Mechanical Interlocking Effect Research Articles

Support membrane pore blockage (SMPB): An important phenomenon during the fabrication of thin film composite membrane via interfacial polymerization

Interfacial polymerization (IP) has become a dominant technique for preparing thin film composite (TFC) membranes. Deep insight into the IP process is crucial for the design of TFC membranes with optimal performance. According to the conventional mechanism, a PA layer would be formed upon a support membrane during the IP reaction. In order to replenish this mechanism, a phenomenon denoted as “support membrane pore blockage (SMPB)” is explored in this study. Different experiments were designed to show how SMPB affected the membrane performance by regulating the monomer concentration, the pore size of the support membrane, the lag time after aqueous phase coating, and using different IP techniques. Various conceptual models were proposed to expound SMPB. The results indicated that the penetration of polyamide polymer into the support membrane may lead to a dual effect: (i) excessive penetration can cause support membrane pore blockage, and therefore increase the flow resistance and decrease the water permeability; (ii) it can produce a “mechanical interlocking effect”, which can enhance the adhesion between the PA layer and the support membrane, thus improving the TFC membrane stability. The SMPB mechanism can be adopted to elucidate phenomena related to membrane synthesis and to understand the structure-property-performance relationship.

Design of laser welding applied to T joints between steel and aluminium

Laser conduction welding was used to directly join DH36 steel to AA5083 aluminium alloy in a T joint configuration, each plate with 6 mm of thickness. The effect of the process energy (via power density and interaction time) on the joint integrity and quality in terms of cracking, porosity and intermetallic compound layer formation was investigated. Successful T joints were produced by melting of the aluminium plate, which was inserted into a 4 mm deep groove machined on the steel plate, with the heat generated by the laser irradiation on the steel surface. The IMC layer thickness was less than 5 μm. Although cracking was observed along the IMC layer with higher levels of energies, the joints were still strong due to the mechanical inter-locking effect resulting from the novel design of the component, whereby the IMCs were subjected to compressive state of stress while loading.

The influence of surface treatment on the tensile properties of carbon fiber-reinforced epoxy composites-bonded joints

The surface characteristics of carbon fiber-reinforced composites significantly influence the tensile properties of adhesive-bonded joints. The main objective of this study was to research the effect of surface treatment by sandpaper rubbing on the strength of adhesive joints. In the present research, surfaces were prepared using four grades of sandpaper with grit sizes of up to 60, 220, 400, 800, and polish grit. Further, the two types of joints (single lap joint and scarf adhesive joint) were tested to investigate the effects of the grit sizes and sanding direction of the sandpaper (parallel to the fiber direction, perpendicular to the fiber direction, and random direction) on the tensile properties. The experimental results showed that the highest bonding strength could be achieved when the surface was sanded in the random direction. Moreover, the grit sizes of the sandpaper significantly influenced the surface characteristics, including the surface profile, surface roughness, surface contact angle, and surface free energy of the specimens, and then affected the bonding strength of the joints by mechanical interlocking and adsorption effect. Furthermore, for both single lap and scarf adhesive joints, the failure mode and the force of the adhesive layer under tensile load were different; therefore, the dominant factors affecting the bonding enhancement mechanism were consequently different.

Interfacial structure and bonding mechanism of AZ31/carbon-fiber-reinforced plastic composites fabricated by thermal laser joining

Multi-material joining is attracting the attention of the automotive industry given its potential to realize lighter vehicles, and therefore fuel savings and reduced emissions. The aim of the present study was to understand the bonding mechanisms whereby metal and plastic/composites are joined and to improve the multi-material joint strength. In this study, the effect of thermal oxidation of Mg alloy sheets on the strengths of Mg–CFRP (carbon-fiber-reinforced plastic) lap joints prepared using laser-assisted metal and plastic joining technique was investigated. Characterization techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro-computed tomography (MCT), x-ray photoelectron spectroscopy (XPS), and atom probe tomography (APT) were used to study the underlying mechanisms of the thermal oxidation. The formation of bubbles, mechanical interlocking and chemical reactions at the joint interface were found to be the three key factors influencing the strength of joints. Thermal oxidation increased the joint strength significantly through the suppression of bubble formation, CFRP decomposition and the creation of mechanical interlocking effects at the joint interface. Moreover, MgCO3, MgO1+x, and Mg(OH)2 phases were detected by XPS analysis at the joints prepared using thermally oxidized Mg alloy sheets. The presence of the high O/Mg ratio phases was also confirmed by APT analysis. The formation of these phases confirmed the occurrence of chemical reactions between the MgO and CFRP matrix at the nanometer level, which are regarded as contributing to the increase in the joint strength.

