Materials Science Forum Vol. 1092

Abstract: This paper focuses on the computational modeling of the crashworthiness performance of designed foam-filled thin-walled tubular structures under quasi-static compression loading. The studied foam sample is designed in SolidWorks using the ‘sphere subtraction method’ and implemented as a filler material in the thin-walled tube. The quasi-static compression was simulated by Abaqus software. The foam porosity is manipulated to enhance the crashworthiness performance of empty tubes. The deformation mode and energy absorption capability of the analyzed structures are introduced in detail. The numerical results showed that foam-filler material could change the deformation mode and improve stability during the compression process of thin-walled tubular structures. The number of lobes significantly increases when introducing the foam filler to the tube. These folds are affected by the foam porosity. Results also indicate that the total crushing load of the foam-filled tube is also a function of foam porosity, the mechanical response of the foam-filled tubes tended towards the response of the empty tube for a high porosity (P >85%), while for low porosity (P<85%) the mechanical response of the foam-filled tubes exhibits the three universal deformation characteristics of foams, namely, initial linear stage, extended plateau stage, and final densification stage. The main mechanical properties: collapse stress, plateau stress, and densification strain were obtained via the energy-efficient method for different configurations. The calculated mechanical properties exhibited a strong dependence on foam porosity. To give a quantitative description of the obtained quasi-static compressive properties, these properties are expressed as a function of foam porosity. The proposed formulas can easily recover the quasi-static compressive properties of the empty tube in the case of the absence of foam. The control of the compressive performance of foam-filled tubes as a function of porosity allows for finding an optimum geometry with a predefined foam porosity value adjusted for a given application.

Abstract: Lightweight, robust, and anti-rust properties of aluminium foam might be a solution for reducing the effect of traffic accidents and for minimum fuel consumption. This research investigated the crashworthiness of vehicle crash-box filled with aluminum foam by varying its cross-sectional structure and its loading angle such as 0°, 10°, 20°, 30°. The variations consisted of structures for example single wall foam filled and double wall foam filled. The material used to construct the wall was Aluminum Alloy 2024 and Aluminium foam. The finite element model using Abaqus CAE Software was operated for both designing the crash-box and analyzing its crashworthiness. Some parameters were determined To obtain the best crash-box design, the finite element analysis was carried on total energy absorption, specific energy absorption, maximum load, average load, and crush-force efficiency. Double wall foam filled crash-box was shown to have better energy absorption ability and this structure of crush box is considered fpr vehicle structure in future.

Abstract: Compatibility between elements in natural fiber based-composite always becomes a hot issue. The presence of lignin in natural fibers inhibits interlock with its matrix. This research investigates the degradation of lignin encapsulating coconut coir fiber using white-rot fungus (Pleurotus Ostreatus) and its effect on composite compatibility. The process of delignification was carried out by exposing coconut coir fibers in the media where the white-rot fungus was incubated and grown. The period of exposure was 10, 20, and 30 days, and the ratio of coconut coir fiber to white-rot fungi were 1:1, 1:1.5, and 1.5:1 (by weight). To find the effect of delignification, several tests were conducted namely lignin content, fiber surface morphology, wettability, and pull-out tensile test. The results show that there is a reduction in the lignin content of the fibers. The largest reduction is 27.11% for 30 days of exposure times with the ratio of 1:1.5. The surface morphology of the fibers is smoother due to the loss of lignin. In the wettability test, it is found a decrease in the contact angle between the fibers and the resin. In line with that, the pull-out tensile test reveals a double increase in the IFSS value reaching 115.54%. This significant improvement might be due to the interlocking ability contributed by surface modification of the fibers. Since this chemical-free treatment promotes good composite compatibility, it might be introduced as an environmentally friendly treatment in the production of natural fiber based-composites

Abstract: Composite with woven ramie as reinforcement is a combination of woven from hemp plant fibers with resin adhesive (matrix) which each has different characteristics, which with the combination will produce a new material with better properties. The purpose of this study is to determine the magnitude of the influence of federate variations on the tensile strength of open holes in drilling, with the test method carried out with reference to ASTM D 5766/D 5766M-02 (Standard Test Method for Open Hole Tensile Strength of Polymer Matrix Composite Laminates). The tensile test speed used is 5 mm/minute. The data taken is the maximum tensile strength when the specimen breaks. The results of this study indicate that the change in feed rate affects the tensile strength of the ramie composite. The greater the feed rate used is in grading the ramie fiber composite, the smaller the composite tensile stress value becomes. In this study, the highest tensile strength is obtained from composites with a feed rate of 0.05 mm/rev and the lowest at a feed rate of 0.15 mm/rev. The change in spindle speed also affects the magnitude of the tensile strength in the ramie composite. As with the feed rate speed, the greater the spindle speed used to grind the composite, the lower the tensile strength of the composite. In this study, the maximum tensile strength value tends to be obtained by a composite with a spindle speed of 88 rpm and the lowest at a spindle speed of 1500 rpm. This study uses the type of chisel "brad and spur" with three kinds of diameter variations. The larger the diameter of the drill chisel used, the smaller the tensile strength of the composite obtained.

