Multilayer Specimens Research Articles

Analyzing the permeability distribution of multilayered specimens using pulsed eddy-current testing with multi-scale 1D-ResNet

The mechanical properties of steel are determined by its microstructure, which is closely related to its permeability profile. In thermal processing, layered structures are formed in steel and different layers have different mechanical and magnetic properties. Therefore, it is crucial to propose a practical method to monitor the change of permeability profile along the depth, which can indicate the evolution of the microstructure of steel during thermal processing, such as hot rolling. This paper presents a method for determining the layered structure and permeability profile of the steel by using pulsed eddy current testing (PECT), which offers better penetration ability. An analytical model has been deduced for calculating the time-domain pulsed eddy current (PEC) response from a Hall sensor of a triple-layer conductor system based on the inverse Laplace transform. It is found the Tau (τ) curve is closely related to the permeability profile of the conductor. For the inverse solution, the Simultaneous Iterative Reconstruction Technique (SIRT) is utilized to determine the permeability profile of the multilayered specimens from the measured response. The approximate Jacobian matrix (sensitivity matrix) is obtained by the perturbation method based on the Tau curve. However, the permeability profile suffers from smoothing effect and sharp features are lost. Deep learning (DL) algorithm based on the Multi-Scale 1D-ResNet model is therefore introduced to address this issue. Numerical simulations and experiments have been performed to evaluate the proposed method for permeability profile estimation with various materials and thicknesses. The DL method can achieve an accurate estimation of the plate permeability profile with a relative error under 5%.

Influence of mechanical anchors on bond performance of fiber fabric-steel joints

This study proposes an experimental model for anchor reinforcement and conducts uniaxial static tensile tests. The influence of anchor reinforcement on the failure mode of specimens is revealed. This includes the effects of bond length, number of layers, and types of fiber fabric under anchor reinforcement on the ultimate bearing capacity and bond-slip curve. The results demonstrate that anchors can effectively increase the ultimate bearing capacity of the test specimens. There are differences in bond-slip behavior between the anchors near the free end and the joint end. Higher stresses are experienced near the joint end. The use of anchor reinforcement can significantly enhance the load-bearing capacity of multi-layer carbon fiber specimens. Increasing the number of anchors and reducing the distance between the anchor and the joint end can further improve the stiffness of the specimens. A finite element model is established using ANSYS, which agrees well with the experimental results and parameterized analysis results reveal a linear increase in load-bearing capacity and stiffness with higher anchor bolt preload, achieving an 84.42 % increase at 11kN. Increased preload enhances friction at the carbon fiber-steel interface, reducing deformation. Similarly, expanding anchor width from 9 mm to 39 mm improves load-bearing capacity by 54.28 %, with larger anchors significantly boosting stiffness and bonding performance, which can be used to predict the mechanical properties of fiber fabric-steel reinforced by anchors.

Comparative analysis of mechanical properties enhancement in SCM440 through similar and dissimilar material deposition using directed energy deposition method

The Directed Energy Deposition (DED) method, which utilizes metal powder and a high-powder laser directed at specific locations on a substrate, is employed across various fields for repairing and refurbishing existing parts. In this study, two types of multi-materials were fabricated by depositing materials similar in alloy composition, and dissimilar, respectively, on an SCM440 substrate using the DED method. Unlike similar material, depositing the dissimilar material resulted in a recrystallized fine microstructure in the interlayer region, which enhanced the tensile properties of the multi-layer specimens. The yield strength, tensile strength, and elongation of the multi-layer specimen with similar material were 562 MPa, 787 MPa, and 14%, respectively, while those of the specimen with dissimilar material were significantly higher at 934 MPa, 1016 MPa, and 30%. These results demonstrate that using dissimilar materials, rather than identical or similar compositions, can improve the tensile properties when repairing and refurbishing parts made of SCM440 material.

Does the internal surface treatment technique for enhanced bonding affect the color, transparency, and surface roughness of ultra-transparent zirconia?

