Materials

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13 pages, 2767 KiB

Open AccessArticle

Mode II Delamination under Static and Fatigue Loading of Adhesive Joints in Composite Materials Exposed to Saline Environment

by Paula Vigón, Antonio Argüelles, Miguel Lozano and Jaime Viña

Materials 2023, 16(24), 7606; https://doi.org/10.3390/ma16247606 - 12 Dec 2023

Viewed by 841

Abstract

This study investigates the fatigue delamination behavior of adhesive joints in epoxy carbon composite materials under Mode II fracture loading. The joints were characterized using the End-Notched Flexure (ENF) test, comprising adhesive joints formed by bonding two unidirectional carbon fiber epoxy matrix laminates [...] Read more.

This study investigates the fatigue delamination behavior of adhesive joints in epoxy carbon composite materials under Mode II fracture loading. The joints were characterized using the End-Notched Flexure (ENF) test, comprising adhesive joints formed by bonding two unidirectional carbon fiber epoxy matrix laminates with epoxy adhesive. These joints were subjected to different exposure periods (1, 2, 4, and 12 weeks) in a saline environment. Prior to dynamic fatigue testing, critical Mode II energy release rate values were determined through quasi-static tests, serving as a reference for subsequent fatigue characterization. This study aimed to comprehend how exposure duration to a saline environment affected the initial stage of fatigue delamination growth and employed a probabilistic model based on the Weibull distribution to analyze the experimental data. The results, gathered over a two-year experimental program, revealed varying behaviors in adhesive joint resistance to delamination based on exposure duration. A noteworthy reduction in fatigue strength capacity was observed, with fracture energies for infinite fatigue life reaching approximately 20% of their static loading capacity. This study sheds light on the deterioration of adhesive joints when exposed to a saline environment. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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13 pages, 3597 KiB

Open AccessArticle

Prototype Test of Resilient Friction Materials for Seismic Dampers

by Antonella Bianca Francavilla, Massimo Latour and Gianvittorio Rizzano

Materials 2023, 16(23), 7336; https://doi.org/10.3390/ma16237336 - 25 Nov 2023

Cited by 1 | Viewed by 1085

Abstract

In recent decades, low-yielding seismic devices based on the use of friction dampers have emerged as an excellent solution for the development of building structures with improved reparability and resilience. Achieving an optimal design for such low-yielding seismic devices requires precise control of [...] Read more.

In recent decades, low-yielding seismic devices based on the use of friction dampers have emerged as an excellent solution for the development of building structures with improved reparability and resilience. Achieving an optimal design for such low-yielding seismic devices requires precise control of bolt preloading levels and predictability of the friction coefficient (CoF) between the damper interfaces. While various types of friction devices exist that are capable of providing significant energy dissipation, ongoing research is focused on the development of novel friction materials that exhibit a stable hysteretic response, high CoF values, minimal differences between static and dynamic CoF, and predictable slip resistance. In this context, an experimental campaign was conducted at the STRENGTH Laboratory of the University of Salerno to evaluate the behaviour of new friction shims employing specially developed metal alloys. Specifically, the influence of the characteristics of the contact surfaces in the sliding area on the behaviour and performance of the friction device was analysed. The tests followed the loading protocol recommended by EN12159 for seismic device qualification. Monitored parameters included preloading force values and the evolution of slip resistance. The friction value was determined, along with its degradation over time. Finally, the material’s performance in terms of hysteretic behaviour was assessed, providing a comparison of the tested specimens in terms of slip force degradation and energy dissipation capacity. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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18 pages, 7054 KiB

Open AccessArticle

Effect of Core Density on the Three-Point Bending Performance of Aluminum Foam Sandwich Panels

by Peng Huang, Qiang Gao, Xixi Su, Zhanhao Feng, Xi Sun and Guoyin Zu

Materials 2023, 16(22), 7091; https://doi.org/10.3390/ma16227091 - 9 Nov 2023

Cited by 1 | Viewed by 1204

Abstract

Using the powder-metallurgy rolling method, aluminum foam sandwich (AFS) panels with a metallurgical bond between the foam core and the panel can be produced. In this study, by manipulating the foaming temperature and duration, AFS panels were fabricated with varying core densities and [...] Read more.

