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As an ideal reinforcing phase, nano-carbon has been widely used to improve the properties of composites. In this paper, Mo–Cu–Zr ternary composites were reinforced with various types and contents of nano-carbon to find the optimal composition and the microstructure and mechanical properties of the composites were systematically characterized and analyzed. The composites were fabricated via a powder metallurgy method to achieve high compactness and structural uniformity. The analysis results show that the increase of nano-carbon may cause a serious agglomeration and subsequent decrease of the composite compactness, while the synergetic effect of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) can improve their dispersion. The 0.8C + 0.2G-MCZ3 composite showed the best comprehensive properties, which achieved a relative density, hardness and compressive strength of 99.7%, 343.6 HV and 953.5 MPa, respectively. Moreover, the component Zr mainly formed solid solution and compound particles with Cu or C through in-situ chemical reactions. It played an important role in solid solution strengthening and dispersion strengthening, and the in-situ synthesized ZrC nanoparticles on nano-carbon surfaces can pin interfaces and improve the effect of load transfer. The synergetic effects and multiple strengthening mechanisms result in the improvement of the microstructure and properties of the composites.

With the advancement of material technology, the use of high-strength and high-performance materials in the construction industry is gaining popularity. Steel–polyvinyl alcohol (steel–PVA) hybrid f...

Although high-strength concrete (HSC) has higher compressive strength than normal-strength concrete (NSC), its application in column construction is often limited by its brittleness and limited post-peak ductility. In this preliminary study, hybrid fibre engineered cementitious composite (ECC) is proposed as a potential encasement material to confine the HSC core and to increase the column's ductility. The behaviours of the proposed ECC-encased concrete stub column under axial compression are studied experimentally. Thirty stub columns, including six NSC/HSC, six ECC and 18 ECC-encased NSC/HSC (ECC–NSC/HSC) are tested under axial compression. The effects of ECC strength, ECC encasement thickness, concrete strength and cross-section shapes (circular, square and rectangular) are then investigated and reported in terms of failure modes, strength ratios, post-peak ductility and energy dissipation capacity of the stub columns. It is found that, when comparing with NSC/HSC stub columns, although no significant improvement in the ultimate strength was observed, the ECC encasement improved the performance of ECC–NSC/HSC stub columns by reducing brittleness and improving the post-peak behaviour during failure.

Multi-layered corrugated sandwich panels can be made up of different core shapes, different arrangements, the variable height, and variable thickness in every layer. In this paper, the crashworthiness behaviors of multi-layered corrugated sandwich panels with different configurations, which are controlled by these four factors, are analyzed and compared. The optimal configuration is found by adopting orthogonal experimental design and range analysis method. A novel multi-layered corrugated sandwich structure with functionally graded thickness is proposed and studied and is proved to better structural crashworthiness. First, finite element models of multi-layered corrugated sandwich panels are established and validated by experiment. Then, the effect of the four factors with three levels on crashworthiness is analyzed, and we obtain the main factor and the optimal configuration with the maximum specific energy absorption by using orthogonal experimental design and range analysis method. Finally, parametric studies and multi-objectives optimization of the proposed novel multi-layered corrugated sandwich structure with functionally graded thickness are conducted. The optimization is aimed at maximizing the specific energy absorption and minimizing the initial peak force under crush loading, based on the non-dominated sorting genetic algorithm and response surface method technique. These findings can provide valuable guidelines for the design of multi-layered corrugated sandwich panels with different configurations under crush loading.

This paper presents an experimental investigation on the behaviour of a new form of engineered cementitious composites (ECC) encased concrete-steel composite stub columns. The proposed column section uses ECC encasement as a potential confinement layer to control the premature concrete spalling and explosive brittle failure of concrete encased steel composite columns. In this study, twelve stub columns including two bare steel and ten composite sections are tested under concentric compression. The effects of some key parameters such as material strengths, steel section type and column section configuration on the performance of proposed column sections were investigated in terms of failure behaviour, load deformation response, toughness and ductility. It was found that ECC encasement improved the compressive failure behaviour of encased composite columns and enhanced their ductility and toughness. Strain analysis was performed to trace the strain development and damage patterns of different materials. Finally, a simple equation to estimate ultimate strength of proposed columns was proposed which gave good predictions agreed well with test results.

The flexural fatigue properties of a recently developed polyvinyl alcohol-engineered cementitious composite (PVA-ECC) using local dune sand were investigated. Fatigue flexural tests were conducted under a four-point bending setup. Normal concrete beams were also tested as a benchmark. To determine the stress range versus fatigue life relationship, five and four stress ranges were applied to the PVA-ECC and the normal concrete specimens, respectively. It was found that, compared with normal concrete specimens, the PVA-ECC specimens showed much superior flexural fatigue performance in terms of fatigue strength and deformation capacity, with a more ductile failure mode. Furthermore, typical fatigue performance indicators of the PVA-ECC specimens, including evolution of the midspan deflection, total crack mouth opening displacement, crack width and crack depth of the critical crack that led to final failure, with number of cycles as well as total dissipated energy, were recorded and compared with those of normal concrete specimens. It was observed that the PVA-ECC specimens tested under a stress range of 3 MPa (32% of the flexural strength) did not fail by fatigue after 5·6 million cycles; subsequent static tests demonstrated that they still had good residual flexural properties, including residual flexural strength, deformation capacity, stiffness and energy absorption capacity.

