During the machining processes of ceramic particle reinforced metal matrix composites, the severe tool wear constrains the quality and cost of the parts. This paper presents the experimental and theoretical investigations of the tool wear behavior and surface quality when micro milling the 45vol% SiCp/Al composites under dry and minimum quantity lubrication (MQL) conditions. The results of scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) show that the wear mechanism of diamond coated micro mills are adhesive, abrasion, oxidization, chipping and tipping, even though it has been reported that abrasion is the most important tool wear mechanism when machining particle reinforced metal matrix composites. Compared with dry lubrication condition, the environmentally friendly MQL technique can enhance the tool life and surface roughness, and reduce the cutting force significantly under given cutting parameters. Then, finite element (FE) simulations are employed to investigate chip formation process in micro orthogonal cutting to reveal the effects of reinforced particle on tool wear and surface quality. The FE simulations shows the local high stress, hard reinforced particles in metal matrix, debonded and cracked particles are the key factors leading to the severe tool wear and the unsmoothed surface morphology.

In the automotive and aerospace industries, cost and overall weight are major opponents that are affecting design opportunities. Research to investigate possible cost and weight reduction methods is continuously being performed focusing especially on the hybrid materials being used to manufacture parts. Currently, different types of metals with polymers are being chosen to make punched parts, but the deformation of the materials has not been fully investigated. The way that the material deforms will dictate the material properties held by the subsequent parts. Without knowing these material properties, it is difficult to prevent manufacturing problems during various processes. One major problem encountered when forming solid metal parts is that when the die is removed, the deformed parts change shape due to the elastic properties of the material. This shape change is called springback. This undesirable result causes the parts to be the incorrect shape and to not align correctly during assembly. One possible solution would be to investigate the material properties of trilayer hybrid materials consisting of metal and composite layers adjoined by adhesive. Trilayer channels will be tested by punching and measuring the resulting springback. Two different trilayer design setups will be tested, composite metal composite sandwich and metal composite metal sandwich, and will be compared with the deformation in a single layer metal channel. The outcome of these tests will determine which trilayer design will have the greatest success in reducing the undesirable springback effects.

The need for lightweight components and non-destructive fastening techniques has led to the growth of adhesive use in many industries. Modeling the behavior of adhesives in fastening joints can help in the design process to make an optimized joint. To optimize joints in the design process, the loading conditions, environmental conditions of service, thickness of bond, and bonding procedures all need to be refined for the adhesive of interest. However, in available technical data sheets of adhesives provided by manufactures there is a gap in what is sufficient to accurately model and predict the behavior of real-world adhesive conditions. This body of research presents the results of the effects of temperature, thickness, and working time on adhesive properties. These effects can be observed with test specimens from the loading modes of interest. The loading modes of interest are mode I and mode II loading for the current study. The specimen for mode I loading is the Double Cantilever Beam, and for mode II loading is the Shear Loaded Dual Cantilever Beam. The effect of temperature will be tested by testing each specimen at −20°C, 20°C, and 40°C. Two bond thicknesses for adhesive thickness effects were tested. The working time had a control group bonded in the recommended working time and an expired working time group where the specimens were not joined until 10 minutes had passed from the recommended working time. Triplicates of each specimen at the respective conditions were tested. The adhesive selected for this research was Plexus MA832. The results of the experiment show that adhesive factors such as temperature, thickness, and working time can have degrading effects on adhesive performance in mode I and mode II.

This study compares the deformation characteristics of steel and carbon fiber composite (CFC) front bumper crush can (FBCC) assemblies when subjected to a full-overlap frontal impact into a rigid wall. Both the steel and composite bumper tests were conducted using a sled-on-sled testing method. Several high-speed cameras (HSCs) and accelerometers were used to gather kinematics data. The applied forces were measured using a load cell wall. For each test, the collective set of data was filtered, sorted, and analyzed to compare the performance of the steel and CFC bumpers. Similarities in Acceleration-Time plots suggested resemblance in the deformation patterns for both types of bumper systems. The difference observed in the velocity and displacement time-histories was because of the brittle nature of the composite material. The velocity-time history of the CFC FBCC had two distinct patterns, events suggesting adhesive bond failure between the bumper beam and the crush cans, which was validated through video tracking. Post-impact photographs showed a clear difference between the material behavior of composite and steel bumpers when subjected to high-velocity impact. The steel bumper beam was bent uniformly with intact, equally crushed crush cans. The composite beam was cracked in the middle and was detached from the crush cans.

