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Über dieses Buch

Experimental Mechanics of Composite, Hybrid, and Multifunctional Materials, Volume 4: Proceedings of the 2014 Annual Conference on Experimental and Applied Mechanics, the fourth volume of eight from the Conference, brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on a wide range of areas, including:

Composites for Energy Applications

Novel/Bio Composites

NDE of Composites

Mechanical Testing of Composites

Strain Measurements Using Digital Image Correlation

Digital Image Correlation for Composite Structures

Particulate Composites

Nanocomposites

Inhaltsverzeichnis

Frontmatter

Chapter 1. Characterizing the Mechanical Response of a Biocomposite Using the Grid Method

This work is aimed at determining the mechanical behavior of a biocomposite made of sunflower stem chips and chitosan-based matrix which serves as a binder. The link between global response and local phenomena that occur at the scale of the chips is investigated with a full-field measurement technique, namely the grid method. Regular surface marking with a grid is an issue here because of the very heterogeneous nature of the material. This heterogeneity is due to the presence of voids and the fact that bark and pith chips exhibit a very different stiffness. Surface preparation thus consists first in filling the voids with soft sealant and then painting a grid with a stencil. The grid images grabbed during the test with a CCD camera are then processed using a windowed Fourier transform and both the displacement and strain maps are obtained. Results obtained show that the actual strain fields measured during compression tests are actually heterogeneous, with a distribution which is closely related to the heterogeneities of the material itself.
S. Sun, M. Grédiac, E. Toussaint, J.-D. Mathias

Chapter 2. Preliminary Study on the Production of Open Cells Aluminum Foam by Using Organic Sugar as Space Holders

This work investigates the production of Al foams using organic sugar granulates as space holders. To the Al matrix hollow glass micro spheres were added to constitute a light weight composite material. The process comprises the following steps: mixing of Al powders and organic sugar granulates, compacting of the mixture, heating the green compact to eliminate the sugar and final sintering of the metallic powder. Open spaces left by the volatilization of the sugar granulates constitute a net of interconnect porosity in the final product, which is, therefore, a metallic sponge. It was analyzed the influence of processing parameters in the different steps of production, in the final quality of products. Products were characterized concerning cells distribution and sintering interfaces. Results showed the general viability of producing composites by the proposed technique, based on a simple and low cost procedure.
F. Gatamorta, E. Bayraktar, M. H. Robert

Chapter 3. Characterization of Shear Horizontal-Piezoelectric Wafer Active Sensor (SH-PWAS)

This paper discusses shear horizontal SH-coupled piezoelectric wafer active sensor (PWAS). The paper starts with a review of the state of the art in modeling SH transducers and their importance in non-destructive evaluation (NDE) and structural health monitoring (SHM). This is followed by basic sensing and actuation equations of shear-poled PWAS transducers. The free SH-PWAS electromechanical (E/M) impedance analytical models are presented, and compared with finite element models (FEM) and experiments. In this study, we extend the analytical development for constrained SH-PWAS bonded to structure on the form of beams. The model is based on normal mode expansion (NME) technique. The interaction between the SH-PWAS and the structure is studied. We developed closed-form equation of structure dynamic stiffness by coupling the mechanical response solution of the SH-PWAS to the structure elasticity solution. Finite element simulations and experiments matched well with analytical predictive model. Impedance spectroscopy is also used in NDE and SHM for composites. We present a predictive FEM for the E/M impedance of bonded SH-PWAS on cross ply GFRP as well as [0/45/45/0]s CFRP plates. The paper ends with summary, conclusion, and suggestions of future work.
Ayman Kamal, Victor Giurgiutiu

Chapter 4. Elastic Properties of CYCOM 5320-1/T650 at Elevated Temperatures Using Response Surface Methodology