A novel and facile fabrication of polyphosphazene nanotube/carbon fiber multi-scale hybrid reinforcement and its enhancing effect on the interfacial properties of epoxy composites

The mechanical properties of carbon fiber (CF) reinforced composites are greatly dependent on the interfacial adhesion between fiber and resin matrix. Introducing nanoscale reinforcements into the interface is an effective approach to improve the interfacial adhesion of CF composites. In this paper, we proposed a facile and effective method for assembling poly(cyclotriphosphazene-co-4,4′-sulfonyldiphonel) nanotube onto CF surface as a novel multi-scale hybrid reinforcement through in situ template polymerization. The effects of surface modification on the surface and interface properties of CF and the resulting composite were investigated. After modification, the interfacial shear strength of fiber reinforced epoxy composites showed an increase of 26.4%. The reinforcing mechanisms were also analyzed, and the improvements on interfacial properties should mainly be attributed to mechanical interlocking effect. In addition, the modification even improved the fiber tensile strength by 6.6–16.3%, rather than deteriorating it.

The Effect of CO2 Laser‐Induced Microhole Formations on Adhesive Bonding Strength of CFRP/CFRP Joints

There are many different techniques to improve the adhesion between carbon fiber‐reinforced plastics (CFRP) which are used in aircraft primary structures. One of the most common techniques is the specific surface structuring of the joining parts in order to obtain mechanical interlocking. In this study, laser‐induced surface structuring effect on adhesion strength of CFRP/CFRP joints was investigated by single lap shear tests. Microholes were created by CO2 laser with different configurations in x and y axis for the best mechanical interlocking effect on adhesive bonding. The effects of microhole numbers (309, 625, and 914) and microhole formations (triangle, inverted triangle, frame, and box) on the adhesive bonding strength of the CFRP/CFRP joints were determined by using single lap shear tests according to ASTM D5868‐01 standard with 60 kN DARTEC universal test machine. Single lap shear tests showed that microhole structuring has a significant effect on mechanical interlocking for adhesive bonding of CFRP/CFRP joints. Results showed that the shear strength of CFRP/CFRP joints improved at 309 microholes and frame type microhole formations. After mechanical tests, damage mechanisms were observed by using the optical microscope. POLYM. COMPOS., 40:2891–2900, 2019. © 2018 Society of Plastics Engineers

Interphase Engineering of a Cellulose-Based Carbon Fiber Reinforced Composite by Applying Click Chemistry.

Given our possible future dependence on carbon fiber reinforced composites, the introduction of a renewable matrix might be advantageous for the vision of a sustainable world. Cellulose is a superior green candidate and provides exceptional freedom in composite design as the free OH groups can be conveniently functionalized to give tailor‐made materials. To obtain a high‐performing carbon fiber reinforced cellulose propionate composite, we accurately tailored the interfacial adhesion by invoking click chemistry. The synthetic strategy involved grafting of a phenylacetylene structure onto the carbon fiber surface, onto which O‐acylated 6‐azido‐6‐deoxycellulose and a number of aromatic azides could be covalently attached. Single‐fiber fragmentation tests indicated that the lipophilicity and size of the substituent on the deposited structure played a crucial role in determining molecular entanglement and mechanical interlocking effects, as penetration into the cellulose propionate matrix was of utmost importance. Enhanced interfacial shear strength was obtained for the carbon fiber covalently functionalized with the cellulose derivative. Nevertheless, the greatest increase was observed for the derivative substituted with a compact and highly lipophilic CF3 substituent. In a broader sense, our study provides a synthetic platform to bind cellulose derivatives to graphitic surfaces and paves the ways towards the preparation of innovative cellulose‐based carbonaceous materials.

