type of adhesive connection that is widely used in industries such as aircraft structures, ships, etc. T-joint is used because it has good performance in terms of resistance to impact, vibration, fatigue load, and also has good energy absorption capability [5], [6]. The T-joints commonly used in the floats of amphibious aircraft are made of a composite sandwich material and reinforced with a composite lamina [7]. There are several studies that have been conducted to find the optimal T-joint configuration. Lystrup et al. [8], found a T-joint configuration with the addition of a triangle core on a horizontal base which resulted in a strength increase of up to 20% over previous designs with only a 40% weight increase. They concluded that with the development of finite element analysis, it would be possible to find a more optimal geometry and T-joint material against tensile loading. In addition, the configuration of the connection with an additional layer (cleat) can improve the performance of the T-joint in receiving and transmitting loads thereby reducing the concentrated force in critical areas. After analyzing the optimum geometry, the next process is to analyze the failure of the T-joint. The geometry will be optimum if given the right loading to avoid failure. Failure analysis of T joints can be carried out by numerical modeling. Several studies on failure analysis with numerical results have been carried out to find failure modes that commonly occur in T-joints [8] – [14]. Dharmawan, et al. [10], using MSC Nastran 2D finite element analysis, under tensile loading found debonding failures between filler and overlaminate. This failure will happen more quickly if there is no filler, because the filler functions to transfer the load. Another T-joint configuration studied by Lystrup et al. [8], conducted a 2D analysis with additional macro code in ANSYS, under tensile loading found core shearing failure to delamination between the skin and the sandwich core on the horizontal panel. In addition, another failure mode that was found was a crack that spread from the sandwich core on the triangular fillet and then spread to the vertical panel of the T-joint. Khalili et al. [11] conducted a 2D analysis using the macro code on ANSYS, also found a failure mode in the form of core shearing on core material with the lowest elastic modulus. Meanwhile, core specimens with higher elastic modulus experience delamination and debonding between connection elements. With a different configuration of the T-joint, Li, et al. [13], using a 2D strain model analysis on ABAQUS/CAE, under tensile loading found the failure mode of the T joint in the form of delamination. Another T-joint configuration studied by Caliskan, et al. [14], using non-linear 3D model analysis on ABAQUS/CAE, with low-speed impact loading produces a failure mode in the form of buckling and crippling and delamination of the sandwich structure. Based on the research that has been done to date, the failures that have been modeled on T-joints are limited to certain failures and models. In this research, a numerical method of T-joints will be studied which can analyze several types of failures such as delamination, core shearing, and core crushing to obtain the optimum geometry of T-joints that will be applied to seaplane floaters in future studies. In this research, the objective is to develop a robust model that can predict multi-mode of failure of T-joint foam-core sandwich composite under various loading conditions. The composite skin was modeled using Hashin-damage model, while the foam core was modeled using crushable foam