Phase Inversion Technique Research Articles

Effect of Mixing Technique on Physico-Chemical Characteristics of Blended Membranes for Gas Separation

Polymer blending has attracted considerable attention because of its ability to overcome the permeability–selectivity trade-off in gas separation applications. In this study, polysulfone (PSU)-modified cellulose acetate (CA) membranes were prepared using N-methyl-2-pyrrolidone (NMP) and tetrahydrofuran (THF) using a dry–wet phase inversion technique. The membranes were characterized using scanning electron microscopy (SEM) for morphological analysis, thermogravimetric analysis (TGA) for thermal stability, and Fourier transform infrared spectroscopy (FTIR) to identify the chemical changes on the surface of the membranes. Our analyses confirmed that the mixing method (the route chosen for preparing the casting solution for the blended membranes) significantly influences the morphological and thermal properties of the resultant membranes. The blended membranes exhibited a transition from a finger-like pore structure to a dense substructure in the presence of macrovoids. Similarly, thermal analysis confirmed the improved residual weight (up to 7%) and higher onset degradation temperature (up to 10 °C) of the synthesized membranes. Finally, spectral analysis confirmed that the blending of both polymers was physical only.

Highly Stable Protonic Ceramic Electrolysis Cells Based on Air Electrodes with Finger-Like Pores Current Collection Layers Running in High-Steam-Content Air.

The steam content in the air electrode is one of the major factors determining the efficiency and stability of protonic ceramic electrolysis cells (PCECs). In this work, the La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) current collection layer (CCL) film with unique finger-like pores was successfully prepared by the phase-inversion tape-casting technique (PT), which promoted the gas diffusion inside the electrode and effectively improved the stability of the single cell in high-humidity air. A screen-printed LSCF-BaCe0.7Zr0.1Y0.1Yb0.1O3 catalytic active layer (CAL) was also applied to match the thermal expansion coefficient (TEC) values and improve the interface combination. The electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) studies of the symmetric cells showed that when the film was used to match different CALs as an air electrode, the gas diffusion inside the electrode was no longer restricted by the increasing steam content in air. The single cell exhibited a high electrolysis current density of 1 A cm-2 (1.25 V) at 650 °C; furthermore, no performance degradation was observed in this high current density when electrolyzed in air with 40 and 60% humidity for more than 250 h. These results present a simplified and economical scheme to develop air electrodes with high stability in wet air with a high steam content.

Halloysite Nanotube-Enhanced Polyacrylonitrile Ultrafiltration Membranes: Fabrication, Characterization, and Performance Evaluation.

This research focuses on the production and characterization of pristine polyacrylonitrile (PAN) as well as halloysite nanotube (HNT)-doped PAN ultrafiltration (UF) membranes via the phase inversion technique. Membranes containing 0.1, 0.5, and 1% wt HNT in 16% wt PAN are fabricated, and their chemical compositions are examined using Fourier transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM) is utilized to characterize the membranes' surface and cross-sectional morphologies. Atomic force microscopy (AFM) is employed to assess the roughness of the PAN/HNT membrane. Thermal characterization is conducted using thermal gravimetric analysis (TGA) and differential thermal analysis (DTA), while contact angle and water content measurements reveal the hydrophilic/hydrophobic properties. The pure water flux (PWF) performance of the porous UF water filtration membranes is evaluated at 3 bar, with porosity and mean pore size calculations. The iron (Fe), manganese (Mn), and total organic carbon (TOC) removal efficiencies of PAN/HNT membranes from dam water are examined, and the surfaces of fouled membranes are investigated by using SEM post-treatment. Mechanical characterization encompasses tensile testing, the Mori-Tanaka homogenization approach, and finite element analysis. The findings offer valuable insights into the impact of HNT doping on PAN membrane characteristics and performance, which will inform future membrane development initiatives.

