Effects of Sinusoidal Vibration of Crystallization Roller on Composite Microstructure of Ti/Al Laminated Composites by Twin-Roll Casting

A new,innovative vibration cast-rolling technology of “electromagnetic stirring+dendrite breaking+asynchronous rolling” was proposed with the adoption of sinusoidal vibration of crystallization roller to prepare Ti/Al laminated composites,and the effect of sinusoidal vibration of crystallization roller on composite microstructure was investigated in detail.The results show that the metallurgical bonding of titanium and aluminum is realized by mesh interweaving and mosaic meshing,instead of transition bonding by forming metal compound layer.The meshing depth between titanium and aluminum layers (6.6μm) of cast-rolling materials with strong vibration of crystallization roller (amplitude 0.87 mm,vibration frequency 25 Hz) is doubled compared with that of traditional cast-rolling materials (3.1μm),and the composite interfacial strength(27.0 N/mm) is twice as high as that of traditional cast-rolling materials (14.9 N/mm).This is because with the action of high-speed superposition of strong tension along the rolling direction,strong pressure along the width direction and rolling force,the composite linearity evolves from "straight line" with traditional casting-rolling to "curved line",and the depth and number of cracks in the interface increases greatly compared with those with traditional cast-rolling,which leads to the deep expansion of the meshing area between interfacial layers and promotes the stable enhancement of composite quality.

Snap-through behaviors and nonlinear vibrations of a bistable composite laminated cantilever shell:an experimental and numerical study

The snap-through behaviors and nonlinear vibrations are investigated for a bistable composite laminated cantilever shell subjected to transversal foundation excitation based on experimental and theoretical approaches.An improved experimental specimen is designed in order to satisfy the cantilever support boundary condition,which is composed of an asymmetric region and a symmetric region.The symmetric region of the experimental specimen is entirely clamped,which is rigidly connected to an electromagnetic shaker,while the asymmetric region remains free of constraint.Different motion paths are realized for the bistable cantilever shell by changing the input signal levels of the electromagnetic shaker,and the displacement responses of the shell are collected by the laser displacement sensors.The numerical simulation is conducted based on the established theoretical model of the bistable composite laminated cantilever shell,and an off-axis three-dimensional dynamic snap-through domain is obtained.The numerical solutions are in good agreement with the experimental results.The nonlinear stiffness characteristics,dynamic snap-through domain,and chaos and bifurcation behaviors of the shell are quantitatively analyzed.Due to the asymmetry of the boundary condition and the shell,the upper stable-state of the shell exhibits an obvious soft spring stiffness characteristic,and the lower stable-state shows a linear stiffness characteristic of the shell.

Theoretical and experimental investigation of the resonance responses and chaotic dynamics of a bistable laminated composite shell in the dynamic snap-through mode

The dynamic model of a bistable laminated composite shell simply supported by four corners is further developed to investigate the resonance responses and chaotic behaviors.The existence of the 1:1 resonance relationship between two order vibration modes of the system is verified.The resonance response of this class of bistable structures in the dynamic snap-through mode is investigated,and the four-dimensional(4D)nonlinear modulation equations are derived based on the 1:1 internal resonance relationship by means of the multiple scales method.The Hopf bifurcation and instability interval of the amplitude frequency and force amplitude curves are analyzed.The discussion focuses on investigating the effects of key parameters,e.g.,excitation amplitude,damping coefficient,and detuning parameters,on the resonance responses.The numerical simulations show that the foundation excitation and the degree of coupling between the vibration modes exert a substantial effect on the chaotic dynamics of the system.Furthermore,the significant motions under particular excitation conditions are visualized by bifurcation diagrams,time histories,phase portraits,three-dimensional(3D)phase portraits,and Poincare maps.Finally,the vibration experiment is carried out to study the amplitude frequency responses and bifurcation characteristics for the bistable laminated composite shell,yielding results that are qualitatively consistent with the theoretical results.

