Papers by Keyword: Laminated Composite

Abstract: The high carbon steel (HCS)/low carbon steel (LCS) laminated composite made by centrifugal casting technology was subjected to hot compression tests on Gleeble 3500 thermomechanical simulator in a range of temperatures (800-1100 ^oC) and strain rates (0.02-10 s^-1). The hot-working behavior of the laminate was characterised by analysing the flow stress-strain curves and constructing the processing map based on dynamic materials model via superimposing efficiency of power dissipation and flow instability maps. The safe and unsafe processing conditions were identified in the processing map which was validated by microstructural examinations. Banded microstructure and micro-shear cracks occurred in the unsafe domains were responsible for the flow instability, while dynamic recrystallisation in stable domains with high efficiency of power dissipation imparted a good workability to the laminate. The optimum hot-working parameters were determined to be: (i) 800-1050 ^oC and 0.02-0.04 s^-1, (ii) 800-1045 ^oC and 2.5-10 s^-1 and (iii) 1050-1100 ^oC and 0.02-2.5 s^-1.

Abstract: Laminated composite plates are greatly used in many applications where high specific strength and stiffness are mandatory. These structures may have holes in order to accommodate windows and doors if it is used for air craft structures or to provide cables and inspection system if it is used in the applications like power transmission systems and automobiles. The laminated composite plates with holes shall be analyzed using finite element analysis. It is necessary to optimize the parameters like thickness, fiber orientation, material and the stacking sequence to obtain the desired characteristics for these structures. But using finite element analysis makes the process more tedious job. With this in mind it is proposed here to construct the artificial neural network to predict the buckling behavior of the composite plate.

Abstract: The typified as flexible thermosetting pipe, is a new product, developed initially in response to the need for a non-metallic replacement for steel pipe used for oil and gas productions. This product may use for high pressure down-hole applications in which the pipe could repeatedly transported onto a drum. The proposed pipe comprise an internal thermoplastic layer play as liner and a fluid-tight cover, and one or more dual-helical wounding tape stacks applied to the internal liner for absorbing axial and bending loads. The tape stacks are wrapped helically onto the pipe structure with adjacent gaps between wrappings tape to reduce the pressure integrity of the tubular pipe structure. The composite tape stacks are formed from a plurality of thin tape strips and are bonded to each other within a stack. All the layers are manufactured from composite material consisting of highly noncorrosive epoxied matrix reinforced by long continuous fibers. Thus, the proposed flexible pipe designed to be stand alone with thermoplastic liner over-wound with one or more of an epoxy-based structural thermosetting laminate. To this aim, a straightforward simulations of thermosetting pipe is developed via using ANSYS software. Apart from possessing an accurate operational condition, on account of its simplicity the proposed simulation seems also very suitable for further developing and prototyping purposes. Finally, it has been shown that the proposed thermosetting pipe, which partially attains some classical characteristic of both offshore and onshore pipeline by a different line of reasoning, is may serve as a reference in designing flexible pipe.

Abstract: The thermosetting pipes are eligible to be used in oil transportation where resistance to crude oil, paraffin build-up as well as ability to withstand relatively high pressures is required. Lamination design of such system could provide better strength and stability for internal and external loadings in both the circumferential and longitudinal directions. To this aim, a straightforward design and modeling of thermosetting pipe is developed via using first order shell theories. Apart from possessing an accurate operational condition, on account of its simplicity the proposed simulation seems also very suitable for further developing and prototyping purposes. Finally, it has been shown that the proposed thermosetting pipe, which partially attains some classical characteristic of both offshore and onshore pipeline by a different line of reasoning, is may serve as a reference in designing thermosetting pipe.

Abstract: By combining mechanical activation and combustion synthesis in ultrahigh gravity field, the laminated composite of TiB₂ based ceramic to stainless steel was achieved in continuously-graded composition and microstructure, and within the Fe-Cr based intermediate Ti-Fe enriched carbides and fine TiB₂ platelets decreased gradually in size and volume fraction from the ceramic to stainless steel. Because of the sequent presence of thermal explosion, the dissolution of the molten stainless steel to TiC-TiB₂ liquid, the formation of diffusion-controlled concentration gradient from the ceramic liquid to the alloy liquid, the rapid sequent solidification of the ceramic and the alloy, the laminated composite is achieved in multilevel, scale-span hybrid microstructure that the different-size, different-morphology Fe-Cr alloy phases alternate with TiB₂ platelets and irregular TiC grains in size from micrometer to micro-nanometer.