Construction of recoverable Ag2SeO3/Ag3PO4/MWCNT/PVDF porous film photocatalyst with enhanced photocatalytic performance for degrading Indigo carmine dye in continuous flow-loop photoreactor

Herein, a facile method was used for fabrication of composite based on Ag2SeO3 and Ag3PO4-Cube nanoparticles by co-precipitation method and subsequently was applied for construction of film composite by a casting solution containing polyvinylidene fluoride (PVDF) matrix, multi-walled carbon nanotubes (MWCNTs) as electron acceptor and carboxymethyl cellulose as a hydrophilic agent and Ag2SeO3/Ag3PO4 as photocatalyst filler via phase inversion technique. The synthesized porous film was used for photo-degradation of indigo carmine (IC) in a continuous flow-loop film photoreactor under LED and sunlight irradiation. The composite properties were described using various analyses such as FE-SEM, EDS, XRD, FTIR, PL and UV-Vis, EIS, Bode phase and water contact angle. The Ag2SeO3/Ag3PO4/MWCNT/PVDF film exhibits extensive photocatalytic activities for IC degradation in comparison to MWCNT/PVDF and Ag2SeO3/Ag3PO4 samples. According to the desirability function at optimum conditions lead to the IC photo-degradation efficiency of was around 97.88%. The enhanced visible light-based photocatalytic performance can be attributed to the high charge separation and the surface plasmon resonance (SPR) effect for IC photodegradation and experimental results illustrate that superoxide radicals as the main active radicals has high contribution on the IC photo-degradation. The low decrease in photocatalytic activity of the fabricated composite film after five uses makes the sample suitable for applications where reusability is a vital factor.

Microplastic Removal in Krueng Aceh River Water Using Ultrafiltration Membrane from Polyethersulfone Polymer (PES)

The Company's input pipes contained microplastics, per the preliminary test findings. While the water yield produced by PDAM Tirta Daroy contains 150 particles/L, the Tirta Daroy Drinking Water Area has 275 particles/L. Microplastics found in the water pose a major risk to living beings if they are consumed. This work aims to characterize the properties, flux, and polyethersulfone (PES) membrane rejection coefficient, which were made utilizing the phase inversion technique with a solvent and additives called N,N-dimethylformamide (DMF). In Sungai Krueng Aceh, titanium dioxide (TiO2) is utilized to filter out microplastics from the water. Results of Scanning Electron Microscopy (SEM) examination of Membrane Morphology demonstrate that the resulting membrane is an asymmetrical membrane of two layers, the upper layer relatively thin and the lower layer porous. When compared to the PES membrane when it was 15% DMF/TiO2, the 20% DMF/TiO2 membrane exhibits a finger-like cross-sectional structure called a macrovoid) with more and larger numbers. Analysis of the microplastic rejection coefficients proved the effectiveness of PES, DMF, and TiO2 membranes in removing microplastics. Results of tests on the effectiveness of rejecting microplastics after undergoing process filtration with a microplastic rejection coefficient of 94% and 14.2 particles/L utilizing a 20% PES/DMF/TiO2 membrane Performance of PES membranes: The PES membrane with 20% DMF/TiO2 has a water flux of 0.467 L/m2.hour compared to 15% DMF/TiO2 0.733 L/m2.hour. This study's findings on membrane Ultrafiltration have the potential to be used as a water filter standard in PDAM.

Influence of the prepared activated carbon on cellulose acetate for malachite green dye removal from aqueous solution

Guava (Psidium guajava) seeds were used for the preparation of activated carbon (AC) activated using zinc chloride (GCZ36), phosphoric acid (GCH36), potassium hydroxide (GCK36), and one other sample was prepared without activation (GC36), carbonized for 3 h at 600 °C. They were added to cellulose acetate to form hybrid membranes (Ms) using the phase inversion technique. The prepared AC was characterized by % ash content, % weight loss on drying, nitrogen adsorption isotherm, TEM, and XRD. FTIR and SEM were used for the ACs and Ms. GCK36 sample exhibited a higher surface area (905.27 m2/g) and total pore volume (0.5360 mL/g). The hybrid membranes were used to remove malachite green dye (MG) from wastewater. The effect of initial dye concentration, adsorbent dosage, pH, and contact time were studied. Pseudo-first-, pseudo-second-order, and intraparticle diffusion rate equations were proposed and the kinetic data were analyzed. Maximum adsorption capacity (31.82 mg/g) was achieved after 100 min, at pH 6 and 0.25% AC. The adsorption capacity of the cellulose acetate membrane was increased by 111.7% using the prepared activated carbon. The results indicated the chemisorption process and the adsorption was fitted to Langmuir > Freundlich > Tempkin due to R2 values.Graphical abstractSchematic diagram of preparation of a composite membrane of cellulose acetate and guava seeds activated carbon

Improvement of salt rejection efficiency of cellulose acetate membrane through modification by poly(amidoamine) dendrimer-functionalized graphene oxide

