Mechanical Characterization, Water Absorption, and Thickness Swelling of Lightweight Pineapple Leaf/Ramie Fabric-Reinforced Polypropylene Hybrid Composites.

Fiber-reinforced composites are among the recognized competing materials in various engineering applications. Ramie and pineapple leaf fibers are fascinating natural fibers due to their remarkable material properties. This research study aims to unveil the viability of hybridizing two kinds of lignocellulosic plant fiber fabrics in polymer composites. In this work, the hybrid composites were prepared with the aid of the hot compression technique. The mechanical, water-absorbing, and thickness swelling properties of ramie and pineapple leaf fiber fabric-reinforced polypropylene hybrid composites were identified. A comparison was made between non-hybrid and hybrid composites to demonstrate the hybridization effect. According to the findings, hybrid composites, particularly those containing ramie fiber as a skin layer, showed a prominent increase in mechanical strength. In comparison with non-hybrid pineapple leaf fabric-reinforced composites, the tensile, flexural, and Charpy impact strengths were enhanced by 52.10%, 18.78%, and 166.60%, respectively, when the outermost pineapple leaf fiber layers were superseded with ramie fabric. However, increasing the pineapple leaf fiber content reduced the water absorption and thickness swelling of the hybrid composites. Undeniably, these findings highlight the potential of hybrid composites to reach a balance in mechanical properties and water absorption while possessing eco-friendly characteristics.

Crashworthiness Assessment of Carbon/Glass Epoxy Hybrid Composite Tubes Subjected to Axial Loads.

The crashworthiness of composite tubes is widely examined for various types of FRP composites. However, the use of hybrid composites potentially enhances the material characteristics under impact loading. In this regard, this study used a combination of unidirectional glass-carbon fibre reinforced epoxy resin as the hybrid composite tube fabricated by the pultrusion method. Five tubes with different length aspect ratios were fabricated and tested, in which the results demonstrate "how structural energy absorption affects by increasing the length of tubes". Crash force efficiency was used as the criterion to show that the selected L/D are acceptable of crash resistance with 95% efficiency. Different chamfering shapes as the trigger mechanism were applied to the tubes and the triggering effect was examined to understand the impact capacity of different tubes. A finite element model was developed to evaluate different crashworthiness indicators of the test. The results were validated through a good agreement between experimental and numerical simulations. The experimental and numerical results show that hybrid glass/carbon tubes accomplish an average 25.34 kJ/kg specific energy absorption, average 1.43 kJ energy absorption, average 32.43 kN maximum peak load, and average 96.67% crash force efficiency under quasi-static axial loading. The results show that selecting the optimum trigger mechanism causes progressive collapse and increases the specific energy absorption by more than 35%.

Mechanical Behaviour of Pin-Reinforced Foam Core Sandwich Panels Subjected to Low Impact Loading.

As a light structure, composite sandwich panels are distinguished by their significant bending stiffness that is rapidly used in the manufacture of aircraft bodies. This study focuses on the mechanical behaviour of through-thickness polymer, pin-reinforced foam core sandwich panels subjected to indentation and low impact loading. Experimental and computational approaches are used to study the global and internal behaviour of the sandwich panel. The samples for experimental testing were made from glass/polyester laminates as the face sheets and polyurethane foam as the foam core. To further reinforce the samples against bending, different sizes of polymeric pins were implemented on the sandwich panels. The sandwich panel was fabricated using the vacuum infusion process. Using the experimental data, a finite element model of the sample was generated in LS-DYNA software, and the effect of pin size and loading rate were examined. Results of the simulation were validated through a proper prediction compared to the test data. The results of the study show that using polymeric pins, the flexural strength of the panel significantly increased under impact loading. In addition, the impact resistance of the pin-reinforced foam core panel increased up to 20%. Moreover, the size of pins has a significant influence on the flexural behaviour while the sample was under a moderate strain rate. To design an optimum pin-reinforced sandwich panel a "design of experiment model" was generated to predict energy absorption and the maximum peak load of proposed sandwich panels. The best design of the panel is recommended with 1.8 mm face sheet thickness and 5 mm pins diameter.

Hybrid and Synthetic FRP Composites under Different Strain Rates: A Review.

As a high-demand material, polymer matrix composites are being used in many advanced industrial applications. Due to ecological issues in the past decade, some attention has been paid to the use of natural fibers. However, using only natural fibers is not desirable for advanced applications. Therefore, hybridization of natural and synthetic fibers appears to be a good solution for the next generation of polymeric composite structures. Composite structures are normally made for various harsh operational conditions, and studies on loading rate and strain-dependency are essential in the design stage of the structures. This review aimed to highlight the different materials' content of hybrid composites in the literature, while addressing the different methods of material characterization for various ranges of strain rates. In addition, this work covers the testing methods, possible failure, and damage mechanisms of hybrid and synthetic FRP composites. Some studies about different numerical models and analytical methods that are applicable for composite structures under different strain rates are described.

Failure of Glass Fibre-Reinforced Polypropylene Metal Laminate Subjected to Close-Range Explosion.

The present study investigates the effects of close-range blast loading of fibre metal laminates (FMLs) fabricated from woven glass polypropylene and aluminium alloy 2024-T3. The polypropylene layers and anodized aluminium are stacked in 3/2 layering configuration to investigate the impact energy absorbed through deformation and damage. In order to study the blast responses of FMLs, a 4-cable instrumented pendulum blast set-up is used. Effects of blast impulse and stand-off distance were examined. Investigation of the cross-section of FMLs are presented and damages such as fibre fracture, debonding, and global deformation are examined. Increasing stand-off distance from 4 to 14 mm resulted in a change of damage mode from highly localized perforation to global deformation.

