Extrusion Conditions Research Articles

Manufacture of Biomimetic Auricular Surgical Implants Using 3D Printed High Density Polyethylene Microfibers

AbstractThis study demonstrates a new approach to manufacturing biomimetic auricular surgical implants using melt electrowriting (MEW) technology to fabricate microfiber high‐density polyethylene (HDPE) scaffolds. An emerging filament‐driven printhead and MEW printer, termed the “MEWron”, is used to enable precise control over the material extrusion process and fiber formation. By predicting the optimal extrusion conditions, continuous and uninterrupted fiber production is achieved, enabling further optimization of filament‐driven MEW fibers with a diameter of 60.5 ± 2.6 µm. As a case study, an application of microfiber HDPE fabrication is selected that comprised the design and fabrication of personalized auricular (ear) surgical implants, specifically tailored to match the unique morphology of individual patients. Patient‐specific implant models matched to the natural shape and structure of the human ear are successfully fabricated. Furthermore, the manufactured implants exhibit excellent mechanical properties, offering a 13‐fold increase in tensile stiffness compared to MEW PCL scaffolds. Overall, this research demonstrates the feasibility and potential of MEW‐based HDPE implants as a promising alternative to traditional auricular reconstruction methods, offering an alternative avenue for improved patient outcomes and enhanced aesthetic results.

Extrapolation of classical rheometry of plant protein pastes to extrusion conditions

This study explores alternative methods to measure the rheology of pastes based on soy and pea proteins, which are commonly used as starting material in extrusion for the preparation of meat analogs. Currently, it is still a challenge to obtain consistent rheological data on such materials for steady shear at conditions that are relevant for the extrusion of such systems. Hence, possibilities are explored for the extrapolation of results obtained with classical rheometers operating at temperatures below boiling point, to conditions that are relevant for the extrusion of such systems. The above was combined, with findings from off-line and in-line capillary rheometers, which can provide steady shear measurements above boiling point and at hydration levels as used in extrusion.We have analysed the consistency of our new results with previous oscillatory shear measurements, performed at conditions similar to those of meat analog extrusion. For validation of the extrapolation we have analysed whether the new rheology data follow similar scaling rules. As classical rheometers can handle only moderate torques, the measurements are limited to hydration levels higher than those used in extrusion (75–85%). Despite this limitation, strain sweeps with classical rheometers show that in this regime the elastic modulus also scales with Tg/T, the ratio of glass transition, and actual temperature. Yet, its dependency on Tg/T appears differently from measurements performed at extrusion-like conditions. Moreover, our current results indicate a strong thixotropic nature of plant protein pastes at temperatures below boiling point. Consequently, flow curves are only stable if performed from high to low shear rates. Nevertheless, our data can be mapped to a single master curve following the Herschel-Bulkley model, with parameters also following a scaling rule dependent on Tg/T.This Tg/T scaling is used to construct master curves with data from the off-line and in-line capillary rheometers. The obtained shift factors for the flow curves are in agreement with old literature data obtained for SPI, but they deviate significantly from our steady shear measurements with classical rheometers. Based on the results of our current and previous study we have a critical, general discussion on the possibility of extrapolation of classical rheometry of plant protein pastes to process conditions used for production of meat analogs.

Impact of protein blend formulation and extrusion conditions on the physical properties of texturised pea protein‐extended beef burgers

SummaryThis study aimed to assess the physical properties of pea‐based texturised vegetable proteins (TVPs) and TVP function as a meat extender (20%–40% w/w) in beef burgers. TVPs were produced with varying protein blend formulas (PBFs) (70%, 76%, 82% protein on a dry basis), extrusion screw speeds (350–450 r.p.m.) and feed moisture contents (FMCs) (38% and 42%, db). Increasing PBF raised TVP hydration time and integrity index, while FMC and screw speed had no discernable trend on these properties. A select group of TVPs were applied as extenders in beef burgers which were tested for their cooking properties and textural quality. Higher FMC lowered total cooking loss (TCL) for some burgers but overall did not impact burger cooking properties or texture. Increasing the extension level reduced TCL and change in burger diameter (CBD). TVPs produced at the lowest PBF and higher FMC studied had the greatest potential in meat extender applications, as they decreased TCL and CBD while maintaining comparable texture to burgers without TVP addition. These lower protein TVPs with enhanced cooking quality can be economically advantageous for the vegetarian and flexitarian applications of plant‐based extenders.