Many engineering structures, in applications such as automobiles, bridges, etc. are assembled by joining the different parts together. Therefore, joints in the mechanical applications play a critical role in durability, flexibility of the mechanical assemblies. Recent advances in adhesive technology have made adhesive joining one of the plausible options in many engineering applications that demand high impact resistance such as ground vehicle armor or civilian vehicles. However, because most of the polymer-based adhesives have non-linear mechanical behavior and loading rate sensitivity caused by their viscoelastic properties, characterization of the adhesives under different loading and environmental conditions become vital in the design of durable and reliable joints in any structure. This study investigated the mode I (bending) response of the adhesive joints to shock-wave loading generated in a large-scale shock tube. The critical failure pressure (P 5 ) of adhesive joints was determined experimentally. Determining the material properties of the adhesive were estimated by the FEM parametric study, and energy absorption capacity of the adhesive joints under different strain rate loadings were investigated.

In this study, the Fickian diffusion formulation is extended to the adhesive layer of a single lap joint model, in order to develop a coupled peel and shear stress-diffusion model. Constitutive equation are formulated for shear and peel stresses in terms of adhesive material properties that are time and location-dependent. Numerical solution is provided for the effect of diffusion on shear and peel stresses distribution. Detailed discussion of the results is presented.

This study investigates the effect of the rate of autoclave heating and cooling on the performance of bonded lightweight material single lap joints (SLJ) after they have been heat cycled at high relative humidity. Two different temperature ramp rates are used for the autoclave bonding of test joints. Joint performance is assessed in terms of the load transfer capacity (LTC) and the corresponding failure mode in a tensile-shear test. Three different combinations of Aluminium and Magnesium adherends are used in test samples using aliphatic polyether (polyurethane) film adhesive. The effect of heating rate on the peel strength of cured adhesive is also investigated. Data analysis and discussion are provided.

Template based chemical vapor deposition (CVD) is a process of effectively fabricating nanostructures such as Carbon nanotube arrays (CNT). During this process, a carbon-carrying precursor gas is used to deposit a layer of solid carbon on the surface of a template within a furnace. Template-based CVD using porous anodized aluminum oxide (AAO) membranes as the template has been applied to efficiently mass-produce CNT arrays which have shown promise for use in gene transfection applications. These AAO membranes are incredibly fragile, making them prone to cracks during handling which can compromise their performance. In order to ease handling of the CNT devices, three-dimensional (3D) printing has been applied to create a support structure for the fragile membranes. The work presented here focuses on the use of 3D printing as a means of integrating CNT arrays into nanofluidic devices, both increasing their useful application and preventing damage to the fragile arrays during handling. 3D printing allows the CNT arrays to be completely encapsulated within the fluidic device by printing a base of material before inserting the arrays. Additionally, 3D printing has been shown to create an adequate seal between the CNT arrays and the printed device without the need for additional adhesives or sealing processes. For this work, a commercially available, fused deposition modeling (FDM) 3D printer was used to print the devices out of polylactic acid (PLA) plastic. This approach has been shown to be effective and repeatable for nanofluidic device construction, while also being cost effective and less time consuming than other methods such as photolithography. Cell culture and has been demonstrated using HEK293 cells on the devices and was found to be comparable to tissue culture polystyrene.

