Single Lap Shear Strength Research Articles

Enhancing resistance welding strength of carbon fiber/polycaprolactam thermoplastic composites through coupling agent‐modified metal heating elements

AbstractThis study investigates the impact of coupling agent‐modified resistance welding heating elements on the welding strength of carbon fiber‐reinforced polyamide 6 (PA6) thermoplastic composites. Silane coupling agent KH550 and titanate coupling agent UP‐201 were used to modify heating elements made of 304 stainless steel mesh. Optimal modification parameters for KH550‐modified stainless steel mesh (SSM) were determined using orthogonal experiments, resulting in maximum single lap shear strength (LSS) of 17.05 MPa under specific welding conditions. Comparative tests demonstrated the enhancement effect of UP‐201‐modified SSM on LSS. Additionally, two experimental schemes were used to study the synergistic enhancement effect of KH550 and UP‐201 on the LSS of resistance welded joints. The findings indicate that both coupling agents improve the welding strength, with significant differences in their individual and combined effects.Highlights This study explores carbon fiber reinforced Nylon 6, an innovative thermoplastic. Analyzed effects of modified heating elements on joint shear strength. Examined silane and titanate coupling agents' effects on weld joint shear strength. Investigated synergistic effects of silane and titanate agents on weld joint strength. Investigated the synergistic enhancement mechanism of silane and titanate agents.

On the Influence of Welding Parameters and Their Interdependence During Robotic Continuous Ultrasonic Welding of Carbon Fibre Reinforced Thermoplastics.

Ultrasonic welding of fibre-reinforced thermoplastics is a joining technology with high potential for short welding times and low energy consumption. While the majority of the current studies on continuous ultrasonic welding have so far focused on woven reinforcements, unidirectional materials are preferred for highly loaded aerospace components due to their better mechanical performance. Therefore, this paper investigates the influence and interdependence of the welding speed, amplitude, and energy director thickness on the weld quality of adherends made of unidirectional composites. The quality of the welded joints is assessed by a single-lap shear strength and fracture surface analysis complemented by the microscopic analysis of cross-sections and comparison to a co-consolidated reference. The results showed that the welding process is highly affected by changing welding speeds for a given amplitude. Furthermore, while lower amplitudes lead to significant scatter in the welding quality, higher amplitudes result in increased heating rates and a fully molten energy director even for high welding speeds. Nevertheless, insufficient consolidation at high welding speeds results in porosity in the weld line. Finally, it was observed that thicker, and therefore more compliant, energy directors lead to more uniform melting of the energy director and less deviation in the weld quality for a wider range of welding speeds.

Curing and Failure Monitoring of Composite Material Single-Lap Joint Based on CNT/PSF Sensor

Abstract Composite bonded structures are widely used in the field of aerospace. The safety of composite structures can be ensured by the health monitoring and early warning of their whole life. In this paper, a composite CNT/PSF film sensor based on asymmetric porous PSF film was designed and prepared. Through integrated molding with epoxy film, in-situ monitoring of gel point (142.1°C) and curing time (36min) of epoxy film is realized. After optimization of curing process, tensile strength of epoxy film casting body is increased by 86.3%. The single lap shear strength of the composite is increased by 45.7%. The CNT/PSF film sensor with composite material has high response sensitivity (GF≈1.4) and linearity (0.998) to cyclic strain (0-3000με). In the shear experiment of composite single lap joint, the adhesive layer presents a typical cohesive failure mode of first compression, then tensile and finally failure. The resistance changes of CNT/PSF film sensor first decreases from 0 to -1‰, and then rises to 2.7‰. Finally, the fracture response is good, and the in-situ failure behavior monitoring of the joint can be fully realized.

Bio‐composite using polyhydroxyalkanoates and sustainable nanofillers derived from cellulose nanofibers and its application for an environmentally friendly packaging material

