Interfacial Cohesive Strength Research Articles

Molecular dynamics simulation of interfacial interaction mechanisms between ground tire rubber and styrene-butadiene rubber enhanced by nanomaterial incorporation

The recycling of ground tire rubber (GTR) is an effective method for addressing black pollution. In this study, we investigated and compared the effects of acidic oxidation treatments and different nanomaterial contents on the interfacial properties of styrene-butadiene rubber (SBR) and GTR. Molecular models of GTR modified by acidic oxidation and nanomaterials, as well as SBR, were established. The interfacial interaction mechanisms between SBR and GTR were studied through tensile and shear behaviors. The results indicated that the properties of SBR-GTR interface were enhanced through acidic oxidation and nanomaterial modification, with the latter demonstrating superior advantages in augmenting the interfacial strength. Specifically, the addition of a carbon nanotube and graphene increased the interfacial cohesion strength by 55.12 % and 82.93 %, and the interfacial shear strength by 29.87 % and 43.05 %, respectively. Moreover, graphene exhibited superior performance in enhancing interfacial interactions compared to carbon nanotubes and increasing the nanomaterial content did not positively impact the improvement of interfacial properties. The interfacial properties of SBR and GTR were quantitatively analyzed using molecular dynamic (MD) simulations. This study provides a theoretical foundation for enhancing the mechanical properties of recycled rubber by using nanomaterials, thereby guiding the experimental preparation of recycled rubber.

Interfacial characteristics of fiber asphalt mastic and aggregates: Impact on mixture crack resistance performance

The interfacial characteristics between fiber-modified asphalt mastics and aggregates play a crucial role in the performance of asphalt mixtures. To explore these interfacial interaction characteristics, three types of fibers (basalt, glass, and polyester), five levels of fiber content (ranging from 0.1% to 0.5% by mixture mass), and two types of aggregates (limestone and basalt) were selected, and an optimal mixture design was established. Contact angle tests, binder bond strength tests, and disk-shaped compact tension tests were conducted to investigate the impact of fiber type, fiber content, and aggregate type on interface characteristics. The results indicate that the addition of fibers can enhance the interfacial strength, with basalt fibers exhibiting superior reinforcement effects. As fiber content increases, the influence of aggregate type on interfacial strength decreases. Under ambient conditions, a composite failure mode was observed, while at low temperatures, cohesive failures dominated. The incorporation of fibers led to an increase in interfacial cohesion strength. The interfacial interaction strength between fiber asphalt mastic and aggregates exhibits a favorable linear correlation with the fracture energy and peak crack mouth opening displacement of the asphalt mixture. Overall, this study elucidates the microscopic mechanisms involved in fiber asphalt mixtures, laying the foundation for further in-depth research.

Ultrathin coordination-crosslinked nacre-inspired hydrogel superwetting membranes with enhanced mechanical stability for high-performance emulsion separation

Superwetting membranes have considerable potentials in the field of water treatment, especially for oil-water separation, however it still keeps great challenges to prepare ones with high mechanical property and strong interfacial cohesion strength. Herein, inspired by high hardness yet toughness of natural nacre, we proposed a polyphenol-mediated inner-outer through type modification strategy to fabricate ultrathin coordination-crosslinked nacre-inspired hydrogel superwetting membranes (named PVDF/GPT/Fe), using 2D graphene oxide (GO) nanosheets, flexible polyvinyl alcohol (PVA) and branched structure tannic acid (TA) as the assembly units, and Fe3+ ion as the cross-linking agent. It is found that PVA-TA interface assembly is key to realize the inner-outer through type hydrophilic modification for the hydrophobic PVDF membrane, to achieve superhydrophilicity and underwater superoleophobicity with the UOCAs of above 150°, ultra-low oil-adhesion and self-cleaning property, with a high flux recovery ratio of 96.3 % after six cycles. The PVDF/GPT/Fe membrane exhibits the boosted mechanical strength and damage resistance, with the Young's modulus of up to 1076 MPa, which is enhanced by 4.4 times, compared to the pristine PVDF membrane, benefiting from the formation of the layered brick-and-mortar structured nacre-inspired hydrogel coating and strong bonding strength of the interfaces between the base membrane and the top coating layer. The separation efficiencies of the PVDF/GPT/Fe membrane for various oil-in-water emulsions are higher than 99.5 % and the largest emulsion permeance is 611.2 L m-2 h-1 bar-1. Our research extends the path route to design and manufacture novel biomimetic superwetting membranes with high mechanical strength and durability.