In this work, the grafting method using graphene oxide (GO) - poly(amidoamine) dendrimer (PAMAM) nanocomposite as filler for the functionalization of cellulose acetate membrane is reported. Here, cellulose acetate membrane incorporated by nanocomposite in the polymer solution was prepared through the phase inversion technique. The effect of embedding GO-PAMAM on the characterization properties and rejection performance was studied. The results of zeta potential, thermogravimetric analysis (TGA), contact angle measurements, Fourier-transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FE-SEM) established successful modification. Based on the data found, adding the filler improves membrane properties. Loading of 1.00 wt% of GO/PAMAM was found to be the optimized amount of the filler in the membrane processing with the highest porosity (74%), antifouling behavior (88%), reversible fouling ratio (45.71%), and the least contact angle (∼40°). Hence, the rejection and permeability tests of the prepared membrane were examined by Na2SO4 (98.40%), NaCl (52%), and MgCl2 (57%) solutions through a lab dead-end cell. According to the results, the value of salt rejection established more permeability and rejection than neat cellulose acetate membrane.

Chitosan-Based High-Intensity Modification of the Biodegradable Substitutes for Cancellous Bone.

An innovative approach to treating bone defects is using synthetic bone substitutes made of biomaterials. The proposed method to obtain polylactide scaffolds using the phase inversion technique with a freeze extraction variant enables the production of substitutes with morphology similar to cancellous bone (pore size 100-400 µm, open porosity 94%). The high absorbability of the implants will enable their use as platelet-rich plasma (PRP) carriers in future medical devices. Surface modification by dipping enabled the deposition of the hydrophilic chitosan (CS) layer, maintaining good bone tissue properties and high absorbability (850% dry weight). Introducing CS increases surface roughness and causes local changes in surface free energy, promoting bone cell adhesion. Through this research, we have developed a new and original method of low-temperature modification of PLA substitutes with chitosan. This method uses non-toxic reagents that do not cause changes in the structure of the PLA matrix. The obtained bone substitutes are characterised by exceptionally high hydrophilicity and morphology similar to spongy bone. In vitro studies were performed to analyse the effect of morphology and chitosan on cellular viability. Substitutes with properties similar to those of cancellous bone and which promote bone cell growth were obtained.

Scale Design of Dual-Layer Polyphenylsulfone/Sulfonated Polyphenylsulfone Hollow Fiber Membranes for Nanofiltration.

This study focuses on the synthesis and characterization of dual-layer sulfonated polyphenylenesulfone (SPPSu) nanocomposite hollow fiber nanofiltration membranes incorporating titanium dioxide (TiO2) nanoparticles through the phase inversion technique. Advanced tools and methods were employed to systematically evaluate the properties and performance of the newly developed membranes. The investigation primarily centered on the impact of TiO2 addition in the SPPSu inner layer on pure water permeability and salt rejection. The nanocomposite membranes exhibited a remarkable three-fold increase in pure water permeability, achieving a flux of 5.4 L/m2h.bar compared to pristine membranes. The addition of TiO2 also enhanced the mechanical properties, with an expected tensile strength increase from 2.4 to 3.9 MPa. An evaluation of salt rejection performance using a laboratory-scale filtration setup revealed a maximal rejection of 95% for Mg2SO4, indicating the effective separation capabilities of the modified dual-layer hollow fiber nanocomposite membranes for divalent ions. The successful synthesis and characterization of these membranes highlight their potential for nanofiltration processes, specifically in selectively separating divalent ions from aqueous solutions, owing to their improved pure water flux, mechanical strength, and salt rejection performance.

Poly(ether ether ketone) Conferred Polyolefin Separators with High Dimensional Thermal Stability for Lithium-Ion Batteries.

The traditional polyolefin separators used in lithium-ion batteries (LIBs) are plagued by limitations such as poor wetting of electrolytes and insufficient thermal stability, hindering the progress of LIBs. To overcome these limitations, we have developed a modified phase inversion technique to efficiently and durably coat polyolefin separators with poly(ether ether ketone) (PEEK). The resulting PEEK-coated polyolefin separators exhibit mechanical properties similar to those of unmodified polyolefin separators, with comparable tensile strength and modulus. Furthermore, the PEEK coating provides outstanding thermal stability, as the modified separators maintain their stability even at temperatures up to 200 °C, which is among the best results reported for polyolefin-based separators. In addition, the PEEK coating enhances ionic conductivity by more than 100% compared to polyolefin counterparts, leading to significant improvement in the electrochemical performance of prototype half cells. The modified phase inversion technique presented here offers a practical solution for coating polyolefin separators with functional polymers, paving the way for next-generation separator materials.

