Interlayer Strength Research Articles

Extending applicability of 3D-printable geopolymer to large-scale printing scenario via combination of sodium carbonate and nano-silica

Adequate printable time is crucial for the application of extrusion-based concrete 3D printing. 3D-printing geopolymer concrete (3DPGC) possesses a rapid hardening feature intrinsically, limiting its applicability in large-scale printing scenarios. Herein, we jointly use Na2CO3 (Nc) and nano-silica (Ns) to improve the printability (particularly extending printable time) and mechanical properties of 3DPGC. We first evaluated the effects of Nc replacement to a traditional activator (waterglass) on the 3D-printing-related rheology and mechanical properties to obtain an optimum Nc dosage. Subsequently, the influences of Ns incorporation on rheology, extrudability, buildability, bulk mechanical strengths, and interlayer properties were investigated based on the optimum Nc dosage. The combination of Nc and Ns (Nc-Ns) manifested a much better extrudability with a sixfold longer printable time (>120 min) due to the decreased hardening rate. Better buildability, higher compressive strengths and a stronger interlayer strength retention capacity were further achieved simultaneously. Nc adoption enables a slower hardening process owing to the lower solution alkalinity and the existence of carbonate, while the overall hardening profile can be adjusted with Ns addition. We successfully printed a special-shaped structure for validation, which requires a long printable time (>40 min). It demonstrates the exceptional printability of the proposed mixture formulation. This work contributes a feasible solution for 3DPGC in large-scale printing scenarios from the material perspective.

Thermo-mechanical and metallurgical preliminary analysis of SiC MOSFET gate-damage mode under short-circuit based on a complete transient multiphysics 2D FEM

For the first time, a complete 2D transient multiphysics electro-thermo-mechanical and metallurgical model of a 1.2 kV-80mΩ gate-planar SiC MOSFET power chip has been developed in a single FEM software. This model is used to quantify the short-circuit critical time and energy density with respect to the local SiO2 interlayer strength at high temperatures and the Al source-metal solidus-liquidus phase transition temperature. Repetitive experimental short-circuits were conducted to confirm the gate-aging existence in coherence with the critical values extracted from the proposed model.

Additive Manufacturing of Polyaryletherketone (PAEK) polymers and their composites

Polyaryletherketone (PAEK) polymers are unique thermoplastics certified for aerospace and biomedical applications, demonstrating exceptional thermo-mechanical characteristics and superior chemical resistance. They are adaptable to material extrusion (ME) and laser powder bed fusion (L-PBF) additive manufacturing systems. While various PAEK grades for additive manufacturing (AM) exist, their printing suitability, especially inter-layer strength, is not well-understood. Adding small amounts of short carbon fibers to PAEKs enhances their stiffness and service temperature but modifies their processing, structure, and properties. This study examines the effects of the AM method (L-PBF and ME) and carbon fiber addition on the structure, mechanical properties, and crystallinity of three different PAEK polymers. We characterize and correlate tensile properties, fracture modes, degree of crystallinity, fiber length and orientations, and porosity of the samples. Our findings aim to refine AM processes and feedstock materials for semi-crystalline polymers and their composites, offering insights for designing robust, economical AM parts.

Effects of TiB2 content and gradient structure on microstructural characterization and mechanical properties of TiB2/Al7050 composites

TiB2 particle reinforced Al7050 matrix homogeneous composites (HC), TiB2/Al7050 three-layer conventional linear gradient functionally gradient materials (TFGM), and TiB2/Al7050 five-layer functionally gradient materials with a bionic structure (FFGM) were successfully prepared using vacuum hot-pressed sintering (VHS) method. The effects of gradient structure and TiB2 particle content on the microstructural characterization and mechanical properties of these composites were investigated. The results demonstrate that the bending strength of all composites improves with the increase in TiB2 content. Comparatively, the bending strength of functionally gradient materials (FGM) are generally superior due to a combination of the interlayer strength of each layer, heterogeneous deformation-induced strengthening, strength-plasticity synergy of the whole material, and synergistic interlayer strengthening under strong bonding. Notably, the enhancements in bending strength and strain exhibited by FFGM are more pronounced, highlighting its "soft-hard interleaved" and "strong-tough complementary" structural pattern. The research provides valuable insights for the application and further development of FGM.