Inter-well internal resonance analysis of rectangular asymmetric cross-ply bistable composite laminated cantilever shell under transverse foundation excitation

The chaotic dynamic snap-through and complex nonlinear vibrations are investigated in a rectangular asymmetric cross-ply bistable composite laminated cantilever shell,in cases of 1:2 inter-well internal resonance and primary resonance.The transverse foundation excitation is applied to the fixed end of the structure,and the other end is in a free state.The first-order approximate multiple scales method is employed to perform the perturbation analysis on the dimensionless two-degree-of-freedom ordinary differential motion control equation.The four-dimensional averaged equations are derived in both polar and rectangular coordinate forms.Deriving from the obtained frequency-amplitude and force-amplitude response curves,a detailed analysis is conducted to examine the impacts of excitation amplitude,damping coefficient,and tuning parameter on the nonlinear internal resonance characteristics of the system.The nonlinear softening characteristic is exhibited in the upper stable-state,while the lower stable-state demonstrates the softening and linearity characteristics.Numerical simulation is carried out using the fourth-order Runge-Kutta method,and a series of nonlinear response curves are plotted.Increasing the excitation amplitude further elucidates the global bifurcation and chaotic dynamic snap-through characteristics of the bistable cantilever shell.

Effects of Hydrothermal Environment on the Deformation of the Thin Bamboo Bundle Veneer Laminated Composites

To overcome warping in thin bamboo bundle veneer laminated composites(TBLC),their hydrothermal deformation characteristics were systematically investigated in this study.It was found that TBLCs accelerated the release of internal stress in the thickness direction in a hydrothermal environment,which increased their warpage.TBLCs showed increased warpage in the width and diagonal directions upon increasing the temperature.The warpage of Type E increased by 155.88%and 66.67%in the width and diagonal directions,respectively,when the temperature increased from 25
C to 100
C.The symmetrical TBLC with cross-lay-up and odd layers displayed better hydrothermal stability.We revealed that the deformation of the TBLCs could be regulated under the synergistic effect of water and temperature.These results provide a scientific basis for improving the uniformity of bamboo bundle composite materials and for developing thin bamboo bundle fiber composite materials with designable structures and controllable performance.

PROGRESSIVE FAILURE ANALYSIS OF LAMINATED COMPOSITES WITH TRANSVERSE SHEAR EFFECTS

This paper deals with the progressive failure analysis of composite laminates. Triangular elements which include the transverse shear effects are us.d for the stress analysis. A new method for the calculation of the shear correction factors is presented. Several failure criteria are used to check the first ply failure and distinguish the laminate failure modes into fiber breakage or buckling, matrix cracking and delamination. After the failure is detected, the stiffness of the failed ply is modified according to the failure modes. The ultimate strength of the laminate is obtained by an iterative way. Several examples are given in the paper for stress analysis and progressive failure analysis of composite laminates.

Dynamic analysis of bio-inspired helicoid laminated composite plates resting on Pasternak foundation excited by explosive loading

This paper uses isogeometric analysis(IGA)based on higher-order shear deformation theory(HSDT)to study the dynamic response of bio-inspired helicoid laminated composite(B-iHLC)plates resting on Pasternak foundation(PF)excited by explosive loading.IGA takes advantage of non-uniform rational Bspline(NURBS)basic functions to exactly represent the structure geometry models and the attainment of higher-order approximation conditions.This method also ensures a C1 continuous function in the analysis of transverse shear deformation via HSDT.Furthermore,IGA eliminates the requirement for correction factors and delivers accurate results.Pasternak foundation with two stiffness parameters:springer stiffness(k_(1))and shear stiffness(k_(2)).The derivation of the governing equations is based on Hamilton's principle.The proposed method is validated through numerical examples.A comprehensive analysis of the impact of geometrical parameters,material properties,boundary conditions(BCs),and foundation stiffness on dynamic response of B-i HLC plates is carried out.