The structural health of composite structures is dependent on environmental conditions during their service life. Elevated temperatures can reduce the overall stiffness and strength of the composite, thereby increasing the likelihood of premature failure. The effect of elevated temperature on the elastic properties (longitudinal modulus, transverse modulus, shear modulus and Poisson’s ratio) of the out-of-autoclave carbon/epoxy prepreg (CYCOM 5320-1/T650) was investigated using a design of experiments approach. Tensile tests at four temperatures (24, 71, 118, and 166 °C) below the glass transition temperature (Tg) (177 °C) of the polymer matrix were performed according to a completely randomized design. Response surface models (RSMs) for predicting the elastic properties were developed using the analysis of variance procedure. The RSMs indicate that elevated temperatures have no significant effect on the longitudinal modulus and Poisson’s ratio of the material system. However, the degradation of the transverse and shear moduli due to increasing temperature is successfully represented by a linear and a cubic RSM, respectively.
Arjun Shanker, Rani W. Sullivan, Daniel A. Drake

Chapter 5. Coupon-Based Qualification of Bonded Composite Repairs for Pressure Equipment

Bonded composite repairs are increasingly installed on degraded pressure equipment and are frequently treated as permanent repairs. These repairs are installed on both external and internal corrosion defects. For external corrosion, the repair is assumed to halt further corrosion and therefore prevents further metal loss. However, for internal corrosion the damage process can continue and eventually lead to complete loss of the pressure vessel wall. In this scenario, the bonded repair failure mode switches from a tensile-based failure to an interfacial fracture scenario. As such, the current repair codes require the characterization of the interfacial fracture energy of the repair for input into a fracture-mechanics-based design approach. Currently these characterizations are performed on test vessels with a simulated through-wall defect. In this paper we describe a simple coupon-based test using a width-tapered-double-cantilevered beam specimen. Using fracture energy values derived from this test we can successfully predict the failure pressure of pressure vessels with simulated through-wall defects.
Michael W. Keller, Ibrahim A. Alnaser

Chapter 6. Compression-After-Impact of Sandwich Composite Structures: Experiments and Simulation

A combined experimental and numerical study of compression-after-impact strength of honeycomb core sandwich composite panels is described. Barely-visible impact damage was induced using quasi-static indentation. Specimens consisted of 16-ply carbon-epoxy facesheets with an aluminum honeycomb core. The facesheet stacking sequence, core geometry and thickness were varied as was the indentor diameter to study the effect of these parameters on damage resistance and post-impact damage tolerance. Computational models of the quasi-static indentation and compression after impact are underway. Results to date compare the experimental and simulate indentations for 25.4 mm diameter indentors. Future work will include modeling the larger, 76.2 mm indentor as well as compression-after-impact.
Benjamin Hasseldine, Alan Zehnder, Abhendra Singh, Barry Davidson, Ward Van Hout, Bryan Keating

Chapter 7. Compact Fracture Specimen for Characterization of Dental Composites

Dental composites are becoming increasingly popular due to their tooth-like color and appearance. Most short-term failures of dental composites are due to mechanical damage, such as cracking. Therefore, many of these failures might be prevented through the use of a self-healing dental composite. High-quality characterization is critical in the development of self-healing materials. Since healing creates uncertainty about the location of the crack-tip, tapered double cantilever beam (TDCB) specimens are often used for their crack length independence when measuring the fracture toughness and healing efficiency of self-healing materials. Because of the high cost of dental composite materials, small cost-effective TDCB samples, about one third of the standard size, were designed and optimized using rapid prototyping (Objet 3D Printer).
Kevin Adams, Douglas Ivanoff, Sharukh Khajotia, Michael Keller

Chapter 8. Mechanics of Compliant Multifunctional Robotic Structures

In this investigation, we report on experiments and models we have developed for compliant multifunctional robotic structures using arrays of conducting polymer composites have been developed to form a “nervous system” to sense shape and force distributions. The objective of this research is to enable better training of robots by enabling them to physically communicate via human touch using new compliant multifunctional structures. To achieve this, arrays of conducting polymer composites have been developed to form a “nervous system” to sense shape and force distributions. This sensor array is integrated into compliant composite structures using a scalable additive manufacturing process. These sensor arrays are being developed for a variety of model robotic structures, for example flapping wing MAVs (i.e., bird-like robots) and stair-walking robots. Experimental details of the associated deformation response are quantified in real-time using Digital Image Correlation (DIC). Output from the sensor array is related to shape and force distributions by solving the nonlinear inverse problem using a novel Singular Value Decomposition (SVD) method. This research is leading to new compliant, scalable, sensing structures that simultaneously monitor in real-time both global and local shapes, as well as force distributions. Since compliant multifunctional sensing structures do not yet exist for robots, it is envisioned that it will enable realization of new bio-inspired control principles for training robots. This will significantly advance the ability to make safer interactions and decisions in co-robotics by differentiating robotic interactions with humans from other objects in their environment.
Hugh A. Bruck, Elisabeth Smela, Miao Yu, Abhijit Dasgupta, Ying Chen