Effects of Process Variables on the Physicochemical, Textural, and Structural Properties of an Isolated Pea Protein-Based High-Moisture Meat Analog.

This study investigated the optimal extrusion conditions required to produce an isolated pea protein (IPP)-based meat analog. High-moisture extrusion cooking (HMEC) was performed. The effects of the moisture content (55 and 60%), barrel temperature (165 and 175 °C), and screw speed (150 and 200 rpm) on the physicochemical, textural, and structural properties of the high-moisture meat analog (HMMA) were determined. The results showed that the moisture content had a significant effect (p < 0.05) on the physicochemical and textural properties of the HMMA. A lower moisture content had significant impact (p < 0.05) on enhancing the texturization of the HMMA and the formation of fibrous structures, thereby increasing the texture profile analysis (TPA) and cutting strength of the HMMA. Protein denaturation during HMEC resulted in a lower protein solubility of the meat analog than the raw material. The content of β-sheets and β-turns in the meat analogs were higher than that in the raw material, while the content of random coils and α-helices is inversely proportional. The process variables had no significant (p > 0.05) effect on the secondary structures. In conclusion, the moisture content is the most important factor affecting the properties of HMMAs. The extrusion process variables for HMMAs are a moisture content of 55%, a barrel temperature of 175 °C, and a screw speed of 200 rpm.

Influence of elevated temperature and high pressure treatments on structural changes of soy protein concentrate

This study focused on investigating the influence of elevated temperature (95–140 °C) and high pressure treatments (30–6000 bar) in different model process systems on protein-protein interactions, particularly in the domain of high-moisture extrusion (HME) conditions, with a specific emphasis on plant-based proteins. The effects of thermomechanical treatments on soy protein concentrate (SPC) were examined at different scales. Macroscopic analysis showed structural changes only at heat treatments exceeding 95 °C, while the application of high pressure alongside elevated temperature treatments did not result in additional changes. On a microscopic scale, protein melting occurred at temperatures above 95 °C, leading to alterations in tertiary and secondary protein structures. For significant protein denaturation and structure formation, a material-temperature threshold of 120 °C for 60% moistened SPC was required. This study sheds light on the key parameters influencing texturization complexity during elevated temperature and high pressure processes like HME. The findings enhance our understanding of protein texturization mechanisms under these conditions.

The effect of extrusion condition and blend proportion on the physicochemical and sensory attributes of teff-soybean composite flour gluten free extrudates

The effects of soybean-to-teff ratio (SB), feed moisture content (FM) and barrel temperature (BT) on physico-chemical properties and sensory attributes of extruded product from teff-soybean flour blend was studied. Increase in BT resulted in increase in expansion ratio(ER), water absorption index (WAI), and water solubility index (WSI) whereas the bulk density (BD) and hardness decreased with increase in BT. Increase in the proportion of SB resulted in increased BD, hardness, and reduced water solubility index (WSI) and sensory scores. Three principal components explained 89.1 % of the variations where the first (PC1), the second (PC2) and the third (PC3) principal components explained 62.4, 20.2 and 6.5 % of the variations respectively. BD, WAI and Hardness are strongly and positively associated with each other whereas they are negatively associated with WSI, crispiness, Specific length (Lsp) and ER. Graphical optimization gave best results for BT between 128 and 137 °C and SB proportion between 2 and 7.3 % where the FM is fixed at 10 %. Besides, BT of 135 °C to137 °C, FM of 10–12 % when the SB proportion is fixed at 7.5 % gave optimal product quality. The numerical optimization resulted in optimal extrusion conditions for optimal product quality were BT of 135 °C, FM of 10 % and SB proportion of 5 % with a desirability value of 0.875. The results revealed that SB can be incorporated up to 7.5 % to obtain an acceptable product. Therefore it is possible to produce gluten-free extruded snack by blending teff and soybean flour.