AbstractPolyhydroxyalkanoates (PHA) is a carbon neutral material that contributes to reducing greenhouse gas emissions due to manufactured from biomass and easily degraded by the enzymatic effects of microorganisms in the natural environment. However, PHA exhibits poorer mechanical properties and processability compared with petroleum‐based plastics. This study used cellulose nanofiber (CNF) to improve limit of PHA. Moreover, CNF was silylated to reduce polarity difference with PHA and enhance the dispersibility of nanocellulose at PHA. At a result, the silylation process was successfully performed by Si‐CH3 stretching peaks in Fourier transform infrared spectroscopy spectra and hydrophobicity of TEOS‐MTES‐CNF (TECNF) was confirmed by observed water contact angle (147°). In addition, nanostructure of TECNF was maintained during silylation and drying process through field emission scanning electron microscopy. Moreover, the PHA/TECNF composite showed enhanced processability, and tensile strength was increase almost 37% (0.52 MPa) compared with PHA. Oxygen transmission rates (300 cc/m2۰day) and single lap shear strength (225 kPa) were determined to be at least equivalent or superior to those of commercial packaging materials. Therefore, TECNF could be considered as a reinforcing agent, nucleating agent, and plasticizer in PHA. Also, this composite has possibilities to using as environmentally friendly packaging materials.

Effect of the percentage of MUF adhesive coverage on shear strength when bonding different wood species

Due to climate changes, it is necessary to consider the use of other wood species to replace currently used woods. This work deals with the determination of the shear strength of bonded veneers (eight European wood species: spruce, larch, pine, beech, oak, poplar, birch, and alder) with Silekol® 311 melamine-urea-formaldehyde adhesive (MUF) with a variable coverage on the surface of the samples: 10, 15, 20, 25, 30, 50, 75, and 100%. The Automated Bonding Evaluation System (ABES) was used to evaluate and compare adhesive bond strengths. The larch, beech, and oak samples exhibited greater single-lap shear strength than the control samples from spruce. There was no statistically significant difference in shear strength regarding the adhesive coverage from 100% to 20% on the surface of the samples, for almost all wood species. The results of the project provide basic information about the bonding strengths with different coverage in the adhesive layer, comparing non-commonly used wood species in wood-based composites such as oriented strand board and particleboard.

Experimental evaluation of atmospheric plasma treatment effects on different textures of CFRP composite for aircraft applications

This article examines the impact of Atmospheric Plasma Treatment (APL) on the chemical composition and fracture properties of various textured surfaces (tool and bag side) of carbon fiber/epoxy (CFRP) composites utilized in aircraft applications. For this purpose, parameters of atmospheric plasma (APL) surface treatment were evaluated in comparison to chemical cleaning and peel-ply applications, taking into account its effects on surface properties and adhesive bond strength. A comprehensive variety of surface characterization techniques were utilized to analyze surface modifications, including water and diiodomethane contact angle measurements for assessing surface hydrophilicity, Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR) and X-ray Photoelectron Spectroscopy (XPS) for analyzing chemical composition and functional groups, and Profilometry, Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM) for evaluating surface topography and morphology. Experimental results indicated that the reduction in the contact angle following plasma treatment correlated with the elevated oxygen concentration and the presence of polar functional groups (e.g. -OH, -NH2, -NH3, C=O, O-C=O) on the composite surface. Plasma treatment, especially at low nozzle speeds, increased surface roughness on the bag side surfaces. This prevented adhesive penetration and led to gas entrapment, resulting in adhesive failure mode and reduced single lap shear strength for the bag side. In contrast, on the tool side surfaces, the plasma treatment led to a remarkable 19.7% enhancement in shear strength, highlighting its effectiveness.

Influence of air DBD plasma treatment on the shear and flexural strength of adhesively bonded glass fiber reinforced epoxy composite joints

In this study, air dielectric barrier discharge (DBD) plasma treatment was applied at various voltages and treatment durations to improve the bonding strength of glass fiber reinforced epoxy composites (GF/EP). In addition, single lap shear and three-point bending strengths of adhesively bonded joints were compared between untreated and surface-treated (sanding, peel ply, and plasma) samples. Surface properties of GF/EP composites were examined using contact angle, surface free energy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Atomic Force Microscopy (AFM). Then, mechanical tests (single lap shear and three point bending) were performed and the damage modes were determined. Surface analyses revealed that wettability and polar functional groups increased on the GF/EP surface after plasma treatment. From the mechanical test results, it was observed that the plasma treatment applied to GF/EP composites increased both single lap shear and flexural strength compared to untreated, sanding and peel ply surface treatments. After both single lap shear and 3-point bending tests, adhesive, and light fiber tear failure modes were observed.

Core-Shell Rubber Nanoparticle-Modified CFRP/Steel Ambient-Cured Adhesive Joints: Curing Kinetics and Mechanical Behavior.