This paper presents an experimental investigation of the flexural fatigue behaviour of steel reinforced polyvinyl alcohol-engineered cementitious composite (PVA-ECC) beams. The influence of the PVA-ECC matrix and stirrups on the fatigue strength of steel reinforced beams was studied. Eleven beams, including three steel reinforced normal concrete beams (RC beams), four reinforced PVA-ECC beams with stirrups (RECC beams) and four reinforced PVA-ECC beams without stirrups (RECC-NS beams), were tested under a constant amplitude cyclic loading. The minimum load of each cycle was set at 20% of the static strength of the corresponding beam while the maximum loads ranged from 60% to 90%. Experimental results showed that the RC and RECC beams exhibited flexural failure with fracture of tensile reinforcement bars. By contrast, RECC-NS beams tested under 20–90%, 20–70% and 20–60% load ranges were respectively failed by shear, combined of shear and flexural, and flexural with tensile reinforcement bars yielded. The test results showed that the RECC beams generally had shorter fatigue life than the RC beams when tested under relatively high load ranges. This could be due to greater stiffness degradation which eventually led to a higher stress increasing rate in tensile reinforcement bars of the RECC beams.

In this paper, by designing the UV irradiance, the compositions and the initial concentrations of automobile exhaust, an asphalt mixture test system – photocatalytic decomposition of automobile exhaust performance (AMTS-PDEP) was developed based on the photocatalytic mechanism of titanium dioxide (TiO2). Testing method and calibration method of test data were also proposed in this paper. Accumulative decomposition ratio (ADr) was used as the evaluation indicator of photocatalytic decomposition of automobile exhaust performance (PDEP) and the influencing factors of PDEP were proposed. Based on the mechanical behavior and PDEP, the design method of asphalt mixture material composition was developed and the attenuation law of PDEP was also demonstrated. The results show that the PDEP of anatase TiO2 is much better than Rutile TiO2. The PDEP of asphalt mixture with 0.3 μm TiO2 is better than other particle sizes. Affected by particle adhesion, the PDEP of asphalt mixtures with 3.5% content of TiO2 reaches the maximum value. The PDEP has positive correlations with volume (VV) of asphalt mixtures, irradiance and temperature. It is recommended that anatase TiO2 (0.3 μm) is used as the photocatalyst, the optimum TiO2 content is 3.1%, TPS modified bitumen is used as the binder, and porous asphalt concrete with a nominal maximum aggregate size of 13 mm (PAC-13) is used as the optimal structural carrier. The PDEP of asphalt mixture decreased with the increase of test times, but it returns to its original level immediately after simply rinse, and repeated rinse does not reduce the PDEP. The PDEP of asphalt mixture decreases with the increase of the pollution index or the decrease of VV caused by compacting.

Aiming at the characteristics of small diameter and thin wall of coiled tubing (CT), arc specimens were cut from a length of CT longitudinally. Tensile tests were conducted to get elastic-plastic constitutive curve, and fracture tests were done to obtain relationships among loading force, load line displacement, crack tip opening displacement (CTOD) and crack propagation. Based on the results of the fracture tests, optimal cohesive parameters of Park-Paulino-Roesler (PPR) model for CT steel were determined by means of an inverse analysis based on the modifieded Levenberg-Marquardt optimization algorithm, and an effective cohesive zone model (CZM) was proposed for CT steel. By embedding the optimal CZM into the ABAQUS software via a user-defined subroutine UMAT, the ductile fracture of CT with a transverse surface crack was studied under two typical operating conditions: working in a wellbore and being wound back to a reel. Critical loading forces and critical crack sizes corresponding to crack initiation are determined, and methods of safety assessment for the cracked CT are given.

A systematic study of the tensile properties of all-grade strain hardening cementitious composite (SHCC) from normal strength to high strength was conducted in the present research. The compressive strengths of the cylinder specimens ranged from 43 MPa to 115 MPa. Different combinations of fiber volume fractions and fiber aspect ratios (fiber length/diameter) were employed to investigate the effects of the fiber reinforcement index (the product of fiber volume fraction and fiber aspect ratio) on the tensile properties of SHCC, including mechanical properties and crack patterns. The relationships between the fiber reinforcement index and tensile properties were established at all compressive strengths and compared with the previous experimental values. Moreover, a performance-based design concept was proposed for designing SHCC based on the required mechanical and crack pattern properties, corresponding to the ultimate limit state and serviceability limit state, respectively.

Background: Short carbon fibre reinforced epoxy composites have many advantages such as high strength-to-weight ratio, corrosion resistance, low cost, short fabrication time and easy manufacturing. Researches on the mechanical performance of the composites are mainly carried out by means of experimental techniques and numerical calculation. Objective: The study aims to report the latest progress in the studies of mechanical properties of short carbon fibre reinforced epoxy composites. Methods: Based on recently published patents and journal papers, the experimental studies of short carbon fibre reinforced epoxy composites are reviewed and the effects of short carbon fibre on the mechanical properties of the composites are discussed. Numerical studies using representative volume element in simulating macroscopic mechanical properties of the short fibre reinforced composites are also reviewed. Finally, future research of short carbon fibre reinforced epoxy composites is proposed. Results: Experimental techniques, experimental results and numerical simulating methods are discussed. Conclusion: Mechanical properties of epoxy can be improved by adding short carbon fibres. Fiber surface treatment and matrix modification are effective in enhancing interfacial adhesion between fiber and matrix, and as a result, better mechanical performance is achieved. Compared to the studies on equivalent mechanical properties of the composites, researches on the micro-mechanism of interaction between fiber and matrix are still in infancy due to the complexity of both the internal structure and reinforcing mechanism.

