Glass Fiber Research Articles

Lightweight and hydrophobic silica aerogel/glass fiber composites with hierarchical networks for outstanding thermal and acoustic insulation

Silica aerogels are regarded as potential thermal and acoustic insulation materials with low density and porous structure. However, the hydrophilicity due to surface hydroxyl groups and the low mechanical intensity have limited its further application. Generally, it can be achieved by adjusting the process parameters of the sol-gel to refine the structure of silica aerogels and optimize performance. In this study, we adopted an appropriate modification strategy of incorporating glass fiber felts as the reinforcing phase and trimethylchlorosilane (TMCS) as the hydrophobic modifier. By adjusting the solvent exchange time, the micro-nano structure, i.e. hierarchical networks, was optimized. The TMCS-modified silica aerogel/glass fiber/hot-melt fiber composites (TSGMs) exhibited great sound insulation, and the maximum sound transmission loss (STL) was up to 34 dB at 6300 Hz. Compared to unmodified, STL improved by 8 dB in simulated practical applications. In addition, TSGMs also exhibited high hydrophobicity with a water contact angle of 147° and excellent thermal insulation with a thermal conductivity of 0.0345 W (m k)-1. The results could contribute to the refinement in the preparation process of silica aerogel composites and use in the fields of thermal and acoustic insulation.

Evaluation of mode-I delamination toughness of composites for automotive applications

Abstract With the increasing need for energy efficiency, fiber-reinforced composites are being widely used in the automotive industry. This study investigates the inter-laminar fracture behavior of fiber-reinforced composite double cantilever beam specimens considering a non-zero slope at the root. Experiments were conducted on unidirectional and cross-ply glass fiber reinforced epoxy composite specimens and the critical delamination toughness G I C has been evaluated by the proposed weighted residual equation. The proposed mathematical model requires crack length and the load versus displacement data to evaluate delamination fracture energy. This method accounts the measurement scatter and the rotation at the crack tip. For a particular specimen, the proposed model gives a unique value of critical delamination toughness value. The critical interface failure load estimates utilizing the evaluated delamination toughness agrees well with literature and in-house test results of double cantilever beam specimens.

Interfacial adhesion of polycarbonate to graphene and silicon oxide: A comparative molecular dynamics analysis

In this study, molecular dynamics was used to evaluate the adsorption-free energy of polycarbonate on a solid wall surface that represented a fiber material. Three solid surfaces were used: clean graphene without functional groups to represent surface-treated carbon materials, graphene with OH groups without surface treatment, and SiO2 to represent glass fiber. The results showed that the adsorption free energy per unit area for clean graphene was greater than the adsorption free energy per unit area for the other two solid wall surfaces, which is different from the experimental results where the surface treated carbon fiber had a smaller adsorption free energy. The structure of benzene rings was analyzed, and it was found that benzene rings are deposited almost parallel to the solid wall on all solid walls and that the density of benzene rings with SiO2 and OH groups is the smallest on Graphene with the smallest angle and closest to the solid wall, resulting in smaller adsorption energy. This suggests that the π-π interaction between the benzene ring and the solid surface may account for a large proportion of the adsorption energy. It also suggests that chemical reactions between the solid surface and the polymer, which were not considered in this study, may have a significant effect on the adsorption energy.

Investigating the mechanical properties and crashworthiness of hybrid PLA/GFRP composites fabricated using FDM-filament winding