Optimization of Extrusion Conditions for an Extruded Food Enriched with Mango By-Products (Mangifera indica var. Tommy Atkins) via Response Surface Methodology

Today, mango by-products are produced in significant amounts, posing an environmental problem. Their incorporation into food products offers a solution to this problem. An extruded food product formulated with the flours of white corn, mango peel, and mango kernel was developed. To obtain the desired quality regarding the physical and chemical characteristics of the extruded food product, an optimization study was carried out. Response surface methodology was used to evaluate the effect of the following extrusion process variables on the physical (expansion index (EI), hardness, water absorption index (WAI), water solubility index (WSI)) and chemical properties (total polyphenol content and antioxidant capacity): the die temperature (DT, 100–130 °C), the feed moisture content (FMC, 17–21%), and the screw speed (SS, 80–120 rpm). Response surface and regression models were performed to determine the responses as a function of the process variables. Model optimization was carried out with an R2 of &gt;0.60, maximizing the WAI and minimizing the hardness and the WSI. The optimal conditions were a DT of 120.66 °C, an FMC of 21.88%, and an SS of 66.36 rpm. The extruded product’s characteristics were an EI of 1.10, a hardness of 63.66 N, a WAI of 5.41 g/g, a WSI of 16.20%, a TPC of 3402 mg GAE/100 g sample, and an antioxidant capacity of 90.09 mg Etrolox/g (measured by DPPH) and 79.38 mg Etrolox/g (measured by ABTS); the overall desirability value was 0.870.

Tensile Properties of 3D Printed Recycled PLA Filament: A Detailed Study on Filament Fabrication Parameters

Polylactic acid (PLA), a biodegradable and biocompatible thermoplastic commonly utilized in 3D Printing filaments, undergoes changes in properties upon recycling. The objective was to elucidate the role of extrusion temperature and screw speed in modulating the quality of recycled PLA filament, as well as in controlling its dimensional attributes. Recycled PLA pellets (3D850D) were extruded using a single filament extruder machine within an extrusion temperature range of 145°C to 165°C and a screw speed varying from 2 rpm to 6 rpm. The extruded filaments were subsequently 3D printed into specimens adopting a 0° raster angle, line infill pattern, and a 100 percent infill density, then tested as per ASTM D638 mechanical standards. The study revealed a profound influence of extrusion parameters on the filament's ultimate tensile strength, yield strength, and diameter. Optimal extrusion conditions - 155°C and 5 rpm - resulted in maximum mechanical strengths, while the parameters yielding filament diameters closest to commercial standards were identified as 5 rpm and 155°C. These results under-score the possibility of optimizing the recycled PLA filament's properties through adept control of extrusion parameters. Consequently, this investigation supports the potential use of recycled PLA filament in the 3D printing industry as a sustainable and performance-efficient material, offering a tangible step towards environmentally friendly additive manufacturing practices.

Controlled hydrogel-based encapsulation of macrophages determines cell survival and functionality upon cryopreservation

The development of novel cell-based therapies has increased the necessity to improve the long-term storage of cells. The current method of cryopreservation is far from optimal, causing ice-associated mechanical and osmotic damage to sensitive cells. Cell encapsulation is emerging as a new strategy to overcome those current limitations; however, few data are applicable to slow freezing, with conflicting results and multiple experimental conditions. The objective of this research work was to evaluate the impact of capsule size and encapsulation method on cell survival and functionality after a conventional freezing protocol. To this end, cells were encapsulated in alginate beads of different sizes, spanning the range of 200–2000 µm thanks to multiple extrusion techniques and conditions, and further cryopreserved using a slow cooling rate (−1°C/min) and 10 % DMSO as cryoprotectant. Our data show that there is a strong correlation between bead size and cell survival after a slow cooling cryopreservation process, with cell viabilities ranging from 7 to 70 % depending on the capsule size, with the smallest capsules (230 µm) achieving the highest level of survival. The obtained results indicate that the beads’ diameter, rather than their morphology or the technique used, plays a significant role in the post-thawing cell survival and functionality. These results show that a fine control of cell encapsulation in alginate hydrogels is required when it comes to overcoming the current limitations of long-term preservation techniques by slow cooling.