Abstract: By taking combustion synthesis in ultrahigh gravity field to prepare solidified TiC-TiB₂ composite ceramic, laminated composite of the ceramic to Ti-6Al-4V was achieved by fusion bonding and atomic inter-diffusion, and within the joint there formed the unique microstructure of multiscale (micrometer-micro/nanometer-nanometer) and multilevel characterized by size and distribution of TiB₂ and TiB due to the presence of a series of metallurgical reaction including peritectic reaction of solidified and Ti liquid, direct growth of TiB solids from liquid Ti and subsequent eutectic reaction of TiB solids and liquid Ti. FEMSEM images of crack propagation paths at the joint showed despite the contribution from crack bridging of micro-nanometer TiB₂ and TiB platelets to crack propagation resistance, residual stress toughening and subsequent crack pinning by micro-nanometer TiB₂ ,TiB platelets and needle-like nanometer TiB grains as well as ductile phase toughening and bridging toughening by Ti metallic phases became the primary resistances to crack propagation, thereby presenting the delayed fracture behavior in the joint, so that shear fracture usually occurred at the solidified Ti alloy rather than the joint, and shear strength of 375 ± 55 MPa was achieved between the solidified ceramic and Ti alloy.

Abstract: Damage caused by low-velocity-impact in laminated composite will significantly reduce the strength of the structure. A new numerical model is proposed for the research on the impact induced damage of laminated composite. Multiple forms of damage within and between layers are considered in this model. The cohesive contact technology is used to simulate the bonding properties between layers. The model can describe the information of delamination more accurately and efficiently. Then, a study is carried out to investigate the relationship of delamination and matrix cracking caused by low-velocity-impact. The result reveals that the area and axis of the delamination zone is affected by the direction of the matrix cracking zone.

Abstract: Laminated polyurethane foam composite was produced by incorporating Cloisite 30B clay as filler and aluminium sheet as the skin. Initially, PU foams were synthesized with reaction of natural oil polyol and isocyanate with ratio of 1:1.1 by weight. Water was used as the blowing agent and appropriate surfactant and catalyst were added to ensure better performance of end product. Cloisite 30B was added as filler and the percentages were varied from 1 to 5 wt%. Al skin was attached at the top and bottom of the foam to increase the stiffness of the composite and improve its mechanical properties. In order to evaluate its impact characteristic, drop weight impact test was done and the drop height was varied from 5 cm to 20 cm. The results showed that there was no pattern that exists in the impact force, but found the results for the control PU foam (PU foam without filler) has a high impact force values at 5cm, 10 cm and 15 cm drop heights. The incorporation of clay particles were found to give lower impact force to the sample, especially at low filler percentage of 1%. It was found that the addition of clay particles has decrease the impact force of PU foam due to brittleness. Besides, the impact force of the laminated composite is higher than PU foam at the same drop height. For laminated composite at 10 cm, the impact force is higher with an average value of 817% as compared to PU foam. This shows that the addition of Al sheets have improved mechanical characteristics of foam and its ability to withstand higher impact force.

Abstract: Ti-(Al₃Ti+Al) and Ti-Al₃Ti laminated composites have been fabricated in vacuum using 50, 100, 150, 200, 400 and 600 μm thick titanium and 50 μm thick aluminum foils. The composites were synthesized with controlled temperature and treating time. Microstructural examinations showed that Al₃Ti was the only phase formed during the reaction between Ti and Al. The initial foil thicknesses only affected the volume fraction of the resultant Ti, Al and Al₃Ti layers. Treating time at 650 °C was a main factor determining microstructures and properties of the composites. After 20 minutes not all aluminum was consumed and therefore the composites consisted of alternating layers of Ti, Al and Al₃Ti. After 60 minutes aluminum layers were completely consumed resulting in microstructures with Ti residual layers alternating with the Al₃Ti layers. Mechanical tests were performed on the materials with different microstructures to establish their properties and fracture behavior. The results of investigations indicated that mechanical properties of the composites strongly depended on the thickness of individual Ti layers and the presence of residual Al layers at the intermetallic centerlines.

Abstract: This investigation attempts to improve the wear resistance of low chromium white cast iron (LCCI) by thermomechanical treatment. The thermomechanical treatment of the brittle LCCI with crack-free was successfully carried out by bonding it with a ductile low carbon steel firstly. Afterwards the dry sliding wear behavior of as-cast (LCCI-A) and thermomechanically processed (LCCI-B) samples was studied using a pin-on-disc apparatus under different test conditions. The microstructural examination shows that the refined supercooled austenite and plenty of secondary carbides in LCCI-B replaced the original microstructure of martensite and retained austenite with network carbide in LCCI-A. This significant evolution is beneficial to form and stabilise the oxide layer on the substrate, which makes the oxidational wear rather than abrasive wear or delamination dominating the wear process so that the improvement of the wear resistance of LCCI was achieved by hot working.