Papers by Keyword: Laminate

Abstract: The trade-off between strength and toughness remains a major challenge in structural materials engineering, especially for titanium-based materials. This study explores the potential of titanium-based laminates for lightweight armor, aimed at improving anti-ballistic properties through the use of layered structures. Titanium alloy Ti-6Al-4V (Ti64) was combined with metal matrix composites (MMCs) reinforced with TiC or TiB particles (up to 40 vol%) using two powder metallurgy (PM) techniques. The first approach used press-and-sinter blended elemental powder metallurgy (BEPM) to create the laminates in a single step, while the second involved post-processing via hot isostatic pressing (HIP) to enhance material properties. Both fabrication methods produced laminates that significantly outperformed commercial alternatives in ballistic testing against 7.62 mm armor-piercing bullets. The use of HIP post-BEPM enhances material properties by reducing porosity and increasing hardness, highlighting the complementary nature of these technologies in producing efficient and cost-effective armor materials.

Abstract: This research improves the mechanical properties of laminates in ship hulls made of glass fiber reinforced plastics (GFRP) with the design of auxetic sheets, to take advantage of the property in their geometry to reduce the damage energy due to surface impacts absorbed by the laminate. 3D printing of second generation auxetic components to produce modified specimens. Laboratory reproductions of mechanical damage were compared with those of specimens extracted from a ship under construction. The mechanical properties of the bending and tensile tests demonstrated that the insertion of the core in the laminate protected the matrix from damaged energy, prolonging its useful life. Comparative results are presented, which will allow GFRP hull designers to insert auxetic sheet cores into their design. Mechanical tests allowed us to compare the progress of delamination.

Abstract: Fiber Reinforced Polymer (FRP) has been used as one of the repair or strengthening materials for deteriorated concrete structures. However, the elastic properties of FRP materials cause a limitations on the ductility of the reinforced concrete structure. This research focuses on the study of the behavior of reinforced concrete beams strengthened using a hybrid Carbon-Glass Fiber Reinforced Plastic (Hybrid FRP). Hybrid FRP is a combination of two layers of FRP that have different elastic modulus, namely Glass Fiber and Carbon Fiber. The objective of using hybrid composites is to obtain a combined elastic mode behavior from two kind of fibers. Flexural testing of reinforced concrete beams with FRP hybrid reinforcement was carried out to study the flexural behavior and also the effectiveness of strengthening. The test material is a reinforced concrete beam with dimensions of 150 mm x 200 mm x 3300 mm. Two types of beams were prepared, namely control beams (BN) and beams with FRP Hybrid strengthening (BGC). The composition of the FRP hybrid was 100% of Glass fiber and 40% of Carbon fiber to the width of the beam. The test results show that the beam with FRP hybrid strengthening has a moment capacity of 12% higher than the control reinforced concrete beam (BN). The mode of failure of the BN beams was the crushing of the concrete that was initiated by yielding of the steel reinforcement. For BGC beams, failure mode was in the form of debonding of the hybrid FRP layer.

Abstract: This research work aims to perform a comparative study on the effect of fiber orientation distribution (FOD) on the mechanical properties of composite laminates for aircraft and automobile structure. The objective of this project works is to use an analysis method to study the effect of significant parameters namely, with and without orientation on the glass fibre epoxy composites. The experimental work is used to investigate the mechanical behavior and to examine the properties with respect to fibre orientation on the composite laminates. The glass fibre orientation characteristics for the composite laminates is considered since they affect the strength of the specimen laminates. In this connection, the specimens were fabricated with different orientations and undergone for mechanical testing like tensile, compression and impact tests with Data Acquisition System. The experimental results indicate that the specimens with orientation provide more strength, high stiffness and good toughness than the normal specimens without orientation.

Abstract: The normal stress of each layer of the laminate composite material will undergo complex changes after normal compression, and shear stress will also appear between the layers. In order to explore the distribution laws of normal stress and shear stress, this paper uses Hooke's law and the equilibrium condition of force to carry out mathematical derivation, the analytical formulas for normal stress and shear stress are obtained, and their respective maximum values ​​are given. Studies have shown that the maximum normal stress occurs at the center of the laminate, and its value is proportional to the external load, and is also closely related to the length, width, thickness, elastic modulus of the cementing agent, elastic modulus and Poisson’s ratio of the laminate; The maximum shear stress occurs at the four corners of the laminate, and its value is proportional to the external load and the shear modulus of the cementing agent, inversely proportional to the thickness of the cementing agent layer, and its value is also closely related to the length, width, elastic modulus and Poisson's ratio of the laminate. The analytical formulas for normal stress and interlayer shear stress is helpful to deepen the understanding of the internal force distribution law of laminated plates, and the maximum value calculation formula can greatly facilitate the calculation of strength.