Chapter 9. In Situ SEM Deformation Behavior Observation at CFRP Fiber-Matrix Interface

This paper studies deformation of CFRP at microscopic area and observing technique. Tensile test is carried out for CFRP specimen and digital image correlation (DIC) method is used to observe deformation of microscopic area, especially around its fiber interface. CFRP specimen is loaded by tensile testing machine for investigating deformation around vertical section of fiber. Diameter of carbon fiber used which is mainly interested in the specimen is micro scale, therefore scanning electron microscope (SEM) is used to gain high magnification and resolution pictures as they deforms. To achieve this in situ experiment, testing machine which can be used in SEM is developed. The essential to achieve DIC is selection of random pattern used to follow up change of the area, which greatly influences accuracy of result. Colloidal silica and the other particles are utilized for random pattern with adjustment of concentration. The pattern must be seen clearly and small enough compared to fiber vertical section. Through this research, examination of deformation observation at microscopic area and consideration of starting and fracturing procedure of CFRP are performed.
Y. Wachi, J. Koyanagi, S. Arikawa, S. Yoneyama

Chapter 10. High Strain Gradient Measurements in Notched Laminated Composite Panels by Digital Image Correlation

Digital Image Correlation (DIC) was used to measure the in-plane strains induced in laminated graphite-epoxy panels containing a central circular hole and loaded in tension. Panels with three different stacking sequences and two hole diameters (0.25 and 0.375 in.) were tested. Measured strains were compared with predictions based on the Savin solution. Reasonable agreement between predicted and measured whole-field strain patterns was achieved. However, it was found that filtering of the DIC strain data, which is performed routinely to reduce noise, can mask the high strain gradients that actually exist near the edge of the hole. It will be shown that stacking sequence of the composite laminate as well as the hole size in addition to the correlation variables such as subset, step, and filter size have direct effect on strain values measured by DIC. In this study, strain measurements from the predictions were used to tune the correlation variables.
Mahdi Ashrafi, Mark E. Tuttle

Chapter 11. Intermittent Deformation Behavior in Epitaxial Ni–Mn–Ga Films

This study is conducted to measure intermittent and continuum deformation behaviors in epitaxial Ni–Mn–Ga films under uniaxial tensile loading. First, epitaxial Ni–Mn–Ga film is prepared on a substrate by magnetron sputtering. Secondly, the constraint film is released from substrate by wet-chemical etching of Cr. Thirdly, we simultaneously measure phase transformation band nucleation and strain field arising in epitaxial freestanding Ni–Mn–Ga films. The band nucleations are measured using Stress Drop Analysis (SDA) in macroscopic stress–strain curve, and strain fields are measured using Digital Image Correlation (DIC) method. Results show that smaller size bands nucleated on the beginning stage of stress induced martensite transformation in stress–strain curve, then larger size bands did on the latter stage. The strain field shows macroscopic inhomogeneity under tensile loading. Especially in the latter stage of stress induced martensite transformation in stress–strain curve, the inhomogeneous region propagates along to loading direction although the shape is not distinct. Present Ni–Mn–Ga film microstructure has an order structure with some disorder structures consisting of some martensite arrangements. Their structures will affect intermittent and continuum deformation behaviors in epitaxial Ni–Mn–Ga film.
Go Murasawa, Viktor Pinneker, Sandra Kauffmann-Weiss, Anja Backen, Sebastian Fähler, Manfred Kohl

Chapter 12. Experimental Analysis of Repaired Zones in Composite Structures Using Digital Image Correlation

