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This paper presents the compact and efficient Matlab codes for the concurrent topology optimization of multiscale composite structures not only in 2D scenario but also considering 3D cases. A modified SIMP approach (Sigmund 2007) is employed to implement the concurrent topological design, with an energy-based homogenization method (EBHM) to evaluate the macroscopic effective properties of the microstructure. The 2D and 3D Matlab codes in the paper are developed, using the 88-line 2D SIMP code (Struct Multidisc Optim 43(1): 1–16, 2011) and the 169-line 3D topology optimization code (Struct Multidisc Optim 50(6): 1175–1196, 2014), respectively. This paper mainly contributes to the following four aspects: (1) the code architecture for the topology optimization of cellular composite structures (ConTop2D.m and ConTop3D.m), (2) the code to compute the 3D iso-parametric element stiffness matrix (elementMatVec3D.m), (3) the EBHM to predict the macroscopic effective properties of 2D and 3D material microstructures (EBHM2D.m and EBHM3D.m), and (4) the code to calculate the sensitivities of the objective function with respect to the design variables at two scales. Several numerical examples are tested to demonstrate the effectiveness of the Matlab codes, which are attached in the Appendix, also offering an entry point for new comers in designing cellular composites using topology optimization.

Transdermal drug delivery has been widely studied in recent years. Compared with other methods of drug delivery, this method has many advantages, such as convenient, improving patient compliance and avoiding first-pass effect. However, the low efficiency of this method needs to be overcome. In this paper, a micro-invasive transdermal drug delivery mechanism with synergic coupling of microneedle force field and triboelectric field is proposed, which can enhance the efficiency of transdermal drug delivery and is easy to operate and use. First, a silicon solid microneedle array was fabricated by micromachining technology, and its size parameters could be flexibly adjusted. Second, a metal layer with microstructure was fabricated on the back of the microneedle by sputtering technology as the positive friction layer of the triboelectric structure. Last, the microneedle and the triboelectric structure were combined into a single composite structure by using FPC wires. The experimental results showed that the transdermal amount increased with the increase of external excitation force, frequency and the number of microneedle arrays. Under the same conditions, the skin penetration of the two mechanisms combined was 3-8 times higher than that of the single use.

The article presents the results of modeling various modes of vacuum infusion molding of thin-walled polymer-composite structures of arbitrary geometry. The small thickness of the manufactured structures and the fixation of their back surface on the rigid surface of the mold made it possible to significantly simplify the process model, which takes into account the propagation of a thermosetting resin with changing rheology in a compressible porous preform of complex 3D geometry, as well as changes in boundary conditions at the injection and vacuum ports during the post-infusion molding stage. In the four modes of vacuum-infusion molding studied at the post-infusion stage, the start time, duration and magnitude of additional pressure on the open surface of the preform and in its vacuum port, as well as the state of the injection gates, were controlled (open–closed). The target parameters of the processes were the magnitude and uniformity of the distribution of the fiber volume fraction, wall thickness, filling of the preform with resin and the duration of the process. A comparative analysis of the results obtained made it possible to identify the most promising process modes and determine ways to eliminate undesirable situations that worsen the quality of manufactured composite structures. The abilities of the developed simulation tool, demonstrated by its application to the molding process of a thin-walled aircraft structure, allow one to reasonably select a process control strategy to obtain the best achievable quality objectives.

It is not uncommon that the rock–backfill composite structure (RBCS) material in underground mine stopes being exposed to alternative fatigue and creep loading condition. Understanding the failure and energy evolution is critical to maintain the backfilled stope stability and ensure safe mining activities. This work aims to investigate the effect of disturbed stress amplitude (DA) on the failure and energy evolution characteristics of RBCS under alternative fatigue and creep loading using a specially designed triaxial-shear fatigue loading apparatus and post-test CT scanning technique. Testing results show that the equivalent lifetime of RBCS is the largest for a specimen with low stress disturbance, and the volumetric strain increases with increasing disturbed stress amplitude. It is found that much more energy is consumed for a sample subjected to high stress disturbance, and the cyclic loading induced damage is much more severe at the whole process. A damage evolution model was established using the dissipated energy to express damage propagation at the respective fatigue loading stage and creep loading stage and the entire process. A series of CT images reveal the cracking pattern, typical tensile failure, and shear failure are found for the surrounding rock and backfill material, respectively. It is suggested that the backfill material plays crucial role in preventing hole spalling and collapse, especially under high stress disturbance.HighlightsAlternative fatigue and creep loading experiments were conducted on RBCS samples.The equivalent lifetime of RBCS decreases with increasing disturbed amplitude.The accumulative energy consumption at a FLS is larger than at a CLS.Tensile failure and shear failure is found for the surrounding rock and backfill material, respectively.