Effect of cumulative deformation and interlayer mechanical properties on bonding strength of corrugated interface steel/aluminum composite plate

Interface oxidation during hot rolling limits high quality fabrication of steel/aluminum composite plates. Q235/5083 composite plates were prepared by a process combining cold corrugated rolling (CCR) and hot flat rolling (HFR) in this study. The CCR & HFR process effectively prevents the oxidation of the base Q235 when bonding with clad 5083 aluminum alloy during hot rolling, by pre-rolling a thin interlayer 1060 aluminum on Q235, to improve the bonding strength. Bonding performance of steel/aluminum composite plate is studied in relation to the cumulative deformation when 1060 is the interlayer. The rolling experiments and performance analysis show that the shear strength initially increases and then stabilizes as the cumulative reduction rate increases since the shear fracture position occurs in the interlayer 1060. High-strength aluminum alloys including 6061, 5052, and 7075 are used as interlayers to increase the shear strength. The results show the shear strength rises first and then declines as the interlayer strength increases when the cumulative reduction rate is 40 %. The main reason for this phenomenon is the rupture of the hard brittle layers of components decreases when the interlayer strength exceeds a specific value in the CCR. This situation hinders the outflow and bonding of fresh metal, and reduces the bonding quality of steel/aluminum interface, which inhibits the high-strength interlayer from enhancing the shear strength.

Printing strategies to fabricate a disk through the fused deposition modeling method

The fused deposition modeling (FDM) technique is widely used in different industries due to its low cost and ability to produce complex geometries from polymers. In this technique, some manufacturing parameters are essential because of their effects on the mechanical performance of the final fabricated part. The current study investigated the impact of path strategy and printing speed, two key manufacturing factors, on the mechanical performance of printed disks. Six types of path strategies of rasters corresponding to the loading direction, namely unidirectional-vertical, unidirectional-horizontal, unidirectional-45, cross, cross-45, and concentrate, were used for printing some disks, and compressive tests were done on them. The results showed that these path strategies’ average compressive failure loads were 2955, 4957, 2342, 4640, 3971, and 5893 N, respectively. The lower compressive strength of the unidirectional path pattern was due to the weak zones that were located between the printed layers and rasters. Besides, three printing speeds of 40, 60, and 80 mm/s were considered to fabricate the disks with a concentrate path pattern, and compressive experiments were performed. The results showed that the 40 mm/s printing speed conducted a compressive failure load of 4544 N, while 60 and 80 mm/s resulted in 3008 and 2828 N, respectively. Finally, inter-layer strength as a major factor in controlling the compressive strength of the disks was comprehensively discussed.

Achieving injection molding interlayer strength via powder assisted hot isostatic pressing in material extrusion polyetheretherketone

Achieving injection molding interlayer strength via powder assisted hot isostatic pressing in material extrusion polyetheretherketone

Thermal and tribo-mechanical properties of high-performance poly(etheretherketone)/reduced graphene oxide nanocomposite coatings prepared by electrophoretic deposition

The thermal stability and degradation, near-to-surface mechanical properties, and scratch resistance and damage mechanism of poly(etheretherketone) (PEEK)/reduced graphene oxide (RGO) nanocomposite coatings are analyzed and discussed in terms of their nanosheet content and microstructure. Although RGO modified the thermal stability and degradation of the polymeric matrix, for instance, by slightly reducing the onset degradation temperature, its addition was not a limiting factor in the PEEK processing. Respecting the microstructural features induced by the nanosheets, the nanocomposite coatings were found to exhibit (i) a partially exfoliated and large-scale co-continuous morphology related to RGO nanosheets whose basal planes were mainly aligned with the coating surface, (ii) a dendritic morphology of PEEK domains related to transcrystallinity, (iii) and irregular domains associated with the deposition of PEEK particles wrapped by the nanosheets. The changes provoked by RGO in the morphology and PEEK crystalline phase influenced the near-to-surface mechanical properties, scratch resistance, and scratch damage mechanism of the nanocomposite coatings. Within this context, the interlayer strength between the nanosheets in the large-scale co-continuous morphology and PEEK transcrystallinity had an important effect. Furthermore, the random-bumpy surface texture formed by the irregular PEEK domains together with the conformal cracking damage mechanism was decisive in the scratch response of the PEEK/RGO nanocomposite coatings. The comprehensive characterization carried out in this work concludes that PEEK/RGO electrophoretic coatings are suitable for a variety of applications requiring tribo-mechanical resistance.Graphical

Multiplanar continuous fiber reinforcement in additively manufactured parts via co-part assembly