Phosphinated polyimide hybrid films with reduced melt-flow and enhanced adhesion for flexible copper clad laminates

Adhesion properties of phosphinate-contained polyimide (P-PI) hybrid films were studied to develop suitable heat resistant adhesive film with excellent hot-melt processability. The diamine, 1,1-bis(4-aminophenyl)-1-(6-oxido-6H-dibenz<c, e><1, 2> oxaphosphorin-6-yl) ethane (i.e. DMA), was introduced to synthesize a series of P-PI films with different contents of DMA. The presence of the bulky phosphinate pendant group on PI backbone increased the adhesion strength and effectively reduced the melt flow after hot-pressing to flexible copper clad laminates (FCCL) without the usage of adhesive. The P-PI film tended to produce rougher surface that facilitated the mechanical interlocking effect between P-PI hybrid film and copper. The presence of characteristic phosphinate functional groups and the formation of polyphosphate layer on P-PI film were confirmed by FTIR and XPS results. The storage modulus and glass transition temperature of P-PI films were increased because of the enhanced rigidity by phosphinate groups. The presence of bulky phosphinate pendant group also reduced the coefficient of thermal expansion and dielectric constant of PI films. Although the introduction of phosphinate in PI reduced the initial weight loss temperature, the thermal stability of P-PI films was sufficient for the following manufacturing processes. Furthermore, another interesting observation was the enhancement of transparency at 400 nm for P-PI. Those properties make P-PI films useful in FCCL application.

Mechanical interlock effect between polypropylene/carbon fiber composite generated by interfacial branched fibers

Weak interface is a limiting factor to prepare polymer composite with excellent properties. Here, we report an interfacial interlocking strategy to improve interfacial strength of polypropylene (PP)/carbon fiber (CF) by manipulating interfacial diffusion and aggregation of amide-based self-assembling nucleating agent (WBG) and studied the effect of CF surface nature on the interfacial structures. The experimental results showed that when the interfacial energy between CF and WBG became low, it was favorable that the preferential localization of WBG toward the CF surfaces from polymer matrix, leading to the laterally growth of WBG fibers and the formation of interlocking interface. Single fiber fragmentation testing proved that there was a critical size of the laterally grown WBG fibers for the interfacial improvement. Only when the size exceeded 100 μm, the interfacial interlocking was strong enough to enhance the interfacial interaction, as evidenced by the substantial increases of 97% in interfacial shear strength compared to conventional PP/CF composite.

Deposition characteristics and behaviour of high-pressure cold-sprayed silicon powder

ABSTRACTThe high-pressure cold spraying technology was adopted to deposit silicon particles on the copper substrates for preparing the silicon-based electrode of lithium-ion batteries. The deposition of silicon powder was accomplished at two spray process parameter sets by impacting the particle stream or individual particle. The microstructure and the morphology of the silicon coatings were characterised by scanning electron microscopy. A single-silicon particle represents three different deposition behaviours. The mass gains of as-sprayed samples are negative over multiple spray passes, but the thin silicon coating with the particular covered structures is formed. Increasing the number of spray pass cannot cause the obvious increase in the coating thickness. The interfacial morphology of the silicon coatings indicates that, except for the plastic deformation of the copper substrate, both the mechanical interlock effect among the deposited silicon particles and even the chemical binding contributing to the effective bond of silicon particles to the substrate.

Plasticized and reinforced poly(methyl methacrylate) obtained by a dissolution-dispersion process for single point incremental forming: Enhanced formability towards the fabrication of cranial implants

A plasticized and reinforced material made of poly(methyl methacrylate), PMMA, was developed via an effective dissolution-dispersion method to enhance its formability in Single Point Incremental Forming process (SPIF). Different contents of triacetine (plasticizer), and Cloisite 30B nanoclay (C-30B) used as reinforcement, were added to PMMA based on a factorial design of experiments with center points. A synergistic effect between triacetine and C-30B was evidenced during the SPIF processing of the PMMA composite material. The addition of triacetine produced the relaxation and mobility of polymer chains, while C-30B improved the mechanical properties without affecting the formability. The transfer of stresses during SPIF of cone-shaped parts was enhanced due to a mechanical interlocking effect between the nanoclay and the PMMA chains, in addition to the formation of intercalated nanostructures within the clay galleries. The potential application of these PMMA-based composite materials for manufacturing cranial implants is addressed in this work as well.