To investigate the effects of different surface treatments and thicknesses on the color, transparency, and surface roughness of ultra-transparent zirconia. A total of 120 Katana ultra-translucent multi-layered zirconia specimens were divided into 12 groups according to the thickness (0.3, 0.5, and 0.7mm) and surface treatment (control, airborne particle abrasion [APA], lithium disilicate coating, and glaze on). Color difference (ΔE00) and relative translucency parameter (RTP00) were calculated using a digital spectrophotometer. The surface roughness (Ra, Rq, Sa, and Sq) was measured using a non-contact profile scanner. The surface morphologies and microstructures of the samples were observed using a tungsten filament scanning electron microscope. Statistical analyses were performed by one-way and two-way analysis of variance (ANOVA) followed by post hoc multiple comparisons and Pearson's correlation (α = 0.05). The results showed that the surface treatment, ceramic thickness, and their interactions had significant effects on ΔE00 and RTP00 (p < 0.001). The surface treatment significantly altered the micromorphology and increased the surface roughness of the ceramic samples. APA exhibited the lowest transparency, largest color difference, and highest surface roughness. Zirconia with 0.3mm and 0.7mm thicknesses showed strong negative correlations between Sa and RTP00. The three internal surface treatments significantly altered the surface roughness, color difference, and transparency of ultra-transparent zirconia. As the thickness increased, the influence of the inner surface treatment on the color difference and transparency of zirconia decreased. For new zirconia internal surface treatment technologies, in addition to considering the enhancement effect on the bonding properties, the potential effects on the color and translucency of high-transparency zirconia should also be considered. Appropriately increasing the thickness of zirconia restorations helps minimize the effect of surface treatment on the optical properties.

High-performance functional coatings manufactured by integrated extremely high-speed-rate laser directed energy deposition with interlayer remelting

Extremely high-speed-rate laser directed energy deposition has attracted considerable attention for large-scale industrial component manufacturing owing to its outstanding fabrication efficiency. However, interlayer metallurgical defects and thickness fluctuation stacking caused by the previous non-uniform rough surface layer hinder the preparation of customized thicknesses of large-scale components with high performance. Herein, an integrated extremely high-speed-rate additive manufacturing technology, that is, extremely high-speed-rate laser-directed energy deposition accompanied by extremely high-speed-rate laser remelting, is proposed to eliminate porosity and reconstruct the microstructure of multilayer parts. The remelted specimens exhibited uniform roughness and ultrafine grains when defocusing amount was less than zero. The relatively lower temperature gradient G and morphology factor G/R in the remelting process led to more favorable subcooling, which further promoted more nucleation sites and contributed to grain refinement and columnar-to-equiaxed transition. A multilayer 316 L stainless steel material with an interlayer remelting treatment was further prepared, and a typical heterogeneous structure dominated by ultrafine equiaxed grains was obtained. The multilayer specimen characterized by such a special structure exhibited a higher yield strength of 546 MPa, along with a ductility of 49.1 %. This novel integrated manufacturing technology highlights a new strategy that can expand the extremely high-speed-rate additive manufacturing window and achieve simultaneous improvements in the manufacturing efficiency and performance of large-scale components.

Development of Hot-Wire Laser Additive Manufacturing for Dissimilar Materials of Stainless Steel/Aluminum Alloys

The formation of brittle intermetallic compounds (IMCs) at the interface between dissimilar materials causes considerable problems. In this study, a multi-material additive manufacturing technique that employs a diode laser and the hot-wire method was developed for stainless steel/aluminum alloys. An Al-Mg aluminum alloy filler wire (JIS 5183-WY) was fed on an austenitic stainless-steel plate (JIS SUS304) while varying the laser power and process speed and using paste-type flux and flux-cored wire. The effects of laser power and process speed on phenomena during manufacturing and IMC formation were investigated. Finally, the wall-type multilayer specimens were fabricated under optimized conditions. The suppression of IMC formation to a thickness of less than 2 μm was achieved in the specimens, along with a high interfacial strength of over 120 MPa on average.