PurposeMany additively manufactured parts suffer from reduced interlayer strength. This anisotropy is necessarily tied to the orientation during manufacture. When individual features on a part have conflicting optimal orientations, the part is unavoidably compromised. This paper aims to demonstrate a strategy in which conflicting features can be functionally separated into “co-parts” which are individually aligned in an optimal orientation, selectively reinforced with continuous fiber, printed simultaneously and, finally, assembled into a composite part with substantially improved performance.Design/methodology/approachSeveral candidate parts were selected for co-part decomposition. They were printed as standard fused filament fabrication plastic parts, parts reinforced with continuous fiber in one plane and co-part assemblies both with and without continuous fiber reinforcement (CFR). All parts were loaded until failure. Additionally, parts representative of common suboptimally oriented features (“unit tests”) were similarly printed and tested.FindingsCFR delivered substantial improvement over unreinforced plastic-only parts in both standard parts and co-part assemblies, as expected. Reinforced parts held up to 2.5x the ultimate load of equivalent plastic-only parts. The co-part strategy delivered even greater improvement, particularly when also reinforced with continuous fiber. Plastic-only co-part assemblies held up to 3.2x the ultimate load of equivalent plastic only parts. Continuous fiber reinforced co-part assemblies held up to 6.4x the ultimate load of equivalent plastic-only parts. Additionally, the thought process behind general co-part design is explored and a vision of simulation-driven automated co-part implementation is discussed.Originality/valueThis technique is a novel way to overcome one of the most common challenges preventing the functional use of additively manufactured parts. It delivers compelling performance with continuous carbon fiber reinforcement in 3D printed parts. Further study could extend the technique to any anisotropic manufacturing method, additive or otherwise.

In situ experimental study on mechanical properties of interlayer in roller compacted concrete (RCC) dam

Roller compacted concrete (RCC) is a kind of dry concrete widely used in the construction of large dams. As the weakest plane of the structure, the interlayer of the RCC dam is easy to deteriorate under the action of hydraulic shear load, geological action and environmental influence. Therefore, in this study, in combination with actual engineering, in-situ tests were carried out to study the shear properties of RCC interlayers under different cementing material treatments, different surface roughness, different exposure time and different stress. In addition, the failure modes were classified and analyzed, and the factors affecting the angle and depth of the plane undulation in the failed surface of RCC were summarized. The result shows that the shear strength of the RCC interlayer increases with the increase of normal stress. The increase of surface roughness results in better interlayer bonding and higher shear strength. After mortar treatment, the shear strength, cohesion and friction angle of the RCC layers are higher than those of the mortar treatment. The strength parameters of the RCC layer treated with cementing material are improved to a certain extent compared with that of the untreated layer. With the increase of layer exposure time, the interlayer strength parameters decreased gradually. The change of cementation between layers and the bite force of aggregate under different conditions is an important reason for the change of mechanical properties between layers of RCC. The experimental results are expected to enhance the understanding of the construction of hydraulic dams.

Experimental and numerical modelling of shear bonding between asphalt layers

Interlayers in asphalt pavements are potential structural damage initiators. In order to better understand the quantitative role of interlayer parameters, such as surface roughness, binder type, binder content and loading type on interlayer shear strength, this paper focuses on the effects of particle interlock and contact conditions on interlayer strength through experimental and numerical modelling. Experimentally, interlayer shear box strength tests on a model material consisting of stiff binder blended with steel balls are performed with and without normal force confinement. A Discrete Element method model of the test is developed using measurements of the model material for calibrating the contact law and for validating the model. It is shown that this model captures adequately the measured force-displacement response of the specimens. It is thus a feasible starting point for numerically and experimentally studying the role of binder and tack coat regarding interlayer shear strength of real asphalt layers.

Integrated modeling of heat transfer, shear rate, and viscosity for simulation-based characterization of polymer coalescence during material extrusion

The material extrusion process (MEX), also known as the fused filament fabrication process, has attracted attention in the manufacturing industry. A major obstacle to further application of the technology is the lack of mechanical strength due to the weak interlayer strength and poor coalescence between the adjacent beads. Understanding the effect of printing parameters on the coalescence of the adjacent beads is a step toward the improvement of the process. In this study, a novel two-phase flow numerical simulation approach coupled with heat transfer simulation has been applied to the high-viscosity polymers to determine the coalescence in the MEX process. The influence of printing temperature, substrate temperature, and the temperature of the printing chamber, as well as material deposition strategy (unidirectional and bidirectional) on the coalescence of the beads, has been investigated by numerical simulation and validated by experimental study. The modeling approach is applied to Glycerol, Polyether ether ketone (PEEK) and Polylactic acid (PLA). The results show that increasing temperature points (substrate temperature, chamber temperature, and printing temperature), increase the coalescence between the beads in the MEX process. The heat transfer model reveals that the cooling rate of the deposited bead in the MEX process is relatively high, and hence, the time window for reaching the coalescence between beads/layers is short. The heat transfer model also indicates that deposition of the further layers and beads does not influence the coalescence. The coalescence in the bidirectional deposition is higher compared to the unidirectional all conditions remaining similar. Unidirectional deposition leads to a uniform coalescence between the beads. However, the coalescence is not uniform for bidirectional deposition. The main novelty of this research is to simultaneously model heat transfer, shear rate and coalescence for numerical simulation to study the effect of printing parameters on the coalescence in the MEX process. Since the modeling of coalescence is time-consuming, two empirical equations based on obtained results have been proposed to predict the coalescence for PLA and PEEK separately.