Preparation, structure and properties of Mg/Al laminated metal composites fabricated by roll-bonding, a review

Laminated metal composites(LMCs) are a unique composite material and have great application prospects in automobiles, ships, aircraft,and other manufacturing industries. As lightweight materials, the Mg/Al LMCs are expected to combine the advantages of both Mg and Al alloys to broaden their application prospects. Roll-bonding is the most popular process for the fabrication of Mg/Al LMCs due to high production efficiency and good product quality stability. The roll-bonding process involves the deformation of the substrates and the formation of the interfacial diffusion layer. The latter will directly determine the interface bonding strength of Mg/Al LMCs. Bonding strength is very sensitive to the thickness of the reaction layer in the diffusion layer. When the thickness of the reaction layer exceeds 5 μm, the bonding strength decreases sharply. Therefore, controlling the thickness of the reaction layer is very important for the design of rolling parameters.The latest research also showed that the addition of intermediate layer metal and the construction of three-dimensional interfaces can further improve the interface bonding strength. How to apply these methods to roll-bonding is the focus of future research. Recently, a new rolling technique, corrugated roll/plat roll rolling+flat roll/flat roll rolling has been developed to fabricate Mg/Al LMCs. It can effectively promote the deformation of the hard layer and generate a wavy interface, resulting in the enhancement of the bonding quality and rolling quality.In the current review, the effects of rolling parameters and subsequent annealing on the interface structure of Mg/Al LMCs were elaborated in detail. The application of some special rolling techniques in the preparation of Mg/Al LMCs was also summarized. The latest research results on the relationship between interface structure and mechanical properties of Mg/Al LMCs were reviewed. Finally, further research directions in this field were proposed.

Experimental and simulation studies on delamination strength of laminated glass composites having polyvinyl butyral and ethyl vinyl acetate inter-layers of different critical thicknesses

The laminated glasses(LGs)composites are gaining popularity as protectivestructural material. Delamination strength(DS) of(LGs) with different inter-layers and their different nominal thicknesses were compared. The effect of inter-layer thickness, delamination load, and inter-layer type on DS is clearly observed from this brief study. It is concluded that inter-layer thickness has the significant role in determining the DS of LGs. The statistical analysis confirmed the strong association of DS with inter-layer thickness and the interlayer type. It was found that the LG-PVB composite has the comparatively lower DS than LG-EVA composite and inter-layer thickness has the prominent role in the determination of DS in the LG-EVAcomposite. There is an increment in DS with an increment in critical inter-layer thickness in both LG-EVA and LG-PVBcomposites. The increment in the inter-layer thickness from 0.38 mm to 0.76 mm increases DS significantly; whereas, the further increment in the inter-layer thickness to the higher value has a lesser effect. The finite element model was constituted(without considering the effect of temperature) for determining DS of LG composite. The simulation results were in a good match with experimental results. The results of the present work can be utilized by the design engineers while selecting LG for structural applications.

FRACTURAL PROCESS AND TOUGHENING MECHANISM OF LAMINATED CERAMIC COMPOSITES

Based on the model of multi-layer beam and the assumption of micro-inhomogeneity of material, the 3D fractural characteristics of laminated ceramic composites have been studied with numerical simulation. Under three-point bending load, crack initiation, coalescence, propagation, tuning off in the weak interface and final rupture have been simulated. The spatial distribution and evolution process of acoustic emission are also presented in the paper. The simulation verifies the primary mechanism of the weak interface inducing the crack to expand along there and absorbing the fractural energy. The disciplinary significance of the effect of strength and properties of material on the toughness and strength of laminated ceramic composites is, therefore, discussed in this paper.

Elastic and Plastic Behaviors of Laminated Ti-TiBw/Ti Composites

The novel laminated Ti-TiBw/Ti composites composed of pure Ti layers and TiBw/Ti composite layers have been successfully fabricated by reactive hot pressing. Herein, two-scale structures formed： the pure Ti layer and TiBw/Ti composite layer together constructed a laminated structure at a macro scale. Furthermore, TiBw reinforcement was distributed around Ti particles and then formed a network microstructure in TiBw/Ti composite layer at a micro scale. The laminated Ti-TiBw/Ti composites reveal a superior combination of high strength and high elongation due to two-scale structures compared with the pure Ti, and a further enhancement in ductility compared with the network structured composites. Moreover, the elastic modulus of the laminated composites can be predicted by H-S upper bound, which is consistent with the experimental values.