Reliable understanding of load transfer in repaired zones of composite structures is needed for optimization of repair solutions and enhancement of post-repair behavior. Specific interest is in the analysis of local stress-strain states of composite repair, where digital image correlation (DIC) technique seems to be especially helpful. Thus, the objective is to develop and demonstrate a DIC-based experimental approach for analysis of repaired zones in composite structures including characterization of damage initiation and growth. The approach is based on experimental analysis of through-thickness distributions of internal strains as a function of applied load. Corresponding test coupons are either cut from actual repaired structures or specifically manufactured to represent topology, geometry, lay-up and properties of repaired structures. Demonstration of the approach is considered on an example of generic laminated carbon fiber composites IM7-977-3 with different lay-ups and geometrical configurations of repaired solutions. It is shown that distributions of internal strains, areas of strain concentrations, locations of damage initiation, and processes of damage growth can be experimentally observed and quantified with good accuracy.
Mark R. Gurvich, Patrick L. Clavette, Vijay N. Jagdale

Chapter 13. Mechanics of Curved Pin-Reinforced Composite Sandwich Structures

Pin-reinforced sandwich composites have recently attracted the attention in lightweight structural applications where it substantially improves out-of-plane and shear properties for sandwich composites. However, there is not a great deal of understanding in regards to how shaping these composites affects their mechanical performance when the orientation of the pin-reinforcement may change due to the shaping process. In this investigation, singly curved pin-reinforced sandwich composites using K-Cor have been fabricated using a bend fixture to curve the specimen and heat treatment to soften the core during before bonding with the composite face sheets in order to prevent any damage to the core during the shaping process. Experiments were then performed on the curved sandwich specimens using different boundary conditions on the edges. The boundary conditions were found to result in increased load bearing capacity when supported at the edge compared to support at the bottom due to increased lateral constraint that delayed the onset of bending shear failure. Digital Image Correlation (DIC) was also used to determine the deformation fields from the images captured during deformation to quantify the effects of boundary conditions on the onset of failure initiation, and the results were used to develop a new Finite Element Analysis (FEA) model that is capable predict the mechanical behavior of the curved K-Cor sandwich composites.
Sandip Haldar, Ananth Virakthi, Hugh A. Bruck, Sung W. Lee

Chapter 14. Experimental Investigation of Free-Field Implosion of Filament Wound Composite Tubes

The mechanisms and energies associated with the hydrostatic implosion of composite cylinders are investigated experimentally and numerically. Experiments are conducted in a large pressure vessel, designed as to provide an adequate reflection-free window to best capture pressure waves resulting from the collapse. Both glass-fiber/polyester and carbon-fiber/epoxy filament wound thin-walled (R/t > 15) tubes are tested with varying L/D ratios to explore the effect of geometry on the collapse pressure and mechanics of the collapse. 3D Digital Image Correlation (DIC) is used to capture the full-field displacements and strains during the implosion event, and dynamic pressure transducers are employed to measure the pressure pulse generated by the collapse. Computational models are developed to verify and better understand key mechanisms of failure during hydrostatic buckling.
M. Pinto, A. Shukla

Chapter 15. Experimental Investigation of Bend-Twist Coupled Cylindrical Shafts

A new and unique way of orienting carbon fiber lamina in cylindrical shafts results in bend-twist coupling. A beam is said to possess bend-twist coupling when a pure bending moment applied to the beam results in simultaneous bending and twisting. This effect is normally associated with asymmetric cross-sections (such as c-shaped sections) but can result from a symmetric cross-section if the beam is anisotropic. In this case we study the bend-twist coupling resulting from a cylindrical shaft fabricated using a unique, non-obvious anisotropic lay-up. This research covers the design and manufacturing of these carbon fiber shafts to maximize the bend-twist coupling while simultaneously achieving acceptable torsional and flexural rigidity. Once constructed, the composite shafts are tested using DIC to measure the degree of rotation and deflection given an applied bending and twisting moment. The results are used to determine the shear center, degree of bend-twist coupling, torsional rigidity, and flexural rigidity as well as to verify the Finite Element Models. These models are used to predict the success of potential designs and to provide greater understanding of the phenomenon. Closed-form solutions provide a third means of verification, analysis, and optimization.
S. Rohde, P. Ifju, B. Sankar

