Mechanics of Composite, Hybrid and Multifunctional Materials , Volume 6

The performance of fiber-reinforced polymer (FRP) composites is limited by susceptibility to transverse microcracking and interfacial debonding. In this work, we introduce a microcapsule-based self-reporting and self-healing strategy for simultaneous detection and repair of cracks in FRPs. This dual functionality is achieved via the microencapsulation of a solvent-based healing agent doped with aggregation induced emission (AIE) luminogens and the subsequent dispersion of such microcapsules in carbon prepreg containing a thermoplastic-toughened epoxy matrix. Composite specimens are fabricated with a [0/90/0] stacking sequence from self-healing prepreg tapes and loaded in transverse tension until crack saturation is achieved. The transverse cracks rupture the microcapsules and release of the encapsulated solvent into the crack plane. Crack healing is achieved by the dissolution and redistribution of thermoplastic-rich regions into the damage volume. Evaporation of the solvent leaves solid thermoplastic in place of the crack and allowing AIE luminogens to aggregate and fluoresce. Using a small load frame that mounts under an optical microscope, we measure full-field surface strains during loading of the composite specimens via digital image correlation (DIC). The self-reporting functionality is evaluated by correlating the presence of microcracks with regions of damage-induced fluorescence. The healing efficiency of the composite specimens is assessed by comparing the applied stress levels and strain fields associated with cracking events pre- and post-healing.

The integration of composite laminates into automotive structures can provide weight reduction and improvement in occupant safety. However, the adoption of such materials requires characterization and efficient modeling of the damage behaviors of composite laminates which may occur during crash events, such as delamination. Numerical modeling techniques such as cohesive zone modeling require a traction-separation response for each mode of loading. The standard test technique used to characterize Mode I delamination, the double cantilever beam (DCB), measures the critical energy release rate; however, additional tests or inverse fitting techniques are required to characterize the full traction-separation response. Additionally, compliance inherent in the DCB specimen can influence the measured energy release rate while the large size of the specimen complicates the high deformation rate testing needed for crash analysis.

In this study, a novel Mode I test specimen adapted from a recent advancement in structural adhesive characterization is applied to evaluate composite delamination. The hybrid Rigid Double Cantilever Beam (RDCB) test specimen presented herein consists of rigid steel adherends co-molded to a composite plate containing a crack initiator. The use of steel adherends eliminates compliance in the composite laminate and ensures the interface of interest is loaded consistently and uniformly during tests, enabling measurement of the Mode I traction-separation behavior of composite delamination in a single test. As an example, the hybrid RDCB geometry is used to characterize the Mode I delamination behavior of a unidirectional E-glass fiber/epoxy laminate under quasi-static conditions, highlighting the ability of this specimen geometry to extract a full traction-separation behavior from a single test.

Aluminium Metal Matrix Composites (AMMCs) have very light weight, high strength, and show better resistance to corrosion, oxidation, and wear. Impact resistance is an especially important property of these AMMCs which is essential for automotive applications. In this study, recycled aluminium matrix composites were designed through the powder metallurgy route. As matrix, fresh scrap aluminium chips (Alumix-123), by-product of machining coming from the French aeronautical company, were used. Fine -alumina particles (γ-Al₂O₃, 10 wt %), were used as main reinforcement element for the present work. As secondary reinforcements, Mo and Cu were added in the matrix. In this study, a typical low cost but high performance metal matrix composite was designed by using recycled aluminum chips (Alumix-123). This process comprises of the mixing, blending and compacting of aluminum chips through press moulding and pre-sintering and finally forging. In the final stage, material parameters were optimized for improving physical and mechanical properties of these composites. Further, the influence of reinforcement’s type and content on the mechanical properties has also been reviewed and discussed. Damping capacities and damage were analysed by drop weight and quasi static compression tests. Microstructures were analysed by the Scanning Electron Microscope (SEM).