Using the powder-metallurgy rolling method, aluminum foam sandwich (AFS) panels with a metallurgical bond between the foam core and the panel can be produced. In this study, by manipulating the foaming temperature and duration, AFS panels were fabricated with varying core densities and thicknesses, all maintaining a panel thickness close to 1 mm. Through the three-point bending test, this research deeply delved into how core density influences the mechanical behaviors of these AFS panels. It became evident that a rise in core density positively affects the bending strength and failure load of the panels but inversely impacts their total energy absorption efficiency. Differing core densities brought about distinct failure patterns: low-density samples primarily showed panel indentation and core shear failures, whereas those of high density demonstrated panel yield and fractures. Furthermore, the research offers predictions on the initial failure loads for different failure modes and introduces a comprehensively designed failure diagram, laying a foundational theory for the production of AFS panels. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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19 pages, 13447 KiB

Open AccessArticle

On the Efficiency of Laser Alloying of Grey Cast Iron with Tungsten and Silicon Carbides

by Eugene Feldshtein, Oleg Devojno, Justyna Patalas-Maliszewska, Marharyta Kardapolava and Iryna Kasiakova

Materials 2023, 16(18), 6230; https://doi.org/10.3390/ma16186230 - 15 Sep 2023

Cited by 1 | Viewed by 984

Abstract

Cast iron is widely used in engineering production and in the surface alloying of workpieces, which is exploited to improve the properties of the material. Research on cast iron is still valid and needed for the manufacturing processes throughout the product life cycle. [...] Read more.

Cast iron is widely used in engineering production and in the surface alloying of workpieces, which is exploited to improve the properties of the material. Research on cast iron is still valid and needed for the manufacturing processes throughout the product life cycle. In this study, the gray, cast iron GJL 200 laser processing is described based on surface alloying with WC and SiC particulates. SEM analysis and XRD analysis, as well as microhardness testing and tribological behavior studies, were employed. It was revealed that laser alloying with carbide particulates affects structural, mechanical, and operational properties compared to cast iron in its initial state. Most importantly, the right choice of laser processing conditions can increase the wear resistance of the cast iron base. The wear resistance after WC alloying was 4–24 times higher compared to the initial material, while after SiC alloying, it was 2–18 times lower than that of the initial material. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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16 pages, 10928 KiB

Open AccessArticle

Microstructural Changes Caused by the Creep Test in ZK60 Alloy Reinforced by SiC_p at Intermediate Temperature after KOBO Extrusion and Aging

by Yang-Yang Wang, Chen Jia, Min Xu, Mosab Kaseem and Morteza Tayebi

Materials 2023, 16(10), 3885; https://doi.org/10.3390/ma16103885 - 22 May 2023

Cited by 9 | Viewed by 1515

Abstract

In this study, we investigated the creep properties of ZK60 alloy and a ZK60/SiC_p composite at 200 °C and 250 °C in the 10–80 MPa stress range after the KOBO extrusion and precipitation hardening process. The true stress exponent was obtained in [...] Read more.

In this study, we investigated the creep properties of ZK60 alloy and a ZK60/SiC_p composite at 200 °C and 250 °C in the 10–80 MPa stress range after the KOBO extrusion and precipitation hardening process. The true stress exponent was obtained in the range of 1.6–2.3 for both the unreinforced alloy and the composite. The apparent activation energy of the unreinforced alloy was found to be in the range of 80.91–88.09 kJ/mol, and that of the composite was found to be in the range of 47.15–81.60 kJ/mol, and this indicated the grain boundary sliding (GBS) mechanism. An investigation of crept microstructures using an optical microscope and scanning electron microscope (SEM) showed that at 200 °C, the predominant strengthening mechanisms at low stresses were the formation of twin, double twin, and shear bands, and that by increasing the stress, kink bands were activated. At 250 °C, it was found that a slip band was created in the microstructure, and this effectively delayed GBS. The failure surfaces and adjacent regions were examined using SEM, and it was discovered that the primary cause of failure was cavity nucleation around precipitations and reinforcement particles. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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14 pages, 3116 KiB

Open AccessArticle

Micromechanics Modeling of Transverse Tensile Strength for Unidirectional CFRP Composite

by Liangbao Liu, Xiaohui Zhang, Zibiao Wang, Yana Wang and Jiangzhen Guo

Materials 2022, 15(23), 8577; https://doi.org/10.3390/ma15238577 - 1 Dec 2022

Cited by 4 | Viewed by 2279

Abstract

Transverse tensile strength of unidirectional (UD) composites plays a key role in overall failure of fiber-reinforced composites. To predict this strength by micromechanics, calculation of actual stress in constituent matrix is essentially required. However, traditional micromechanics models can only give the volume-averaged homogenized [...] Read more.