The failure and crashworthiness performance of hybrid Polylactide (PLA)/Glass Fiber Reinforced Polymer (GFRP) composite tubes subjected to axial and radial quasistatic compression loads were investigated in the present study. The composite tubes are fabricated using hand lay-up and Fused Deposition Modeling (FDM)-filament winding processes. The crashworthiness performance was studied using parameters such as the peak load, energy absorption, crush load, crushing load efficiency, and specific energy absorption. The highest peak loads from the compression test results in the axial and radial directions are calculated using variations in the filament winding PLA/GFRP (FPG) specimen, whose values were 16130.50 N and 12077.33 N, respectively. The highest mean crush load is found in the material variation with the FPG specimen, which is 5734.43 J/mm for axial loading and 4886.75 J/mm for radial loading. The highest energy absorption (EA) value is found in the material variation with the FPG specimen, which is 262.18 J for axial direction loading and 94.02 J for radial direction loading. The highest specific energy absorption (SEA) value is found in the material variation with the specimen Filament Winding PLA/GFRP, which is 16.92 J/g for axial loading and 10.98 J/g for radial loading. There are three main types of failure of the composite: matrix cracking, fiber damage, and folding. The study showed that by combining Additive Manufacturing and composite lamination, the hybrid PLA/GFRP specimen outperformed the existing structures.

Fiber-Reinforced Thermoplastic Sucker Rods Provide Artificial Lift Efficiencies

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 23949, “Fiber-Reinforced Thermoplastic Sucker Rods Providing High-Strength, Lightweight, Low-Cost, and Environmentally Responsible Artificial Lift Efficiencies,” by Jeff Saponja, SPE, Oilify, and Corbin Coyes, SPE, and Michael Conner, SPE, Q2 Artificial Lift Services. The paper has not been peer reviewed. Copyright 2024 International Petroleum Technology Conference. _ The complete paper focuses on the development of fiber-reinforced thermoplastic (FRTP) sucker rods, highlighting their potential advantages and challenges, for rod pumping (in general) and for offering an earlier transition from electrical submersible pump (ESP) pumping or gas lifting to reliable deep high-rate rod pumping. A unique feature of an FRTP composite rod is its remarkably high shear failure resistance compared with that of a thermoset composite rod. A high shear-failure resistance means the rods have compressional loading tolerance and that an entire sucker rod string could be comprised of FRTP sucker rods. Introduction Sucker rods made from steel are relatively heavy. Extensive well-specific designs require tapering of rod strings to optimize the overall sucker rod string weight relative to the strength and fatigue requirements and consideration of the dynamic loadings from accelerations and decelerations of the rods and fluids, frictional effects, and structural or power limitations of the pump jack or unit at surface. Steels suffer from corrosion risks. Corrosion, which rapidly can accelerate fatigue failure, often is the root cause of sucker rod failure. Fiber-reinforced composites (i.e., fibers surrounded by or wetted by a resin matrix) have gained considerable popularity because they can be tailored to have outstanding mechanical, thermal, and physical properties, and have superior material mechanical properties to metal. The fatigue behavior of composite materials and structures is complex because composites fail by a series of, or collection of, damage mechanisms, including fiber breakage, matrix cracking, fiber/matrix debonding, delamination, and the effect of shear-induced damage on cracks. Cracking can be slowed somewhat if the reinforced fibers are of high stiffness. Composite materials can offer a lower environmental footprint over their entire life cycle. They can require less energy to manufacture, thereby reducing CO2 emissions. A high strength/weight ratio offers less energy consumption during operational use, further reducing CO2 emissions. Composite materials can be recycled and reused. Composite sucker rods, in the form of thermoset fiberglass sucker rods, have offered a high strength/weight ratio with greater corrosion tolerance, but they are too stretchy from a low glass fiber tensile modulus of elasticity for deep high-rate rod pumping and when a high production-rate decline is likely. This limitation results in a large bottomhole pump-stroke variability as operating conditions change. Such rods have low tolerance to compressional and impact loads, forcing a larger proportion of a sucker string to remain as steel. They are also more costly than steel rods. For sucker rod pumping, an ideal composite rod should tolerate compressional loads and feature high impact resistance and high fatigue endurance with an ability to limit or control crack formation. A composite material that potentially offers these important sucker rod properties is FRTP.