Ultrasonic phased array imaging of multi-layered structures using full-matrix migration and normalized cross-correlation matching technique

Multi-layered structures play a critical role in aerospace, automotive and electrical industries, so the non-destructive evaluation and maintenance of such structures must be accurate and rapid. The application of conventional ultrasonic phased array imaging methods is limited due to computational complexity, image quality and image size. In this paper, we proposed a cost-effective, high-quality imaging method that uses full-matrix migration total focus method (FM-TFM) and produces large-area scanned image with the aid of normalized cross-correlation (NCC) template matching technique. The FM-TFM method eliminated the need for iterative refraction point calculations by using full matrix migration extrapolation, and the optimization of NCC was also investigated in the study. The verification was divided into two parts, fixed transducer experiment and manual scanned experiment, to demonstrate the advantages of FM-TFM with improved SNR (22 % or greater) and one order of magnitude reduction in computational time when compared to ray tracing total focus method (RT-TFM) and NCC matching accuracy of multilayer specimen, respectively. The proposed method can help eliminate the need for costly scanning equipment and shows great potential for extension to other TFM-based approaches.

The impact of interfacial characteristics on the interfacial properties of 316 L/CuSn10 multi-material manufactured by laser powder bed fusion

Multi-material additive manufacturing (MMAM) enables the simultaneous creation of multi-material components in a single process, accomplishing customized different performances in specific regions of the same components. In particular, the copper-steel multi-material structure can provide considerable strength and high thermal conductivity, thus playing a crucial role in electronic components, heat exchangers and injection molds. However, few studies have explored the relationship between the microstructure and properties of the copper-steel fusion zone. Therefore, this study aims to reveal the heterogeneous evolution of the microstructure in the copper/steel fusion zone and its impact on the interfacial properties of 316 L/CuSn10 multi-material structure fabricated by laser powder bed fusion (L-PBF). We characterized the multi-layer specimens using laser confocal microscopy and SEM to obtain the macroscopic and microscopic microstructure, liquid metal embrittlement (LME) microcrack characteristics and precipitation evolution of the copper-steel fusion zone. The generation of liquid phase separation (LPS) was explored based on block specimens, and the textural characteristics of the fusion zone were analyzed using EBSD. As a result, because of multiple element precipitation and the high thermal conductivity of copper alloy, abrupt grain size changes occur in the fusion zone, affecting the fusion zone's corrosion resistance and nano-hardness. In tensile tests analyzing the anisotropy, the results show that LME microcracks have little impact on the interfacial bonding properties of the copper-steel bimetallic structure, among which the ultimate tensile strength of the specimens formed at 30° to the substrate reached a maximum of 562.9 MPa. These findings add substantially to our understanding of the relationship between the microstructure and properties of copper-steel bimetallic interface, and provide a theoretical reference for additive manufacturing copper-steel multi-material components.

Reduction in the transport of sour gases and hydrocarbons to underlying PE-RT through thin films of PVDF

Raised temperature polyethylene (PE-RT) is being studied for use in the conveyancing of sour hydrocarbon fluids in spoolable composite pipe at temperatures above 90 °C. This grade of polyethylene swells on exposure to all hydrocarbons but specifically aromatic hydrocarbons and so there is a requirement to reduce the flux of hydrocarbons and gases into the base PE-RT. A multi-material pipe wall is one solution to reduce these fluxes but new experimental methods are required for design and validation while saturated in sour hydrocarbon fluids.In this study the simultaneous transport of species such as CO2, H2S, CH4, water vapour and aromatic hydrocarbon vapours such as toluene, xylene, IRM902 and cyclohexane were measured in real time through single films of PVDF and PE-RT and multilayer walls of PVDF/tie layer(s)/PE-RT extracted from a built (co-extruded) pipe section. The permeation test facility contained specialized gas chromatographs modified for continuous quantification of all species. The experimental methods were designed to run at 93 °C with gas pressures of 104 barg or 250 barg. Experiments were run with gas only mixtures (dry tests) and also with gas cap above a mixture of liquid hydrocarbons and water (wet tests). When possible, transport properties such as diffusion and solubility coefficients were derived from the permeation traces. The volume flow rate of all species was higher through PE-RT compared to PVDF and the volume flow rate for CO2, H2S, and CH4, increased when the gas pressure was increased from 104 to 250 barg. The gas permeability was calculated for the base polymers and also the combined multilayer structure. The flow rates estimated for a multilayer specimen using the values measured on individual films were confirmed experimentally. A simple mathematical model was proposed to derive the apparent permeability of the multilayer system and the steady-state concentration profiles across the specimen wall. Specimens were inspected for damage after a final depressurization at 70 bargmin−1. Post exposure assessment of the laminates showed that the adhesion levels were improved and the failure mode was altered from adhesive to cohesive on ageing.

