Mechanics of Composite and Multi-functional Materials, Volume 5

This study is focused on development of experimental capabilities to (a) understand and (b) quantify progressive damage processes (PDP) in thick composite structures; as well as (c) generate experimental outputs sufficient for confident validation of corresponding modeling solutions. It specifically addresses crucially important, yet relatively unexplored, load scenario of through-thickness penetration. This scenario is associated with quite complex patterns of damage which present obvious challenges for both characterization and modeling. Based on developed internal analytical modeling capabilities, clear expectations of inter- and cross-laminar damage patterns are generated as functions of composite lay-up, thickness (number of layers), and specific implementations of boundary conditions. For experimental assessment of these patterns, a general testing rig is developed with high level of flexibility to accommodate key variables of load conditions and material design. The rig provides a clear through-thickness view of the damage process as function of monotonically increased quasi-2D load. Also, coupling with Digital Image Correlation (DIC) allows one to monitor through-thickness strain distributions before and during PDP up to complete penetration through tested composite samples. Experimental demonstration of the rig is considered on examples of nine different thick composites with distinct failure processes. Details of experimental implementation and observed patterns of multi-step PDP are systematically discussed.

In this work, an alternative aluminium matrix composite (AMCs) was designed from the recycled chips of the aluminium series of AA7075 (90 wt %) and Al-Zn-Mg-Si-Ni (10 wt %) given by French aeronautic company to prepare a typical matrix after that we have designed a composite through combined method of powder metallurgy followed by Sintering + Forging. Basically, B₂O₃ (4 wt %, 8 wt %), TiC (5 wt %), fine Al₂O₃ Fibre (5 wt %), Zn (4 wt %) and Nb₂Al (4 wt %) were added as the main reinforcements. To increase wettability of the reinforcements, we doped them through a thermomechanical treatment. The main idea of this research is to propose an alternative low cost composite for the application in a mechanism to transfer motion for the connection links, for example; between the two railways wagons etc. and also some connecting link in aeronautical pieces as an alternative replacement for conventional alloys used in this area. Mechanical properties, static compression 3-Point Bending (3PB) and dynamic drop weight tests and also micro-hardness results of these composites have been carried out. The microstructure analyses were evaluated by Scanning Electron Microscope (SEM).

Aluminum based hybrid composites were produced from recycled AA7075 chips with the addition of TiC (d ≤ 3–5 micron), MoS₂ and Al₂O₃ fiber. In the two groups of composites produced, the content of MoS₂ and Al₂O₃ were fixed as 2 wt % and 3 wt % respectively, whereas TiC content was at two levels (5–10%). The combined method of powder metallurgy route, sintering followed by forging, was used to manufacture these composites. These composites are targeted for aeronautical and automotive industries for components subjected to static as well as cyclic and dynamic loading. In addition to mechanical properties, machinability of these composites is of importance hence, MoS₂ was included in the formulation. Micro hardness, 3 point bending, low velocity impact and nanoindentation (creep and wear) tests were performed on samples manufactured by just sintering and sintering followed by forging. The results showed that, in generals, the samples that were forged after sintering yielded better properties. The microstructure analyses (matrix/interface) have been carried out by Scanning Electron Microscope (SEM).

Structural materials should be stronger, tougher, and lighter to withstand the extreme conditions in the aeronautic and automotive applications. In this work, alternative intermetallic based composites (IMBCs) were designed from Mgx (1-x) Ti-Al recycled intermetallic alloy reinforced with the different percentages of CNT/Al₂O₃ fiber and Boron/Al₂O₃ fiber. Aluminum powder (~ 5 wt %) obtained from fresh scrap was added to the compositions to improve the homogenization of the mixture. Then, final composites were produced through sintering, combined method of sintering followed by forging and/or sintering followed by thixoforming which are low cost and efficient methods to manufacture light, multifunctional materials. Two different composites were designed by using these manufacturing processes: First group was considered as matrix +0.5 wt % CNT +1% Al₂O₃ fiber and the second group was designed as matrix +0.5wt % Boron +1% Al₂O₃ fiber. Quasi-static compression tests, nanoindentation (wear, modulus, hardness) test were performed to study the effect of the reinforcements and the manufacturing methods. The microstructure analyses (matrix/interface) have been carried out by Scanning Electron Microscope (SEM).