Synthesis and characterization of MOF/silica cellulose acetate based membranes: Removal of uremic toxins in haemodialysis spent dialysate

The phase inversion technique associated to the Loeb-Sourirajan membranes made possible the creation of membranes in all the range of pressure-driven membrane processes.The present work addresses the synthesis and characterization of CA/SiO2 and CA/SiO2/MOF membranes specific for the removal of the uremic toxins - urea and p-cresil sulfate - from the spent dialysate fluid of haemodialysis. The MOF (Metal Organic Framework) synthesized - UiO2–66(Zr) - is added to casting solutions that differ on the acetone/formamide ratio – CA22, CA22/SiO2, CA34 and CA34/SiO2. The membranes with the higher acetone/formamide ratio, CA22 and CA22/SiO2, have lower hydraulic permeabilities,1.29 Kg/h/m2/bar and 4.1 Kg/h/m2/bar, respectively. The incorporation of UiO2–66(Zr) leads to the increase of their hydraulic permeabilities. This pattern is not verified for the CA34/SiO2 membranes.The molecular weight cut-off for the series of CA22 membranes ranges from 2.9 to 28.3 kDa and for the CA34 series ranges from 8.9 to 35.7 kDa.The incorporation of UiO2–66(Zr) leads to lower rejection coefficients to the two uremic toxins - urea and p-cresil sulfate. In average over the transmembrane pressure range of 0.5–4.0 bar the rejection coefficients are below 5 %.

Fabrication and kinetic evaluation of dye adsorption capability of metal Oxide@RGO nanocomposites integrated cellulose triacetate membranes

Reduced Graphene Oxide (RGO) and its derivatives exhibit remarkable removal abilities of water pollutants that can further be enhanced by the incorporation of the metallic nanoparticles. However, the challenging collection of GO sheets and fabrication method of RGO-based materials during the adsorption process, constraint their practical uses. The integration of the RGO-based materials on the polymeric matrix offers a solution to this problem. In current study, three types of metal oxide@RGO nanocomposites integrated Cellulose Triacetate (CTA) membranes with adsorption abilities were prepared by a facile blending and phase inversion technique. The fabricated membranes exhibited selective adsorption for azo dyes at room temperature. The adsorption parameters depicted the Langmuir and pseudo-first order kinetic order reaction. It was found that the adsorption process was directed by the inter-particle diffusion. These membranes were found to be effective against varying range of the pollutants and can be fabricated by the facile techniques.

Synthesis and characterization of p-carboxy phenyl amino maleimide-g-cellulose acetate/ZrO2 nanocomposite membrane for water desalination

Abstract The reaction of p-carboxy phenyl amino maleimide (CHM) with cellulose acetate (CA) led to the formation of a modified cellulose acetate polymer (MCA), which was characterized by UV/Vis, 1H NMR, and 13C NMR. The active sites of the reaction were the –NH group of (CHM) and the OAc of CA. CA was grafted with (CHM) to build branches on its main chains, using benzoyl peroxide as an initiator. The results of 1H NMR and 13C NMR revealed the presence of (CHM) moieties inside the polymeric matrix. The (CA-g-CHM) ZrO2 was fabricated into a membrane, using a phase inversion technique. The effect of ZrO2 content on the water flux was discussed. The SEM/EDS was also used to characterize the membrane contents and morphology. The morphology of the membrane showed the grafted parts and the EDS confirmed the presence of nitrogen atoms in the polymeric matrix. The thermogravimetry (TGA) results showed that the membrane exhibited high thermal stability which would adjust the membrane for the desalination process. The desalination test indicated the removal of NaCl salt by the membrane, as shown by the EDS and 1H NMR spectroscopy results. The membrane exhibited good antibacterial and antifungal properties.

Development of anticorrosive self-adhesives from post-consumer poly(ethylene terephthalate) bottles for industrial applications