Externally bonded wet-layup carbon fiber-reinforced polymer (CFRP) strengthening systems are extensively used in concrete structures but have not found widespread use in deficient steel structures. To address the challenges of the adhesive bonding of wet-layup CFRP to steel substrates, this study investigated the effect of core-shell rubber (CSR) nanoparticles on the curing kinetics, glass transition temperature (Tg) and mechanical properties of ambient-cured epoxy/CSR blends. The effects of silane coupling agent and CSR on the adhesive bond properties of CFRP/steel joints were also investigated. The results indicate that CSR nanoparticles have a mild catalytic effect on the curing kinetics of epoxy under ambient conditions. The effect of CSR on the Tg of epoxy was negligible. Epoxy adhesives modified with 5 to 20%wt. of CSR nanoparticles were characterized with improved ductility over brittle neat epoxy; however, the addition of CSR nanoparticles reduced tensile strength and modulus of the adhesives. An up to 250% increase in the single-lap shear strength of CFRP/steel joints was accomplished in CSR-modified joints over neat epoxy adhesive joints.

Mechanical response of carbon fiber reinforced epoxy composite parts joined with varying bonding techniques for aerospace applications

As a result of the widespread use of composite materials in primary structures of aerospace platforms, composite joining became more crucial. This study addresses the effect of joining methods on the strength of composite joints experimentally, numerically and analytically. Single lap joint shear strengths of carbon fiber reinforced epoxy composite parts joined by mechanical fastening with a pop and solid rivet, secondary bonding with a paste adhesive, co-curing and co-bonding techniques were compared. In addition, the effect of adhesive thicknesses (0.2, 0.4, 0.6, 0.76 mm) on the single lap shear strength was investigated. Carbon fiber reinforced composite (CFRP) samples were produced according to the ASTM 5868 standard. After the production of samples with varying joining methods, single lap shear tests were implemented. Moreover, the interface damage in the composites was examined by use of a scanning electron microscope (SEM) for the purpose of studying the damage mechanism. Fracture mechanisms corresponding with bonding methods were also assessed by examining the fracture surface of the composite samples. Furthermore, results were analyzed by Hypermesh, ABAQUS and ESAComp. For instance, the co-bonded sample with an adhesive film exhibits an experimental shear strength of 24.03 MPa which deviates only 3 % from the numerical expectation.

Improving film adhesive joining performance of poly(phenylene sulfide)/carbon fiber thermoplastic composite laminates by plasma surface treatment

The main purpose of this study was to observe the degree of the improvement on the film adhesive joining performance of Poly(phenylene sulfide)/Carbon Fiber (PPS/CF) thermoplastic composite laminates when their surfaces were treated by atmospheric plasma technique. For this purpose, plasma treated surfaces were compared with untreated and the traditional grit-blasted surfaces. Treated surfaces were characterized by various techniques including contact angle, surface energy, surface roughness, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. Then, joining performance of the PPS/CF composite samples bonded by an epoxy-based film adhesive was determined by using three different mechanical tests; single-lap shear strength, mode-I interlaminar fracture toughness energy, and drop-weight impact toughness. Grit-blasting surface treatment increased surface roughness of the specimens enormously (7 times more), leading to mechanical interlocking as the dominant bonding mechanism. Contrarily, plasma surface treatment resulted in formation of chemically reactive sites, thus dominant bonding mechanisms in the film adhesive joining were certain polar interactions and chemical bonding. Mechanical tests pointed out that compared to grit-blasting, plasma surface treatment resulted in considerably higher joint performance regarding interlaminar shear strength (35% more), interlaminar fracture toughness (67% more) and impact toughness (28% more), with the cohesive failure mode. Accordingly, it could be stated that traditional grit-blasting could be replaced with plasma surface treatment applied before film adhesive joining of PPS/CF composite parts in aircraft industry.

Multifunctional heating film as susceptor for induction-welded single-lap carbon fiber reinforced polyetherketoneketone thermoplastic composite joints: Thermal and mechanical behavior

In this study, a novel multifunctional film known as susceptor, containing silver nanoparticles, was proposed to improve the induction welding performance of unidirectional carbon fiber-reinforced polyetherketoneketone (CF/PEKK) thermoplastic composites. A group of Ag/PEKK films was synthesized with different amounts of silver nanoparticles. Good thermal performance was obtained, including the maximum temperature and thermal growth time constant, leading to the selection of films with 60 wt.% and 70 wt.% silver nanoparticles. In addition, the mechanical performance was evaluated for single-lap joints fabricated with the selected films and stainless-steel mesh. Specifically, the highest interlaminar shear strength and single-lap shear strength of 25.2 MPa and 20.9 MPa, respectively, were achieved with a susceptor containing 60 wt.% silver nanoparticles. The mechanism of these increases in thermal and mechanical performance is discussed using numerical and experimental methods (non-destructive test and optical microscope observation). In conclusion, the multifunctional heating film incorporated into the adhesive can improve the thermal and mechanical efficiency of single-lap joints of thermoplastic composites fabricated using the induction welding method.