Chapter 16. Processing and Opto-mechanical Characterization of Transparent Glass-Filled Epoxy Particulate Composites

A transparent glass-filled epoxy composite was developed by matching the refractive index of the filler and the matrix. This material was processed at varying volume fractions (V f) from 0 to 15 % of filler with transparency being maintained at each V f. Initial investigation included quasi-static three-point bending to determine the critical SIF (K Icr) values. Improvement over the neat epoxy was seen in each case with a maximum improvement of approximately 30 %. Furthermore, this material was observed to exhibit birefringent properties, thus making mechanical characterization through photoelastic methods feasible. The samples were loaded using a symmetric four-point bending set up and isochromatics were observed using a dark-field polariscope. The stress intensity factors for each sample were evaluated at various loads and compared to those determined analytically. Experimental measurements closely matched analytically determined ones, thus validating the use of this method. This work-in-progress includes investigating the fracture behavior of these composites under low and high strain rate conditions.
Austin B. Branch, Hareesh V. Tippur

Chapter 17. Study of Influence of SiC and Al2O3 as Reinforcement Elements in Elastomeric Matrix Composites

Rubber is an important polymer type that is widely used due to its high and reversible deformability. Since the modulus and strength of neat rubber are low, an additional reinforcing phase is necessary for the use of rubber materials in practical applications. Rubber is generally reinforced with fibers, carbon black (CB), and silicates. In our study we also use carbon black as filler reinforcement but in order to increase the mechanical properties even more we have added different particles (SiC and Al2O3) in rubber based composites. In the frame of the common research project, NR/BR based composites with different curing systems were characterized with respect to their curing characteristics and mechanical properties. The cure characteristics of the rubber compounds were studied by using the Monsanto MDR 2000 rheometer. Microindentation test was used for studying the viscoelastic behaviour of the compounds. Addition of different reinforcing particles can improve certain properties of rubber blends, such as stiffness, vulcanisation rate and crosslink density.
D. Zaimova, E. Bayraktar, I. Miskioglu, D. Katundi, N. Dishovsky

Chapter 18. Manufacturing of New Elastomeric Composites: Mechanical Properties, Chemical and Physical Analysis

Filler-reinforced vulcanized rubber and its blends are frequently used for engineering applications for over a century. Traditional applications include tires, seals, bushings, and engine mounts. The rubbers for tire manufacturing must have high elasticity and frictional properties as well as the high load bearing capacity. Conforming to these needs, rubbers are vulcanized by various materials such as sulphur, carbon black, accelerators, and retardants in different conditions. The reactivity of sulphur vulcanization and physical properties of the final product are affected by the chemical structure, molecular weight, and conformation of the base elastomers. The aim of this study is to investigate the influence of accelerator-vulcanizing agent system and the vulcanization temperature on the mechanical and aging properties of vulcanizates based on Natural rubber/Polybutadiene rubber (NR/BR) compounds. This preliminary study will allow optimizing the composition for improving the mechanical properties and understanding the damage behavior.
NR/BR based composites with different vulcanization temperatures and curing systems were characterized. The mechanical properties investigated were tensile strength, elongation at break, tensile modulus at 100 % (M100) and at 300 % (M300) deformation. Hardness (Shore A) and molecular mass of the samples were also determined. Scanning electron microscopy was used to study the microstructure of the fracture surfaces.
D. Zaimova, E. Bayraktar, I. Miskioglu, D. Katundi, N. Dishovsky

Chapter 19. The Effect of Particles Size on the Thermal Conductivity of Polymer Nanocomposite

The variation in thermal conductivity of polymer nanocomposite with different particle sizes and volume fractions have been investigated. Particle reinforced nano-composites with two different particle sizes and the volume ratio of each size ranging from 0 to 50 % is considered. The test is conducted using a unidirectional/linear heat transfer device that has six thermocouples to monitor the temperature flow through and across the cross section of the specimen. In addition, based on Lewis-Nielson and modified effective medium approximation, a three phase analytical model is proposed to determine the thermal conductivity of different nanocomposites. It is observed that the thermal conductivity linearly increases as the volume fraction of the particles increases. On the other hand, though the particle size has an effect on the thermal conductivity of the nanocomposites, the effect is minimal compared with the volume fraction. The analytical model has been applied to different batches of specimens, and the results from the experiment and analytical model are compared.
Addis Tessema, Addis Kidane

