Influence of Interface on Mechanical Behavior of Al-B4C/Al Laminated Composites under Quasi-Static and Impact Loading

In this study, Al-B4C/Al laminated composites with high interlayer bonding strength were fabricated by integrated hot-pressed sintering accompanied with hot rolling. The mechanical properties and interface behavior of the Al-B4C/Al laminated composites were investigated under quasi-static and impact loading. The results show that the Al-B4C/Al laminated composites obtain a high interface bonding strength, because no interlayer delamination occurs even after fractures under quasi-static and impact loads. The Al-B4C/Al laminated composites exhibit a better comprehensive mechanical performance, and the fracture can be delayed due to the high bonding strength interface. Moreover, laminated composites can absorb more impact energy than the monolithic material under impact loading due to the stress transition and relaxation.

Effect of Mortise and Tenon Structure on the Properties of Wood Flour Polyvinyl Chloride-Laminated Veneer Lumber Co-Extruded Composites

Core-shell composites with strong weather resistance, mechanical strength and creep resistance can be prepared using co-extrusion technology. Considering the weak bonding strength between core-shell interfaces, this study started from the concept of a mortise and tenon combination; three types of conical, rectangular and trapezoidal mortise and tenon joints were prepared, and their bending properties, long-term creep properties, interfacial bonding properties, and dimensional stability properties were tested. Results showed that the mortise and tenon structure could form a mechanical interlock between the outer-shell-layer polyvinyl chloride (PVC) wood-plastic composite (WPVC) and the inner-core-layer laminated veneer lumber (LVL), which could effectively improve the interface bonding property between the two layers. Among them, the trapezoidal mortise and tenon structure had the largest interface bonding force compared with the tapered and rectangular mortise and tenon structure, where the interface bonding strength reached 1.01 MPa. Excellent interface bonding can effectively transfer and disperse stress, so the trapezoidal mortise and tenon structure had the best bending properties and creep resistance, with a bending strength of 59.54 MPa and a bending modulus of 5.56 GPa. In the long-term creep test, the deformation was also the smallest at about 0.2%, and its bending properties, creep resistance and interface bonding performance were also the best. The bending strength was 59.54 MPa and the bending modulus was 5.56 GPa; in the long-term creep test, the strain curve was the lowest, about 0.2%. In addition, the mortise and tenon structure could disperse the stress of the inner shell LVL after water absorption and expansion, thus significantly improving the dimensional stability of the co-extruded composite after water absorption.

Preliminary Exploration of Economic Polypropylene-Fiber-Reinforced ECC with Superfine River Sand (SSPP-ECC) Applied to a Bridge Pavement Leveling Overlay

In response to the current common disease of concrete leveling overlays of bridge pavement in China, the feasibility of using an economic SSPP-ECC with local waste superfine sand as an alternative material for a leveling overlay was proposed in this study. To evaluate the interface bonding property in the girder between the SSPP-ECC and concrete, a slant shear test and split tensile test were designed to study the interfacial shear and tensile properties of the ordinary concrete/ordinary concrete (OC/OC) and ordinary concrete/SSPP-ECC (OC/ECC), where the results showed that SSPP-ECC could significantly improve the interface shear stress and split tensile strength compared to ordinary concrete. Furthermore, the damage status of OC/ECC no longer involved fracturing along the interface; instead, each of the two substrates was partially destroyed, which revealed that OC/ECC had a high bonding effect. Moreover, a restrained shrinkage test was carried out to evaluate the shrinkage property of SSPP-ECC, where the result showed that the shrinkage strain of SSPP-ECC was slightly lower than concrete, where the average cracking time for SSPP-ECC was far longer than for ordinary concrete under the same ambient drying conditions; furthermore, the stress rate for SSPP-ECC revealed that it was a low-cracking-risk material. Meanwhile, the crack width of SSPP-ECC was only 0.1 mm after 35 d, which showed that SSPP-ECC had a more substantial crack width control capacity relative to concrete. The test results initially verified the feasibility and great potential of economic SSPP-ECC applied in a bridge pavement leveling overlay.