Strain sensor is widely desired for flexible and wearable electronic devices, such as human motion capturing and electronic skin. In strain sensing, it is a challenge to ensure that the strain sensor based on CNTs–PDMS has both high-performance flexibility and sensitivity. Here, this study reports a flexible strain sensor based on the AuNPs/CNTs/PDMS composite films fabricated by in-situ reduction, which has high sensitivity and wide linear strain range. DFT revealed that the AuNPs effectively improved the conductivity of the composite films, which show high consistency with electrical test. The AuNPs synergistically improved the sensitivity and flexibility of strain sensors with CNTs in PDMS. The flexible strain sensors with 3 wt% CNTs and 16 h AuNPs’ reduction time have the higher gage factor of 366.7 at a linear strain ranging from 0 to 15%. We demonstrated the applicability of our high-performance strain sensors by testing the tiny motion sensing caused by wrist bending, finger bending, wrist raising, neck rotation, and facial muscle movement. The AuNPs/CNTs/PDMS composite film with high sensitivity, flexible, and stability provides a new elastomer nanocomposite as strain sensor for strain-sensing applications.

Additive manufacturing technology is a novel approach for the development of the modern industry. Additive manufactured aluminium (Al) becomes the hotspot of current research in order to achieve the high-precision products. However, the additive manufactured Al parts easily generate void defects due to the poor fluidity and low density of the materials, which in turn affects the mechanical properties. This paper studies the damage behavior of additive manufactured Al parts with void defects under tensile load in a mesoscale by using a two-dimensional rate-dependent crystal plasticity theory. The stress-strain curves and the plastic damages of single crystal and bicrystal with void defects are determined with different combinations of crystal orientations and loading conditions. It is found that the mechanical properties of additive manufactured aluminium severely depend on the crystal orientations and shapes of void defects.

The orientation of distributed synthetic fibres in the matrix of engineered cementitious composites (ECCs) governs their capability of bearing stress and bridging micro-cracks. Understanding the orientation of synthetic fibres in ECCs matrix of different thickness specimens, therefore, is necessary. In the present work, the effect of specimen thickness on the orientation of synthetic fibres in self-consolidating (SC) ECC, a typical member of family ECC materials, is numerically investigated through the simulation of the casting of fresh SC-ECC into different thicknesses of moulds. The moulding of fresh SC-ECC, which is discretised by a limit number of separated mortar and fibre particles, is simulated using the mesh-free smoothed particle hydrodynamics (SPH) method. The synthetic fibre utilised in SC-ECC is considered as flexible fibre and virtually connected by a drag force between two adjacent fibre particles. The SPH allows tracking the movement of mortar and fibre particle during their flow, thus providing the real image of flexible synthetic fibres orientation in specimens during the casting process. A simple method is proposed to evaluate the orientation of flexible synthetic fibres at various sections of specimens after the SC-ECC stop flowing in the moulds. The results of this study reveal that thin specimens tend to have higher fibre orientation factors than thick specimens. Synthetic fibres tend to parallel with the longitudinal direction of specimens at the bottom of the formwork and rotate freely at the top surface of specimens.

This study investigates the confined compression behaviour of a shear thickening fluid (STF) with concentrated submicron particles. The styrene/acrylate particles suspended in an ethylene glycol (EG) show a narrow size distribution, with a mean size of 0.4 µm. The confined compression test results show the significant compressibility of the STF corresponding to the compression of the liquid medium EG and the compressibility of the STF starts to lessen when the applied compression stress is greater than 4 MPa. It is also found that the confined compression results of the STF are not sensitive to the loading rate ranging from 1 to 50 mm/min. Finally, the bulk moduli of the STF and the EG are obtained.

Effective diffusivity of a cementitious material mainly depends on the connectivity of the capillary system and the material integrity. A number of influencing factors could lead to variation in capillary connectivity by growth of porosity and loss of material integrity mainly by cracking, and thus it is difficult to estimate the material diffusivity in general. In this paper, a mixed effective medium theory (MEMT) is developed so as to consider the influence of arbitrary capillary connectivity and crack density. The model takes advantage of the Mori-Tanaka (MT) method, interaction direct derivative (IDD) and the self-consistent (SC) method. Using a three-level homogenization scheme, the proposed model is validated against a series of experimental measurements on cement pastes. Furthermore, the MEMT model is adopted in the numerical simulation of the external sulfate attack (ESA) on cement paste, and the influence of crack density on the effective diffusivity is studied. The obtained results on the mineralogical degradation during the ESA agree very well with the reported experiments.

A multiscale modelling framework is developed in this paper for analysing the degradation of mechanical behaviour of Engineered Cementitious Composites (ECCs) under fatigue tensile loading. Degradation models for calibrating fatigue-induced deterioration of the fibre-matrix interface and fibre fatigue rupture are proposed at the microscale. Based on these, the cycle-dependent crack bridging relation is derived at the mesoscale. At the macroscale, the degradation behaviour of the bridging stress in ECC with presence of multiple cracks is modelled using extended finite element method. This multiscale characterisation method is validated by comparing the computed degradation relation of the bridging stress to that obtained from the experiment. Good agreement is obtained, which demonstrates the effectiveness of the developed multiscale modelling framework for the analysis of fatigue behaviour of ECCs. In addition, the deterioration of the fibre-matrix interface is found to be responsible for a steady decreasing bridging stress, while the fibre fatigue rupture is found to contribute to an accelerated loss of bridging stress.

An integrated numerical method is developed to model the deterioration of mechanical properties of cement mortar under external sulfate attack (ESA). The proposed method is module-oriented, which includes three modules, i.e. an ionic diffusion module, a chemical reaction module and a mechanical module. In the mechanical module, an analytical model is developed for evaluating the variation of flexural strength under ESA. The development of internal pressure obtained from numerical computations and the degradation of elastic property estimated using the conventional Mori-Tanaka (MT) method are both considered in the proposed analytical model. Ionic diffusion and chemical reactions during the ESA are solved by the modified Poisson-Nernst-Planck (MPNP) model and chemical thermodynamics in the ionic transportation and the chemical reaction modules respectively. The developed method is validated against the reported ESA experiments in terms of the deterioration of both the elastic modulus and the flexural strength. Furthermore, the key factors governing the mechanical deterioration of cement mortars under ESA are discussed in details, and an estimation model is developed.