Towards sturdy and sensable pressure-sensitive adhesive through hierarchical supramolecular interaction

Endowing a robust pressure-sensitive adhesive (PSA) with sensable properties is of great significance for in-situ stress detection and information encryption in the fields of electronics, energy storage, flexible sensing, etc. However, it remains great challenge due to the difficulty in balancing interfacial wetting and cohesive strength. Herein, a microphase-separated strategy is proposed to construct an ionogel with a lower modulus of 1.96MPa, a strength of 728kPa as well as a remarkable toughness of 2258.9kJ/m3, which can be used as a sturdy PSA bonded to various substrates (metals, polar plastics, non-polar plastics) under gentle pressure. The comparable modulus and cohesive strength give it an excellent adhesion strength of 1340kPa, which far exceeds most of reported high-performance PSAs. Furthermore, due to the orientation of a large number of ionic groups, the adhesion strength increases by 31.3% once a voltage of 20V is applied. Finally, the sensitive force-resistance response of such PSA that can be used for encrypted messaging was demonstrated.

Simulation and experimental studies of mechanical delamination characteristics of REBCO tapes and lap joints under transverse tension

In this study, we investigate the delamination properties of high-temperature superconducting REBa2Cu3O7−x (REBCO) coated conductor (CC) tapes and lap joints under transverse tension by a finite element model (FEM) based on the cohesive zone model. The interfacial cohesive strength and the initial penalty stiffness used in the FEM calculations are adopted based on the experimental data obtained from the anvil tensile tests. Compared to previous theoretical studies, our calculation results of the delamination behaviors for the REBCO CC tapes and the lap joints are more approaching to the experimental data, and the abrupt failure behavior of the transverse load–displacement curves, which appears in the anvil tests, is reproduced by the simulations. Moreover, the effects of welding strength between the upper and lower tapes and internal tape damage during the welding process on the delamination characteristics, including the delamination strength, initial separation, delamination locations, and damage distribution of the CC lap joints, are presented.

Enhanced mechanical and tribological properties of polymer nanocomposites by improving interfacial properties by hexagonal boron nitride nanosheets: Molecular dynamics simulations

AbstractTo comparatively investigate the mechanical, tribological, and interfacial properties of polytetrafluoroethylene (PTFE) strengthened by graphene (Gr) and hexagonal boron nitride (h‐BN) nanosheets, molecular models of PTFE nanocomposites containing a similar weight fraction of Gr and h‐BN nanosheets were established. The constant‐strain approach, the three‐layer friction structures, and the pull‐out simulations were respectively employed to calculate the mechanical, tribological, and interfacial properties of the nanocomposites. Results indicate that the Young's, shear, and bulk moduli of the nanocomposites are increased by 17.22%, 20.72%, and 4.78%, respectively, by introducing h‐BN nanosheets than those by introducing Gr nanosheets. Meanwhile, a decrease of 8.49% in the friction coefficient of the nanocomposites is obtained by incorporating h‐BN nanosheets than that by incorporating Gr nanosheets. In addition, 84.71% and 5.18 times higher in the interfacial cohesive strength and interfacial shear strength, and 91.58% and 128.7% higher in the interfacial fracture toughness of PTFE nanocomposites in the normal separation and shear separation, respectively, are achieved by incorporating h‐BN nanosheets than those by incorporating Gr nanosheets. To provide a deeper understanding of the enhancement mechanisms of h‐BN nanosheets, the interfacial interaction energies, radial distribution functions, and von Mises stress distributions of the two PTFE nanocomposites were evaluated and interpreted accordingly.

Molecular architecture regulation for the design of instant and robust underwater adhesives.

Development of underwater adhesives with instant and robust adhesion to diverse substrates remains challenging. A strategy taking the structural advantage of phenylalanine derivative, N-acryloyl phenylalanine (APA), is proposed to facilely prepare a series of underwater polymeric glue-type adhesives (UPGAs) through one-pot radical polymerization with commonly used hydrophilic vinyl monomers. The adjacent phenyl and carboxyl groups in APA realize the synergy between interfacial interactions and cohesion strength, by which the UPGAs could achieve instant (~5 seconds) and robust wet tissue adhesion strength (173 kilopascal). The polymers with varied hydrophobicity and substitutional groups as well as carboxyl and phenyl groups in separated components are designed to investigate the underwater adhesion mechanism. The universality of APA for the construction of UPGAs is also verified by the copolymerization with different hydrophilic monomers, and the applications of the UPGAs have been validated in diverse hemorrhage models and distinct substrates. Our work may give a promising solution to design potent underwater adhesives.