Polyetheretherketone is a widely used engineering polymer that is especially suitable for high-temperature applications. Graphene is a two-dimensional form of carbon nanomaterial that has been studied extensively for its mechanical, electrical and thermal properties and its use as a filler in polymer matrices. Compounding graphene into polymers has the potential to improve various properties, even at very low concentrations. In this work, we have examined the incorporation of graphene nanoplatelets (GNP) into PEEK. We have fabricated composites using melt-mixing techniques, as well as by graphene functionalization and in-situ polymerization of the PEEK. In this way, we can compare the performance of the composites by two different processing methods. The GNP-PEEK composites were characterized by DSC, TGA, and SEM. Lap-shear joints using the GNP-PEEK as the adhesive were made and mechanically tested. Results show that the weight fraction of GNP has a major effect on the strength of the joint. In this work, we aim to produce a material that functions as a reusable high-temperature, thermoplastic adhesive, which can be activated by conventional heating methods, or by microwave heating. The GNPs act as microwave absorbers and heat the surrounding PEEK matrix to the point of melting, in contrast to the neat PEEK, which does not melt upon exposure to the microwaves under the same parameters. Additionally, we explore 3D printing methods to fabricate a lap shear joint, where the adherends are pure polymer and the adhesive region is a polylactic acid/carbon nanofiber (PLA/CNF) composite that can be activated by microwaves. We show that solid adherends can be bonded together when a solid PLA/CNF piece is placed between the adherends and melted by microwave exposure. The microwave absorption properties and adhesive properties will be discussed.

Adhesive joint technology has been developed gradually, and the application fields of this type of joints have been expanded increasingly since they reduce the weight of the applications, provide uniform stress distribution across the joints, allow to bond similar, and dissimilar materials, and contribute to dampen the shock, and vibration. However, the performance of the adhesive joints under high loading rate such as blast or ballistic loading has been studied by few researchers. In this study, fully laminated plates consisting of 6061 aluminum plates (15” in diameter and 1/16” thick) and FM300K epoxy film adhesive were tested under shock wave loading. Full displacement field over the testing plates were obtained by TRC-SDIC technique, and the strain on the plates were computed by classical plate theory for large deflections. FEM model was analyzed and the results were compared with experimental results.

The growth of lightweight components and need for non-destructive fastening techniques leads to the use of adhesives in many industries. Modeling the behavior of adhesives in fastening joints can help in the design process to make an optimized joint, with minimal waste. However, in available material properties provided by manufactures of adhesives there is a gap in what is sufficient to accurately model and predict the behavior of real-world adhesive conditions. An adhesive joint may be loaded in mode I, mode II, mode III, or a combination of these in service. In components with outdoor application the ambient temperature outside in many regions can vary to below freezing to over 40 °C. The environmental conditions at these temperatures may influence the adhesive material properties. This body of research presents the results of adhesive properties subject to temperature testing. The needed material properties to compose an accurate model have been shown to be the mode I cohesive strength, mode I cohesive toughness, mode II cohesive strength, and mode II cohesive toughness. These properties can be measured with a test specimen designed to isolate that loading mode and condition. The specimens used are the Dog Bone Tensile Specimen (DBTS), the Double Cantilever Beam (DCB), Shear Loaded Dual Cantilever Beam (SLDCB), and Double Lap Shear (DLS). The effect of temperature will be tested by testing each specimen at −30°C, 20°C, and 45°C. Triplicates of each specimen at the respective temperature were tested. These results will be used in a cohesive zone model that will be validated with additional testing. The results from the two tested adhesives, Plexus MA832 and Pliogrip 7779/220, indicate these temperature conditions can change the cohesive strength in mode I by −60 to −40 % and mode II by −13 to 2% when at high temperatures (HT). The cohesive toughness in mode I by −40 to −20% and mode II by −40 to −2% when at high temperatures. The cohesive strength in mode I by −50 to 15% and mode II by 8% to 60% when at low temperatures (LT). The cohesive toughness in mode I by −70 to −20% and mode II by 30 to 60% when at low temperatures. As compared with those tested at room temperature (RT). The ranges here represent the response for both adhesives.