Aluminum matrix syntactic foams (AMSF’s) may perform an important role on aerospace and automobile industry duo to its features like low density, good specific stiffness, vibration damping and high energy absorption efficiency. AlSiMg0.5Mn matrix syntactic foam was produced by thixoinfiltration of fly ash micro balloons. Expectometry, DSC and Thermo-Calc analysis were conducted prior the synthesis of the foam to comprehend the aluminum alloy thixoability. Compressive tests, SEM analysis and x-ray microtopography (Micro CT) were performed to investigate the compressive characteristics and failure mechanisms of the composite. The compressive tests showed an usual foam behavior with a plato and a compressive offset stress of 40.5 MPa. The Micro CT analysis confirmed a homogeneous densification resulting in a high energy absorption capacity.

The copper-aluminium (Cu-Al-Zn) based structures show shape memory behaviours that are low cost engineering applications, such as actuators, valves, etc., regarding to Ni-Ti-Al structures. These alloys have a useful transformation temperature that can be modified to lie between −100 and 100 °C. For a low cost production, a combined method through powder metallurgy processes (sinter-Forging) have been performed for the production the composite called “Zn-Cu-Al-1X” with addition of small amount of reinforcements. For two basic production methods, sintered-forging process have been carried out at the temperature of 550 °C and 650 °C with 1 h dwell time followed slow quenching and final cooling operation respectively. In the frame of the common research project, production of the scrap thin sheet copper based composites reinforced with pure nano aluminium (~5 wt %) and fine zinc particles were produced with addition of small amount of fine particles as secondary reinforcements. These composites will be used for the applications of the coupling and actuators in the aeronautical area. For mechanical basically for the tailored behaviour of this composite, three point bending (3 PB) and impact tests were performed. Microstructural analyses was carried out with Scanning Electron Microscopy (SEM). Ductility and tailored behaviour of this composite will be discussed through the toughness mechanism depending on the processing parameters.

Niobium is the best and excellent metal for many different industrial applications. Europe has not a Niobium reserve whereas Brazil has a major Niobium mining and produce %90 of the Niobium in the world as a raw material.

However, the processing of this metal beginning from mining up to the advance processing for the real manufacturing engineering applications is very expensive and require a sophisticated equipment and investment. However, very huge amount of scraps of the niobium coming from manufacturing of the pieces is not reprocessed efficiently as valuable and economic way because quasi all of the scarps goes to the waste. The niobium scraps as an important secondary source of the raw materials should be evaluated for the manufacturing of the new composite design. As not possible to extract in an economical way, the recycling of niobium could be a sustainable occasion for the industrial applications.

The present work review of the efficient and sustainable recycling of the fresh scraps of niobium metal in the frame of the common research project carried out between UNICAMP-Brazil and SUPMECA-France. In this work, aluminium (AA 7075) matrix composites were designed by using the combined method, sinter + forging through the powder metallurgy route. Niobium powder obtained fresh scrap by using high energy milling were used as main reinforcement element for the present work. As secondary reinforcements, fine Ni–Al intermetallic, TiB2, TiC, B4C and Mo powders were added in the matrix in order to prepare five different compositions. This process consists of the mixing, blending by high energy milling and compacting of the final composition through the combined method, sinter + forging. In the final stage, material parameters were optimized for improving physical and mechanical properties of these composites. Damping capacities and damage were analyzed by drop weight and quasi static compression, scratch wearing tests, etc. Microstructures were analyzed by the Scanning Electron Microscope (SEM).

The present work, reviews the mechanical and microstructural analyses, of copper and silicon carbide reinforced recycled aluminium matrix (Alumix 431) composites manufactured by sinter+forging technique. Static compression, impact tests and also scratch damage tests were carried out. Detail analyses of Scanning Electron Microscopy (SEM) supported by XRD, thermal and electrical conductivity measurements have been carried out on the specimens before and after the tests.

The results exposed that, the composites have homogeneous structure without porosity and very homogeneous distribution of fine silicon carbide (SiC) particles. The failure damage in composites occurs in both matrix and particles implying good chemical bonding diffusion between matrix and particles. This composite will be applied on the pieces with high thermal conductivity and high surface damage resistant.