This study characterises the compressive behaviours of 3D-printed carbon fibre (CF) reinforced polyamide (PA) composite metamaterials with negative Poisson's ratio (NPR) or enhanced effective elastic modulus (EEEM), which were designed via a multidisciplinary approach and additively manufactured with fused filament fabrication. The continuous carbon reinforced PA (CCF/PA) metamaterials are compared to those made of short carbon fibre reinforced PA (SCF/PA) when subjected to in-plane compression. A numerical model based on continuum damage mechanics is developed to describe the response and failure of the 3D-printed CCF/PA composites while another one based an elastic-plastic model is developed for the 3D-printed SCF/PA parts. For metamaterials with NPR, the stiffness, peak force, energy absorption (EA) and specific energy absorption (SEA) of CCF/PA metamaterials are respectively 152.1%, 90%, 107.6% and 86%, respectively, larger than those of SCF/PA, while the SCF/PA metamaterials can reach a greater NPR (about −0.3) than CCF/PA (−0.2 ~ −0.1). For composites with EEEM, the stiffness, peak force, EA and SEA of CCF/PA are significantly improved by 433.3%, 183.3%, 228.7% and 208.2%, respectively, in comparison to those of SCF/PA. Based on experimental observation and numerical simulation, matrix failure is found to be predominant for CCF/PA NPR and EEEM composites.

The demand for various types of fibre-reinforced cementitious composites (FRCCs) has increased over the past few years owing to their enhanced performance as a result of denser microstructure and the presence of fibres. However, the effectiveness in preventing mechanical decay and spalling damage on exposure to elevated temperatures has been a concern for FRCC. The results obtained from existing studies on the fire performance of FRCCs differ considerably due to the differences in adopted type of cementitious matrix, fibre types and their dosage, or testing methods. This paper aims to understand the combined influence of such factors and provide an in-depth review of their effects on the performance of FRCC at elevated temperatures. Temperature variation of different mechanical and thermal properties of FRCC and the factors contributing to its spalling resistance are comprehensively discussed and some potential areas for further research have been identified. In addition, available data and existing prediction models on the residual or hot-state mechanical properties of FRCC are also summarized which may be used in future numerical or other computational studies for the fire resistance design of structures.

Low velocity impact responses of a newly developed sandwich panel with aluminium foam core and fibre metal laminate (FML) skins, comprised of aluminium sheets and plain woven E glass fibres, are investigated in this paper. Drop weight impact tests were conducted and the effect of the thickness of foam core and FML skin on the impact response of the panels was investigated via the experimental study. A finite element model is also developed and validated against the experiments to prove the effectiveness and accuracy for analyzing the impact responses of the sandwich panels under low-velocity impact. The research findings are summarized and concluded finally.

In this paper, the results of an experimental investigation on the flexural and shear behaviours of plain and reinforced polyvinyl alcohol-engineered cementitious composite (PVA-ECC) beams are presented. The PVA-ECC employed in this study, which has a tensile strain capability up to 1%, has been recently developed by the authors using local sand to reduce cost. The aim of this study is to investigate the effects of PVA-ECC matrix, transverse reinforcement (stirrups) and longitudinal reinforcement bars on the flexural and shear structural performances of reinforced PVA-ECC beams. Four-point bending tests were conducted and normal steel reinforced concrete beams were tested for comparison. Digital Image Correlation technique was used to monitor single crack development and was validated by LVDT measurements. Experimental results show that PVA-ECC beams present significantly improved flexural behaviour compared with normal concrete beams. Furthermore, PVA-ECC beams without stirrups eventually fail in flexure rather than in shear, and exhibit similar load-deflection, moment-curvature relationships and crack development history when compared with PVA-ECC beams with stirrups.

The crack bridging behaviour of Engineered Cementitious Composites (ECCs) under fatigue tensile loading is investigated experimentally in this paper. Uniaxial fatigue tension tests were conducted on pre-cracked specimens under deformation control with constant crack opening displacement amplitude. The crack bridging stress at the maximum crack opening displacement was obtained against the number of loading cycles. Eight maximum crack opening displacement levels were tested in total. The crack bridging stress was found to decrease with the increase of loading cycles. The crack bridging stress degradation is generally more significant in ECCs than in steel fibre reinforced concrete. In addition, the crack bridging stress degradation behaviour of ECCs reinforced with polymeric fibres was found to be distinct from that of steel fibre reinforced concrete with presence of accelerated stress degradation. The experiment demonstrates that it is important to take the fibre fatigue rupture into account in the analysis of mechanical behaviour degradation of ECCs and that the crack opening affects the crack bridging degradation behaviour.

In this article, a new engineered cementitious composite reinforced with 0.6% volume steel fibres and 1.5% volume polyvinyl-alcohol fibres is developed aiming for enhanced impact resistance compared to other construction materials. Fundamental mechanical properties of the new composite including the compressive strength, Young’s modulus, tensile strength and flexural behaviour were tested. To calibrate the impact resistance of the new composite, high-velocity impact tests of panels made of the new material were conducted when subjected to impact from a standard 7.62 mm round in-service bullet fired from a knight armament SR-25 military rifle. For comparison, plain concrete panels and concrete panels reinforced with 2% volume steel fibres were also tested. The post-impact responses of the panels in terms of crater sizes, damage failure mode, fragmentation size, weight and regress velocity are analysed and compared to characterize the impact resistance of the new engineered cementitious composite. The test results demonstrate significantly enhanced impact and shatter resistance of the new hybrid fibre-reinforced cementitious composite with reduced spalling and fragmentation, localized damage areas and improved cracking resistance.