Optimization of wear and friction behaviour of fish scale powder filled natural fibre/glass fibre hybrid epoxy composite in dry sliding condition

Abstract The purpose of this research is to look at the wear and friction properties of a unique composite material made up of fish scale powder, natural fibres, and glass fibres embedded in an epoxy matrix. The growing demand in many industries for eco-friendly and sustainable materials has resulted in the development of hybrid composites that combine natural and synthetic reinforcements. The goal of this study is to improve the wear resistance and frictional qualities of composite material under dry sliding conditions. The wear and friction behaviour of the composite is optimized using the Response Surface and Taguchi approach, which entails constructing a set of trials based on a statistical model. The significant components, which include fish scale powder content, natural fibre type and content, and sliding parameters, are carefully varied to determine the best combination that results in the least amount of wear and friction. The accuracy of the regression models exceeded expectations. According to Taguchi’s findings, F and V have the largest impact on wear loss and friction, respectively. Fish scale powder has shown great promise as a filler for enhancing the wear resistance of composites, as seen by the study’s findings. The optimized composite has exceptional wear resistance and low friction, making it a suitable alternative for dry sliding applications.

Experimental insights into increasing laser output at 2.8 µm in Er3+-doped zinc-tellurite fibers.

In this paper, we provide a new experimental insight into the lasing process in the erbium-doped tellurite glass fiber at high diode-pump powers and pumping pulse durations. It is shown that lasing occurs at two wavelengths. Initially, at a fixed wavelength of 2.718 µm corresponding to the luminescence maximum, lasing takes place during the first ∼100 µs from the start of the pump pulse, while the main laser power occurs at the 2.8 µm for the rest of the pump pulse and shifts to longer wavelengths with increasing pump power. At pumping durations essentially exceeding the lifetime of the upper laser level, no self-termination of lasing occurs; on the contrary, the lasing power increases, which indicates the key role of the energy transfer upconversion (ETU) process. We demonstrate for the first time to our knowledge efficient lasing with an average power of 60 mW and a pulsed energy of 1.2 mJ in an erbium-doped zinc-tellurite fiber.

Improving dynamic energy absorption performance and stability loss prediction of an all-PET sandwich structure through artificial neural networks

Abstract One key characteristic that is frequently studied in composite sandwich structure mechanics is low-velocity impact performance. Single polymer composites present higher ductility when compared to traditional glass fibre and carbon fibre reinforced plastic composites (GFRP, CFRP), which makes them strong candidates for impact energy absorption. These lightweight structures are also fully recyclable due to their all-PET constituents, an important aspect when considering possible applications. In this paper an existing second order composite SrPET and PET foam sandwich structure (self-reinforced poly-ethylene terephthalate matrix and fibre) is numerically investigated for optimal structural design configuration under out-ofplane, low velocity, dynamic loading. The study explores the parametric geometry interdependencies of the structure’s configuration with respect to its energy absorption potential. The results are then compared to the quasi-static loading performance behaviour studied by M.N. Velea et all [1]. This work provides a deeper understanding of how geometry configurations can influence energy absorption capabilities highlighting structural strengths and weaknesses while exploring non-equilateral triangle configurations. The Design Space Exploration (DSE) is carried out by using an optimization algorithm for a dynamic out of plane 3D impact simulation based on the finite element (FE) method software. The synergy between DSE and FE generates a guided simulation loop that can successfully be used to train a neural network to predict the dynamic behaviour of different geometric configurations from the exploration space. Based on the data samples obtained, an artificial neural network (ANN) is built to predict the energy absorption capacity for a given set of structural design parameters, useful in experimental validation test cases.