Inspired by biological suture joints with wavy morphology, wavy adhesive joints were designed and the shear resistance of the designs were explored via finite element (FE) simulations. The influences of waviness and material properties of the layer on the mechanical behaviors of the adhesive joints were quantified. Both adhesive and cohesive failure mechanisms were explored: (1) delamination along the interface between the softer layer and the harder substrates, and (2) layer material failure. In the FE models, both cohesive interaction and ductile damage mechanics models were used to capture the two failure mechanisms. The effects of Young’s modulus and damage evolution parameters on the force-displacement relation were studied. Both failure mechanisms were observed by varying the material properties in the adhesive layer. It was found that, the stiffness, strength and the failure mechanisms of the wavy adhesive joints are largely dependent on the geometry and material properties of the layer.

With the advantage of having a high strength to weight ratio, composite materials are frequently being implemented as alternatives to steel and aluminum in military vehicles. To perform satisfactorily, joined composite laminates on a vehicle must be able to absorb a significant amount of energy under high strain rate loading events such as ballistic impact. In this paper the dynamic behavior and failure modes of adhesively bonded S2-glass/epoxy laminate joints are investigated. For this experiment, two structural adhesives are selected for comparison: a brittle methacrylate and a more compliant epoxy. The tests are conducted on an in-house assembled gas-gun to achieve the high strain rates necessary to break the adhesive bonds in two configurations, Mode I and II. Results obtained from the ballistic impact tests are compared to quasi-static test results to emphasize the rate-sensitivity of the bonded joints. Irrespective of the material configuration, the failure load of the adhesively bonded joint is seen to increase with the loading rate. Overall, epoxy appears to be 35–50% stronger than methacrylate by most measures. Under bending loading (mode I), most cases exhibit some amount of damage within the composite surrounding the bonded area, demonstrating a fiber-tear failure rather than a cohesive failure. The failure strength of the composite joint is thus not always proportional to the adhesion strength of the adhesive due to the weakness of delamination of the composite material, especially when loaded through the thickness of the composite. As compared with metal adherends, the composites are shown to absorb three times more energy per unit area.

Adhesive bonding of composite structures has been widely applied in aviation, aerospace, automotive and other industry fields due to the advantages of no holes required, no stress concentration, relative light weight, corrosion resistance and capability of connecting dissimilar materials. However, the strength of joining is greatly influenced by the properties of adhesives and surface treatment of adherents, the geometry and dimension of joints, loading and environmental factors, as well as the curing process and so on. When the finite element (FE) method is used to investigate the influence of above factors on structural response and to optimize the joining design, parametric modeling is required to avoid huge repetitive preprocess work at each evaluation. In this paper, the three-dimensional parametric FE models of Single Lap Joint (SLJ) between carbon fiber-reinforced polymer (CFRP) and steel was established and updated based on the published test data. Using the verified parametric model, the influence of adhesive layer thickness and relative stiffness on the joining strength is investigated, and the results provide a theoretical basis for the design of adhesion joints between CFRP and steel.

Application of 3D printing to works of art is not new. However, with the advent of larger and more affordable 3D printers, it is possible to fabricate works of art including statues, sculptures, and architectural structures from biomimicked composites. Made of hard ceramic and soft polymer with or without reinforcement, these composites have shown to be much tougher than their monolithic counterparts. The use of biomimicking will increase the durability and strength of such artifacts. In this study, a newly developed architectural 3D printer is used to create works of art using concrete, with and without reinforcement fibers. The challenge that face creating tough artistic display structures include durability, hardness and resistance to impact. To determine the right combination of hard ceramic and soft polymer, a series of experiments were conducted. These included the fabrication of biomimicked composites with different materials and testing them for fracture energy as well as maximum strength. Earlier published works demonstrate the effect of various parameters such as type of ceramic layer, layering, fiber reinforcement type, fiber length, and fiber loading. In this paper, the effect of hard layer thickness and the type of polymer on the mechanical properties of the biomimicked composites was investigated. Preliminary results show the highest fracture energy for composites made with concrete bonding adhesive (CBA) and Quikrete™ concrete, with a spacing of 5mm. The application of 3D printing to the educational activities of a museum in Newport KY will be explained and its implication in relation with civic engagement activities of Northern Kentucky University will be elucidated.