Development of Polymeric Nanocomposite (Xyloglucan-co-Methacrylic Acid/Hydroxyapatite/SiO2) Scaffold for Bone Tissue Engineering Applications-In-Vitro Antibacterial, Cytotoxicity and Cell Culture Evaluation.

Advancement and innovation in bone regeneration, specifically polymeric composite scaffolds, are of high significance for the treatment of bone defects. Xyloglucan (XG) is a polysaccharide biopolymer having a wide variety of regenerative tissue therapeutic applications due to its biocompatibility, in-vitro degradation and cytocompatibility. Current research is focused on the fabrication of polymeric bioactive scaffolds by freeze drying method for nanocomposite materials. The nanocomposite materials have been synthesized from free radical polymerization using n-SiO2 and n-HAp XG and Methacrylic acid (MAAc). Functional group analysis, crystallinity and surface morphology were investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) techniques, respectively. These bioactive polymeric scaffolds presented interconnected and well-organized porous morphology, controlled precisely by substantial ratios of n-SiO2. The swelling analysis was also performed in different media at varying temperatures (27, 37 and 47 °C) and the mechanical behavior of the dried scaffolds is also investigated. Antibacterial activities of these scaffolds were conducted against pathogenic gram-positive and gram-negative bacteria. Besides, the biological behavior of these scaffolds was evaluated by the Neutral Red dye assay against the MC3T3-E1 cell line. The scaffolds showed interesting properties for bone tissue engineering, including porosity with substantial mechanical strength, biodegradability, biocompatibility and cytocompatibility behavior. The reported polymeric bioactive scaffolds can be aspirant biomaterials for bone tissue engineering to regenerate defecated bone.

Assessment of Compressive Mechanical Behavior of Bis-GMA Polymer Using Hyperelastic Models.

Despite wide industrial applications of Bis-GMA polymer, very few studies are available about the material classification, mechanical properties, and behavior of this material. In this study, the compressive behavior of Bis-GMA polymer was studied using different hyperelastic constitutive models through a hybrid experimental-computational process. Standard uniaxial compression tests were conducted to extract the mechanical behavior and structural response of the Bis-GMA polymer. A nano-indentation experiment was used to verify the compressive behavior of Bis-GMA polymer in the form of hyperelastic behavior. The finite element model and real-time simulation of the test incorporating different hyperelastic models were developed in comparison with the experimental finding to obtain the proper type of hyperelastic behavior of Bis-GMA polymer. The results indicate that a second-order polynomial hyperelastic model is the best fit to predict the behavior of Bis-GMA polymer. Next, the validated model was used to determine the true stress-strain curve of the Bis-GMA polymer.

Modification of the contact surfaces for improving the puncture resistance of laminar structures.

Uncovering energy absorption and surface effects of various penetrating velocities on laminar structures is essential for designing protective structures. In this study, both quasi-static and dynamic penetration tests were systematical conducted on the front surfaces of metal sheets coated with a graphene oxide (GO) solution and other media. The addition of a GO fluid film to the front impact surface aided in increasing the penetration strength, improving the failure extension and dissipating additional energy under a wide-range of indentation velocity, from 3.33 × 10-5 m/s to 4.42 m/s. The coated -surfaces improved the specific energy dissipation by approximately 15~40% relative to the dry-contact configuration for both single-layer and double-layer configurations, and specific energy dissipations of double-layer configurations were 20~30% higher than those of the single-layer configurations. This treatment provides a facile strategy in changing the contact state for improving the failure load and dissipate additional energy.

A study on the spectroscopic, energy band, and optoelectronic properties of α,ω-dihexylsexithiophene/tris(8-hydroxyquinolinate) gallium blends; DH6T/Gaq3 composite system.

In this work the optical response, spectroscopic behaviour, and optoelectronic properties of solution and solid state composite systems based on α,ω-dihexylsexithiophene/tris(8-hydroxyquinolinate) gallium (DH6T/Gaq3) are studied upon the incorporation of different molar percentages of Gaq3. UV-vis, PL, FTIR spectrophotometers and SEM technique were utilized to perform the investigations. The results showed a reduced energy band (Eg) (from 2.33eV to 1.83eV) and a broadened absorption spectrum for the blend system when 29.8% molar of Gaq3 was incorporated. These were attributed to the enhanced intermolecular interactions that are brought about by the increased strength of π-π overlap between the molecular moieties. A mathematical formula was developed to interpret the non-monotonic change occurred in Eg, while numerical calculations have been made to assign the type and nature of the electronic transitions governing the spectroscopic behaviour of the system. The results were elaborated and comprehensively discussed in terms of the exciton generation, energy band theory, molecular interactions, and spatial geometry.

Effects of temperature change and beverage on mechanical and tribological properties of dental restorative composites.

The aim of this study was to investigate the effects of temperature change and immersion in two common beverages on the mechanical and tribological properties for three different types of dental restorative materials. Thermocycling procedure was performed for simulating temperature changes in oral conditions. Black tea and soft drink were considered for beverages. Universal composite, universal nanohybrid composite and universal nanofilled composite, were used as dental materials. The nanoindentation and nanoscratch experiments were utilized to determine the elastic modulus, hardness, plasticity index and wear resistance of the test specimens. The results showed that thermocycling and immersion in each beverage had different effects on the tested dental materials. The mechanical and tribological properties of nanohybrid composite and nanocomposite were less sensitive to temperature change and to immersion in beverages in comparison with those of the conventional dental composite.