Design and characterization of a novel supported epoxy film adhesive reinforced by Ti3C2Tx MXene nanoparticles

Film adhesives made from epoxy resin are typically used in different industries including transportation and aerospace to attach aluminum substrates together. These film adhesives offer a series of advantages including ease of application and handling, control over the adhesive thickness, minimal waste and uniform product as compared to other forms of adhesive like paste adhesives. Here, we try to improve the mechanical and thermal properties of these adhesives as well as to address poor ductility and weak fracture toughness of cured epoxy as major disadvantages. We used two dimensional (2D) Ti3C2Tx nanoparticles (NPs) which is the most well-known member of the emerging MXene family. MXenes a recent class of 2D transition metal carbides, nitrides and carbonitrides, have attracted many attentions since they were synthesized in 2011.The particular structural and functional characteristics of MXenes make them good candidate for multifunctional composites. The addition of inorganic MXene NPs to epoxy matrix at 1 phr accompanied by phenolic resin (novolac type) improves the tensile strength, modulus, and toughness of the adhesive by 16.49%, 43.51%, and 17.19%, respectively. Using MXene NP-containing epoxy film adhesives for attaching aluminum pieces together, we realized that the presence of MXene increases the single-lap shear strength and T-peel strength by 32.69% and 37.94%, respectively.in addition, the thermal stability of the MXene NP-containing film adhesives was improved, as indicated by 10.51% increase in the initial degradation temperature.

Effects of interlayer forms on the resistance welding performance of PAEK/CF thermoplastic composite laminates

The main purpose of this study is to investigate usability of resistance welding joining method for poly (aryletherketone) (PAEK) thermoplastic matrix/carbon fiber (CF) reinforced composite laminates (PAEK/CF). For this purpose, effects of six different Interlayer Forms having different stainless steel meshes as Heating Elements and different woven glass fiber forms as Insulating Layers were studied. After determining welding parameters for each specimen group, performance of the resistance welding operations was compared by ultrasonic inspection, microscopic examination, DSC analyses, and by three different interlaminar mechanical tests. Analyses and tests generally revealed that use of stainless steel meshes as Heating Elements could supply proper amperage level for the heating, melting and crystallization stages of the PAEK matrix during welding consolidation. Depending on the lay-up configuration of Interlayer Forms, “amperage levels” determined for the heating, melting dwell and crystallization dwell were in the ranges of 46–100 A, 40–90 A and 25–50 A, respectively, It was also observed that in order to prevent Current Leakage problem to the other layers in the composite laminate, rather thicker and heavier woven glass fiber forms as Insulating Layers should be used. Otherwise, not only voids could form in the thermoplastic matrix, but also delamination might occur in the upper or lower PAEK/CF composite laminates being welded. When thicker and heavier insulating layer was used; interlaminar mechanical properties of Single Lap Shear Strength, Fracture Toughness under Mode-I and Mode-II were determined as high as 36.77 MPa, 3.76 kJ/m2 and 4.71 kJ/m2, respectively.

Improving epoxy adhesion with steel adherends using a tannic acid‐based additive: Impact on resin properties and interfacial bonding

AbstractTraditional adherend surface treatment techniques such as grit blasting, acid etching, phosphating and primer treatments alone are often inadequate for maintaining interfacial bond durability of adhesively bonded joints. Therefore, the existing interfacial bonds between epoxy adhesive and the adherend should be strengthened. Tannic acid (TA) is a plant‐based polyphenol that is inexpensive and easily available in nature. Its potential as an additive to improve the interfacial bond durability of epoxy adhesives has not been studied adequately. In the present study, an additive (TA‐AGE) was synthesized by grafting allyl glycidyl ether (AGE) onto phenolic hydroxyl groups of TA. With 1 wt% TA‐AGE additive in the epoxy, the single lap shear strength improved by 37%. Further, accelerated aging studies were performed to understand the impact of water uptake on the mechanical and viscoelastic properties and interfacial bond durability of the epoxy with 1 wt% TA‐AGE additive. TA‐AGE modification can increase hydrophilicity and enhance the water uptake characteristics of epoxy. This can negatively impact its mechanical properties and glass transition temperature (Tg) due to plasticization effects. Nevertheless, Boeing wedge test and single lap shear tests reveal that the strengthened interfacial bonds to steel adherends with the additive were robust and durable.