Abstract: This paper shows a mathematical model of shear stress transfer at the interface between fiber and matrix composite. The stress transfer is a key parameter determining the quality of fiber-matrix interface, which directly correlates with the composite performance as load-bearing structures. The model is derived from the energy balance approach in prior and post fiber cracking. The debonding process is included in the model by implementing traction-separation law. The results show the developed model can predict the shear stress along with the interface. There are significant differences in shear stress by considering the debonding process compared with conventional models. The debonding process must be regarded to assure an accurate evaluation of the interface quality.

Abstract: Corrugated cardboard has multilayer construction that produces rigid, durable, and worthy material for shipping heavy goods or hazmat. The numerous advantages offered have made it a worldwide staple in the warehousing, packaging, and transportation industries. Unfortunately, studies on corrugated cardboard’s mechanical properties and behavior are still limited due to the complexity of structures and testing procedures. The present work investigates corrugated cardboard’s mechanical properties and behavior by conducting uniaxial tensile and compressive tests. Three different testing directions in x, y, and z-axes were applied on AA-flute double-wall (AA/F-DW) or virgin pulp paper Bi-Wall corrugated cardboard. The stress-strain curve is measured and evaluated to obtain the mechanical properties, i.e., yield strength and ultimate strength. The result shows that corrugated cardboard has linear and non-linear mechanical behavior or elastic-plastic regions under those different directions. Moreover, the flute on the corrugated cardboard gives jaggedness to the stress-strain curve and makes the material more elastic, more durable, and has better absorbing energy capacity. This finding could be used to design any products, such as a packaging frame made of corrugated cardboard, where the strength of the structure could be predicted based on the mechanical properties and behavior.

Abstract: Due to the growing demand of the textile market, the production of synthetic fibers like polyester (PET), has been increasing compared to any other existing fiber group. However, this type of fiber has its own disadvantages, the main one being its hydrophobic nature. To improve its properties, it was sought to develop a chemical functionalization. This process consisted of three steps, the first one being the cleaning of the polyester with hydrochloric acid, followed by a subsequent hydrolysis of the textile substrate in an alkaline medium in the presence of sodium hydroxide. The last phase, that concerns the textile substrate functionalization with poly (vinyl alcohol), more commonly known as PVA, was made by a process of exhaustion at different pH values (3, 6, and 10), followed by a curing, which allowed the formation of bonds between the PVA and the polyester fibers and consequently improve polyester properties, namely the hydrophilicity, presenting a contact angle of 0º. This process of functionalization of the polyester with PVA at acidic pH, led to very promising results since a significant improvement of its properties was obtained. The functionalized and original polyester samples were further characterized through the application of several techniques, such as SEM, FTIR-ATR and differential scanning calorimetry DSC. These characterization techniques allowed to prove that the textile substrates were effectively modified. It can be concluded that, properties such as, contact angle, tensile strength, air permeability, coefficient of friction and water vapor permeability, were substantially improved by the functionalization of the polyester fabric with PVA.

Abstract: Formic acid, commonly used in bioprocesses of cellulosic polymeric materials, has been considered for the treatment of cellulose-based textile. Therefore, different concentrations of formic acid (10, 20, 30, 40, and 50 g L^-1) were used to treat cotton (CO) and viscose (CV) fabrics to improve their properties. Weight variation, tensile strength, stiffness, drape coefficient, crease recovery angle, and vertical wicking of the treated substrates were assessed. Fourier transform infrared spectroscopy attenuated total reflection (FTIR-ATR) analysis confirmed the acid hydrolysis process of the cellulosic substrates treated with formic acid solutions. Formic acid solutions with concentrations equal to 30 g L^-1 and 40 g L^-1 are the most adequate to treat the CV and CO fabrics, respectively. In addition, the fabrics treated under optimal conditions were dyed with the reactive dye Levafix Blue CA. The dyeing properties were assessed through colour absorption coefficient and scattering coefficient (K/S) values. A clear improvement in the fastness and dyeing performance of the treated substrates was observed. Finally, the antibacterial properties of the treated substrates were evaluated, for the bacteria Escherichia coli and Staphylococcus aureus. It was found that only cotton substrates treated with a 40 g L^-1 formic acid solution could be classified as weak decontaminants against S. aureus bacteria.

Abstract: In this paper, (5,5) single-walled carbon nanotube was doped by substitutional nitrogen (N) atom forming bridgehead C-N bonds in the resulting C₃₉N armchair nanotube. It was then interacted with acetic acid to investigate its detection capability using first-principles calculations in the context of Density Functional Theory (DFT). As known, DFT is a very efficient and accurate method in calculating the properties of the atoms and molecules, and their interactions. Accordingly, the O-H bond of the acid has not undergone a heterolytic dissociation caused by the weak interaction of the materials. In the valence region of the C₃₉N-acid, the O atoms (2p) are the main causes of additional states as shown in the projected density of states (pDOS). Calculations of the charge density difference revealed the occurrence of charge redistribution and nonuniform charge transfer between the acid and the sidewalls of the C₃₉N. Further topological investigation of the system revealed no localized electrons between the interaction points indicating a physical binding mechanism. These electronic responses have shown the biosensing ability of C₃₉N to detect and capture acetic acid.