Corrosion is a spontaneous process that can result in both aesthetic and structural damage, incurring significant costs. One of the most commonly employed methods for mitigating the effects of corrosion is the application of organic coatings. However, no coating is precluded from potential damage, whether due to factors such as end-of-life degradation, inadequate application, poor quality, or impact-related incidents. Within this context, the primary objective of this study is to develop a novel and easy to apply anticorrosive adhesive for carbon steel surfaces from post-consumer poly(ethylene terephthalate) (PET) bottles as a temporary coating. PET films were produced by phase inversion technique, which involves the dissolution of PET bottles in a mixture of trifluoroacetic acid (TFA) and dichloromethane (DCM) solvents, followed by precipitation in a non-solvent bath. The resulting films were utilized as backing materials in the production of self-adhesive tapes with anticorrosive properties. Two different solvent proportions were selected to assess the feasibility of this technique, which are 70/30 and 50/50 (TFA/DCM v/v). For each condition, scanning electron microscopy, Fourier transform infrared spectroscopy, thermal analysis, immersion tests in NaCl aqueous solution 3.5 wt%, and electrochemical impedance spectroscopy were performed. Experimental results revealed that the utilization of a solvent system with a higher concentration of DCM produces a more cohesive and denser film, leading to improved outcomes in both total immersion and electrochemical impedance spectroscopy tests. The impedance modulus value obtained after 168 h of immersion in an aqueous solution of NaCl 3.5 wt% for 50/50 TFA/DCM film was 106 Ω·cm2, with no corrosion product observed on the protected area. Furthermore, thermal and infrared analyzes demonstrated that there is no change in PET chemical and thermal properties after inversion phase process.

Vitamin E encapsulated nano-emulsions formulation, rheological and antimicrobial analysis

Vitamin E is an important food ingredient that individuals ingest to help prevent numerous diseases. Nano-emulsions are frequently employed in pharmaceutical, food, and personal care applications as means of delivering a variety of lipophilic active substances, namely vitamins that are oil-soluble. Both high-energy and low-energy methods are used to create nano-emulsions. The latter, however, offers advantages including less cost, convenience of use, and increased energy efficiency. In this work, we used the emulsion phase inversion technique to create nano-emulsions containing vitamin E. We investigated the rheological and physical characteristics of nano-emulsions created at different stirring rates ranging from 30 to 110 minutes. The emulsion phase inversion approach mixes an organic phase made up of oil, vitamin E, and a surfactant with an aqueous phase. The droplet size, zeta potential, and rheology of all the nano-emulsions were measured. The size distribution of nano-emulsions was measured in the particle size examination method utilizing dynamic light scattering and average droplet diameter was observed to be within a range of 141 nm to 177 nm and to follow a sequence: 110 < 70 < 30 min. The lowest droplet size, 141 nm, with a polydispersity index of 0.234, was obtained at 110 minutes. The zeta potential of formulated nano-emulsions ranged from – 7.1 m to – 14.3 mV. The rheological properties of nano-emulsions revealed non-Newtonian flow behavior. The antimicrobial test of nano-emulsions was examined with Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and the emulsions were resistant to S. aureus.

Cellulose Acetate Membrane Synthesis of Banana Peel

The membranes can be synthesized from organic and inorganic materials. One of the based organic materials used was a cellulose acetate membrane from banana peel. Banana peel comprised 65% cellulose, and therefore it had the potential to be processed into a membrane. Cellulose acetate membranes are synthesized using a mixture of cellulose acetate from a banana skin with 55% acetone and 27% dimethylformamide using a phase inversion technique. SEM results pictured porous membranes with a pore size of about 5 μm. The results demonstrate the flux capability of a synthesized cellulose acetate membrane of 0.440 L / m2.h with a rejection coefficient of 97.6%. It was concluded that banana peel waste could be used as raw material to manufacture cellulose acetate membranes.

Synthesis of Hybrid Cellulose Acetate Membranes and Application of the Flynn-Wall-Ozawa Isoconversional Method

The synthesis of hybrid materials is a promising alternative in the production of materials with optimized properties. In this context, the classic cellulose acetate membranes are being modified. It is worth mentioning that knowing the thermal stability of cellulosic materials is an essential factor in their use since organic polymers have low thermal resistance, limiting their applicability. This work evaluates the synthesis and the study of the thermal degradation kinetics of hybrid cellulose acetate membranes. The synthesis was carried out using the sol-gel process, with the phase inversion technique, through the reaction of cellulose acetate with organometallic precursors: tetraethyl orthosilicate, TEOS; 3-aminopropyl triethoxysilane, APTES, and titanium isopropoxide, TiPOT, in fixed composition. Thermal characterization was performed with thermogravimetric analysis at different heating rates under a nitrogen atmosphere. The kinetic parameter of thermal decomposition activation energy, Ea, was estimated with the isoconversional method proposed by Flynn-Wall-Ozawa (FWO). The degradation kinetics shows that the change in the chemical composition of the samples directly interferes with their thermal properties. Thus, it is possible to observe that the activation energy found for the reference sample, AC-Pure, in the first and second batches was 233.5 and 219.05 kJ/mol, respectively. The composition modification results in an increase in activation energy, in which sample B0//100-30 recorded 310.31 and 226.05 kJ/mol in the first and second batches; and sample B100//0-30 reached 452.73 and 424.74 kJ/mol. It is clear that the increase in the thermal resistance of the samples is associated with the change in the chemical composition and must be attributed to the increase in the TEOS content in the composition due to the formation and increase in the presence of siloxane groups in the material.