Mode I interlaminar fracture characteristics of CNTs doped woven and unidirectional CFRP via acoustic emission

This paper investigates the delamination behavior of two composite structures with carbon nanotubes (CNTs). Double cantilever beam (DCB) samples with CNTs of different areal densities are adopted to analyze the toughening and damage mechanism via acoustic emission (AE) method. The result demonstrates that the CNT layer improves the fracture toughness of unidirectional (UD) sample interfaces effectively, but for the plain woven (PW) samples, only works on initial fracture toughness with low CNTs areal density. In addition, more AE events are recorded in the CNT modified samples than in the reference sample. Combined with the observation of the fracture surface and crack propagation path, the agglomeration with high content CNTs weakens the interlayer strength in PW samples, whereas the fracture toughness is significantly enhanced in UD composites due to the increase of the crack propagation path.

The Relationship Between Fiber Bundle Size and Mechanical Performance of Additively Manufactured Continuous Carbon Fiber Reinforced Thermoplastic Composites.

Additively manufactured continuous fiber-reinforced thermoplastic (CFRTP) composites are still in the early stages of reaching competitive mechanical properties compared with conventional composites. The main reason for this is that their mechanical properties are limited due to weak interlayer strength, porosity, and low fiber fraction. Therefore, the effects of many parameters, such as layer thickness, temperature, printing speed, and fiber fraction, have been extensively studied to improve mechanical properties. With a different perspective on these parameters, this study aimed to investigate the effect of fiber bundle size on the mechanical properties of CFRTP composites. For this purpose, 3K and 6K fiber bundle filaments with the same fiber volume fractions (∼41%) were produced utilizing a polymer impregnation setup. CFRTP samples were printed using fused deposition modeling with polylactic acid as the matrix. The mechanical properties were investigated via three-point bending, interlaminar shear strength (ILSS), and tensile tests. The results showed that fiber bundle size does not particularly influence tensile strength but dominates flexural and ILSS performance. Although increased flexural strength and modulus were observed, the bundle size effect was much more dominant in ILSS tests, and 6K bundle size samples with the same fiber fraction showed much higher strength.

Thermal post‐processing effects on the polycarbonate acrylonitrile butadiene styrene composites manufactured by fused filament fabrication

AbstractThe mechanical properties of components manufactured by fused filament fabrication lack sufficient levels for industrial applications. The need for post‐processing is, therefore, necessary to enhance the interlayer strength and mechanical characteristics. In the present study, experimental analysis of the effects of annealing on polycarbonate acrylonitrile butadiene styrene manufactured by fused filament fabrication is explored. Annealing temperatures are selected in the range from 90 to 210°C based on differential scanning calorimetry analysis. The ultimate tensile strength improved by 20.39% from 32.39 to 38.99 MPa after the heat treatment at 180°C for 1‐h duration. Flexural strength showed a remarkable enhancement of 53.21% after annealing at 180°C for 2 h. The interlayer diffusion and bonding are boosted following heat treatment and microstructural imaging proved the same although the surface had flakes due to the high heat exposure. X‐ray diffraction testing of annealed models demonstrated a maximum crystallinity index of 32.56% when compared with nonannealed samples with 6.58%. The addition of polycarbonate to acrylonitrile butadiene styrene improves the stiffness and impact loading capacity with high heat resistance. The heat treatment process is capable of magnifying the mechanical characteristics of the end functional components, thereby opening up the scope for more engineering applications.