Investigation of the effect of materials and processing conditions in twin-screw extrusion

Three polymeric materials; polystyrene (amorphous), low-density polyethylene (semi-crystalline), and poly(methyl methacrylate) (amorphous) were used to explore their behavior and properties during processing using a co-rotating twin-screw extruder. Injection molding and compression molding were used for preparing the test specimens. Screw speed and barrel set temperatures were considered as the main processing variables while observing the process energy consumption of the extruder. The tensile, thermal, and rheological properties of the extruded materials under different processing conditions were evaluated. Test results confirmed that the motor power of the extruder for processing polystyrene and low-density polyethylene increased with increasing screw speed and decreased with increasing barrel set temperatures. Motor power for processing poly(methyl methacrylate) increased significantly with increasing screw speed. The total power consumption of the barrel heaters for processing polystyrene and low-density polyethylene slightly increased with the barrel set temperatures. The tensile modulus of polystyrene decreased with increasing screw speed at higher barrel set temperatures, while low-density polyethylene showed no significant variation. The tensile modulus of poly(methyl methacrylate) did not exhibit a clear trend with the extruder process settings. The effect of process settings on the glass transition temperature and melting temperature of the polymers was not significant, and no evidence was found of any molecular degradation during processing. Rheological properties of poly(methyl methacrylate) showed a significant variation with increasing screw speed and barrel set temperatures, while those of polystyrene and low-density polyethylene did not exhibit a consistent variation.

Optimization of Machine and Process Parameters for Development of Protein and Antioxidant Rich Composite Food using Twin Screw Extruder

Background: Nutritional quality of extruded products can be enhanced through protein, minerals and antioxidants rich foods viz. legumes, green leafy vegetables, dietary fibres, by-products, etc, leading to improvement in functional properties of products and health of consumers. Methods: Extrudates were prepared from maize, defatted soy meal, sesame and spinach using a co-rotating twin screw extruder and dried in a tray dryer at 50oC up to about 5.5% moisture content (w.b.) and analyzed for important product quality parameters. Result: Quality characteristics of developed food grains-spinach based composite food were affected by variability in independent studied parameters. Optimized extrusion conditions for desired composite food from food grains-spinach were as 14% moisture content, 117oC DHT and 335rpm screw speed. These conditions resulted in the products with 18.26% protein, 73.88% in vitro protein digestibility, 2.46 protein efficiency ratio, 2.84% total minerals, 4.67mg/100g iron, 190 mg/100g calcium, 24.05% antioxidant activity with consumer acceptability ≥7 by 92.52%.

Sorghum- and Chickpea-Based Ready-to-Eat Extrudate Flakes: Quality Attributes and In Vitro Digestibility

The study is aimed at the development of whole sorghum-based ready-to-eat extruded snacks using chickpea at different barrel temperature (BT) (130, 145, and 170°C) and feed moisture (FM) (14, 16, and 18%) conditions, and quality changes on the functionality aspects of prepared snacks were evaluated. Data revealed that with increment in barrel temperature and feed moisture, the antioxidant properties, viz., ferric reducing antioxidant potential (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition, total phenolic content (TPC), and hardness of the flakes amplified; however, elevated barrel temperature and decreased feed moisture enhanced the expansion ratio, water solubility index, and overall acceptability of lakes. The results of the ( L ∗ , a ∗ , and b ∗ ) color values indicated that the rates of Maillard’s reaction were higher when the BT and FM processes were intensified. Enhanced extrusion conditions (BT and FM) lead to higher levels of resistant starch and improved in vitro protein digestibility. The estimated glycemic index of the flakes ranges from 52 to 54, thus showing low estimated glycemic index (E-GI) of flakes. Slowly digestible starch and Exp-GI reveal a positive correlation among themselves. Results from the present study showed that highly acceptable flakes with commercialization properties can be successfully formulated using extrusion processing.