Chapter 20. Curing Induced Shrinkage: Measurement and Effect of Micro-/Nano-Modified Resins on Tensile Strengths

Fiber reinforced composites are widely used in automotive, aerospace and marine applications because of their light weight, low costs and excellent chemical resistance properties. Physical and chemical behavior of these composites is dependent on their matrix properties. The curing process of resins/matrix can introduce considerable shrinkage, which based on the component and its boundary conditions can detriment the strength of these materials and resulting components. One way to control the curing-induced effects is reinforcement of the resins with micro- and nano-fillers. In this work, the effect of various micro- and nano-fillers (3M™ Glass Bubbles iM16K and Cloisite® 30B nanoclay) in epoxy resin (SC-15) on curing-induced shrinkage and resulting tensile strengths was evaluated. Additionally, volumetric shrinkage (un-restrained) and curing-induced strains (ASTM D638 tensile tests) were measured by AccuPyc™ II 1340 pycnometer and fiber Bragg-grating (FBG) sensors respectively. A special technique was developed to correct the pycnometer measurement technique and make them independent on the testing chamber temperature. Results revealed that the morphology of the fillers (platelets/spherical) and their concentration significantly influence the curing-induced strains and associated shrinkage. Although such observations were expected, detailed quantification on the volumetric shrinkage and its effect on structural components made of such resins are not well documented. Overall, the study uses a novel technique to correct the pycnometer measurement technique and provides the groundwork for understanding the influence of the type and content of the fillers on the curing-induced shrinkage process. This will provide improved dimensional stability and reduce curing-induced residual stresses on resulting composites.
Anton Khomenko, Ermias G. Koricho, Mahmoodul Haq

Chapter 21. Graphene Reinforced Silicon Carbide Nanocomposites: Processing and Properties

This study investigates the effect of graphene nanoplatelets on the microstructure and mechanical properties of silicon carbide (SiC). Graphene nanoplatelets are dispersed in a liquid preceramic polymer by ball milling. Pyrolysis of the graphene nanoplatelet–preceramic polymer slurry results in near-stoichiometric SiC–graphene nanoplatelet powder. This method leads to improved dispersion of graphene in the SiC matrix as compared to conventional mechanical blending of dry powders and thereby significantly influences the resulting mechanical properties. Subsequently, spark plasma sintering (SPS) is used to consolidate dense bulk SiC–graphene composites with varying graphene content up to a maximum of 5 wt%. X-ray diffraction (XRD) investigation reveal that inclusion of graphene restricts grain growth of SiC matrix during SPS processing. Fracture toughness of SiC-graphene composite is increased by 40 % with the inclusion of 2 wt% graphene nanoplatelets. However, for higher graphene content the change in fracture toughness is limited. Improvement in fracture toughness is due to crack bridging reinforcing mechanism provided by the graphene platelets. Finally, Raman spectroscopy is used to understand the effect of SPS processing on integrity of graphene nanoplatelets.
Arif Rahman, Ashish Singh, Sriharsha Karumuri, Sandip P. Harimkar, Kaan A. Kalkan, Raman P. Singh

Chapter 22. Experimental Investigation of the Effect of CNT Addition on the Strength of CFRP Curved Composite Beams

Carbon nanotubes (CNT) have been attracting attention as a toughening material in composite matrix due to their excellent mechanical properties. However, superior properties of CNTs have not yet been realized in the strengthening of composites against fracture. This study focuses on investigating the effect of CNT variation in the epoxy resin on the strength of curved composite beams. Specimens are [0/90] fabric carbon/epoxy composite laminates manufactured by hand layup technique 3 % wt CNT fractions in the epoxy resin. Curved beam composite laminates were subjected to four point bending loading according to ASTM D6415/D6415M–06a and the load displacement plot is recorded. Digital Image Correlation technique is used to obtain deformation field in the laminate at the curved region just before delamination failure initiates. A high speed camera at 28,000 fps was used to capture the deformation sequence after initiation of failure. For the CNT added laminate, both CBS and failure load is found to decrease with the load-displacement behavior found to change from single load drop to multiple load drops. In addition, delamination is found to be constrained to the curved region for the CNT added laminate in contrast to the base laminate where delamination extends to the arms.
M. A. Arca, I. Uyar, D. Coker