3D concrete printing of eco-friendly geopolymer containing brick waste

This study investigates alkali-activated brick waste powder as the binder for developing 3D printable geopolymer mixes. The brick waste was used as a partial replacement to fly ash in geopolymer binders. The effect of brick waste content on the fresh properties of printable mixes, such as flow, setting time and rheological properties were investigated. Besides, the hardened properties of 3D printed brick waste geopolymer were evaluated with the varying brick waste content in the mix. The test results demonstrated that the fresh properties of 3D printable mixes were improved with the brick waste content in the mix. Compared to the control mix, the mixes containing brick waste displayed high yield strength and apparent viscosity at an early age. On the contrary, the hardened properties of compressive strength and interlayer strength of 3D printed concrete specimens were decreased with the high brick waste content; however, the incorporation of brick waste for up to 10% has enhanced the hardened properties. Finally, the sustainability assessment of brick waste geopolymer studied with embodied energy and carbon emission calculations reveals the proposed geopolymer concrete could reduce the embodied energy and carbon emission by up to 60–80%, compared to OPC concrete.

Design of welding manufacturing processes for gauze nets based products made of 12Kh18N10Т steel

Rational layout of nets and enhancement of solid-phase wire joints is shown to lead to the growth of the interlayer strength and effective thermal conductivity through the porous net materials thickness, and also to the anisotropy reduction in the sheet plane. It is established that the highest possible interlayer strength of blanks is achieved by the preliminary chemical etch of nets, increase of vacuum level, optimization of temperature and strain rate under solid-phase joint conditions. Manufacturing conditions of sheet porous net materials with high interlayer strength by diffusion welding and net roll welding in vacuum-treated envelopes are found. Manufacturing procedures of argon-arc welding and electron-beam welding for liners of vaporizer-exchangers and stamp-welded filters for the liquid purification of mechanical impurities are elaborated.

Influence of microwave electromagnetic field on interlayer strength in cured polymer composite materials

It has been established that exposure to a microwave electromagnetic field with an energy flux density that is rational for each type of composite (carbon-, glass-, organoplastic) contributes to an increase in the specific work of delamination by 18.6%, 12% and 20%, respectively, which satisfactorily correlates with an increase in strength of these materials under three-point bending and interlaminar shear. Keywords: carbon fiber reinforced plastics, fiberglass plastics, organoplastics, delamination, microwave electromagnetic field.

A Review of Research Progress on Machining Carbon Fiber-Reinforced Composites with Lasers.

Carbon fiber-reinforced composites are widely used in automobile, aerospace and military lightweight manufacturing due to their excellent mechanical properties such as light weight, excellent fracture resistance, corrosion resistance and wear resistance, etc. However, because of their high hardness, anisotropy and low interlayer strength characteristics, there are many problems with machine carbon fiber-reinforced composites with traditional methods. As a non-contact processing technology, laser machining technology has lots of advantages in carbon fiber-reinforced composites processing. However, there are also some defects produced in laser machining process such the heat affected zone, delamination and fiber extraction due to the great difference of physical properties between the carbon fibers and the resin matrix. To improve the quality of carbon fiber-reinforced composites laser machining, lots of works have been carried out. In this paper, the research progress of carbon fiber-reinforced composites laser machining parameters optimization and numerical simulation was summarized, the characteristics of laser cutting carbon fiber-reinforced composites and cutting quality influence factors were discussed, and the developing trend of the carbon fiber-reinforced composites laser cutting was prospected.

Rheology, crystallization, and process conditions: The effect on interlayer properties in three-dimensional printing

Semicrystalline polymers are an attractive feedstock choice for material extrusion (MatEx)-based three-dimensional printing processes. However, the printed parts often exhibit poor mechanical properties due to weak interlayer strength thereby limiting the widespread adoption of MatEx. Improved interlayer strength in the printed parts can be achieved through a combination of process parameter selection and material modification but a physics-based understanding of the underlying mechanism is not well understood. Furthermore, the localized thermal history experienced by the prints can significantly influence the strength of the interlayer welds. In this work, a combined experimental and modeling approach has been employed to highlight the relative impact of rheology, non-isothermal crystallization kinetics, and print geometry on the interlayer strength of printed parts of two semicrystalline polymers, namely, polylactic acid (PLA) and polypropylene (PP). Specifically, the print properties have been characterized as a function of print temperature and print speed. In the case of single road width wall (SRWW) PLA prints, the total crystalline fraction increases due to the broadening of the crystallization window at higher print temperatures and lower print speeds. The results are substantiated by the constitutive modeling results that account for the effects of quiescent crystallization. However, SRWW PP prints display a reduction in the interlayer properties with temperature likely due to significant flow-induced crystallization effects, as suggested by the model. Interestingly, in the case of multilayer PP prints, the repeated heating/cooling cycles encountered during printing counteracts the flow-induced effects leading to an increase in mechanical properties with print temperature consistent with SRWW PLA prints.