In the frame of the common research project, manufacturing of thin sheet Ni-Ti based composites reinforced with Nb and TiB₂ have been carried out through hot-forged bonding process for a high strength sandwich structure for the aeronautical engineering applications. Interface and bonding characteristics of hot forged composites have been evaluated heat treated at 550–600 °C depending on the operational parameters under laboratory conditions. Formability behaviour and delamination phenomenon have also been analysed by 3P Bending tests. An intermetallic phase layer has been carried out between the titanium and nickel sheet layers containing of hard particles reinforcements between the sheets by using hot forging process. Finally a high strength bonding has been carried out by mechanical joining and very strong chemical bonding diffusion during this process depending on the temperature and the time. With the finite element model developed with reference to these tests, the mechanical behaviour of the material is supported by simulations made with the Abaqus software. Finally, more detailed mechanical/physical properties of this developed material were investigated by applying wear and creep tests. Certain area in the microstructure have been analysed with SEM.

A micro-aerial vehicle (MAV) has been developed to achieve high versatility through biological inspiration from bird’s wings. One way of achieving optimized flight performance during different flight regimes is by incorporating a sweeping mechanism in the vehicle. Sweeping mechanisms allow a change in the aspect ratio of the wing as well as the overall span of the wing. The main challenge involves creating the mechanism to control the outboard section of the wing for a robust sweeping authority. A tendon-actuator mechanism with an elastic spring recovery system has been developed for this cause. In addition, macro-fiber composites (MFCs) were used as the control effectors for this vehicle both as ailerons and elevator. The placement of the MFCs was optimized for the required aileron effectiveness and overall aircraft performance. The analytical models were compared with the experimental results obtained through DIC, a full-field deformation measurement technique, for the entire wing.

In the frame of the common research project, the mechanical behaviour of recycled thin sheet Ti-Al based composites reinforced with scrap pure aluminium (AA1050) and boron, B reinforcement elements have been used with thin Ti-Al sheet recycled by hot forging method. The effects of chemical bonds during the production of these multifunctional sandwich composite structures were analyzed by 3-point bending tests to evaluated hyper elasticity behaviour. The same idea has been carried out this time on the Ti-Al based composites performed by sintered + forging through the powder metallurgy route by using different reinforcements such as TiB₂, TiC, and B₄C. Quasi static compression and low velocity impact (drop weight) tests have been performed on the sintered + forging specimens with a drop tower to observe the response of theses composites under the dynamic loading conditions. Interface and microstructure of these composites have been evaluated by Scanning Electron Microscope (SEM).

The present work, reviews the toughening mechanisms and microstructural analyses of recycled aluminium matrix composites reinforced with γ-alumina and pure recycled copper. This composite was manufactured by sintering and sinter + forging called the combined process. Static compression, 3-point bending, impact (drop-weight) tests were conducted to evaluate mechanical response of the composites. Additionally, wear and creep tests were carried out with a nanoindenter to evaluate wear and time dependent behaviour of this composite. Detailed analyses of microstructure of the composites was performed with Scanning Electron Microscopy (SEM) supported by EDS analyses. The results showed that, the composites have homogeneous structure without porosity and very homogeneous distribution of fine γ-alumina (Al₂O₃) and copper particles. Sinter + forging process yielded a material that had higher strength, hardness and better resistance to wear. This composite will be targeted for linkage applications where high toughness and high surface damage resistance is required.

Utilization of industrial waste and secondary materials is very much encouraged in construction industry and gaining importance. This concept supports in minimizing the environmental hazard and health problems. Copper slag is also one of the material considered as an industrial waste which can be used in construction Industry contribute to the reduction in consumption of natural resources. Many researchers have investigated the use of copper slag in the production of cement, cement mortar and cement concrete as raw material for clinker and as a partial replacement for cement, coarse aggregate and fine aggregate. The use of copper slag in cement and concrete extends potential environmental as well as economic benefits for all related industries, particularly in areas where considerable amount of copper slag is produced.

In the present study experimental investigation has been carried out to identify the influence of Copper Slag (CS) on the properties of concrete. Concrete cubes are made with 20%, 30%, 35%, 40%, 45%, 50% and 55% replacement of fine aggregate with copper slag. They were casted and the compressive strength of concrete cubes after 7 and 28 days of curing is determined along with evaluation of workability of concrete. The results have shown that all mixes with different copper slag yield increase in compressive strength than that of the control mix. The workability increased significantly as copper slag percentage increased compared with the control mixture. A substitution of up to 40–55% copper slag as a replacement of fine aggregate yielded good compressive strength compared with controlled concrete mix. The obtained results were compared with those of control concrete made with ordinary Portland cement and river sand. Therefore, it is recommended that up to 40–55% (by weight of sand) of copper slag can be used as a replacement for fine aggregates in order to obtain concrete with enhanced strength apart from minimizing environmental hazard.