Processing of Carbon Nanoparticle-Enriched AISI H11 Tool Steel Powder Mixtures in DED-LB/M for the AM of Forging Tools with Tailored Properties (Part II): Influence of Nanoscale Carbon Additives on Microstructure and Mechanical Properties

A promising approach for producing parts with outstanding properties in directed energy deposition (DED-LB/M) provides the application of tailored powder mixtures processed by applying in situ alloying strategies. In this work, DED-LB/M was used to manufacture multilayer specimens from AISI H11 steel powders enriched with carbon nanoparticles (C-np) in concentrations of 0.1 wt.-% and 0.2 wt.-%. The scientific aim was to investigate the impact of C-np on the microstructural (particularly retained austenite content (RA-c) and grain size) and mechanical properties (specifically hardness and compression yield strength) of the manufactured specimens. It was shown that the addition of C-np to the H11 powder leads to a stronger distortion of martensite as well as significantly enhancing the RA-c. Furthermore, the C-np seem to favor the formation of finer martensite, as can be verified with XRD and EBSD. Under as-built conditions, the mean hardness increases from 653 ± 10 HV1 for the H11 sample to 770 ± 14 HV1 for the sample reinforced with 0.2 wt.-% C-np. At the same time, Y0.2% rises up from 1839 ± 61 MPa to 2134 ± 68 MPa. The hardness- and strength-increasing effect of the added C-np is retained even after heat treatment, similarly to the industrial standard.

J integral strain-curvature approach for multilayer fracture specimens with unknown thickness and stiffness of layers

In the coming years, many wind turbines will reach their planned design life, and it is of great interest to investigate if their service life can be extended so that the turbines can produce a larger amount of electricity before decommissioning. Such an assessment can include the measurement of the fracture mechanics properties of materials interfaces, e.g., for trailing edge bondlines, web foot bondlines and interfaces between layers in the load-carrying main spars. It would then be preferable to conduct the fracture mechanics testing and data analysis by approaches that give accurate results with the smallest amount of testing. In the present work we propose an approach for measurement of mixed mode fracture resistance (and mixed cohesive laws) that does not require knowledge of the stiffness properties and the elastic centre of the laminates of the test specimens. This is advantageous since the layer stiffness, layer thickness and the lay-up of a laminate cut from an old blade may not be known. Furthermore, the elastic properties of polymer resins of bondlines and matrix materials in fibre composites can have changed (aging) due to the blades long-time environmental exposure.

Effect of CAD/CAM Position and Thickness of Ultra-Translucent Multilayered Zirconia on Color Aspects.