Microstructure and mechanical properties of bio-inspired Cf/Ti/Mg laminated composites

Inspired by an old fish skin structure,the Cf/Ti/Mg laminated composites were fabricated by squeeze casting technology.No porous or voids were found in final composite,and carbon fiber was uniformly dispersed in Mg matrix.Furthermore,the addition of net-shaped Ti adsorbed Al element and facilitated the nucleation of Mg_(17)Al_(12)nearby Ti.The reaction product Al_(4)C_(3)was found at the Cf and AZ91 interface.Mechanical tests indicate that the introduction of Ti could greatly improve the toughness of Cf/Mg composites.

Preparation and Mechanical Properties of Al_2O_3/Al Laminated Ceramic Matrix Composites

Three series of Al2O3/Al laminated ceramic matrix composites,named SPA,SPV and HP,were fabricated by different methods.SPA and SPV were prepared using Al2O3 slices and Al slurry via screen printing and subsequent heat treatment in air or vacuum.HP samples were made by hot pressing the layered stack of Al foils and Al2O3 slices.SEM and XRD were applied to analyze the microstructure and the interlayer crystal phase.The bending strength,fracture toughness and fracture work of the samples made by the three methods were measured and compared.The results show that the composites have much better toughness and higher fracture work than the Al2O3 slice.Among the samples made by the three methods,the samples made by hot pressing have the optimum mechanical performance.The displacement-load curves and fracture mechanism were analyzed.

Formation mechanism and growth kinetics of TiAl_(3) phase in cold-rolled Ti/Al laminated composites during annealing

Cold-rolled Ti/Al laminated composites were annealed at 525−625℃for 0−128 h,and the interfacial microstructure evolution was investigated.The results indicate that only the TiAl_(3) phase was formed at the Ti/Al interface;most of TiAl_(3) grains were fine equiaxed with average sizes ranging from hundreds of nanometers to several microns and the TiAl_(3) grain size increased with increasing annealing time and/or temperature,but the effect of annealing temperature on the TiAl_(3) grain size was far greater than that of annealing time.The growth of the TiAl_(3) phase consisted of two stages.The initial stage was governed by chemical reaction with a reaction activation energy of 195.75 kJ/mol,and the reaction rate constant of the TiAl_(3) phase was larger as the Ti/Al interface was bonded with fresh surfaces.At the second stage,the growth was governed by diffusion,the diffusion activation energy was 33.69 kJ/mol,and the diffusion growth rate constant of the TiAl_(3) phase was mainly determined by the grain boundary diffusion owing to the smaller TiAl_(3) grain size.

A Modified Cohesive Zone Model for Simulation of Delamination Behavior in Laminated Composites

Considering the promotion effect of interlaminar normal tensile stress and the inhibition effect of interlaminar normal compressive stress,two kinds of elimination initial criteria were proposed in this paper.Based on these two delamination initial criteria,a modified cohesive zone model(CZM)was established to simulate the delamination behavior in laminated composites.Numerical simulations of double cantilever beam(DCB),mixed-mode bending(MMB)and end notched flexure(ENF)tests were conducted.The results show that the proposed model can do a better job than common ones when it is used to predict laminates’delamination under interlaminar compression stress.Moreover,a factor r,named cohesive strength coefficient,was defined in this paper on account of the difference between cohesive strength and interlaminar fracture strength.With changing factor r,it shows that a moderate variation of cohesive strength will not cause significant influences on global load-displacement responses.Besides,in order to obtain a good balance between prediction accuracy and computational efficiency,there shall be two or three numerical elements within the cohesive zone.

Microstructure and mechanical behavior of Ti/Cu/Ti laminated composites produced by corrugated and flat rolling

Ti/Cu/Ti laminated composites were fabricated by corrugated rolling(CR) and flat rolling(FR) method.Microstructure and mechanical properties of CR and FR laminated composites were investigated by scanning electron microscopy, numerical simulation methods, peel and tensile examinations. The effect of CR and FR was comparatively analyzed. The results showed that the CR and FR laminated composites exhibited different effective plastic strain distributions of the Ti layer and Cu layer at the interface. The recrystallization texture, prismatic texture and pyramidal texture were developed in the Ti layer by CR, while the R-Goss texture and shear texture were developed in the Cu layer by CR. The typical deformation texture components were developed in the Ti layer and Cu layer of FR laminated composites. The CR laminated composites had higher bond strength, tensile strength and ductility.