Structural and adhesion properties of waterborne polyurethane adhesives containing nanosilica dispersion obtained with different physical mixing procedures

Nanosilica dispersion was added to waterborne polyurethane dispersion by using three different physical mixing procedures differing in the flow regime (tangential, laminar, radial) and the stirring rate (300–2400 rpm). The influence of the physical mixing procedure on the structural, thermal, rheological, mechanical, surface and adhesion properties of the polyurethanes (PUs) containing 1 wt% nanosilica was evaluated. The nanosilica in the dispersion was functionalized with acrylic moieties and showed high surface tension and negative Z potential values. The PU + nanosilica blend made with higher shear rate and laminar flow regime showed high homogeneous dispersion of the nanosilica particles and greater extent of intercalation between the soft segments of the polyurethane, this led to higher thermal stability. Unexpectedly, the better dispersion of the nanosilica in the PU matrix decreased the wettability of the PU + nanosilica materials due to the migration of acrylic moieties from the nanosilica particles to the surface. As a consequence, a decrease of the final T-peel strength was found. However, the single lap-shear strength did not change by adding nanosilica because of the scarce improvement of the mechanical properties in the PU + nanosilica materials.

Preparation and Characterization of Cardanol-Based Flame Retardant for Enhancing the Flame Retardancy of Epoxy Adhesives.

Epoxy resin has a versatile set of applications due to its excellent properties. However, its easily flammable property limits further applications. A bio-based flame retardant, cardanyl diphenylphosphate (CDPP), was successfully synthesized via condensation reaction between cardanol and diphenyl phosphoryl chloride. The chemical structure of CDPP was confirmed via 1H nuclear magnetic resonance and Fourier transform infrared spectroscopy. To overcome the flammable property of epoxy resin, different amounts of CDPP were incorporated into the epoxy resin. The thermal stability of epoxy resin with CDPP was reduced due to its phosphorus component, which had a relatively weak bond. Meanwhile, the measured char residue of epoxy resin with CDPP was increased compared to its calculated value, which indicated that CDPP promoted the formation of char residue. The limiting oxygen index of epoxy resin with CDPP was enhanced as the amount of CDPP increased from 22.1% for EP0 to 32.7% for EP10. The maximum value of the heat release rate per unit area and total heat release values of EP10 decreased by 23.23% and 12.02%, respectively, as compared to those of EP0. Additionally, single lap shear strength confirmed the improvement in the adhesion property of EP5. The lap shear strength increased to 7.19 MPa for EP5 compared to 6.27 MPa for EP0. This behavior might be due to the higher polarity of the phosphorus components. Based on the findings gathered in the present study, the incorporation of a bio-based flame retardant (CDPP) in epoxy resin has the potential for improving flame retardancy and adhesion property, which will be promising for the industrial area.

Effect of hygrothermal condition on single-lab shear behavior of induction-welded CF/PEKK thermoplastic composites

This study analyzed the effects of hygrothermal conditions on the single-lap shear strength of a carbon fiber/poly-ether-ketone-ketone (CF/PEKK) thermoplastic composite material fabricated by induction welding. Specimens were exposed to an 85 °C/85% environment using a temperature and humidity chamber to identify the effect of moisture on single-lap shear strength, while their moisture saturation was assessed through weight measurement. Single-lap shear strength tests were performed on the dried and saturated specimens at 25 °C and 100 °C to 180 °C at 20 °C intervals. At 160 °C, the strength of the CF/PEKK thermoplastic composites rapidly declined to 76% (dried specimens) and 78% (moist specimens). The fracture surfaces and failure modes were analyzed using scanning electron microscopy images, which confirmed an increase in the degraded areas and naked fibers at higher testing temperatures. In addition, it was found that exposure to a moist environment changes the failure mode from fiber bundles and fiber/matrix failure to naked fiber and matrix failure owing to the reduction in interfacial adhesion properties. The findings confirmed that hygrothermal conditions directly affect the degradation of the CF/PEKK thermoplastic composites and that a rapid reduction in the single-lap shear strength occurs above Tg.