A Cohesive-Zone-Based Contact Mechanics Analysis of Delamination in Homogeneous and Layered Half-Spaces Subjected to Normal and Shear Surface Tractions

AbstractA contact mechanics analysis of interfacial delamination in elastic and elastic-plastic homogeneous and layered half-spaces due to normal and shear surface tractions induced by indentation and sliding was performed using the finite element method. Surface separation at the delamination interface was controlled by a surface-based cohesive zone constitutive law. The instigation of interfacial delamination was determined by the critical separation distance of interface node pairs in mixed-mode loading based on a damage initiation criterion exemplified by a quadratic relation of the interfacial normal and shear tractions. Stiffness degradation was characterized by a linear relation of the interface cohesive strength and a scalar degradation parameter, which depended on the effective separation distances corresponding to the critical effective cohesive strength and the fully degraded stiffness, defined by a mixed-mode loading critical fracture energy criterion. Numerical solutions of the delamination profiles, the subsurface stress field, and the development of plasticity illuminated the effects of indentation depth and sliding distance on interfacial delamination in half-spaces with different elastic-plastic properties, interfacial cohesive strength, and layer thickness. Simulations yielded insight into the layer and substrate material property mismatch on interfacial delamination. A notable contribution of the present study is the establishment of a computational mechanics methodology for developing plasticity-induced cumulative damage models for multilayered structures.

Theory for the Elementary Time Scale of Stress Relaxation in Polymer Nanocomposites.

We construct a microscopic theory for the elementary time scale of stress relaxation in dense polymer nanocomposites. The key dynamical event is proposed to involve the rearrangement of cohesive segment-nanoparticle (NP) tight bridging complexes via an activated small NP dilational motion, which allows the confined segments to relax. The corresponding activation energy is determined by the NP bridge coordination number and potential of mean force barrier. The activation energy varies nonlinearly with interfacial cohesion strength and NP concentration, and a universal master curve is predicted. The theory is in very good agreement with experiments. The underlying ideas are relevant to a variety of other hybrid macromolecular materials involving hard particles and soft macromolecules.

Adhesion-cohesion balance of prepreg tack in thermoset automated fiber placement. Part 1: Adhesion and surface wetting

The constitution of prepreg tack in automated fiber placement (AFP) is affected by a sensitive balance between adhesive interfacial bond strength and cohesive strength of the prepreg resin. In an effort to explore the role of interfacial liquid-solid interaction on the tack of commercial aerospace-grade epoxy prepreg, a surface wetting analysis was performed on AFP-related substrates. The standard test liquid combination water/diiodmethane and extracted neat epoxy resin were used for contact angle measurement employing the sessile drop method and the Owens-Wendt-Rabel-Kaelble (OWRK) model. Additional rheological and topographical analyses were carried out to account for viscous resin flow on surfaces of different roughness. The results from the material characterization are discussed against the background of tack measurement by probe tack testing utilizing a rheometer. Significant differences between the investigated surfaces in terms of both the maximum tack level and the onset temperatures of adhesion were found as a function of test parameters relevant for contact formation. General agreement with the experimental tack results was observed employing a topographically extended version of the Dahlquist criterion. For each substrate, a temperature-dependent critical storage modulus could be determined that conforms to the onset temperature of tackiness. Contact angle measurements revealed a correlation between the thermodynamic work of adhesion and maximum tack and, moreover, the tack onset in the adhesive regime when additionally incorporating surface topography. Matching ratios of polar and dispersive surface free energy and surface tension components were found to favor the molecular interaction at the interface between prepreg resin and substrate.