An innovative strategy for improving ductility of seawater sea-sand engineered cementitious composites beam reinforced with GFRP bar

Seawater sea-sand engineered cementitious composites (SS-ECC) members with glass fiber reinforced polymer (GFRP) bars have inferior ductility due to the brittle nature of GFRP bars. In the current research, an enlarged head anchorage system (EHAS) was recommended to improve the ductility of GFRP bars reinforced SS-ECC beams. To explore the bond characteristics between SS-ECC and GFRP bars with EHAS, a total of 39 specimens were tested by pull-out loading. The influences of enlarged head shape, stirrup spacing and SS-ECC’s strength grade on the bond characteristics were experimentally investigated. GFRP longitudinal bars in specimens with EHAS presented rupture failure rather than anchorage failure. EHAS could effectively realize the slip hardening of GFRP bars in low strength SS-ECC, and ensure the reliable bond of GFRP bars in high strength SS-ECC. Additionally, the failure mechanism of specimens under pull-out loading was explored by finite element analysis (FEA). The pull-out resistance was mainly provided by EHAS in force transition stage and slip hardening stage. The influences of fiber reinforced polymer (FRP) bar type on the bond performance were investigated by FEA. EHAS could realize the slip-hardening behaviors of aramid, basalt and carbon FRP bars in normal strength SS-ECC. More importantly, to verify the effectiveness of the proposed ductility enhancement strategy, SS-ECC beams reinforced with GFRP bars were tested by four-point bending. These beams with different enlarged head shapes possessed excellent ductility and strong ultimate deformation capacity. It was recommended that low strength SS-ECC and GFRP bars with EHAS were jointly utilized to enhance the ductile performance of the beams.

Performance of tube-in-tube membrane microreactor in E2/EE2 degradation via UV/H2O2/TiO2 process

The tube-in-tube membrane microreactor is an advanced system designed for the continuous removal of contaminants of emerging concerns (CECs) from urban and industrial wastewater. Despite its high removal efficiency, critical questions remain regarding the impact of various operational parameter: (i) flow rate of contaminants, (ii) oxidant dosage, (iii) concentration of the H2O2 stock solution, and (iv) pH of the H2O2 stock solution. This study addresses these questions, with particular focus on the previously unexplored effects of H2O2 concentration and pH. We investigated the degradation of estrogens 17β-Estradiol (E2) and 17α-Ethinylestradiol (EE2) using a UV/H2O2/TiO2 process using a membrane tube-in-tube reactor assembled with an inner glass fiber microfiltration membrane, coated with the catalyst TiO2-P25, and an outer quartz tube. Synthetic contaminated solution [E2/EE2]inlet = 500μgL-1 was fed in the reactor annulus and the H2O2 stock solution with different pHs (2, 3, 4, 5, 6.8, 8) and concentrations ([H2O2]stock solution = 3000, 6000, 9000 and 12000mgL-1) was fed through the membrane pores (radial permeation) or injected upstream the reactor inlet with different dosages ([H2O2]inlet = 0, 5, 10, 15, 20mgL-1) by means of a syringe pump. Experiments were performed under UVC irradiation and dark conditions. The highest observed removal rate was, approximately, 2.9µM/min for both estrogens, achieved after 7min of reactor operation, highlighting the reactor’s potential for effective CEC degradation under optimized conditions.

AE based crack size estimates from delamination propagation in fiber reinforced thermoset composites

In previous research it has been shown that micro-crack sizes estimated from acoustic emission (AE) data recorded during Mode I interlaminar delamination propagation in a carbon fiber reinforced PEEK and micro-crack sizes seen in video recordings from simultaneously performed X-ray projection radiography with a contrast agent indicate reasonable agreement. Now the approach of estimating crack sizes from AE data is extended to a carbon and a glass fiber reinforced epoxy laminate, using the same matrix. In a first step sensitivity of the AE measurement is estimated based on recorded AE data and estimated delamination area. Different signal filtering approaches are applied to AE data resulting in different estimated sensitivities. Furthermore, assumed delamination area affects sensitivity. Optical microscopy is used to account for roughness of the delamination area. Depending on the assumed sensitivity, average crack size diameters are either slightly below or above 100 µm in both investigated laminates.