Effect of defatted rice bran addition on properties of texturized soy and rice protein products

Abstract The objective of this work was to produce low moisture-texturized vegetable protein (LM-TVP). Firstly, SPI:DRB at ratio of 50:50, 65:35 and 80:20 (w/w) was blended to produce TVP with 50–70 % protein (TSP50–70), respectively. In addition, RPI:DRB was also blended at the same ratio to produce non beany odor TVP with 50–70 % protein (TRP50–70). All samples were extruded using twin screw extruder. Extrusion condition was fixed at 25 % of feed moisture, 400 rpm of screw speed and 130 °C of die temperature. Next, properties of TSP50–70 and TRP50–70 before and after rehydration were characterized. For TSP50–70, studied properties consisting of expansion ratio, density, WAC, WHC and OHC of TSP50–70 were 2.20–2.27 %, 0.26–0.34 kg/m3, 414–446 %, 2.87–4.88 g H2O/g and 2.55–2.73 g oil/g respectively. These properties values were closed and in the same range of commercial-TVP (C-TVP). However, texture of TSP50 and TSP70 was significantly different, as decreasing DRB content from 50 (TSP50) to 20 % (TSP70) improved texture in terms of hardness (from 0.51 to 1.88 N), springiness (from 0.73 to 0.96) and cohesiveness (from 0.46 to 0.81) of TSP. Therefore, to add value to DRB, TSP70 (80 % SPI and 20 % DRB) was proposed to produce TSP. For TRP, expansion ratio, density, WAC, hardness, springiness and cohesiveness of TRP50–70 were 1.07–1.34 %, 0.63–0.88 kg/m3, 78–158 %, 1.03–9.10 N, 0.71–0.85 and 0.27–0.29 which were out of range compared to C-TVP.

Effect of extrusion parameters on microstructure and mechanical properties of Mg–6Zn–1Mn–0.2Gd alloy

The microstructure, dynamic recrystallization behavior and texture evolution of an as-extruded Mg–6Zn–1Mn–0.2Gd (ZMG610) alloy at different extrusion conditions (extrusion ratios of 25 and 45, temperatures of 350 and 400°C) were investigated. The as-cast ZMG610 alloy was mainly composed of the α-magnesium (α-Mg) matrix, the Mg7Zn3 phase and Mg3Zn6Gd (I phase). A large number of I-phase particles remained in the matrix after homogenization treatment at 330°C up to 24 h. The as-extruded ZMG610 alloy exhibited a bimodal structure consisting of fine dynamically recrystallized grains with a wide orientation spread and coarse undynamically recrystallized grains with a strong basal texture. All as-extruded samples exhibited a typical basal texture with the basal plane of most grains parallel to the extrusion direction. A lower texture intensity could be obtained by increasing both the extrusion ratio and temperature. Optimal mechanical properties (yield strength of 267 MPa, ultimate tensile strength of 360 MPa and elongation of 14.2%) were obtained through the combination of a low temperature (350°C) and a high extrusion ratio (45). Amelioration of mechanical properties highly depended on the synergistic effect of dynamically recrystallized grains, I-phase particles and texture.

Effects of Food Additives Treatment on the Texture of Artificial Rice prepared from Dried Cassava and Corn Flours Mixture

The purpose of this study is to understand how food additives like Sodium Tri-Polyphosphate (STPP), Guar Gum, and Glycerol Monostearate (GMS) affect the textures of synthetic rice (tiwul rice) produced using a twin screw extruder. 70% (w/w) dry cassava flour and 30% (w/w) corn flour were combined for the extrusion process. By adjusting the amounts of the extra ingredients guar gum, sodium tri poly phosphate (STPP), and glycerol monostearate, it was done in six different formulae (GMS). The moisture content of the raw material mixture was 30-35% (w/w) at the extrusion conditions the feeding screw motor speed was 5-6Hz, the screw speed of the extruder was 7.5-8.5Hz and the barrel temperature from zone 1 to 3 extruder was around 45-50°C. Tiwul rice that is produced with 0.5% GMS addition obtains several characteristics that are nearly similar with native rice, such as hardness, cohesiveness, adhesiveness, springiness, gumminess and chewiness texture.