Ultra-translucent multilayered zirconia restorations fabricated using computer-aided design and computer-aided manufacturing (CAD/CAM) technology have recently gained popularity. Their esthetic appeal is crucially dependent on the color accuracy, influenced by prosthesis thickness and multilayer composition due to CAD/CAM milling positions. This study comprehensively investigated how these two factors impacted color accuracy, thereby enhancing our understanding of color outcomes. One hundred monolithic multilayer zirconia specimens with 10 × 10 mm square shape were milled in four different positions and five different thicknesses (1.0, 1.5, 2.0, 2.5, and 3.0 mm). The specimens were placed on an A3 shade resin composite substrate, and CIELAB values (L ∗, a ∗, and b ∗) were measured using a spectrophotometer. Delta E (ΔE) values were calculated to quantify the color differences between the specimens and the A3 VITA classical shade tab and compared with the perceptibility and acceptability thresholds of ΔE = 1.2 and 2.7, respectively. Pearson correlation, two-way ANOVA, and Tukey multiple comparisons (α = 0.05) were performed. The proportion of the dentin layer was positively correlated with the a ∗ and b ∗ values, while specimen thickness was positively correlated with the a ∗ value and negatively correlated with the L ∗ and b ∗ values. Significant difference in ΔE value due to different CAD/CAM positions was not observed within the same specimen thickness. Perceptible color differences were observed in specimens with thicknesses greater than 1 mm, while specimens with 1 mm thickness fell within the clinically acceptable range. Highest ΔE value was found in the specimen with 1 mm thickness. Different compositions of multilayers in the final restoration due to different CAD/CAM positions do not significantly affect the color appearance of ultra-translucent multilayer zirconia, with color only influenced by specimen thickness.

Interlayer Tailoring of Ti-6Al-4V and 17-4PH Stainless Steel Joint by Tungsten Inert Gas Welding.

The development of robust and efficient methods for constructing and joining complex metal specimens with high bonding quality and durability is of paramount importance for various industries, e.g., aerospace, deep space, and automobiles. This study investigated the fabrication and characterization of two types of multilayered specimens prepared by tungsten inert gas (TIG) welding: Ti-6Al-4V/V/Cu/Monel400/17-4PH (Specimen 1) and Ti-6Al-4V/Nb/Ni-Ti/Ni-Cr/17-4PH (Specimen 2). The specimens were fabricated by depositing individual layers of each material onto a Ti-6Al-4V base plate, and subsequently welding them to the 17-4PH steel. The specimens exhibited an effective internal bonding without any cracks, accompanied by a high tensile strength, with Specimen 1 exhibiting a significantly higher tensile strength than Specimen 2. However, the substantial interlayer penetration of Fe and Ni in the Cu and Monel layers of Specimen 1 and the diffusion of Ti along the Nb and Ni-Ti layers in Specimen 2 resulted in a nonuniform elemental distribution, raising concerns about the lamination quality. This study successfully achieved elemental separation of Fe/Ti and V/Fe, which is vital for preventing the formation of detrimental intermetallic compounds, particularly in the fabrication of complex multilayered specimens, representing the prime novelty of this work. Our study highlights the potential of TIG welding for the fabrication of complex specimens with high bonding quality and durability.

Improving efficiency of local wavenumber estimation for damage detection in thin-walled structures

Full-field imaging of guided ultrasonic waves is an emerging Nondestructive Testing (NDT) technique for the inspection of thin-walled structures. One of the most effective full-field processing techniques is the Local Wavenumber Estimation (LWE) which can be applied to detect various types of damage in both homogeneous and multilayer specimens. In this paper, we discuss the possibilities for optimizing the efficiency of the LWE algorithm to facilitate its practical applications. We propose several different signal processing approaches to optimize the algorithm's computational efficiency without sacrificing the damage imaging quality. We evaluate the influence of these improvements by measuring the computation time necessary to perform particular processing steps of the LWE process. We also provide the implementation guidelines for the proposed optimization techniques. The proposed improvements allow for a considerable reduction in the processing time of the LWE with respect to the baseline implementation of the algorithm, ranging from a factor of 10 to a factor of 24, depending on the input dataset.

Color match of ultra-translucency multilayer zirconia restorations with different designs and backgrounds.