Plastic injection molding is a versatile manufacturing process; constituting a major part of plastic manufacturing industry. Complex sizes and shapes of high-quality everyday products; as well as sophisticated industrial goods are producible with it. In this process, plastic products are manufactured inside a tooling called “mold”. Molten plastic is injected inside the mold, the mold is then closed down. After some time, the die (mold) is opened and the solidified plastic product is taken out of the die. To obtain a better-quality plastic product, the design of the injection molding tooling, specifically the design of die core and cavity is very critical. Traditionally straight holes are drilled into the solid dies to cool the hot molten plastic inside the cavity. Cooling process takes up a major portion of the production cycle, leading to high cost of production. With the rising competition worldwide in the plastic product business, it has become very important to lower the production cost, and one way of doing so is to reduce the production cycle time. Using conformal cooling channels is a good option for this purpose. The conformal cooling channels “conforms” to the shape of the final plastic product, and they have the potential to improve the performance of the molding dies in terms of uniform and fast cooling, less warping and defects. This is totally achievable by recent developments in additive manufacturing. In this paper, a comprehensive study is presented, starting from design, simulation, 3D printing process and experimental testing of an injection mold with conformal cooling channels in industrial production environment. A traditional mold model is provided by our industrial collaborator. To enhance the overall thermo-mechanical performance of the mold and improve final product quality, a redesign of this mold core is done with conformal cooling channels inside. The final design is 3D printed in pre-alloyed tool-steel powder using Truprint 3000 metal 3D printing machine. The printed core required some heat treatment and finishing processes and added features to be incorporated to make it production ready. Once all the preparation was complete, the core was tested experimentally in a multicavity injection molding machine in real industrial environment at our industrial partner’s production facility. This paper describes all the steps starting from design, analysis, die 3D printing and finally ending at final experimental testing.

In this work, an alternative aluminium matrix composite (AMCs) was designed from the recycled chips of the aluminium, Alumix 431 given by Brazilian aeronautic company, through combined method of powder metallurgy followed by Sintering + Forging. We aimed for the application for the connection pieces to transfer motion mainly used in automotive and aeronautical area as an alternative replacement for conventional alloys used in this area. First of all, A typical matrix was developed from recycled aluminium (AA 431) chips by high energy milling in a planetary ball mill with an inert argon atmosphere to prevent oxidation of the powders and this matrix was reinforced basically with TiC (5 wt % and 10 wt %) and molybdenum and copper (Mo 4 wt %, Cu 4 wt %) as a secondary reinforcements respectively. Mechanical and physical properties were evaluated through micro-hardness, static compression and 3 point bending (PB) tests and impact-drop weight tests were carried out. The microstructure analyses have been carried out by Scanning Electron Microscope (SEM).

In this work, magnetic shape memory composites (MSMCs) was designed as an alternative replacement of actuators. A special recycled fresh scrap pure electrolytic copper was obtained from the French aeronautic society and milling of Cu-chips was carried out by high energy milling in a planetary ball milling with an inert argon atmosphere to prevent oxidation of the powders. Composite design has been carried out through combined method of powder metallurgy and sinter Forging. Firstly, Cu matrix was doped with fine powder reinforcements (Ni, Mn-Al and Fe₃O₄ magnetic iron oxide) in different ratios. After that, the ball milling was carried out during the 4 h. Mechanical and physical properties of these composites were analyzed. Magnetic permeability and deformation rate was also measured. The microstructure analyses have been carried out by Scanning Electron Microscope (SEM).

The current work describes the use of DIC (digital image correlation) for full-field strain and deformation response while performing 10° off-axis tensile tests on rigidly clamped unidirectionally carbon fiber reinforced (CFRP-UD) coupon specimens with a nominal reinforcing fraction of 50 volume percent. Off-axis testing of anisotropic materials produces a nonuniform state of stress and strain when the ends are rigidly clamped and bending moments cannot be eliminated by free rotation. Under this configuration, the application of constant end displacements induces shearing forces and bending couples, which result in the nonuniform deformation. The extension-shear coupling compliance causes the coupon to deform into an S-shape, which is qualitatively visualized using DIC. Quantitative photomechanical investigations of vertical and horizontal displacements of the coupon are compared to approximate analytical solutions originally derived in the 1960s. Additionally, a description of deformation and fracture mechanisms using the DIC calculated strains is provided. In addition to the shear strain in the specimen coordinate axis, the maximum shear strain (used to quantify the shear modulus and the strain to fracture) and normal strain (transverse to fiber orientation) are calculated via strain transformation equations and visualized.