Advanced microelectronic packages utilize a multitude of materials with dramatically different mechanical properties. Delamination occurring at the interfaces between these materials, due to poor adhesion and/or moisture exposure, is an important failure mode affecting the thermomechanical reliability of the package. The adhesion strength of these interfaces is a critical mechanical property that plays a role in the reliability performance of these packages. A good adhesion strength metrology is required to perform material selection and enable assembly process optimization in order to avoid the need for expensive assembly builds, followed by reliability testing which leads to long development times. This paper discusses the use of the Double Cantilever Beam (DCB) method for characterizing the adhesion strength of interfaces in advanced microelectronic packages at both room and high temperatures. Previous work in this area was focused only on room temperature testing. However, in order to characterize the adhesion strength of these interfaces at elevated temperatures seen during package assembly and reliability testing, an environmental chamber was designed and fabricated to rapidly and uniformly heat the DCB samples for testing at high temperatures. Depending on the interface tested and the testing temperature, DCB samples failed in one of three fail modes: (1) adhesive (at the interface), (2) cohesive (within the adhesive layer), and (3) brittle cracking of the substrate. Two case studies describing high temperature DCB testing on silicon-capillary underfill samples are presented. With adhesive failure being the desired fail mode in order to rank order materials and processes, it was found that for the underfills tested in this study, the DCB samples failed cohesively within the underfill at room temperature but started failing adhesively at temperatures near 150°C. Adhesion strength also showed a clear degradation with temperature. It is suspected that the change in failure mode from cohesive to adhesive with increasing temperature is due to competing trends of degradation in cohesive strength of the underfill versus degradation in adhesive strength of the interface with temperature.

Adhesive use in fastening is increasing in many industries. Modeling the behavior of adhesives allows joints to be optimized, decreasing costs from over-design and validation testing. Unfortunately, available adhesive material properties provided by manufactures are often insufficient to accurately model and predict behavior under real-world conditions. An adhesive joint in service is often subjected to a combination of mode I (tensile) and mode II (shear) loading. Also, when used in outdoor environments, ambient temperatures can vary from below freezing to over 40°C. This paper describes a project to measure the relevant adhesive material properties at the environmental conditions of interest for two specific adhesives and to use them in subsequent modeling. The needed material properties have been found to be mode I cohesive strength, mode I cohesive toughness, mode II cohesive strength, and mode II cohesive toughness. These properties are measured individually using four tests that isolate each of the material properties by using specimens with distinct geometries and loading conditions. These geometries allow the process zone of the adhesives to be controlled. A large process zone will relate to the cohesive strength, and a small process zone will relate to the cohesive toughness, in either mode I or mode II loading. Since the values of cohesive strength and toughness of the adhesives included in this study are unknown before testing, iterations of each specimen are varied by changing the process zone size to ensure valid properties are measured. Testing is conducted at −30°C, 20°C, and 45°C. In order to conduct this testing a temperature chamber was designed, fabricated, and validated. Commercially available temperature chambers were either too small or prohibitively expensive. The temperature chamber this project created was constructed of laser cut and bent stainless steel sheets with an insulated double-wall construction. Two seals were used at every entry point to maintain an air-tight chamber. A heating and cooling circulator and heat exchanger were used for temperature control. The chamber can heat to 45°C in approximately 15 minutes, and cool to −30°C in approximately 30 minutes.