Fibre-reinforced cementitious composite (FRCC), by adding short discrete fibres randomly in cementitious composites, exhibits substantially improved mechanical properties than conventional cementitious composites due to the fibre bridging action and the existence of multiple micro-cracks. In this paper, based on the general self-consistent method a new micromechanical analytical model is developed to model the material properties of the FRCCs. A hexagonal-shaped representative volume element model with multiple micro-cracks is established based on the microstructure of the FRCC to represent the transversely isotropic material characteristics. The developed model is used to evaluate the equivalent Young’s modulus of a typical FRCC before and after cracking, and the results obtained are compared to those obtained from other analytical models and experimental data for validation. The influence of the aligned orientation of fibre and the crack density of the matrix on Young’s modulus of the composite is also studied.

A polyvinyl alcohol fibre reinforced engineered cementitious composite (PVA-ECC) using local ingredients is developed, aiming for a reduced cost and a tensile strain capacity matching that of steel reinforcement for commonly used reinforced concrete structures. Experiments are conducted to determine mechanical behaviour of the composite. In addition, a finite element model is developed to simulate the flexural behaviour of PVA-ECC beams, and experimental results are used to calibrate the model. The material models of the PVA-ECC under compression and tension are calibrated using experimental results of uniaxial compression and tension tests. Furthermore, a theoretical relationship on the tensile strength between specimens with two-dimensional and three-dimensional fibre distribution is derived, and accuracy of the simulation is improved by using the theoretical ratio. Agreement between the computed results and the experimental data demonstrates the effectiveness of the finite element model.

In this paper, high velocity impact responses of newly designed sandwich panels with aluminium (AL) foam core and metal fibre laminate (FML) skins, which are comprised of aluminium sheets and plain woven E glass fibre composite plies are investigated. Gas gun impact tests were conducted to investigate the high velocity impact response of the panels subjected to the impact from a steel ball bearing at an impact velocity of around 210 m/s. The effect of the thickness of the foam core and FML skin on the impact resistance of the panels is also investigated via experimental study. A finite element model is developed for effective numerical modelling of the impact behaviour of the sandwich panels using the commercially finite element software ANSYS LS-DYNA for more extensive study of the impact response of the sandwich panels. The simplified Johnson Cook material model, the composite damage material model based on the Chang-Chang criteria, and the crushable foam material model are used to model the aluminium sheets, composite plies and the AL foam respectively. Three types of contact algorithms, i.e. the erosion contact type, the tie-break contact type and the general 3D contact type are employed to define the various contacts during the impact and to model the delamination between the FML layers and debonding between the FML skin and the AL foam. The finite element model is validated by comparing the simulated impact behaviour to that from experimental for a sandwich panel subjected to high speed impact and demonstrated to be effective and accurate. The effect of the shape of projectile and impact angle on the impact behaviour of the sandwich panels is studied using the developed finite element model. The research findings are summarized and concluded finally.

Ageing effects on both uniaxial tensile and shrinkage behaviour of new green cementitious composites reinforced with bagasse fibre and steel fibre with ultra-high volume of fly ash are investigated in this paper. The tensile behaviour of the composites is investigated at the age of 28 days, 3 months, 6 months and 10 months after curing in weather conditions. Restrained shrinkage behaviour of the composites after curing for 3 months is tested on ring specimens. SEM tests are also conducted to study the influence of the ageing on the microstructure of the new composites. The test results show that the tensile strength of the composites at all ages increases with the decrease of the content of the fly ash and the bagasse fibre, and that the increasing application of fly ash and bagasse fibre decreases the steel ring strain and restrains the development of crack. It is also found that the tensile strength and the shrinkage of the composites such as crack width ascend greatly with time.

Engineered cementitious composite (ECC), known for its superior tensile strain hardening behaviour and multiple microcrackings, is considered promising to enhance fatigue performance of the structures. However, the performance of ECC structural members under fatigue loading has been rarely investigated. This paper presents the results of an experimental study on the flexural fatigue performance of steel reinforced polyvinyl alcohol-engineered cementitious composite (PVA-ECC) beams. A recently developed PVA-ECC using local dune sand was employed in this study. Cyclic loading with a constant amplitude and a frequency of 1 Hz was applied through a four point loading apparatus. Four steel reinforced PVA-ECC beams were tested under four load ranges, respectively. Experimental results showed that all reinforced PVA-ECC beams tested under different load ranges exhibited flexural failure, which is characterized with the fracture of tensile reinforcement bars and concrete crushing in the compression zone. Furthermore, the development of the mid-span deflection and the load range-fatigue life relationship of the tested beams are presented in this paper.

The effect of nano-CaCO3 with different contents (i.e., 0, 1, 2, 3, 4% by mass of cement) on the mechanical properties including the compressive and tensile strength of ultra-high performance fiber reinforced concrete (UHP-FRC) was investigated experimentally. It was found that the incorporation of nano-CaCO3 enhanced the mechanical properties of UHP-FRC, and the optimal nano-CaCO3 dosage to enhance the compressive and tensile properties of UHP-FRC was 3%. More specifically, the compressive strength increased by 7.7%, while the tensile strength increased by nearly 40% up to dosage of 3%.