The usages of natural fibers as reinforcement material in composites have shown acceptable results. The composite with uniformly distributed fibers under desired orientation is in the usual practice of casting. The studies of natural fiber reinforced composites have shown their utility in real practice. Past researchers have investigated various types of Basalt reinforced materials in the form of fiber, fabric, rods, etc. In this present work, a study on the mechanical properties of uniformly distributed randomly oriented basalt rock fiber (BRF) reinforced composites is presented. The basalt fiber of 13 mm ± 1 mm length having 1 mm width and polymer matrix are used for casting the composite specimen. An unsaturated polyester resin is used as matrix material along with Methyl Ethyl Ketone Peroxide (MEKP) and Cobalt Naphthenate as catalyst and hardener respectively. A ratio of 1:1:50 of Methyl Ethyl Ketone Peroxide, Cobalt Naphthenate, and Unsaturated resin are adopted to prepare the matrix solution for the fabrication process. The composites specimens of 15, 20, 25, 30, 40 and 45% fiber volume fraction are fabricated. The results of the present study have shown the higher value of tensile and flexure strength at 40% fiber volume fraction. Hence the 40% fiber volume fraction is the optimum percentage for uniformly distributed, randomly oriented BRF reinforced composites.

Polyethylene utilities pipes are difficult to detect once buried. Ground penetrating radar is typically used for location, but the electromagnetic signatures of small pipe lines, like the lines that between mains and individual buildings, are often too weak to be detectable. Due to the high number of buried pipelines and the high risks and costs that can occur with damaged lines, improving the locatability of the pipe is an important area of focus. Polyethylene doped with conductive dopants and made into antennas could provide a more distinct electromagnetic target during location. In this work, the electromagnetic properties of the conductive polyethylene material were studied. Mechanical strains were applied to the material to determine how the electromagnetic response would change with the physical deformation.

Recycling is an intensely studied subject in terms of sustainable development and it offers clean and cost-efficient solutions in many industries. For this reason, manufacturers tend to find clean and cost-efficient solutions by utilizing recycled materials to produce new components. In this regard, rubbers have a very wide usage area in aeronautic and automotive industries including structural and interior body components. Rubbers are also used to modify brittle polymer components in the existence of hard, resistant fillers. In this study, fresh scrap EPDM (ethylene propylene diene monomer) rubbers are used to manufacture novel composites by modifying epoxy resin with the inclusion of alumina (Al₂O₃) fibers (AFs). In case of a homogeneous distribution, addition of AFs ensures desired mechanical properties due to its favorable structural characteristics such as interlocking effects of fibers. These novel composites can be used in the manufacture of various solid structural parts of the fuselage and suspension pads in aerospace industry. This paper primarily explains the manufacturing of these composites and after the mechanical characterization, numerical approaches are implemented to test the durability of the structures. The mechanical and physical properties of these composite systems are studied in the present work. Dynamic Mechanical Analysis (DMA) analyses are carried out to determine thermal-mechanical properties. Three-point bending and compression tests are performed to see the mechanical behavior of the composites. In the end, manufactured compositions are tested numerically in terms of the structural reliability of a body component in a commercial aircraft.

Ball valve seats are subject to relative sliding motion during opening and closing making them susceptible to accelerated wear from particles entrapped in the ball-seal interface. The resulting wear channels can lead to a poor seal, sometimes resulting in valve failure, which would necessitate repair or replacement of the valve. Self-healing techniques offer a potential method for autonomously repairing seal leakage that results from abrasive damage. In this work, a microvascular approach is adopted to automatically repair ball valve seats and reduce leakage. Healing is accomplished by circulating healing chemistry through small channels isolated from the environment by a thin surface laminate in order to simulate progressive seal damage due to abrasion. Self-repair is accomplished by autonomously filling surface scratches with a healing agent. The healing agent performs a dual purpose of slowing down the damage rate by lubricating the surface as well as reversing the loss of material by polymerizing to form new material. Manufacturing techniques of microchannels are developed for Polymethylmethacrylate (PMMA, Acrylic) and Polyoxymethylene (POM, Delrin), and wear resistances are measured.