Study on the thermal runaway characteristics and debris of lithium-ion batteries under overheating, overcharge, and extrusion

As the use of lithium-ion batteries (LIBs) becomes more widespread in various fields, incidents of combustion caused by thermal runaway (TR) of LIBs are increasing. However, identifying the causes of TR is challenging. To address this, we employ a method that combines TR characteristics and debris analysis to identify the causes of TR in this study. We investigate a commercial LiFePO4 (LFP) battery and trigger TR under overheating, overcharge, and extrusion conditions. Following TR, we observe that under the overheating and overcharge condition, numerous floccule attach to the anode debris; under the extrusion condition, the anode debris is covered by numerous small particles; and under the overcharge condition, a large number of flocculant and smooth balls attach to the anode debris, and the composition of these substances contains numerous metal oxides. Moreover, under the overheating condition, the heat release, and gas release rate of the debris are the minimum, while they are the maximum under the extrusion condition. Due to the different reaction processes and degrees of TR under different conditions, the properties of the LIB debris also differ. By analyzing the debris and data, we can distinguish the debris under different conditions. This enables us to quickly identify the trigger factors of battery TR after it occurs.

High methoxyl pectin can improve the extrusion characteristics and increase the dietary fiber content of starch-cellulose extrudates.

Improving total dietary fiber content while maintaining the texture/expansion of extruded products is a challenge. Pectin has a dual function; it is a source of dietary fiber and it also functions as a hydrocolloid, which could improve the texture of high-fiber extruded foods. The objective of this study was to evaluate the impacts of pectin types from citrus peel on the expansion characteristics of starch-cellulose extrudates. High and low methoxyl pectin (HMP and LMP) was added to the starch-cellulose mixtures and extruded using a twin-screw extruder. The pasting properties of raw mixtures, extrusion properties, microstructure, and dietary fiber contents of the extrudates were studied. The inclusion of HMP in raw materialimproved the peak viscosity (629.7±8.1 to 754.7±80.1 mPa s) and maintained the final viscosity compared to the control (starch-cellulose mixture alone), unlike LMP. HMP relatively maintained the extrusion process parameters such as torque, back pressure, and specific mechanical energy as the control. Interestingly, the addition of 7% of HMP had a similar expansion ratio (3.41±0.08 to 2.35±0.06) compared to the control (3.46±0.08 to 2.32±0.09) under the extrusion conditions studied. The total dietary fiber content improved from 12.22±0.01% to 18.26±0.63% (w/w). HMP maintained the expansion characteristic of starch-cellulose extrudates and improved its total dietary fiber content relative to LMP. Adding HMP to the mixtures improved the extensibility of the melt, favoring bubble growth and expansion of the starch-cellulose extrudates. Fourier transform infrared spectroscopy data suggested that there could be intermolecular interactions between starch, cellulose, and pectin, but the nature of these interactions needs further investigation. PRACTICAL APPLICATION: The study provides practical information on the influence of the addition of high and low methoxyl pectin on starch-cellulose extrudates. The results can help the industry to produce snack products that are more nutritious but are still well accepted by the consumers.