Apparent shear strength of hybrid glass fibre reinforced composite joints

The incorporation of nano or micro ceramic particles into fibre reinforced composites (FRC) to enhance their stiffness and durability has been widely investigated. This mechanism has been attributed to the increase in stiffness of the polymeric matrix phase and shear strength of FRCs due to the presence of particles at the interlaminar regions. In order to elucidate such effect, hybrid single-lap joints consisted of ceramic particles and glass fibre reinforced composites were evaluated to better assess the mechanical interlocking effect provided by silica and cement inclusions. A full factorial design (23) was performed to identify the effect of the type of particle (silica and cement), particle weight fraction (2.5 and 5 wt%) and glass fibre grammage (200 and 600 g/m2) on the apparent shear strength and adherent strength of single-lap joints under tensile loading. The ceramic particle inclusions led to increased apparent shear strength and adherent strength. The inclusion of 5 wt% ceramic particles into 600 g/m2 cross-ply glass fibre composites enhanced both adherent and apparent shear strengths.

A new method of hybrid friction stir welding assisted by friction surfacing for joining dissimilar Ti/Al alloy

A new method of friction surfacing assisted hybrid friction stir welding (FS-HFSW) technique was developed to improve the joint efficiency and avoid the pin abrasion for joining of dissimilar Ti/Al joints. The FSW tool with enlarged head and concave end-face was designed to broaden the lap width and promote material flow. The maximum tensile load reached 12.2kN, representing 85.3% of the parent Al alloy, with a ductile fracture locating at the heat affected zone of base Al. The excellent bonding of Ti and Al was based on the combined effects of nanoscale TiAl3 IMCs layer and complex mechanical inter-locking.

The best features of diamond nanothread for nanofibre applications

Carbon fibres have attracted interest from both the scientific and engineering communities due to their outstanding physical properties. Here we report that recently synthesized ultrathin diamond nanothread not only possesses excellent torsional deformation capability, but also excellent interfacial load-transfer efficiency. Compared with (10,10) carbon nanotube bundles, the flattening of nanotubes is not observed in diamond nanothread bundles, which leads to a high-torsional elastic limit that is almost three times higher. Pull-out tests reveal that the diamond nanothread bundle has an interface transfer load of more than twice that of the carbon nanotube bundle, corresponding to an order of magnitude higher in terms of the interfacial shear strength. Such high load-transfer efficiency is attributed to the strong mechanical interlocking effect at the interface. These intriguing features suggest that diamond nanothread could be an excellent candidate for constructing next-generation carbon fibres.

Microarc oxidation coating covered Ti implants with micro-scale gouges formed by a multi-step treatment for improving osseointegration

The sub-microporous microarc oxidation (MAO) coating covered Ti implant with micro-scale gouges has been fabricated via a multi-step MAO process to overcome the compromised bone-implant integration. The as-prepared implant has been further mediated by post-heat treatment to compare the effects of –OH functional group and the nano-scale orange peel-like morphology on osseointegration. The bone regeneration, bone-implant contact interface, and biomechanical push-out force of the modified Ti implant have been discussed thoroughly in this work. The greatly improved push-out force for the MAO coated Ti implants with micro-scale gouges could be attributed to the excellent mechanical interlocking effect between implants and biologically meshed bone tissues. Attributed to the –OH functional group which promotes synostosis between the biologically meshed bone and the gouge surface of implant, the multi-step MAO process could be an effective strategy to improve the osseointegration of Ti implant.

Two-component spin-coated Ag/CNT composite films based on a silver heterogeneous nucleation mechanism adhesion-enhanced by mechanical interlocking and chemical grafting

In this paper, a new method for the synthesis of silver carbon nanotube (Ag/CNT) composite films as conductive connection units for flexible electronic devices is presented. This method is about a two-component solution process by spin coating with an after-treatment annealing process. In this method, multi-walled carbon nanotubes (MWCNTs) act as the core of silver heterogeneous nucleation, which can be observed and analyzed by a field-emission scanning electron microscope. With the effects of mechanical interlocking, chemical grafting, and annealing, the interfacial adhesive strength between films and PET sheets was enhanced to 12 N cm−1. The tensile strength of the Ag/CNT composite films was observed to increase by 38% by adding 5 g l−1 MWCNTs. In the four-probe method, the resistivity of Ag/CNT-5 declined by 78.2% compared with pristine Ag films. The anti-fatigue performance of the Ag/CNT composite films was monitored by cyclic bending deformation and the results revealed that the growth rate of electrical resistance during the deformation was obviously retarded. As for industrial application, this method provides an efficient low-cost way to prepare Ag/CNT composite films and can be further applied to other coating systems.