Diffusional bonds in laminated composites produced by ECAP

The microstructure,diffusional and mechanical bonding behavior and microhardness distribution of laminated composites fabricated by ECAP process were investigated.Al?Cu and Cu?Ni laminated composites were produced by ECAP process up to4passes at room temperature and high temperature(300°C).The results of microstructure characterization by SEM and shear strength test revealed that the joints between the layers of4-pass ECAPed samples were considerably stronger than those of1-pass ECAPed samples due to tolerating higher values of plastic deformations during ECAP.Furthermore,shear strength data showed that increasing ECAP temperature caused a notable increase in shear strength of the specimens.The reason lies in the formation of diffusional joint between the interface of both Al/Cu and Cu/Ni layers at high temperature.The shear bonding strength of ECAPed Cu/Ni/Cu composite at high temperature was remarkably higher than that of ECAPed Cu/Al/Cu composite.

Engineered Wood/Bamboo Laminated Composites for Outdoor Hydrophilic Platforms:Structural Design and Performance

Landscape designers increasingly prefer to use wood/bamboo-based composites for outdoor hydrophilic platforms owing to their natural surface texture,high performance,and sustainability to facilitate extensive interaction between people and water and enable the full range of ecological functions of water resources.In this study,four laminated composite(LC)structures were designed and manufactured using fluffed bamboo and wood veneers.Their surface textures,profile densities,water resistances,and mechanical properties were then evaluated.The type of fluffed veneer of the surface layer determined the texture of the LC surface.The specific structures of fluffed bamboo and wood veneer laminations were found to affect the LC profile density variability,water resistance,and mechanical properties owing to the differences in the strength and interfacial properties of bamboo and wood fibers.Finally,the water resistance and mechanical properties of all four LCs were found to be much higher than the highest level specified in GB/T 20241-2006 for“laminated veneer lumber”and GB/T 30364-2013 for“bamboo scrimber flooring”,indicating that they are promising materials for structures and flooring,particularly for outdoor hydrophilic platforms.

Identification of Damage Parameters for Intralaminar Damage Modeling in Laminated Composites Considering Transverse Stress Effects

The aim of this study is to develop an appropriate modeling methodology for the simulation of intralaminar damage in laminated composites under complex loadings. The intralaminar damages are modeled by stiffness reduction controlled by thermodynamic forces as defined in continuum damage mechanics model proposed by Ladevèze. The original method neglected transverse stress in elementary plies during the tensile tests of [45/?45]mS laminates, resulting in variations of the identified damage parameters of Ladevèze model. This study compared the identified damage parameters considering transverse stress effects with those based on the original method. The effect of transverse stress in the identification process on the damage modeling is discussed, and it is found that one of damage coupling parameters and the damage master curves significantly depend on consideration of transverse stress effects. Finally, it is demonstrated that experimental stiffness degradation is well simulated by the prediction using the identified parameters considering transverse stress effects.

Interface analysis of 7B52 Al alloy laminated composite fabricated by hot-roll bonding

The bonding interface of 7B52 Al alloy laminated composite （ALC） fabricated by hot rolling was investigated using optical microscopy （OM）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, ultrasonic flaw detection （UFD）, and bonding strength tests. The results show that metallurgical bonding is achieved at the interface after composite rolling. The TEM analysis and tensile tests indicate that the 7B52 ALC plate combines high strength of the hard individual layer and good toughness of the soft individual layer. However, UFD technology and SEM analysis prove that the defects （thick oxide films, acid washed residues, air, oil and coarse particles） existing in the bonding interface are harmful to the bonding strength. To sum up, the composite roiling process is suitable for 7B52 ALC plate, and the content and size of the defects should be controlled strictly. Advanced surface treatment of each individual layer would be beneficial to further improve the bonding quality.