High-efficiency 1.6 μm-band fiber laser based on single Er3+-doped tungsten tellurite glass with high mechanical strength through tailored glass network

In this study, the correlation between the Raman structure, thermal stability, and mechanical properties of TeO2-ZnO-La2O3–WO3 glasses with varying WO3 contents are systematically established. By exploring the critical point in the transformation process of glass network structural units, the optimal glass components of 74TeO2-12ZnO-5La2O3–9WO3 glass possess the maximum thermal stability (158 °C) and the highest mechanical properties at the same time. The maximum Vicker hardness and Young's modulus of the optimal glass can reach up to 4.007 GPa and 56.212 GPa, which are higher than those of the well-known TeO2-ZnO-Na2O (TZN) and TeO2-ZnO-La2O3 (TZL) glasses. Furthermore, the 0.5 mol% Er3+-doped glass at this critical point (TZLW-0.5Er) exhibits a higher laser figure of merit (54.29 × 10−21 cm2 ms), a larger laser gain bandwidth value (116 nm) and higher emission cross-sections at 1600 nm (2.52 × 10−21 cm2) and 1625 nm (1.06 × 10−21 cm2) than other host glasses. Finally, high-efficiency laser outputs at 1600 and 1625 nm based on TZLW-0.5Er glass fiber are successfully achieved by simulation. These results show the greater practical potential of TZLW-0.5Er glass with higher mechanical strength compared to TZN and TZL fibers for the 1.6 μm-band laser.

Synthesis of SiC nanowires from retired wind turbine blades and their microwave-absorbing property

Retired wind turbine blades (RWTBs) mainly consist of glass fibers and resins, which have abundant of carbon and silicon resources. This study synthesized SiC nanowires (SiC NWs) by using the RWTBs for the first time. The RWTBs were grinded into powders and pyrolyzed at 600 °C for 2 h, the pyrolysis solid residues (P-RWTBs) mixed with apricot shell char (ASC) and silicon powder in a stoichiometric ratio (C/Si=4), and then the mixture calcined at 1550 °C for 4 h in an argon atmosphere. XRD, FTIR and XPS results indicating that SiC NWs had been successfully synthesized. SEM and TEM micrographs show that the produced SiC NWs exhibit a worm-like shape, with diameters of 50–100 nm, and interweave into a 3D network body. The minimum reflection loss (RLmin) of the SiC NWs 3D network body reached -18.17 dB at the thickness of 4.8 mm, which meet the requirements of microwave-absorbing materials. Its good microwave-absorption property is due to the various loss types of the electromagnetic waves that caused by the special structure. This study provides a new approach for high-value utilization of the RWTBs, which is of great significance in realizing the "green retirement" of glass fiber reinforced polymers.

An Exploration of Dissolution Tests for Inhalation Aerosols.

This study aimed to establish a feasible dissolution method for inhalation aerosols. A method of collecting fine particles was investigated to capture aerosol particles less than 4μm in diameter for dissolution tests. This dose collection method enabled the aerosol particles to be uniformly distributed on the glass fiber filter, thus considerably reducing particle agglomeration. Budesonide was used as a model drug. The aerodynamic particle size distribution (APSD) of the meter-dose inhaler (MDI) was compared by replacing actuators with different orifice sizes. Dissolution tests were conducted on fine particle doses collected using various actuators, and the dissolution profiles were modeled. The fine particle dose decreased with an increasing orifice size of the actuator. Actuators with different orifice sizes would affect the dissolution behavior of inhaled drugs. This finding was supported by similarity factor f2 analysis, suggesting the dissolution method has a discriminative capacity. The results of various model fits showed that the dissolution profiles produced by the different actuators could be fitted well using the Weibull mathematical model. The method employed in this study could offer a potential avenue for exploring the relationship between the orifice size of the actuator and the dissolution behavior of inhaled corticosteroids. This dissolution method was simple, reproducible, and suitable for determining the dissolution of inhalation aerosols.