Thin-walled structures have been widely used in automotive and aerospace industries to improve the system crashworthiness and impact protection. However, during manufacturing, transporting and handling processes, initial geometric imperfections are inevitably introduced to the thin-walled structures, which imposes negative impacts to the mechanical performance and service life of the thin-walled structures. In this study, we have introduced structural imperfection with controlled geometry and dimension to thin-walled steel tubes and characterized the mechanical response of these empty tubes and LN-filled tubes by quasi-static compression tests. Results show, the structural imperfection reduces the energy absorption capacity of empty tubes by about 20%. As the tube is filled with LN, the structural imperfection does not affect the energy absorption capacity of LN filled tube. The enhanced imperfection resistance is attributed to the suppression of imperfection growth caused by the strong liquid-solid interaction between the LN and tube wall. These findings suggest that the LN filling material can effectively reduce the adverse impact of structural imperfection and shed light on future design of thin-walled energy absorption devices.

Physical aging of polymers is a thermodynamic phenomenon that occurs in the glassy regime. Upon cooling, the thermal contraction is restricted by a lack of adequate free volume within the polymer structure. This leaves the polymer in a state of thermodynamic non-equilibrium which relieves itself over long timescales. Time temperature superposition is typically used to accelerate this aging process to achieve validation of properties over the service life of the material. The shift factors determine the degree to which the material time is accelerated in an isothermal environment at elevated temperature. This is typically achieved with dynamic mechanical thermal analysis (DMTA). This method works well for neat polymers but fiber reinforced polymer composites (FRPC) have significantly higher stiffnesses and typical DMTA testing is limited to under 20 N of force. Due to the large unit cell for a fabric composite and geometrical limitations in the thickness of a ply, a higher force method would be more useful. In this study, an electrodynamic test frame was used to determine the shift factors for a glass fiber reinforced polymer (GFRP) composite which has a thermoset matrix. The goal is to determine whether the shift factors differ for different orientations of the composite. For an orthotropic material, directional dependent shift factors would increase material model complexity significantly.

An investigation to observe the morphing capabilities of actuated macro fiber composite patches on multi-curved aircraft surfaces was conducted. Inattentive positioning of these patches can reduce desired surface deflection and mitigate aerodynamic performance. An initial study was performed on a 2-D fiber reinforced airfoil to observe the morphology of the cross-section when macro fiber composite patches were actuated in different chordwise positions. This was achieved through iterative finite element analysis using a thermal expansion method analogous to piezoelectric effects. The study was adapted to a complex 3-D wing surface where positioning and fiber orientation were considered. The kinematic performance was evidently affected for multi-curved versus more curvy-linear structures, where reduced surface curvature was favorable for more trailing edge deflection. In addition, effects of non-linearity of piezoceramic composites were observed in tandem on these complex surfaces using digital image correlation. Hysteresis and creep effects by virtue displayed kinematic behavior as a function of time and structural geometry. For a multi-curved wing, the residual strain due to hysteresis and creep were less apparent than for a reduced multi-curved surface.

Metal matrix composites are widely used in modern engineering as a result of the needing for distinct features into the same material, and for presenting such characteristics, the metallic foams have been increasingly used mainly from the mobility industry. Therefore a semisolid processing route for producing an AlSiMg0.5Mn matrix syntactic foam was idealized, by the thixoinfiltration of an industrial waste known as fly ash micro balloons. Preliminary a thorough study of the balloons morphology and chemical composition had been done, as also the AlMg2.5 thixoability through Spectrometry, Differential Scanning Calorimetry (DSC). The process parameters were defined to obtain a homogeneous pore distribution into the matrix and good wettability of balloons analyzed by x-ray micro tomography (Micro CT) and optical microscopy.