Methylethynyl-Terminated Polyimide Nanofibrous Membranes: High-Temperature-Resistant Adhesives with Low-Temperature Processability.

As an alternative to traditional riveting and welding materials, high-temperature-resistant adhesives, with their unique advantages, have been widely used in aviation, aerospace, and other fields. Among them, polyimide (PI) adhesives have been one of the most studied species both from basic and practical application aspects. However, in the main applications of solvent-type PI adhesives, pinholes or bubbles often exist in the cured PI adhesive layers due to the solvent volatilization and dehydration reaction, which directly affect the adhesive performance. To address this issue, electrospun PI nanofibrous membranes (NFMs) were employed as solvent-free or solvent-less adhesives for stainless steel in the current work. To enhance the adhesion of PI adhesives to the metal substrates, phenolphthalein groups and flexible ether bonds were introduced into the main chain of PIs via the monomers of 4,4′-oxydiphthalic anhydride (ODPA) and 3,3-bis[4-(4-aminophenoxy)phenyl] phthalide (BAPPT). At the same time, the methylethynyl group was used as the end-capping component, and the crosslinking reaction of the alkynyl group at high temperature further increased the adhesive strength of the PI adhesives. Three kinds of methylethynyl-terminated PI (METI) NFMs with the set molecular weights of 5000, 10,000, and 20,000 g/mol were first prepared via the one-step high-temperature polycondensation procedure. Then, the PI NFMs were fabricated via the standard electrospinning procedure from the soluble METI solutions. The afforded METI NFMs showed excellent melt-flowing behaviors at high temperature. Incorporation of the methylethynyl end-capping achieved a crosslinking reaction at 280−310 °C for the NFMs, which was about 70 °C lower than those of the phenylacetylene end-capping counterparts. Using the METI NFMs as adhesive, stainless steel adherends were successfully bonded, and the single-lap shear strength (LSS) was higher than 20.0 MPa at both room temperature (25 °C) and high temperature (200 °C).

Effect of surface treatment on the performance of composite‐composite and composite‐metal adhesive joints

AbstractThe use of Fiber‐Reinforced Polymer Composites (FRPCs) in automotive, aerospace, and naval applications has increased significantly due to the requirement for a high performance‐to‐weight ratio. One the issue in using composite parts is their joining to the metal parts in the global structure. Several joining techniques such as mechanical joining, adhesive, vibration joining, and hybrid joining are used for this purpose. Being lighter in weight and lower in cost in comparison to other techniques, adhesive bonding is mostly used for composite‐composite and composite‐metal joining. To achieve reliable adhesive joining, surface preparation of the joining substrates is of utmost importance. Though the effect of physical surface treatments on the performance of joints has been reported in the literature, however, the effect of chemical surface treatment of composites on the mechanical performance of adhesive joints was rarely studied. In this article, the effect of chemical treatment (alkaline permanganate), of the composite surfaces on the single lap shear strength and Izod impact strength of composite‐composite and composite‐metal adhesive joints is reported. The results showed that the chemically treated joints demonstrate a significant improvement in these properties.

Optimization of additive manufacturing for the production of short carbon fiber-reinforced polyamide/Ti-6Al-4V hybrid parts

The present work is aimed at utilizing an adapted version of the Fused-Filament Fabrication process as a means to produce hybrid joints comprised of sandblasted, rolled Ti-6Al-4V substrates and additively manufactured short carbon fiber-reinforced polyamide (PA-CF). Layer height (h), printing speed (v) and printing bed temperature (Tbed) for the coating layer (i.e. initial layer with unreinforced polyamide) were varied. Using the ultimate single-lap shear strength (ULSS) of the produced joints as a response, linear and polynomial regressions were fit to the experimental dataset using an approach based on Machine Learning. The linear model achieved a better accuracy, with a test R2 of 0.76. It was possible to conclude that the ULSS is strongly dependent on the actual coating layer height (hreal), which in turn depends on h and v. The optimal set of parameters resulted in an ULSS of 23.9 ± 2.0 MPa. Additionally, specimens for a three-point bending test based on the ISO 14679:1997 were produced and tested to further evaluate the influence of coating layer on mechanical behavior of hybrid joints, this time focusing exclusively on their interphase component. For this test, v did not play a statistically significant role, whereas h did.