Efficient methodology for the preparation and fabrication of cation exchange membranes using trichloroacetic acid and cellulose biopolymer

This article presents a new method for preparing enhanced cation exchange membrane (CEM) for water treatment using cellulose biopolymer. The preparation methodology of CEM membranes was performed in two steps; functionalization followed by fabrication. Firstly, cellulose powder was functionalized with trichloroacetic acid at different reaction times to prepare carboxymethyl tricellulose (CMTC). In the second step, the exchange memberane was fabricated via phase inversion technique using the functionalized cellulosic material and polyethylene glycol as a pore former. The prepared CEM was fully characterized using FTIR, SEM, mechanical properties, and degree of substitution (DS) determination. The morphological microstructure of the CEM membrane was investigated and discussed. The microstructural analysis by FTIR confirmed the functionalization process. The tensile values obtained at different reaction times showed the effectiveness of using trichloroacetic acid in the carboxymethylation and consequently, the stability of the obtained functionalized cellulose. The obtained DS values are higher than that of the commercial CMC and also the published values. It has been observed that the prepared CEM have an average DS value of 1.5 and therefore much higher than the DS value of commercial CMC whose DS ranges between 0.7 and 1.2. The prepared CEM membranes were morphologically investigated by SEM. The SEM photos showed homogeneously distributed small pores on the entire surface of the membrane, and its cross-section is a multilayer with large pores.

Characterization of Polysulfone Membrane with Variation of Ethanol Concentrations in Coagulation Bath for Ultrafiltration Membrane

The aim of this research is to study influence of ethanol concentrations in coagulation bath to charecteristic of physical properties and polysulfone membrane performance. Ethanol concentrations that used is 0; 40; 50; 60 ; 70; 80; 90 %. Process of making for polysulfone ultrafiltration membrane is prepared with phase inversion technique. Polysulfone membrane is made from polysulfone solved in N,N- dimetilacetamida (DMAc) and additive poly(ethylene glikol) (PEG) 600 in proportion 18 %: 77 %: 5 %. The result showed that increasing ethanol concentrations causes the increasing of density and increase concentrations from 0 - 50 % causes increasing swelling degree, but decreasing swelling degree from concentrations 60 - 90 %. However influence of ethanol concentration in coagulation bath to membrane performance is increasing of water flux, permeability coefficient, and rejection coefficient to dextran. It based on of result that polysulfone membrane with ethanol concentrations 80 dan 90 % included membrane classification ultrafiltration by rejection coefficient value above 90 %.

Evaluation of Early-Stage Fatigue Damage in Metal Plates Using Quasi-Static Components of Low-Frequency Lamb Waves

Abstract Nonlinear Lamb waves including second harmonic and acoustic-radiation-induced quasi-static components (QSC) have a potential for accurately evaluating early-stage fatigue damage. Most previous studies focus on second-harmonic-based techniques that require phase velocity matching and are hard to isolate interferences from ultrasonic testing systems. The aforementioned requirement and deficiency limit applications of the second-harmonic-based techniques. In this study, a QSC-based technique of low-frequency Lamb waves is proposed for early-stage fatigue damage evaluation of metal plates, which does not need to require phase velocity matching and can remove interferences from ultrasonic testing systems. Both in simulations and in experiments, the primary Lamb wave mode at a low frequency that meets approximate group velocity matching with the generated QSC is selected. In finite element simulations, different levels of material nonlinearities by changing the third-order elastic constants are used to characterize levels of fatigue damage. Numerical results show that the magnitude of the generated QSC pulse increases with the levels of fatigue damage. Early-stage fatigue damage in aluminum plates with different fatigue cycles is further experimentally evaluated. The generated QSC pulse is extracted from received time-domain signals using the phase-inversion technique and low-pass digital filtering processing. The curve of the normalized relative acoustic nonlinearity parameter versus the cyclic loading number is obtained. Numerical simulations and experimental results show that the early-stage fatigue damage in aluminum plates can effectively be evaluated using the QSC generated by low-frequency Lamb waves.