On the delamination of polyvinyl butyral laminated glass: Identification of fracture properties from numerical modelling

This work investigates the delamination behaviour of polyvinyl butyral (PVB) laminated glass under quasi-static loading based on a cohesive zone model (CZM) with an isotropic bilinear traction - separation (T – δ) law. It presents a 2D model of a through-cracked tensile (TCT) test within an implicit finite element framework of the commercial software ANSYS. Test results from literature are used to calibrate the adhesion properties of the PVB-glass interface in a numerical cohesive zone approach. The previous TCT tests were performed at a loading rate of 6 mm/min and a temperature of approx. 22 °C. Three different PVB adhesion grades, i.e., BG R10 (low), BG R15 (medium) and BG R20 (high) are considered. Given the uncertainty in the identification of adhesion parameters, including interfacial fracture energy, cohesive strength and stiffness, a parametric analysis is conducted quantifying the influences of model parameters on the simulation results. The study allows for decoupling of individual parameters in the calibration. Then, interfacial fracture energies and cohesive strengths of the PVB-laminated glass are calibrated by matching the force – displacement curves of the numerical simulations with those from the TCT experiments. One representative case was chosen for each adhesion grade. We obtain interfacial fracture energies of 425 J/m2, 650 J/m2 and 1000 J/m2 for BG R10, BG R15 and BG R20 PVBs, respectively, while the corresponding cohesive strengths are 3 MPa, 5 MPa and 10 MPa, respectively. Moreover, based on numerical simulation results, the conversion of energy during the delamination process is extracted and discussed. The mixed-mode delamination mechanism is investigated by calculating the mode I and mode II energy release rates with respect to different PVB thicknesses and adhesion. The results show that the proportion of the mode I energy release rate is around 30%∼40% of the total energy release rate at the stable delamination stage and increases with PVB thickness. The presented study contributes to the adhesion properties of various types of PVB interlayers reported in open literatures and proposes a methodology for the unique identification of adhesion properties.

Analysis of delamination and heat conductivity of epoxy impregnated pancake coils using a cohesive zone model

Epoxy-impregnated pancake coil is observed to delaminate locally when its temperature is cooled from room temperature to 77 K. The delaminations cause the degradation of the critical current of the coil. Besides, the delamination may degrade the thermal conductivity and affect the thermal conductive path. Thus, in this study, the delamination behavior of epoxy-impregnated pancake coil during the cooling process is analyzed through a coupled thermal–mechanical cohesive zone model. The measured transverse tensile strength of coated conductors has shown considerable scatter and Weibull distribution has been adopted to fit the transverse tensile strength. The simulations are able to capture the main characterizations of the observed delaminations with the cohesive strength of the cohesive element following a Weibull distribution. After the cooling process, a heat spot is applied to the degraded positions to analyze the temperature field and the thermal conductive path in the damaged coil. Compared to the original undamaged coil, the delaminations indeed degrade the thermal conductivity and increase the thermal resistance. What’s more, the effects of the variation of the thickness of the epoxy and different interfacial cohesive strength distributions of the coated conductor are considered. The results show that reduction of the thickness of the epoxy can lower the radial stress and release the damage, and the random distribution of the cohesive strength inside the coated conductor dominantly determines the delamination pattern of the coil.

Advances in Photoreactive Tissue Adhesives Derived from Natural Polymers

To stop blood loss and accelerate wound healing, conventional wound closure techniques such as sutures and staples are currently used in the clinic. These tissue-piercing wound closure techniques have several disadvantages such as the potential for causing inflammation, infections, and scar formation. Surgical sealants and tissue adhesives can address some of the disadvantages of current sutures and staples. An ideal tissue adhesive will demonstrate strong interfacial adhesion and cohesive strength to wet tissue surfaces. Most reported studies rely on the liquid-to-solid transition of organic molecules by taking advantage of polymerization and crosslinking reactions for improving the cohesive strength of the adhesives. Crosslinking reactions triggered using light are commonly used for increasing tissue adhesive strength since the reactions can be controlled spatially and temporally, providing the on-demand curing of the adhesives with minimum misplacements. In this review, we describe the recent advances in the field of naturally derived tissue adhesives and sealants in which the adhesive and cohesive strengths are modulated using photochemical reactions.