Reprint of “Biomimetic apatite coating on yttria-stabilized tetragonal zirconia utilizing femtosecond laser surface processing”

Yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) have been used in orthopedic and dental implants because of their excellent physicochemical properties. In this study, we developed an apatite coating technique with low thermal effects for Y-TZP ceramics based on a biomimetic process using a supersaturated calcium phosphate solution (CP solution) as a coating medium. To achieve this, we performed femtosecond laser processing with low thermal effects as a surface pre-modification tool for Y-TZP ceramics. By changing the laser scanning mode, we fabricated two different submicro-/micro-structures on the Y-TZP sample. Both laser-treated samples showed increased water wettability due to ablation plasma and partly formed an apatite layer on their surfaces in the CP solution within 7 days. To further enhance the apatite-forming ability, we applied an alternate dipping process to the laser-treated sample in order to precoat the sample with apatite precursors. The laser-treated and precursor-precoated sample successfully formed an apatite layer on the entire surface in the CP solution within a shorter time period (24 h). The thus-coated apatite layer adhered to the sample so strongly that the layer remained on the sample even after the tape-detaching test. This strong adhesion may be attributed to the mechanical interlocking effects due to laser-induced surface roughening. Our proposed apatite-coating technique using the laser- and precursor-assisted biomimetic process would be useful for the creation of apatite-coated Y-TZP ceramics for orthopedic and dental applications.

Enhancement on mechanical strength of adhesively-bonded composite lap joints at cryogenic environment using coiled carbon nanotubes

Abstract The hardness, tensile and lap joint shear behaviors of pure epoxy, straight multi-walled carbon nanotube (MWNT)/epoxy and coiled multi-walled carbon nanotube (CCNT)/epoxy adhesives conditioned at room temperature (RT) and cryogenic temperature (CT) were investigated in the present study. Experimental results showed that all adhesives had greater Vickers hardness values, Young's moduli and tensile strengths at CT. The performance of CCNT/epoxy adhesive at CT was outstanding due to the enhancement of mechanical interlocking effect between CCNTs and epoxy at low temperature. This effect led to a greater Vickers hardness value, Young's modulus and lap joint shear strength of this adhesive at CT when compared with MWNT/epoxy type. The result from finite element analysis (FEA) also proved that the contraction of matrix at CT induced additional clamping force onto the surface of nanotubes. Due to the larger surface area of CCNTs, a relatively stronger bonding strength was achieved, and thus, CCNT/epoxy adhesive had better mechanical properties at low temperature condition.

Fabrication of Bioactive Glass Fiber Reinforced Polyamide with High Mechanical Performance by the Function of Apatite Nuclei

We immersed micropores-formed glass fiber reinforced polyamide MXD6 (GFR-MXD6) in SBF and precipitated apatite nuclei in the pores of the substrate by raising both the pH and the temperature of SBF and obtained bioactive GFR-MXD6. By immersing in SBF, hydroxyapatite formation was induced by the apatite nuclei in the pores and grew to the surface of the substrate. High adhesive strength between the formed hydroxyapatite and the substrate was obtained by a mechanical interlocking effect.

Bioactivity Treatments for Zirconium and Ti-6Al-4V Alloy by the Function of Apatite Nuclei

Micropores were formed on the surfaces of Zirconium (Zr) and Ti-6Al-4V alloy plates by soaking in sulfuric acid. In order to provide bioactivity to these metals, Apatite Nuclei (AN) were precipitated in the pores. By soaking in SBF, it was observed that the whole surfaces of Zr and Ti-6Al-4V alloy with the AN treatment were covered with the bone-like apatite within 1 day. The formed apatite layer showed high adhesive strength by a mechanical interlocking effect.