The Effect of Reinforcement Preheating Temperatures on Tribological Behavior of Advanced Quranic Metal-Matrix Composites (QMMC)

The growing applications of iron/copper bimetallic composites in various industries are increasing. The relationship between the properties of these materials and manufacturing parameters should be well understood. This paper represents an experimental study to evaluate the effect of reinforcement (steel rod) preheating temperature on the mechanical properties (bond strength, microhardness, and wear resistance) of copper matrix composites (QMMC). In preparing the QMMC samples, the melted copper was poured on a steel rod that had been preheated to various temperatures, namely, room temperature, 600 °C, 800 °C, and 1200 °C. Properties of the QMMC (interface microstructure, interfacial bonding strength, microhardness, and wear) were investigated. The experimental results revealed that the best bond between the copper matrix and steel rod formed only in the composites prepared by preheating the steel rods with temperatures lower than the recrystallization temperature of steel (723 °C). This is because the oxide layer and shrinkage voids (due to the difference in shrinkage between the two metals) at the interface hinder atom diffusion and bond formation at higher temperatures. The microhardness test showed that preheating steel rod to 600 °C gives the highest value among all the samples. Furthermore, the QMMC’s wear behavior confirmed that the optimization of preheating temperature is 600 °C.

3D Printing of Conductive Hydrogel-Elastomer Hybrids for Stretchable Electronics

Electronically conductive hydrogels integrated with dielectric elastomers show great promise in a wide range of applications, such as biomedical devices, soft robotics, and stretchable electronics. However, one big conundrum that impedes the functionality and performance of hydrogel-elastomer-based devices lies in the strict demands of device integration and the requirements for devices with satisfactory mechanical and electrical properties. Herein, the digital light processing three-dimensional (3D) printing method is used to fabricate 3D functional devices that bridge submillimeter-scale device resolution to centimeter-scale object size and simultaneously realize complex hybrid structures with strong adhesion interfaces and desired functionalities. The interconnected poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) network endows the PAAm hydrogel with high conductivity and superior electrical stability and poly(2-hydroxyethyl acrylate) functions as an insulating medium. The strong interfacial bonding between the hydrogel and elastomer is achieved by incomplete photopolymerization that ensures the stability of the hybrid structure. Lastly, applications of stretchable electronics illustrated as 3D-printed electroluminescent devices and 3D-printed capacitive sensors are conceptually demonstrated. This strategy will open up avenues to fabricate conductive hydrogel-elastomer hybrids in next-generation multifunctional stretchable electronics.

Effect of graphene on the mechanical and anisotropic thermal properties of Cu-Ta composites

Strong interfacial bonding is the basic requirement for metal-graphene composites for higher thermo-mechanical properties. In the present work, a novel metal tantalum is introduced in the metal-graphene composites prepared by (ball-milling + molecular level mixing) followed by hot press sintering. SEM, transmission electron microscopy and high transmission electron microscopy are observed to check the interface area which shows the presence of tantalum carbide on the interface area which is formed during the sintering process. The formation of the carbide element significantly enhances the mechanical properties of composites. The addition of a very low amount of 0.1 vol% of rGO give the very high yield strength 200 MPa and ultimate tensile strength value 375 MPa with the good agreement of ductility, Vickers hardness 95 HV and bending strength 617 MPa which are much higher than unreinforced copper-tantalum composites and even from pure copper. The anisotropic thermal conductivity values are also significantly improving due to the better interfacial bonding and the ratio was 5 which is just 1.01 for pure copper. The formation of carbide elements and extraordinary high mechanical values with good ductility and anisotropic thermal conductivity ratio can lead to these materials used in thermal packaging systems and the electronic industry.

Effects of pullulan on the biomechanical and anti-collapse properties of dicalcium phosphate dihydrate bone cement

In this work, a modified dicalcium phosphate dihydrate (DCPD) bone cement with unique biodegradable ability in a calcium phosphate cement system was prepared by the hydration reaction of monocalcium phosphate monohydrate and calcium oxide and integration with pullulan (Pul), a non-toxic, biocompatible, viscous, and water-soluble polysaccharide that has been successfully used to improve defects in DCPD bone cement, especially its rapid solidification, fragile mechanical properties, and easy collapse. The effect of different contents of Pul on the structure and properties of DCPD were also studied in detail. The modified cement was characterised by X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, ultraviolet-visible absorption, X-ray photoelectron spectroscopy analysis, and rheological property measurements. The results indicated that Pul promoted the hydration formation of DCPD, and interface bonding occurred between Pul and DCPD. With increasing content of Pul, the setting time of the DCPD bone cement increased from 2.6 min to 42.3 min, the compressive strength increased from 0 MPa to 20.4 MPa, and the anti-collapse ability also improved owing to the strong interface bonding, implying that the DCPD bone cement improved by Pul has better potential for application in the field of non-loading bone regenerative medicine compared to unmodified DCPD bone cement.