As a high-demand material, polymer matrix composites are being used in many advanced industrial applications. Due to ecological issues in the past decade, some attention has been paid to the use of natural fibers. However, using only natural fibers is not desirable for advanced applications. Therefore, hybridization of natural and synthetic fibers appears to be a good solution for the next generation of polymeric composite structures. Composite structures are normally made for various harsh operational conditions, and studies on loading rate and strain-dependency are essential in the design stage of the structures. This review aimed to highlight the different materials’ content of hybrid composites in the literature, while addressing the different methods of material characterization for various ranges of strain rates. In addition, this work covers the testing methods, possible failure, and damage mechanisms of hybrid and synthetic FRP composites. Some studies about different numerical models and analytical methods that are applicable for composite structures under different strain rates are described.

Controlled photocatalytic conversion of CO2 into premium fuel such as methane (CH4) offers a sustainable pathway towards a carbon energy cycle. However, the photocatalytic efficiency and selectivity are still unsatisfactory due to the limited availability of active sites on the current photocatalysts. To resolve this issue, the design of oxygen vacancies (OVs) in metal–oxide semiconductors is an effective option. Herein, in situ deposition of TiO2 onto SiO2 nanospheres to construct a SiO2@TiO2 core–shell structure was performed to modulate the oxygen vacancy concentrations. Meanwhile, charge redistribution led to the formation of abundant OV‐regulated Ti–Ti (Ti–OV–Ti) dual sites. It is revealed that Ti–OV–Ti dual sites served as the key active site for capturing the photogenerated electrons during light‐driven CO2 reduction reaction (CO2RR). Such electron‐rich active sites enabled efficient CO2 adsorption and activation, thus lowering the energy barrier associated with the rate‐determining step. More importantly, the formation of a highly stable *CHO intermediate at Ti–OV–Ti dual sites energetically favored the reaction pathway towards the production of CH4 rather than CO, thereby facilitating the selective product of CH4. As a result, SiO2@TiO2‐50 with an optimized oxygen vacancy concentration of 9.0% showed a remarkable selectivity (90.32%) for CH4 production with a rate of 13.21 μmol g−1 h−1, which is 17.38‐fold higher than that of pristine TiO2. This study provides a new avenue for engineering superior photocatalysts through a rational methodology towards selective reduction of CO2. In this work, we describe the construction of a SiO2@TiO2 core–shell composite structure through a controlled growth strategy to achieve the precise modulation of the oxygen vacancy (OV) concentration in TiO2. The abundant Ti–OV–Ti dual sites enable not only efficient adsorption and activation of CO2 but also a stable adsorption configuration of the *CHO intermediate, thereby contributing to remarkable catalytic activity and selectivity for photoreduction of CO2 towards CH4.

This work deals with the layout optimization of piezoelectric fiber composite patches on a vibrating laminated composite plate and the discrete material design of the composite plate. The vibration of the composite plate is excited by an external mechanical loading, and a sinusoidal voltage with given amplitude and frequency is applied on the piezoelectric fiber composite patches. The analysis of the composite structure with piezoelectric fiber composite patches is performed via a finite element method in condensed form, where the piezoelectric effects are considered as induced force. As a view to minimize the dynamic response of the vibrating laminated composite structure, the Discrete Material Optimization method is employed to perform the design optimization of piezoelectric fiber composite patches and the stacking sequence, fiber angles, and selection of material for the composite structure. Numerical examples are presented to demonstrate the effectiveness of the proposed method.