Abstract: This paper presents an experimental study of the influence of the orientation of the outer layer of polypropeylene (PP) reinforced with E-glass fiber laminate (GF/PP) and the influence of the fiber volume fraction on the quality of the welded joint using an ultrasonic welding process. An orthogonal L 16 array (OA) design of experiment was conducted in this paper based on the Taguchi method to evaluate the effect of the orientation of the outer layer and the fiber volume fraction, on the welding process parameters; the welding energy, the amplitude of vibration, the welding pressure, the holding pressure and the holding time were considered in order to achieve a high weld quality. The experiments were carried out using a 15 kHz ultrasonic welding unit with a maximum supplied power of 4000-Watt. GF/PP laminates with fiber volume fraction of 36% and 46% were used in this paper, and the GF/PP laminates were either unidierctional or had a 90 degree outer layer orienation. A 0.127 mm thick polypropeylene film was used as a flat energy director (ED). The evaluation of the weld quality was measured by the apparent shear strength of the single lap welded joints, and by using laser shearography as a non-destructive inspection technique . The failure mechanism of the single lap joint was monitored, using a high speed digital imaging system. A combination of the highest selected level of welding energy, lowest level of amplitude, lowest level of welding pressure, and the lowest level of both hold time and hold pressure of a unidirectional GF/PP with the lowest fiber volume fraction, were found to achieve a higher apparent shear strength of the welded adherends, as compared with the apparent shear strength obtained with the presence of the flat energy director for the same level of factors. A confirmation experiment was conducted to measure the predicted apparent shear strength and compare it with the measured apparent shear strength from the test.

Abstract: The Fiber metal laminates (FMLs) combine the advantages of fiber-reinforced polymer properties, like stiffness and strength, with metallic alloys, like toughness and durability. These hybrid materials can unravel some problems in the industrial sector, particularly in aerospace, and advanced automotive industry. Still, there are significant challenges in the GLARE sheets forming process even for small drawing ratios, notably smaller and complex-shaped fiber metal laminate with low thickness. As a case study, a cylindrical GLARE cup was chosen. This shape with sharp bends and vertical geometrical features, still face many challenges and difficulties in the forming process. Numerical simulations have been used utilizing ABAQUS and compared with the experimental results in the Hydro-mechanical deep drawing to achieve good forming quality with higher depth. An extensive investigation of the effect of process variables has been done such as cavity pressure, blank holding force, and blank diameter. Also, their roles in wrinkles formation, tearing and thinning, and formability has been performed. Furthermore, the friction in two cases; cured, and semi-cured condition, has been considered. The results show that the application of cavity pressure within specified limits has a positive effect on the quality of the formed cup and leads to higher depths. The same conclusion for the blank holder, which has a positive impact on wrinkling elimination and friction reducing between the aluminum layers and the fiberglass. The result shows that the semi-cured condition of the GLARE has a good effect on wrinkling reduction, due to the uniform movement of the fiberglass inside the aluminum layers. Understanding these parameters and the GLARE forming behavior and have a good selection of these parameters can give the advantage to achieve smaller and more complex shapes with higher depth, particularly for mass production. Finally, this study can extend the industrial application areas of FMLs and GLARE parts.

Abstract: Freestanding diamond foils are an exceptionally strong material. A major problem that prevents industrial use is their inherent brittleness. We here present a first approach to introduce metallic interlayers into a diamond matrix by brazing stacks of diamond foils. This represents a potential route to toughen the material. Laminates of two and four layers of diamond were produced from the same batch of diamond foils. A first attempt to approximate the bending strength of this new material was made using a Ball-on-three-Balls (B3B) setup. Substantially higher strength values were achieved for the laminates compared to the freestanding (monolithic) foil.

Abstract: Composites are extensively using in modern industry (aircraft and automobile manufacturing, construction, etc.). Nowadays high-strength and lightweight composite materials, such as FRPs, exhibit elastic and strength anisotropy and deform nonlinearly at high stresses. Also, such materials have small enough failure strain in comparison with metals, and they are drastically more expensive than steel and aluminum alloys. The most important task in the design of structures made of composite materials is the minimization of its weight without loss of strength properties. We presented the method for modeling a UD FRP with randomly arranged fibers at the micro-and meso-level. These two approaches were compared on the problem of the composite panel tension. The selection of the mesomodel mechanical characteristics was based on data of the micro-level model. In the mesomodel, the damage accumulation of middle layer (90° layer) was simulated using the Stochastic Failure criterion (random Mott scatter of layer strength). The calculated curves and data, obtained in micro-and mesomodels, correlate well with each other.

Abstract: In this study flax fabrics were treated with polyethylene imine (PEI) and afterwards, in combination with carbon fabrics, integrated into epoxy resin via vacuum infusion process. The influence of the 2 stacking sequences of the fabrics and 2 PEI concentrations were evaluated with regard to the mass fractions of the composite components and mechanical properties of the manufactured composites, namely, flexural and interlaminar shear properties. The results showed that the effect of the surface treatment is dependent on the stacking sequence. Namely, increase of the PEI concentration resulted in a corresponding increase of the mass fraction of the polymer matrix in the case of interchanging arrangement of flax and carbon fabrics. Further remarkable results showed that the same specimen provided the highest values of the supported maximum load after the surface treatment. Influence of the PEI treatment on the strength values with regard to the stacking sequence and polyelectrolyte concentration led to controversial results. Decrease of flexural modulus after the surface treatment was observed in the case of all samples.