Hierarchical, branched carbon nanotube (CNT) forest assemblies were created by synthesizing a second generation of CNTs directly from the alumina-coated surface of a parent CNT forest. First, a parent CNT forest generation was synthesized using floating catalyst chemical vapor deposition (CVD) in which gaseous argon and hydrogen are flowed into a tube furnace, along with a controlled flow rate of ferrocene nanoparticles suspended in xylene solvent. Next, a thin alumina coating was applied to the parent CNT forest using atomic layer deposition (ALD). The ALD process pulses alternating gases of water vapor and trimethylaluminum (TMA) and is repeated for 100 cycles, yielding a 10nm coating. This coating adheres to the outer walls of the larger CNTs and serves as a supportive surface to enable the growth of a second CNT generation. Finally, a second CNT generation was synthesized from the parent CNT forest using a floating-catalyst CVD method similar to that used for the parent generation. The relatively low areal density of the parent CNT generation allows for gas-phase additive processing (i.e. ALD and floating catalyst CVD) to occur deep within the volume of the original parent CNT forest. Transmission electron microscopy analysis of the hierarchical CNT forests shows that second-generation CNTs nucleate and grow from the alumina-coated walls of the parent generation rather than nucleating from the original growth substrate, as has been previously reported. Further, physical confinement of the second-generation catalyst particle on the external surface of the parent generation CNTs (28 nm average diameter) leads to small-diameter CNTs (8 nm average) for the second generation. Further, radial breathing modes are detected by Raman spectroscopy, indicating single-walled or few-walled CNTs are synthesized in the second generation. The hierarchical forests exhibit many desirable properties compared to single generation forests. Because the second generation CNTs within the interstitial regions of the parent CNT forest, they increase the structural rigidity of the cellular CNT forest morphology, increasing in mechanical stiffness by ten-fold, relative to the parent CNT forest. Further, we demonstrate that electrical continuity between the CNT generations is retained. Because a thin alumina buffer layer exists between CNT generations, electrical continuity is not guaranteed. Cyclic voltammetry and electrochemical impedance spectroscopy are used to characterize the electrical resistance elements within the hierarchical forest. This hierarchical structure offers a new avenue to tailor the performance of CNT forests and offers performance enhancements for applications in thermal interfaces, electrical interconnects, dry adhesives and energy generation and storage.

This study investigates the effect of cure temperature and pressure on the mechanical performance of autoclave-bonded single lap joints (SLJ). Joint load transfer capacity (LTC) and failure mode analysis are provided. Test joints are made of two polycarbonate lexan adherends that are autoclave-bonded together using aliphatic polyether (Polyurethane) film adhesive (Huntsman PE399). Two levels of cure pressure and cure temperature are investigated, for their effect on joint load transfer capacity and failure. Data analysis and discussion are provided.

Wire Electrical Discharge Machining (WEDM) is a versatile process to generate intricate and complex shapes on conductive work material with high dimensional accuracy and surface finish. Since the process is stochastic, its input parameters play critical role for achieving desired accuracy and precision of the component. Inconel 718, High-Strength-Temperature-Resistant (HSTR) material, has wide applications in the field of aerospace, automobile, mould making and medical industries. Hence, machining of Inconel 718 using WEDM is a challenging task. Also experimentation on Inconel 718 with WEDM is costly as well as time consuming process. Therefore to study the behavior of WEDM process with different process parameters for effective and efficient operation, process modeling and simulation using appropriate software is highly essential. In the present investigation, a 3-D single spark finite element thermal model for WEDM process has been developed using ANSYS software. This model has some more realistic assumptions like heat flux following Gaussian distribution and spark radius as a function of time and energy. Plasma incident region is meshed by keeping elemental size equal to one tenth of entire plasma radius, so that exact ten elements can be fitted. Identified elements were thermally loaded by applying element wise different temperatures for getting more accurate temperature distribution profile. This profile was found to be having crater shape matching with earlier Finite Element Models (FEM) available in the literature. Along with the shape, it also helps to decide the elements having temperatures greater or equal to melting point leading to estimate Material Removal Rate (MRR). Later on single spark MRR can be used to estimate multi-discharge-MRR by calculating pulse rate. Model MRR is validated with the experimental MRR which show a very good agreement, but little variation. This variation in the modeling could possibly due to assumptions like no delay in ignition, non-deposition of recast layer (100% flushing efficiency), etc. The factors like incomplete flushing of debris and inter-electrode gap arcing cause the variation in machining conditions thus reducing the actual MRR. In the present investigation, the use of dielectric is considered only for convection, but in reality, it acts as an insulator, coolant and also as debris remover. Melting and vaporization of material is the main phenomena for material removal. Dielectric fluid partially removes the molten metal because at the same time, the molten metal is under very high pressure due to plasma channel. Its adhesive property resists the material removal. It is very difficult to incorporate all real effects in the model, however the obtained results in the present study show good agreement between model MRR and experimental MRR within 10% variation.