Fabrication and Characterization of Thermal-responsive Biomimetic Small-scale Shape Memory Wood Composites with High Tensile Strength, High Anisotropy

Intelligent responsive materials have become one of the most exciting fields in the research of new materials in the past few decades due to their practical and potential applications in aerospace, biomedicine, textile, electronics, and other relative fields. Here, a novel thermal-responsive biomimetic shape memory wood composite is fabricated utilizing polycaprolactone-based (PCL) shape-memory polymer to modify treated-wood. The shape memory wood inherits visual characteristics and the unique three-dimension structure of natural wood that endows the shape memory wood (SMW) with outstanding tensile strength (10.68 MPa) at room temperature. In terms of shape memory performance, the shape recovery ratio is affected by multiple factors including environment temperature, first figuration angle, cycle times, and shows different variation tendency, respectively. Compared with shape recovery ratio, the shape fixity ratio (96%) is relatively high and stable. This study supplies more possibilities for the functional applications of wood, such as biomimetic architecture, self-healing wood veneering, and intelligent furniture.

Hyperbranched Polymers in Modifying Natural Plant Fibers and Their Applications in Polymer Matrix Composites-A Review

Natural plant fibers have been widely used in the agricultural and forest industries, and even in the automobile industry, especially for producing fiber reinforced polymer matrix composites. However, the low mechanical properties of composites remain the key problem in the applications. A hyperbranched polymer has lots of advantages such as low viscosity, high reactivity, and so on. Multireactive end groups of hyperbranched polymers are ideal for modifying natural plant fibers to achieve better interface bonding between a fiber and resin matrix. This manuscript reviews some research advances in hyperbranched-polymer-modified natural plant fibers and summarizes the applications of the modified fibers in polymer matrix composites with a particular focus on the chemical modification of fibers and interface bonding.

Mechanical, Thermal, and Shape Memory Properties of Three-Dimensional Printing Biomass Composites

In this study, a series of heat-induced shape memory composites was prepared by the hot-melt extrusion and three-dimensional (3D) printing of thermoplastic polyurethane (TPU) using wood flour (WF) with different contents of EPDM-g-MAH. The mechanical properties, microtopography, thermal property analysis, and heat-induced shape memory properties of the composites were examined. The results showed that, when the EPDM-g-MAH content was 4%, the tensile elongation and tensile strength of the composites reached the maximum value. The scanning electron microscopy and dynamic mechanical analysis results revealed a good interface bonding between TPU and WF when the EPDM-g-MAH content was 4%. The thermogravimetric analysis indicated that the thermal stability of TPU/WF composites was enhanced by the addition of 4% EPDM-g-MAH. Heat-induced shape memory test results showed that the shape memory performance of composites with 4% EPDM-g-MAH was better than that of unmodified-composites. The composites' shape recovery performance at a temperature of 60 °C was higher than that of the composites at ambient temperature. It was also found that, when the filling angle of the specimen was 45°, the recovery angle of the composites was larger.

Preparation and Characteristics of Biocomposites Based on Steam Exploded Sisal Fiber Modified with Amphipathic Epoxidized Soybean Oil Resin

Sisal fiber was pretreated by continuous screw extrusion steam explosion to prepare steam exploded sisal fiber (SESF) preforms. An amphipathic bio-based thermosetting resin with poor mechanical properties was cured by epoxidized soybean oil (ESO) and citric acid (CA). The obtained resin was used to modify SESF preforms and prepare eco-friendly biocomposites. The molar ratios (R) of carboxylic groups to epoxy groups and resin contents in biocomposites were adjusted. The biocomposites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transfer infrared spectroscopy (FT-IR), tensile testing, scanning electron microscopy (SEM), water absorption and water contact angle measurements. The maximum thermal decomposition temperature of the biocomposites was 373.1 °C. The curing efficiency of the resin in the biocomposites improved with the increase of resin content, and reached a maximum at R = 1.2. The tensile strength of the biocomposites reached a maximum of 30.4 MPa at R = 1.2 and 40% resin content. SEM images showed excellent interfacial bonding and fracture mechanisms within the biocomposites. The biocomposites exhibited satisfactory water resistance. ESO resin cured with polybasic carboxylic acid is therefore a good bio-based modifier for lignocellulose, that prepare biocomposites with good mechanical properties, hydrophobicity, and thermostability, and which has a potential application in packaging.