Effect of laser ablation on mechanical performance of graphene-filled glass fibre reinforced polymer repaired composites

Abstract This paper aims to investigate the effect of laser ablation on the mechanical performance of graphene-filled glass fibre reinforced polymer (GFRP) repaired lap joints. The performance characteristics of repaired laminates were measured in terms of surface roughness, tensile strength and flexural strength according to ASTM standards. While the surface morphology was examined using a confocal microscope, scanning electron microscopy was adopted to analyse the laser ablated fibre–matrix interface. The average surface roughness significantly increased with an increase in laser power from 4 to 10 W which was attributed to the presence of graphene and burnt fibres. The laser ablation conditions corresponding to 10 W laser power, 300 mm s−1 scanning speed, 20 kHz of pulse frequency, 0.05 mm line spacing and 5 laser passes lead to the highest tensile strength (36.033 MPa) and bending strength (30.972 MPa) of GFRP laminates. The laser ablated microstructure was characterised by fibre pull-out, epoxy residue, burnt, clean fibres as evidenced by scanning electron microscopy.

Ultrathin PVP/ZnMoO4@PE separator for high-safety sodium-ion batteries

In this work, an ultrathin (∼19 μm) PVP/ZnMoO4@PE separator is designed and achieved with much enhanced thermal performance for high-safety sodium-ion batteries (SIBs). The PVP/ZnMoO4@PE separator is prepared by coating the polyvinyl pyrrolidone (PVP)/ZnMoO4 ceramic slurry on one side of commercial polyethylene (PE) separator in an economically efficient way. It is found that the superior PVP binder would interact with ZnMoO4 nanoparticles and enhance the bonding strength of heat-resistant ZnMoO4 ceramic nanoparticles on the surface of PE substrate, which significantly improves the thermal performance of the optimized separator. The optimized PVP/ZnMoO4@PE separator shows high thermal stability with no shrinkage at 180 °C for 30 min. In addition, the PVP/ZnMoO4@PE separator shows improved wettability with electrolyte, larger porosity and better electrolyte storage capacity than bare PE separator, which are quite beneficial to ionic conductivity. Furthermore, the electrochemical results show that half-cell (hard carbon/sodium) assembled with the optimized PVP/ZnMoO4@PE separator shows better electrochemical performance that the half-cell assembled with commercial glass fiber separator (thickness of ∼ 455 μm), while bare PE separator does not work properly in SIBs. This study provides insight into the practical application of ultrathin and high-safety PVP/ZnMoO4@PE separator in commercial SIBs.

Enhancing wind turbine blade protection: Solid particle erosion resistant ceramic oxides-reinforced epoxy coatings

Wind energy has been regarded as one of the renewable energy sources to rely on in the future. In this aspect, wind turbine blade maintenance is quite a challenge in tropical areas like India. One of the main reasons why wind turbine blades get damaged and produce less energy is solid particle erosion. In the present work, nanocomposite epoxy (EP) coatings reinforced with Al2O3, ZrO2, and CeO2 nanoparticle fillers have been applied on glass fiber reinforced polymer (GFRP) substrates using a simple spray coating method. These nanoparticles have been prepared in-house by solution combustion synthesis (SCS) route using urea, glycine, and oxalyl dihydrazide fuels. X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy have been used to characterize the materials and coatings. EP coatings with different Al2O3, ZrO2, and CeO2 nanoparticle concentrations have been subjected to solid particle erosion resistance tests at impinging angles of 30°, 60° and 90°. ZrO2 and CeO2 nanoparticle-reinforced EP coatings show better resistance to solid particle erosion than Al2O3-reinforced coatings. Estimated average erosion rates are 17 and 11.3 × 10−3 mm3 g−1, respectively, for epoxy coatings with 20 and 40 wt% ZrO2 nanoparticles. However, GFRP substrate and neat EP coating show much higher erosion rates with respect to nanoparticles-reinforced EP coatings. To ascertain a correlation between H3/E2 and the solid particle erosion rates of the coatings, nanoindentation tests have been carried out. Tensile strength and initial modulus of all the coatings are found to be directly proportional to the average erosion rates, whereas, elongation at break shows an inverse relationship with the average erosion rate. This correlation of mechanical properties with solid particle erosion performance can play a critical role in the development of realistic simulation of protective coatings for wind turbine blades.