Metal-crosslinked ɛ-poly-L-lysine tissue adhesives with high adhesive performance: Inspiration from mussel adhesive environment

Strong glue of mussels has long been considered as an ideal model to design synthetic bio-adhesives but the adhesive strength of metal-crosslinked mussel-inspired glues is not often satisfactory. Herein, inspired by the adhesive environment of mussels, we obtained metal-crosslinked ε-poly-L-lysine adhesives with high adhesive performance by introducing the elements of suitable adhesive environment (SAE) into the adhesives. The elements of SAE were clarified as weak alkaline conditions (pH ∼ 7.4) and low Fe3+ contents. The adhesive strength (∼105 kPa) of the metal-crosslinked adhesives endowed with the elements of SAE (PL-Cat/Fe-SAE) was about 8 times higher than that of fibrin glues. The high adhesive strength was found to originate from distinctive interfacial adhesion and cohesion strength of PL-Cat/Fe-SAE. PL-Cat/Fe-SAE showed strong interfacial adhesion capacity and nearly comparable cohesion strength to those PL-Cat/Fe adhesives with higher Fe3+ contents. The nearly comparable cohesion strength of PL-Cat/Fe-SAE was then found to be due to more amount of stable tris-complex existed in PL-Cat/Fe-SAE. In addition, PL-Cat/Fe-SAE was able to efficiently close the full thickness skin incisions. The study highlighted the importance of introducing SAE elements into the design of tissue adhesives and provided a facile and efficient strategy for constructing tissue adhesives with high adhesive performance.

Adhesives to empower a manipulator inspired by the chameleon tongue

Existing grasping technologies have persistent challenges with unstructured objects and environments, highlighting an increasing demand for methods that conform to various application scenarios. Inspired by the chameleon tongue, a soft-contact grasping manipulator empowered by a class of adhesive gels has been demonstrated. The adhesives enable the manipulator to rapidly and strongly adhere to diverse substrates with varied surfaces, shapes and sizes, also to release objects under mild conditions. The robustness of such adhesive gels was highlighted with the remarkable recyclability, broad temperature tolerance and long-term stability. Furthermore, a general approach was developed to reconcile the contradiction of simultaneously enhancing their interfacial adhesion and cohesion strength that exists in conventional glues. We anticipate that this work will offer a strategy of developing adhesive materials and pave the way towards new applications of soft materials in the emerging fields of soft robotic devices and smart manufacturing.

The construction and verification of toughening model and formula of binary poly(lactic acid)-based TPV with co-continuous structure

Co-continuous morphologies have attracted substantial attention recently as it possesses a significant toughening effect. However, these investigations of toughening poly (lactic acid) (PLA) with co-continuous structure have been limited to simply qualitative explanation. The “reinforced concrete”-like structure is obviously different from the classic “sea-island” structure. Therefore, considering these toughening elements of the rubber content, interfacial cohesion strength and the strength of rubber, and referring to relevant theory models of reinforced concrete, we have established an original theoretical toughening model, at least semi-quantitatively, of the binary PLA-based thermoplastic vulcanizates (TPVs) with co-continuous structure based on PLA/natural rubber (NR) TPVs. Moreover, we reveal that the calibration model is suitable for PLA/nitrile butadiene rubber (NBR) and PLA/epoxidized natural rubber (ENR) systems, with a perfectly Adj. R-Square of 0.97 and 0.94, respectively. It should be mentioned that natural properties of NBR and ENR are significantly distinguished from NR. This study opens up a viable way to quantitatively understand the toughening mechanism with co-continuous structure.

Reactive force-field molecular dynamics study on graphene oxide reinforced cement composite: functional group de-protonation, interfacial bonding and strengthening mechanism.