Five types of material, styrene-butadiene-styrene block copolymer (SBS), ethyl-vinyl-acetate (EVA), naphthenic oil, maleic anhydride grafted ethylene-vinyl acetate copolymer (EVA-g-MAH) and butylated hydroxytoluene (BHT) were used as the raw ingredients for manufacturing direct-to-plant SBS in this paper. Thirteen kinds of direct-to-plant SBS with different EVA/SBS and naphthenic oil/SBS were prepared as well as the processes diagrammatic sketch of dispersion and swelling of direct-to-plant SBS modifier in bitumen were discussed. Microscopic images of direct-to-plant SBS modified bitumen with different components were obtained using fluorescence microscopy. The micro-images were analysed and quantified with MATLAB software. The influence of key components on the micro-morphology of direct-to-plant SBS-modified bitumen is discussed, followed with the tests on melting points and the melting indexes of direct-to-plant SBS with different EVA/SBS and naphthenic oil/SBS. The performances test of bitumen and bituminous mixture modified by these direct-to-plant SBS were also conducted. Results show that, with the ratio improvement of EVA/SBS or naphthenic oil/SBS, the number of the pixel dot number of area (SBS) in microscopic images increased. Enlargement of the pixel dot number of centre line elongate and the structure fineness was observed, indicating that the dispersion and swelling effect of the SBS modifier in bitumen had been improved. Meanwhile, the macro index, such as the melting point and melting index of direct-to-plant SBS, was also improved corresponding to the increase of EVA/SBS ratio or naphthenic oil/SBS ratio. With the addition of EVA or naphthene oil content, penetration and ductility of direct-to-plant SBS modified bitumen received gradual enhancement, but the softening point and viscosity were found out to be decreased. The high-temperature and low-temperature performances of direct-to-plant SBS modified bituminous mixture can be effectively improved by adding EVA or naphthenic oil. By meeting the required performances of direct-to-plant SBS, modified bitumen and bituminous mixture, the component of direct-to-plant SBS is recommended as, SBS:EVA:naphthenic oil:EVA-g-MAH:BHT is 1:0.1&ndash, 0.5:0.05&ndash, 0.2:0.03:0.05. For the compatibleness of SBS with different bitumen are different, necessary tests verification is recommended to be carried out prior to usage.

Ductile adhesives are more appropriate than brittle adhesives for steel structure strengthening by adhesively bonding carbon fibre reinforced polymer (CFRP) due to its greater strain capacity, leading to larger loading and deformation capability. This paper investigated the bond behaviour of CFRP-to-steel joints bonded with a ductile adhesive via numerical studies. Single lap pull tests were also conducted, and the load-displacement relationship at the loaded end and the strain distribution along the CFRP plate were examined. A bond-slip relationship was derived from the test, and based on this, an isosceles trapezoid bond-slip model was proposed. A finite element model was developed for FE analysis of the bond behaviour of the CFRP to steel interface by using the proposed bond-slip model. The finite element model was used to model the experiments, and the good agreement between the experimental results and numerical results demonstrate the effectiveness and accuracy of the finite element model. Finally, a systemically parametric analysis was performed to investigate the effect of FRP modulus, adhesive equivalent strain, adhesive tensile strength and adhesive thickness on initial stiffness, effective bond length and ultimate load. Finally based on the numerical results, a model of effective bond length was proposed.

In this paper a micromechanical modelling method is developed to investigate the mechanical behaviour of the aluminium foam. A new Representative Volume Element (RVE) model denoted as ORVE is proposed based on thin-walled close octadecahedron cells, and then finite element models of these ORVEs are developed for the numerical modelling of the mechanical behaviour of the aluminium foam. The developed numerical model is validated by comparing the computed stress-strain relationship to that from experiments from literatures. The effect of compressing air on the compressive stress is also investigated and it is found that it can be neglected. An intensive parametric investigation is consequently conducted to study the effect of cell size and relative density on the mechanical behaviour of the aluminium foam based on the ORVE model. It is found that the mechanical behaviour of the aluminium foam depends mainly on the relative density/porosity or the ratio of cell wall thickness to cell height. The size of the cell is found to affect the Young's modulus but not the yielding strength, and for the aluminium foam of the same porosity, the Young's modulus slightly goes up with the increase of cell height. It is also found that the mechanical behaviour of the foam is not sensitive to the strain rate. In addition, a relationship between porosity and mechanical properties of the foam is proposed based on the ORVE model.

An extended finite element model is developed.Micromechanics of fibre bridging is considered in the model.The variation of matrix flaw size and local fibre volume fraction are accounted for in the model.The model can model the tensile strain-hardening and multiple-cracking behaviour of ECC. In this paper, an extended finite element model is developed for accurate and effective modelling of the tensile strain-hardening and multiple-cracking behaviour of engineered cementitious composites (ECC) under uniaxial tension. The crack is modelled using the cohesive zone model with a simplified cohesive constitutive model accounting for the matrix and fibre bridging effect, and multiple cohesive zones are adaptively embedded within the model upon the occurrence of sequential cracking based on the extended finite element method (XFEM). The extended finite element model is implemented in the ABAQUS via the user element subroutine (UEL) for the numerical analysis of the tensile behaviour of ECC. Material randomness including random matrix flaws and random fibre distribution, which can significantly affect the tensile behaviour of ECC, has been accounted for in the proposed model. Three ECC mixes are modelled and good agreement between the computed and experimental results demonstrates the effectiveness of the proposed method for modelling the tensile behaviour of ECC. It is also shown that the two aspects of material randomness should be considered simultaneously in the model.

In this paper a hierarchical multiscale modelling method is proposed to analyse the strain-hardening and multiple-cracking tensile fracture behaviour of engineered cementitious composites. A simplified multi-linear crack bridging relationship is proposed at a lower mesoscale based on analytical crack bridging analysis for a single crack. A representative volume element model is developed at an upper mesoscale accounting for random fluctuations of internal material properties and sequentially occurred cracking, and it is analysed using the extended finite element method. The multiscale modelling method is validated, and the effect of fibre distribution uniformity on the tensile behaviour of ECC is investigated.