The mechanical polishing is one of the critical microfabrication processes in semiconductor and a host of other critical industries. There has been a great effort in consumable development (pads, slurries, etc.) to improve the overall polishing efficiency and resulting surface quality. In this study, we explored a unique composite polishing wheel with integration of magnetorheological elastomers (MREs). The proposed design aims to control local contact area and contact pressure during fine polishing process and thereby control the material removal rate with precise adjustment of the magnetic field. Two (Two MRE microstructure) MRE, isotropic and chain structured orthotropic, materials were included in the design. The feasibility of the designed wheel and the workpiece-wheel contact characteristics were tested under compression loading. An experimental setup was designed to apply vertical and horizontal magnetic fields. Digital image correlation technique was utilized to measure the local in-plane strain field around contact region. It was found that addition of MRE inserts can alter the local stress field around the contact area, resulting in a strong modulation with up to three-fold increase of both the contact area and the local pressure distribution. Finite element analysis highlighted the intricate role of the MRE inserts in modulating the local strain field around the contact area, and thereby inducing a concurrent increase in both the contact area and the local pressure distribution under the same nominal macroscopic applied load. The observed demand modulation of the contact pressure is anticipated to have a marked effect on the polishing process and the resulting surface quality.

In the proposed study, we synthesize a clickable polyhedral oligomeric silsesquioxane (POSS) carbon fiber coating to enhance the fiber-matrix interfacial properties using the highly selective “thiol-ene click” chemistry. The unique hybrid structure of POSS molecules creates a spring-like effect when strongly bound to a surface, resulting in a smooth load transfer across the interphase region, making it uniquely suited for use as a fiber surface treatment to develop damage-tolerant composite laminates. This is the first study to date that reports on the use of “thiol-ene click” chemistry to create a controlled POSS coating to enhance the interfacial properties between the fiber and matrix. Thiol-ene chemistry is the reaction between a thiol (-SH) group and alkene group, creating a bond between the two materials. PAN-based carbon fibers undergo a series of chemical modification resulting in thiolated-carbon fibers. Octavinyl-POSS is selectively “clicked” to the carbon fiber surface, creating a strongly bound uniform POSS coating. These POSS-coated carbon fibers can now be used as a prepreg for the manufacturing of composites for aerospace applications requiring enhanced composite strength and durability. The fiber-matrix adhesion is characterized using fragmentation tests to determine the interfacial shear strength. Meanwhile, the surface treatment chemistry is characterized using FTIR and XPS techniques.

The interphase region in fiber reinforced polymer (FRP) composites exhibits time dependent behavior due to the viscoelasticity of the matrix. AFM based (Atomic Force Microscopy) indentation utilizing different dwell periods for various constant loads are employed to analyze the creep behavior of the near–fiber region in carbon fiber reinforced epoxy. It is observed that along a radial line to the fiber, the relaxation of the polymer is lower closer to the fiber. Loading in the interphase region is known to be influenced by the fiber constraint effect. Therefore, 3D FE (Finite Element) simulations using an assumed non-linear elastic and linear viscoelastic behavior of epoxy is used to determine the extent of the influence of the fiber constraint on the viscoelastic response of the interphase region.

A micro air vehicle that can achieve a versatile flight condition is being designed. One way of achieving such versatility is through biomimicry. One aspect of this design utilizes a bird-like wing that changes shape to match four flight regimes; take-off-and -landing, cruise, high speed dash and one that enhances maneuverability. A joint mechanism using a tendon actuator between the inboard and the outboard portions of the wing is used to modify wing sweep. Macro fiber composites (MFCs) piezoelectric actuators in a bi-morph configuration are incorporated into the MAVs as control mechanism. Camber changes are implemented with tendon actuators. Finite element is used to model the wing section and perform a full-field deformation study and compared with experimental results. Digital image correlation is used to validate the wing deformations predicted by finite element method (FEA).