Chapter 23. Mechanical and Tribological Performance of Aluminium Matrix Composite Reinforced with Nano Iron Oxide (Fe3O4)

Aluminium matrix composite materials are used in aerospace, defence, automotive applications especially in the thermal management areas. Aluminium Matrix Composite (AMCs) reinforced with Nano Iron Oxide (Fe3O4) exhibit good physical and mechanical behaviour (electrical conductivity and wear resistance), which makes it an excellent multifunctional lightweight material. The present paper is based on low cost manufacturing of light and efficient materials for aeronautical applications. To that end, a study has been carried out on an aluminium matrix composite reinforced with Fe3O4-iron oxide and other alloying elements produced in our laboratory. Micro indentation tests were conducted on the AMC to investigate its elastic modulus, hardness, and scratch tests with very long cycles were performed to study its wear performance. Scanning Electron Microscopy examinations were made to study the morphology of damage surfaces. The goal was to get more information about the influence of fillers on the corresponding reinforcing and wear mechanism.
E. Bayraktar, M.-H. Robert, I. Miskioglu, A. Tosun Bayraktar

Chapter 24. Particle Templated Graphene-Based Composites with Tailored Electro-mechanical Properties

A capillary-driven particle level templating technique was utilized to disperse graphite nanoplatelets (GNPs) within a polystyrene matrix to form composites that possess tailored electro-mechanical properties. Utilizing capillary interactions, highly segregated composites were formed via a melt processing procedure. Since the graphene particles only resided at the boundary between the polymer matrix particles, the composites possess tremendous electrical conductivity but poor mechanical strength. To improve the mechanical properties of the composite, the graphene networks in the specimen were deformed by shear. An experimental investigation was conducted to understand the effect of graphene content as well as shearing on the mechanical strength and electrical conductivity of the composites. The experimental results show that both the mechanical and electrical properties of the composites can be altered using this very simple technique and therefore easily be tailored for desired applications.
Nicholas Heeder, Abayomi Yussuf, Indrani Chakraborty, Michael P. Godfrin, Robert Hurt, Anubhav Tripathi, Arijit Bose, Arun Shukla

Chapter 25. Novel Hybrid Fastening System with Nano-additive Reinforced Adhesive Inserts

Structural joining of materials and components involves complex phenomena and interactions between several elements of either similar or dissimilar materials. This complex behavior, coupled with the need for lightweight structures and safety (human occupants in aerospace, automotive and ground vehicles), propels the need for better understanding and efficient design. A novel joining technique that incorporates the advantages of both bonded (lightweight) and bolted (easy disassembly) techniques was invented (Provisional Patent 61/658,163) by Dr. Gary Cloud at Michigan State University. The most basic configuration of this invention consists of a bolt that has a channel machined through the bolt-shaft that allows injection of an insert compound that fills the hole-clearance of the work-pieces and acts a structural component. The hole may contain additional sleeves or inserts. Several combinations of the proposed technique are possible, and in particular, the effect of the adhesive inserts, with and without nano-modification was studied in this work. Glass Fiber Reinforced Plastic (GFRP) composite plates were used as adherends with 12.5 mm holes, grade 8 bolts and preloaded to a torque of 35 N m. Pristine and Cloisite® 30B nanoclay reinforced SC-15 epoxy were used as adhesive inserts in the hybrid bolts. Tension lap-shear tests were performed on conventional (no-inserts) and hybrid bolted joints (inserts: adhesives + nanoclay), and their performance was compared. Results reveal that hybrid bolted joints can eliminate joint slip and considerably delay the onset of delamination. The addition of nanoclay increases the strengths but most importantly can prevent moisture from reaching the bolts shaft due to its excellent barrier properties. The proposed joining technique holds great promise for multi-material joining and a wide range of applications.
Mahmoodul Haq, Anton Khomenko, Gary L. Cloud
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