In this paper, a new numerical model is developed to model the tensile behavior of the cementitious composites reinforced with hybrid bagasse fibres and steel fibres based on the extended finite element method. The numerical model considers random fibre distribution, which is generated automatically, and the cohesive behavior, which represents the bonding between fibres and the matrix. The cementitious matrix is modeled using extended finite element method. The developed numerical model is implemented in commercial software ABAQUS and the computed results are compared with the corresponding experimental results for numerical validation. It is found that the tensile behavior of the composites predicted from the new numerical model is consistent with that obtained from experimental study, and that the developed numerical model can accurately predict the uniaxial tensile behavior, including the post-cracking behavior of fibre reinforced cementitious composites.

This paper presents a representative volume element (RVE)-based modelling method to capture the mechanical behaviour of aluminum foams under compressive loadings. Octadecahedron is selected as a geometric basis shape to form closed cells of the aluminum foams in the microstructured RVE model to simulate the mechanical behaviour under compressive loadings. The stress-strain relationship obtained from the numerical modelling is compared to that from experimental study and agreements between these results demonstrate the validity of the proposed RVE model. Through observing the deformation evolution of cells during a compressive loading process, the failure modes of aluminum foams are identified and analysed using the proposed RVE model. Further the influence of strain rate on the mechanical behaviour of aluminum foams under compressive loadings is numerically studied via a parametric study.

In this study, a numerical method is developed to simulate the degradation of cement paste when subjected to sodium sulfate solutions. The proposed numerical method accounts for ionic diffusion, chemical reactions and the damage propagations, which are three main phenomena accompanied with degradation. A modified Poisson-Nernst-Planck model is developed to model the diffusion of multiple ions in a gradually degraded material. The cracking suction effect is introduced to consider the suction action caused by the newly-formed unsaturated cracks, which would accelerate the diffusion process within the cracking area. The proposed model is applied to model the experiments reported in the literature. The numerical results obtained agree very well with those from experiments.

Mo–Cu composites exhibit excellent physical and mechanical properties, while the problems of densification and interface seriously limit their application. In this paper, the effect of element Zr on the properties of Mo–Cu composites is investigated aiming to overcome these critical issues. Various compositions of Mo–Cu–Zr ternary composites were fabricated via ball milling, cold isostatic pressing and microwave sintering. Microstructures and mechanical properties of the prepared composites were systematically characterized and analyzed. The results show that the density and mechanical properties of the composites increase with the increase of Zr content, and the 50Mo30Cu20Zr composite achieves the highest relative density of 97.6%, hardness of 314.4 HV and compressive strength of 805.9 MPa. The increase of Zr content reduces the sintering activation energy and leads to the improvement of density. Simultaneously, the element Zr can form solid solutions and in-situ synthesis intermetallic compounds with Cu matrix, which leads to solid solubility strengthening and dispersion strengthening. Moreover, the interface between Mo and Cu phase is found to have been reinforced by the in-situ intermetallic compound particles embedded in the interface. This work provides an important reference for research of densification and mechanical property of Mo–Cu composites.

When using high strength materials in concrete partially encased steel (CES) composite columns, the major issues encountered are strain incompatibility of high strength steel and high strength concrete, premature concrete spalling and explosive brittle failure with poor ductility. In order to improve the compressive behaviour and ductility of CES columns, Engineered Cementitious Composites (ECC) encasement is proposed as a confinement and protection layer for concrete and steel, respectively. In order to evaluate the effectiveness of ECC cover on performance of CES columns, compressive behaviours of ECC-CES short columns were experimentally investigated to study the effects of material strengths, ECC encasement thickness, steel section shape and column’s aspect ratio. Findings were discussed and reported in terms of failure behaviours, load-deformation responses, post-peak ductility and toughness. Test results suggested that while only an insignificant increase of axial compressive resistance was observed, ECC encasement improved failure behaviour of ECC-CES columns by effectively controlling brittleness and explosive spalling of high strength concrete. ECC-CES generally showed improved ductility and energy absorption capacity but the strength enhancements were minimal. Reliability of current design codes in predicting the column ultimate strength was investigated and a new approach based on effective stress method was proposed. Finally, a 3D non-linear numerical model was also developed to predict the compressive behaviours of the proposed form of columns and a small scale parametric study was conducted.

A new category of magnesium oxychloride cement-based strain-hardening cementitious composites (MOC-SHCC) with high-strength and high-ductility is developed in this research. The eco-friendly and high-strength MOC mortar is used as the matrix and ultra-high-molecular-weight polyethylene (PE) fiber is deployed as reinforcement. The development of mechanical properties of the MOC-SHCC with the curing ages varying from 12 h (h) to 28 days (d) is fully investigated and the high-early-strength characteristic of MOC-SHCC is demonstrated. The compressive, flexural, and tensile strength of the MOC-SHCC at 1d reach 71.4 MPa, 25.2 MPa, and 8.28 MPa respectively, accounting for 56%, 84%, and 75% of the corresponding values at 28d. The tensile capacities of the MOC-SHCC decrease slightly with the curing age, while all the values are beyond 6% accompanying with the evenly distributed microcracks. Additionally, water resistance of the MOC-SHCC is systematically investigated by using an accelerating method through immersing specimens into 60 °C hot water for 7d and 28d at the curing ages of 1d, 3d and 28d, respectively. The developed high-performance MOC-SHCC features with high early strength, high ductility, and satisfactory water resistance, which would have a strong potential application in practical engineering.