Graphene oxide (GO) reinforced cement nanocomposites open up a new path for sustainable concrete design. In this paper, reactive force-field molecular dynamics was utilized to investigate the structure, reactivity and interfacial bonding of calcium silicate hydrate (C-S-H)/GO nanocomposite functionalized by hydroxyl (C-OH), epoxy (C-O-C), carboxyl (COOH) and sulfonic (SO3H) groups with a coverage of 10%. The silicate chains in the hydrophilic C-S-H substrate provided numerous non-bridging oxygen sites and counter ions (Ca ions) with high reactivity, which allowed interlayer water molecules to dissociate into Si-OH and Ca-OH. On the other hand, protons dissociated from the functional groups and transferred to non-bridging sites in C-S-H, producing carbonyl (C[double bond, length as m-dash]O) and Si-OH. The de-protonation degree of the different groups in the vicinity of the C-S-H surface was in the following order: COOH (SO3H) > C-OH > C-O-C. In the GO-COOH sheet, most COOH groups were de-protonated to COO- groups, which enhanced the polarity and hydrophilicity of the GO sheets and formed stable COOCa bonds with neighboring Ca ions. The de-protonated COO- could also accept H bonds from Si-OH in the C-S-H gel, which further strengthened the interfacial connection. On the contrary, in the GO-Oo sheet, only 8% of the epoxy group was stretched open by the Ca ions and transformed to carbonyl group, showing weak polarity and connection with the C-S-H sheet. Furthermore, uniaxial tensile test on different C-S-H/GO models revealed that C-S-H reinforced with GO-COOH and GO-OH had better interfacial cohesive strength and ductility than that observed under tensile loading. Under the reaction force field, the dissociation of water, the proton exchange between the C-S-H and GO structure, and Oc-Ca-Os bond breakage occurred to resist tensile loading. The weakest mechanical behavior observed in the G/C-S-H, GO-Oo/C-S-H and GO-SO3H/C-S-H composites was attributed to the poor bonding, dissociation of functional groups and instability of atoms in the interface region. Hopefully, the molecular-scale strengthening mechanisms could provide a scientific guide for sustainable design of cement composites.

The Interphase Influences on the Particle-Reinforced Composites with Periodic Particle Configuration

This work improved upon an effective micromechanical method to analyze the mechanical properties of three-dimensional particle-reinforced composites (PRC) with consideration of the interfacial debonding. By incorporating the interfacial debonding model, Mises yield criterion, and failure theory, the effects of particle shape, particle volume fraction, and loading condition on the mechanical properties are studied. A comparison of simulation results obtained from the established method and published experimental data is presented. Good consistency can be found in this study. On this basis, the interfacial cohesive strength and particle shape effects on the biaxial failure strength of particle-reinforced composites with interfacial debonding were also studied. The results revealed that both interfacial strength and particle shape have significant effects on biaxial tensile failure strength. However, the different interfacial strength influence on failure envelope can hardly be discerned in biaxial compressive loading.

Effects of interface roughness on cohesive strength of self-assembled monolayers

Self-assembled monolayers (SAMs) are aggregates of small molecular chains that have the property to form highly ordered assemblies. The choice of terminal groups on the chains makes them excellent contenders of molecular-level tailoring. Molecular dynamics (MD) simulations and experimental observations of spallation of two SAM-enhanced gold-film/silicon-substrate interfaces have shown that the cohesive strength of SAM-enriched transfer-printed interfaces is strongly dependent on the choice of terminal groups. Though the MD results of perfectly ordered atomistic surfaces show the same qualitative trend as the experiments, they over-predict the interfacial cohesive strengths by a factor of about 50. Results from AFM studies have revealed that the roughness of these interfaces is of the same order (∼1nm) as the range of atomistic interactions. Hence, surface roughness is a key contributor in significantly reducing interfacial cohesive strength in these systems. In this manuscript, a continuum-level study is performed to investigate the influence of surface roughness on the cohesive strength of the interface between a Si/SAM substrate and a transfer-printed gold film. We approximate the film as a deformable continuum interacting with a rough substrate of SAMs represented by a harmonic function. Using a cohesive law derived from MD, spallation is simulated to evaluate the effective traction-separation characteristics for the rough SAM–gold interface. Our analysis shows that incorporating roughness may reduce the interfacial cohesive strength by an order of magnitude depending on the film properties and the surface roughness. Additionally, we observe that the gold film adopts unique separation attributes based on roughness parameters and material properties.

Effects of Processing Parameters on Properties of SiCp/Al Composites

The effects of hot pressing and hot extrusion temperatures on the properties of 12%SiCp/6066Al (volume fraction) composites fabricated by powder metallurgy have been studied. The experimental results indicate that the hot extrusion, an essential stage of powder metallurgy to produce this sort of particle reinforced metal matrix composites, can redistribute SiC particles in metal matrix and refine the matrix grain size, and that the hot pressing can improve the interfacial cohesion strength between SiC particles and metal matrix. When hot-pressed at temperatures slightly higher than the solidus temperature of the composite and hot-extruded at lower temperatures, the composites are stronger due to the high metal matrix strength and interfacial cohesion. The optimum parameters of hot pressing and hot extrusion in the composites are 560 and 430 °C, respectively.