An Experimental Investigation of Surface Roughness And Cutting Forces On GFRP

In the current study, the emphasis was on finding experimental results on machinability of Glass fibre reinforced plastic composite with milling machine. Study is carried out with objectives of examination of cutting parameter on GFRP materials. Speed , feed, depth of cut & number of flute are consider for analyzing effect on surface finish & cutting forces of composites. Design of experiment is carry out by Taguchi’s L18 orthogonal array. To find out more about the machining parameters on GFRP composite using end mill of cemented carbide, an analysis of variances (ANOVA) utilizing Minitab 15 software was finally carried out.

Experimental analysis of quasi‐static indentation in composite sandwich multilayers with corrugated core

AbstractThis study examines the effects of multilayering in sandwich panel composite structures with different corrugated core configurations under quasi‐static indentation loading. The panels were fabricated using woven glass fibers and epoxy resin via the Vacuum Infusion Process. Experiments were conducted using two hemispherical cylindrical indenters with a diameter of 20 mm (ID = 20 mm) and 10 mm (ID = 10 mm) and the behavior of the composite structure in terms of contact force and fracture mechanisms for different core corrugations (square and butterfly) were investigated in two ways with foam and without foam. The experimental results demonstrate that, among corrugated core geometries without foam, butterfly cores outperform square cores in terms of structural strength, maximum force, moment force, energy absorption, specific energy absorption, and displacement until full indentation. Moreover, the butterfly core shows a higher peak load and different failure mechanisms compared to the square core. Under loading with a 10 mm indenter, the butterfly core without foam only experienced perforation in the loading area, without fracture completely. Also, adding foam did not change failure mechanisms and mechanical behavior in the butterfly geometry. However, in the square geometry, foam filled gaps between the core, preventing fracture completely and leading to only perforation in the loading area, unlike the specimen without foam. The visual analysis during the quasi‐static indentation process revealed several significant damage mechanisms, including matrix cracking, fiber breakage, delamination, buckling and crushing of cell walls, damage to top sheets, core separation, and complete indentation of the samples.Highlights Delamination and indentation failure mechanisms were seen on the butterfly core. Skin indentation and rib fracture failure mechanisms were seen on the square core. Butterfly corrugated cores revealed the best performance without/with foam. The core shape was more effective on the strength than the foam addition.

STUDY OF THE USE OF THERMAL DRILLING IN MECHANICAL JOINING OF MG SHEET AND GFRP/CFRP COMPOSITES WITH THERMOSOFTENING MATRIX

The paper discusses the joining of magnesium based metallic sheet and composites with thermosoftening polypropylene matrix reinforced with bi-directional continuous glass and carbon fibers by thermal drilling technology. The bushing formation has been investigated by separately drilling AZ91 Mg alloy sheet at two rotational speeds and feed rates to find out the parameters at which a bushing with optimum length and thickness, suitable for joining with the composite, is formed. Under these conditions, the joining of the metal sheet and composite was then carried out by simple thermal drilling. During simple drilling, delamination of the composite occurred in the vicinity of the hole, which was resolved by flanging the bushing with a penetration of the tool from the opposite side. When AZ91 was joined to carbon fibers reinfirced composite, there was a lack of bushing formation due to the higher resistance of the carbon fibers, which are present in the composite in greater numbers compared to the glass fibers. This problem was solved by sequential drilling, which means that a flowdrill tool was used to create a hole in the composite itself, then overlaid with Mg sheet and again drilled, forming the bushing and flanging the bushing from the opposite side. The sequential drilling resulted in joints with a load capacity of 0.8 - 1.4 kN, which exhibit the characteristics of a hybrid - mechanical and adhesive joint.