In this study, the size effects on tensile properties and compressive strength of engineered cementitious composites (ECC) were investigated via experimental studies. Plane (2-D) and block (3-D) dogbone-shaped specimens were tested under uniaxial tension to study the size effect on tensile properties. Cubes and cylinders of different sizes were tested under uniaxial compression to study the size effect on compressive strength. The effect of water/binder (w/b) ratio on the compressive strength of ECC was also studied. Five w/b ratios (i.e., 0.20–0.42) were considered to cover a wide strength range. Three polyethylene (PE) fiber volume contents 0%, 1% and 2% were added to cubes for three different sizes (i.e., L = 40 mm, 50 mm and 100 mm) under five w/b ratios. Both of the plane and block dogbone-shaped specimens exhibited strain-hardening behavior accompanied with multiple micro-cracks under uniaxial tension. The size effects on the tensile properties of ECC were discussed, and the experimental scaling factors of tensile properties of block specimen to plane specimen were established and compared with the theoretical value. Additionally, the influences of specimen shape and specimen size on the compressive strength of ECC were stressed. The compressive strength of ECC decreased as the increasing specimen size regardless of the w/b ratio. It is also concluded that the compressive strength discrepancy caused by different specimen shape was negligible at 2% fiber volume content when the cube edge length was equal to the cylinder diameter. Furthermore, a size effect law for cubes with a high reliability was proposed based on fracture mechanics, and a correlation between the compressive strength of cube at any size and that of standard cylinder was deduced, providing a helpful strength conversion reference for ECC.

The use of high strength steel (HSS) in the construction of concrete encased steel (CES) composite columns is often limited by the strain incompatibility issue between HSS and concrete at peak-load. This study proposes an alternative approach to confine the high strength concrete with Engineered Cementitious Composite (ECC) to improve its compatibility with high strength steel. The main purpose of this study is to experimentally evaluate the axial compressive performance of the proposed composite column cross-section configuration. Behaviours of fifteen short columns including twelve ECC-CES columns are investigated in terms of failure modes, load-deformation curves, ductility and energy absorption capacity. The test parameters included ECC and concrete strengths, ECC cover thickness, steel section shape and column section’s aspect ratio. It was found that ECC generally improved the failure behaviour of high strength steel CES columns and increased the deformation and energy absorption capacity. On average ECC-CES columns showed around 12% and 8% higher ductility and toughness than control concrete column, respectively. A detailed 3D nonlinear finite element model was developed and validated against experimental results. Applicability of current design codes to predict the ultimate strength of ECC-CES columns was also evaluated. Finally, a method to calculate the ECC-CES column’s capacity considering effective material stresses at peak-load was proposed.

The bond behaviour of CFRP-to-steel bonded joint considerably depends on the properties of adhesives, and is significantly influenced by temperature. Meanwhile, different adhesives behave differently at elevated temperatures. Therefore, an in-depth understanding of the effect of temperature on CFRP-to-steel bonded joints with different adhesives is crucial. In this study, a total of 24 single-lap shear joints with four different types of adhesives, were investigated to examine the bond behaviour of CFRP-to-steel bonded joints at a temperature of 23 °C, at 15 °C below the glass transition temperature Tg-15 °C, and at 15 °C above the glass transition temperature Tg + 15 °C. The results indicate that 1) the failure mode of specimens was transformed from cohesive failure or CFRP delamination failure at room temperature to adhesive-steel interface failure with an increase in temperature, 2) the bond strength of all specimens was reduced by approximately 10% at Tg-15 °C, and 70% at Tg + 15 °C. Based on a literature review, an analytical model was proposed to predict the bond strength of the CFRP-to-steel bonded joints at elevated temperatures, 3) the bond-slip relationship of the joints with linear adhesive was changed from a trapezoidal to a triangular with an increase in temperature; However, the bond-slip relationship of the joints with a nonlinear adhesive didn’t change, and 4) the stiffness of the joints decreased with temperature owning to the degradation of the elastic modulus of adhesive.

This research investigates the mechanical performance of adhesive joints using high-performance epoxy (EP) based nanocomposite adhesive materials modified by ozone functionalized carbon nanotubes (OZ-CNTs) and two types of triblock copolymers (BCPs) including Methylmethacrylate-Butylacrylate-Methylmethacrylate (MAM) and Styrene-Butadiene-Methylmethacrylate (SBM). Different mechanical tests such as double-lap shear, tensile-butt, and Mode I long-crack extension tests were conducted to evaluate the effect of the BCP and OZ-CNT modification on the mechanical performance of the epoxy adhesive material. From the double-lap shear test, the strength of the 0.5 wt% OZ-CNT + SBM hybrid epoxy adhesive joint achieved a 112% increase compared to that of the unmodified epoxy. The ultimate plastic shear strain of the modified adhesives was significantly increased by 100% for the 0.5 wt% OZ-CNT + SBM/EP, representing a significant improvement in strain energy density and superior resistance to failure for any joints that would be applied in practice. However, the tensile-butt joint strength of the BCP/EP and OZ-CNT + BCP/EP joints was slightly lower than that of the unmodified epoxy, which was due to the presence of the lower strength and stiffness nanophase BCPs. The long-crack extension studies revealed a very large increase of Mode I fracture toughness of 1190% for the nano-modified hybrid joints with 0.5 wt% OZ-CNT + SBM/EP, showing that the OZ-CNT addition greatly enhances the fracture toughening processes provided by the SBM. It was also found that the addition of OZ-CNTs increased the electrical conductivity by 4 orders of magnitude compared with the unmodified and BCP modified epoxy. Rheological studies were also carried out to study the change in viscosity of the epoxy with the addition of BCPs and OZ-CNTs. The viscosity of the epoxy was increased with the addition of BCP or OZ-CNTs and the viscoplastic behaviour was observed for the hybrid OZ-CNT and BCP/EP adhesives, which was analysed using Casson's model.