Influence of germination and pulse type on texture of high moisture meat analogs

Enhancing the texture profile of high moisture meat analogs (HMMAs) presents a notable challenge, one that can potentially be addressed by diversifying the ingredients used. This research examines how the type of pulse - specifically peas and lentils - and the germination process can impact the functional properties and structural transformation of proteins within these ingredients. A twin-screw extrusion cooking process was used to produce HMMAs with an optimized screw speed of 800 rpm and a final zone temperature of 140 °C. The quality of the HMMAs was evaluated through an analysis of their textural properties and Scanning Electron Microscopy (SEM). Generally, germination and variations in pulse types were seen to create significant (p < 0.05) changes to the protein profile. These changes resulted in reduced subunit molecular weight, altered melting temperatures (120–127 °C), and increased quantities of disulfide bonds. In turn, these shifts elicited corresponding adjustments in the HMMAs when subjected to identical extrusion conditions. Notably, the protein-rich fraction derived from lentils was markedly different (p < 0.05) from that of peas, contributing to lower levels of cohesiveness, chewiness, and gumminess in HMMAs. SEM images taken at 250 × -1000 × magnification demonstrated filaments in HMMAs, illustrating the transformation of proteins from a globular to a fibrous form. Guided by the influence of melting temperature and shear force on pulse protein, the “Thermo-shear Protein Structuring Principle” was proposed. Overall, our findings offer critical insights into how germination and pulse selection can affect protein behavior during the production of HMMAs.

Dry sliding wear behavior of additively manufactured cenosphere-filled PETG syntactic foam composites

PurposeThis study aims to deal with developing composite filaments and investigating the tribological behavior of additively manufactured syntactic foam composites. The primary objective is to examine the suitability of the cenosphere (CS; 0–30 Wt.%) to develop a high-quality lightweight composite structure with improved abrasion strength.Design/methodology/approachCS/polyethylene terephthalate glycol (PETG) composite feedstock filaments under optimized extrusion conditions were developed, and a fused filament fabrication process was used to prepare CS-filled PETG composite structures under optimal printing conditions. Significant parameters such as CS (0–30 Wt.%), sliding speed (200–800 rpm) and typical load (10–40 N) were used to minimize the dry sliding wear rate and coefficient of friction for developed composites.FindingsThe friction coefficient and specific wear rate (SWR) are most affected by the CS weight percentage and applied load, respectively. However, nozzle temperature has the least effect on the friction coefficient and SWR. A mathematical model predicts the composite material’s SWR and coefficient of friction with 87.5% and 95.2% accuracy, respectively.Practical implicationsBecause of their tailorable physical and mechanical properties, CS/PETG lightweight composite structures can be used in low-density and damage-tolerance applications.Social implicationsCS, an industrial waste material, is used to develop lightweight syntactic foam composites for advanced engineering applications.Originality/valueCS-reinforced PETG composite filaments were developed to fabricate ultra-light composite structures through a 3D printing routine.

Investigation of the mechanisms on the abnormal features observed in thermal-mechanical testing of AA6061 under extrusion conditions

Hot extrusion is the most common forming technology for aluminium alloy AA6061 due to its good extrudability, and thus it is important to study its high-temperature deformation characteristics. In this study, three abnormal features are observed in thermal-mechanical testing under extrusion conditions of AA6061 specimens from one billet: 1) Two types of specimens with grey-coloured surface or silver-coloured surface appear after solution heat treatment (SHT); 2) The silver-coloured specimens show orange peel surface after hot compression tests; 3) The silver-coloured specimens have lower flow stresses than the grey-coloured specimens. This paper investigates the mechanisms behind the above abnormal features. A laser scanning confocal microscope is employed to examine the surface roughening, and electron back scatter diffraction is used to characterise microstructural changes. It is found that the main causes of the above behaviour are due to different initial grain morphologies and the evolution of dislocation density after SHT. The silver-coloured specimens initially have smaller columnar grains which undergo recrystallisation and extensive growth during SHT, and the dislocation density decreases significantly, leading to orange peel defect and low flow stress during compression tests, respectively. The grey-coloured specimens have larger columnar grains. After SHT, some grains undergo recrystallisation, but others still maintain the shape of the large columnar grains, and the dislocation density does not change significantly, resulting in surface oxidation with smooth surface after thermal-mechanical testing and 10–25 MPa (30–50%) higher flow stress compared to the silver-coloured specimens in compression tests.