The purpose of this in vitro study was to assess the color match of ultra-translucency multilayer zirconia restorations with different designs and backgrounds. Thirty ultra-translucency multilayer zirconia crown specimens were made in VITA classical shade B2 for a prepared maxillary central incisor. The specimens were divided into three groups based on the restoration design: veneered zirconia with a trestle design (VZT), veneered zirconia with a dentin core design (VZD), and full-contour zirconia (FCZ). In the groups VZT and VZD, the zirconia specimens were layered with a feldspathic veneering ceramic. The specimens were seated on five different backgrounds: shade B2 composite resin, shade B2 zirconia, copper-colored metal alloy, silver-colored metal alloy, and the prepared central incisor. CIELab values of the labial middle sections of the crown specimens were measured with a spectrophotometer. Color differences between the specimens and a shade B2 VITA classical tab (as a control) were calculated from the ΔE* ab formula and compared with an acceptability threshold (ΔE* ab=3.7) to be clinically explicated. Mean ΔE* ab values ranged between 1.17 and 8.48. The restoration design, the background type, and their interaction affected the ΔE* ab (p<0.001). The mean ΔE* ab values for VZT with all backgrounds and for VZD with the silver-colored metal background were greater than the threshold (p<0.001), whereas the mean ΔE* ab values for VZD with the other backgrounds and FCZ with all backgrounds were less than the threshold (p=1). Restoration design and background type affected the color match of ultra-translucency multilayer zirconia restorations. VZT restorations on all backgrounds and VZD restorations on a silver-colored metal background showed color mismatches. However, VZD restorations on the other backgrounds and FCZ restorations on all backgrounds demonstrated color matches.

Laser shock-wave adhesion test (LaSAT) and ab initio calculations for adhesive strength evaluation of thin metallic films

In electronic devices, thin metallic films are generally deposited on brittle substrates such as silicon and quartz glass, which are chemically stable. As interfacial delamination causes the functional degradation of these materials, it is imperative to quantitatively evaluate their adhesion strength. In this study, Laser Shock-wave Adhesion Test (LaSAT) was developed, which could be performed in a non-contact manner. However, such brittle substrates are extremely weak under impact loading, making it difficult to conduct general LaSAT. Therefore, a multilayer specimen is developed to enable LaSAT, which successfully generates exfoliation of thin films from fused quartz substrates. The critical laser energy at which exfoliation occurred on various films was determined, and adhesion strength was quantitatively evaluated. In addition, to elucidate the delamination mechanism, the interface was modeled using first-principles calculations to clarify adhesion strength behavior.

Modelling and validation of the non-linear elastic stress–strain behaviour of multi-layer silicone composites

Multi-layer silicone composites are commonly used to mold deformable silicone vocal folds replicas. Nevertheless, so far the stress–strain characterisation of such composite specimens is limited to their effective Young’s modulus (up to 40 kPa) characterising the elastic low-strain range, i.e. up to about 0.3. Therefore, in this work, the characterisation is extended to account for the non-linear strain range. Stress–strain curves on 6 single-layer and 34 multi-layer silicone specimens, with different layer stacking (serial, parallel, combined or arbitrary), are measured at room temperature using uni-axial tensile tests for strains up to 1.36, which amounts to about 4.5 times the extent of the linear low-strain range. Cubic polynomial and exponential two-parameter relationships are shown to provide accurate continuous fits (coefficient of determination R2≥99%) of the measured stress–strain data. It is then shown that the parameters can be a priori modelled as a constant or as a linear function of the effective low-strain Young’s modulus for strains up to 1.55, i.e. 5 times the low-strain range. These a priori modelled parameter are confirmed by approximations of the best fit parameters for all assessed specimens as a function of the low-strain Young’s modulus. Thus, the continuous stress–strain behaviour up to 1.55 can be predicted analytically from the effective low-strain Young’s modulus either using the modelled parameters (R2≥85%) or the approximations of the best fit parameter sets (R2≥94%). Accurate stress–strain predictions are particularly useful for the design of composites with different composition and stacking. In addition, analytical expressions of the linear high-strain Young’s modulus and the linear high-strain onset, again as a function of the effective low-strain Young’s modulus, are formulated as well.