In recent times, the utilisation of marine composites in tubular structures has grown in popularity. These applications include composite risers and related SURF (subsea umbilicals, risers and flowlines) units. The composite industry has evolved in the development of advanced composites, such as thermoplastic composite pipes (TCP) and hybrid composite structures. However, there are gaps in the understanding of its performance in composite risers, hence the need for this review on the design, hydrodynamics and mechanics of composite risers. The review covers both the structure of the composite production riser (CPR) and its end-fittings for offshore marine applications. It also reviews the mechanical behaviour of composite risers, their microstructure and strength/stress profiles. In principle, designers now have a greater grasp of composite materials. It was concluded that composites differ from standard materials such as steel. Basically, composites have weight savings and a comparative stiffness-to-strength ratio, which are advantageous in marine composites. Also, the offshore sector has grown in response to newer innovations in composite structures such as composite risers, thereby providing new cost-effective techniques. This comprehensive review shows the necessity of optimising existing designs of composite risers. Conclusions drawn portray issues facing composite riser research. Recommendations were made to encourage composite riser developments, including elaboration of necessary standards and specifications.

A new type of bamboo–concrete composite structure using perforated steel plates as connectors was proposed. To study the composite effect of this new type of composite structure, the slip behavior of bamboo–concrete shear connectors was first studied through push-out tests. Subsequently, four-point bending tests of ten bamboo–concrete composite beams were carried out. The results show that the failure of bamboo–concrete shear connectors occurred between the perforated steel plate and the concrete, and there was no obvious damage between the perforated steel plate and the bamboo. The load carrying capacity of perforated steel plate connectors was relatively stable. The failure mode was moderate failure. Considering the three stages of the load–slip curve, an exponential function is proposed to describe the load–slip curve. The failure modes of composite beams can be summarized as two types. In the first type, the bamboo beam ruptures on the bottom and the concrete dose not suffer significant damage; in the second type, the top surface of the concrete first exhibits longitudinal cracks, and finally, the bamboo beam ruptures. Compared with bamboo beams, the ultimate load of composite beams increased by 1.2–1.5 times, and the sectional stiffness of composite beams increased by 2.9–4.2 times. The equivalent section stiffness was obtained after determining the connection coefficient, and the connection coefficient γ b ranged between 0.50 and 0.80 and decreased as the center spacing of the perforated steel plate increased. The equivalent cross-section stiffness obtained by different load stages of the shear slip stiffness was calculated to predict the mid-span displacement. The calculation results show that the effect of slip stiffness on the equivalent stiffness of cross section is not sensitive, and a 35% increase in slip stiffness results in a maximum increase in equivalent section stiffness of only 6%.

Ultra-high-performance concrete (UHPC) is a cement-based material with excellent impact resistance. Compared with traditional concrete, it possesses ultra-high strength, ultra-high toughness, and ultra-high durability, making it an ideal material for designing structures with impact resistance. The research on the impact resistance performance of UHPC and its composite structures is of great significance for the structural design of protective engineering projects. However, currently, there is still insufficient research on the impact resistance performance of UHPC composite structures. To study the impact resistance performance, experiments were conducted on UHPC targets using high-speed projectiles. The results were compared with impact tests on granite targets. The results indicated that when subjected to projectile impact, the UHPC targets exhibited smaller surface craters compared with the granite targets, while the penetration depth was lower in the granite targets. Afterwards, the process of a projectile impacting the UHPC composite structure was numerically simulated using ANSYS 16.0/LS-DYNA finite element software. The numerical simulation results of penetration depth and crater diameter were in good agreement with the experimental results, which indicates the rationality of the numerical model. Based on this, further analysis was carried out on the influence of impact velocity, impact angle, and reinforcement ratio on the penetration depth of the composite structure. The results show that the larger the incident angle or the smaller the velocity of the projectile is, the easier it is to deflect the projectile. There is a linear relationship between penetration depth and reinforcement ratio; as the reinforcement ratio increases, the penetration depth decreases significantly. This research is of great significance in improving the safety and reliability of key projects and also contributes to the application and development of ultra-high-performance materials in the engineering field.