Semi-solid wire-feed additive manufacturing of AlSi7Mg by direct induction heating

• Demonstration of an induction heating based additive manufacturing process. • The novel process enables high speed additive manufacturing with build rates of around 20 mm 3 /s (0.054 g/s). • Adaptation of induction power during the process allows multilayer specimen fabrication. • Defects in the novel process are analysed for the first time using µCT to pave the way for their future prevention. In this study, a novel process is presented in which direct induction heating with frequencies in the MHz range is used for the wire-feed additive manufacturing of the alloy AlSi7Mg. The high frequency of 1.5 MHz enables processing of 1.2 mm diameter wires without the need for indirect heating via a nozzle. The feasibility of the process is proven by the experimental identification of a proper process window regarding the influential parameters such as the distance between inductor and substrate, induction power and wire feed rate for the fabrication of single layers. Furthermore, a strategy for the successful fabrication of multi-layered cubes is developed. The microstructure of the cubes exhibits a characteristic variation along the build direction. Micro-computed tomography is used to reveal defects like lack of fusion and spherical pores in test cubes. The presented results are used to derive possible process improvements, which will allow the novel process to be used as a fast and powder-free alternative metal additive manufacturing route in future.

Concept of Sustainable Demolition Process for Brickwork Buildings with Expanded Polystyrene Foam Insulation Using Mealworms of Tenebrio molitor.

The traditional demolition process for brickwork buildings results in a significant volume of mixed debris. The debris consists of ceramic bricks (and other wall elements), mortar, thermal insulation (usually expanded polystyrene or rockwool), smaller steel elements, pieces of wood, and glass. Such mixed debris is difficult to recycle. Separating thermal insulation that is "glued" by cement mortar to brickwork is probably the most difficult and time-consuming task in processing mixed debris. This task can be performed in a very different and fully "automatized" manner using Tenebrio molitor mealworms. The mealworms remove expanded polystyrene from brickwork surfaces and transform it into frass. In the paper, a research program aiming to prove the concept of using the mealworms of Tenebrio molitor for processing mixed debris is presented. The tests were conducted using two models of a three-layered brickwork wall, which is very common in Europe. The proposed approached was successful. Both types of used expanded polystyrene foam (EPS) were fully removed from multilayer wall specimens. The possibilities and limitations of the proposed processing method were discussed and analyzed. The conducted research proved that it is feasible to clean brickwork debris from the EPS using Tenebrio molitor mealworms. Differences in the speed of cleaning process regarding the type of EPS were noted. More research is needed to scale the process, and to find the best method for using frass. By using Tenebrio molitor mealworms, one can make the demolition process much cleaner.

The effects of toolpath and glass fiber reinforcement on bond strength and dimensional accuracy in material extrusion of a hot melt adhesive

In this work, a polyamide hot melt adhesive (Technomelt PA 6910) and its glass fiber-filled composite (Loctite 3D 6910) were evaluated as feedstocks for desktop-scale thermally-driven material extrusion additive manufacturing (AM). Technomelt PA 6910 is a semicrystalline polymer with a sub-ambient glass transition temperature, intermediate melting temperature, and low recrystallization temperature. This paper aims to study the effect of glass fibers and toolpath on mechanical properties, warpage, and dimensional accuracy of prints. Glass fibers improved the yield strength of 0° raster angle bars, but reduced the strength of 90° raster angle samples. The reduced weld strength was more significant in samples cut from single road width boxes than multilayer (≈3.2 mm thick) specimens due to fast cooling of thin parts. Glass fibers prevented warpage and excessive spread of initial layers of boxes. Toolpath affected tensile properties for Technomelt PA 6910, in which longer toolpaths resulted in higher warpage and decreased tensile strength of parts due to longer layer times, but did not affect tensile properties for Loctite 3D 6910. While Technomelt PA 6910 exhibits isotropic tensile properties, the addition of glass fibers resulted in anisotropic properties of Loctite 3D 6910 bars, which was more significant in single road (≈0.4 mm thick) parts. Multilayer Loctite 3D 6910 structures are stronger, which makes this material more appropriate for larger scale applications in which there is a high thermal mass and slumping is a significant printing challenge.