Transverse tensile strength of unidirectional (UD) composites plays a key role in overall failure of fiber-reinforced composites. To predict this strength by micromechanics, calculation of actual stress in constituent matrix is essentially required. However, traditional micromechanics models can only give the volume-averaged homogenized stress rather than an actual one for a matrix, which in practice will cause large errors. In this paper, considering the effect of stress concentration on a matrix, a novel micromechanics method was proposed to give an accurate calculation of the actual stress in the matrix for UD composite under transverse tension. A stress concentration factor for a matrix in transverse tensile direction is defined, using line-averaged pointwise stress (obtained from concentric cylinder assemblage model) divided by the homogenized quantity (obtained from a bridging model). The actual stress in matrix is then determined using applied external stress multiplied by the factor. Experimental validation on six UD carbon fiber-reinforced polymer (CFRP) specimens indicates that the predicted transverse tensile strength by the proposed method presents a minor deviation with an averaged relative error of 5.45% and thus is reasonable, contrary to the traditional method with an averaged relative error of 207.27%. Furthermore, the morphology of fracture section of the specimens was studied by scanning electron microscopy (SEM). It was observed that different scaled cracks appeared within the matrix, indicating that failure of a UD composite under transverse tension is mainly governed by matrix failure. Based on the proposed approach, the transverse tensile strength of a UD composite can be accurately predicted. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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15 pages, 5610 KiB

Open AccessArticle

Simulation Analysis of Delamination Damage for the Thick-Walled Composite-Overwrapped Pressure Vessels

by Houcheng Fang and Di Wang

Materials 2022, 15(19), 6880; https://doi.org/10.3390/ma15196880 - 3 Oct 2022

Cited by 6 | Viewed by 2107

Abstract

In order to verify the delamination damage occurring in thick-walled composite-overwrapped pressure vessels, firstly, for composite delamination damage, a composite laminate model was established. Model I and model II delamination failure processes of composite structures were simulated and verified based on a tiebreak [...] Read more.

In order to verify the delamination damage occurring in thick-walled composite-overwrapped pressure vessels, firstly, for composite delamination damage, a composite laminate model was established. Model I and model II delamination failure processes of composite structures were simulated and verified based on a tiebreak contact algorithm for different mesh sizes, respectively, and the approximate equivalent results were achieved by correcting the inter-ply strength. Then, for in-plane damage to composite materials, the elastic–plastic process was verified by selecting a progressive damage model, with quasistatic nonlinear tensile shear of sample specimens as an example. Further, under the purpose of generality and simplicity, the location of the first occurrence of delamination failure was simulated and analyzed with the tiebreak contact algorithm and a reasonable mesh size, using quasistatic loading of a thick composite-overwrapped pressure vessel cylindrical section as an example. The results showed that delamination occurred at approximately the center, which is in general agreement with the experimentally observed phenomenon. On this basis, the locations of the first significant delamination phenomena in composite-overwrapped vessels under three different ratios of plus or minus 45-degree layup angles were predicted. Finally, the differences in structural strength between the single laying methods and the combined laying method were compared. The results showed that the ratio of 50% had a higher modulus value than a pure 0° ply, but too large a ratio was detrimental to the improvement of structural properties. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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13 pages, 5556 KiB

Open AccessArticle

Effect of Post-Heat Treatment Temperature on Interfacial Mechanical Properties of Cold-Rolled Ti/Al Clad Material

by Sang-Kyu Yoo, Ji-Won Kim, Myung-Hoon Oh and In-Chul Choi

Materials 2022, 15(17), 6103; https://doi.org/10.3390/ma15176103 - 2 Sep 2022

Cited by 1 | Viewed by 1505

Abstract

Titanium and titanium alloys possess low density, high specific strength, and excellent corrosion resistance, but are expensive and have low formability at room temperature. Therefore, to reduce cost and achieve excellent properties, titanium and titanium alloys are jointed with aluminum and its alloys, [...] Read more.

Titanium and titanium alloys possess low density, high specific strength, and excellent corrosion resistance, but are expensive and have low formability at room temperature. Therefore, to reduce cost and achieve excellent properties, titanium and titanium alloys are jointed with aluminum and its alloys, which are inexpensive and have low density and excellent room temperature formability. Cladding is a widely used solid-state bonding technique, and the post-heat treatment of titanium/aluminum clad materials is required to improve their interfacial properties, which is important to ensure the reliability of Ti/Al-clad materials. The interfacial properties of Ti/Al-clad materials are significantly affected by changes in the microstructure and mechanical properties after the post-heat treatment. Thus, in this study, the relationship between the microstructure and mechanical properties at the interface of Ti/Al-clad materials was analyzed after the post-heat treatment at several different temperatures. The thick diffusion and intermetallic compound layer was formed with post-heat treatment owing to the active diffusion of Al atoms. As a result, their uniaxial and nanomechanical properties were varied with the interfacial characteristics of the Ti/Al-clad material. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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16 pages, 7144 KiB

Open AccessCommunication

Oblique Low-Velocity Impact Response and Damage Behavior of Carbon-Epoxy Composite Laminates

by Jin Sun, Linhai Huang and Junhua Zhao

Materials 2022, 15(15), 5256; https://doi.org/10.3390/ma15155256 - 29 Jul 2022

Viewed by 1451

Abstract

The low-velocity impact behavior of carbon-epoxy cross-ply composites was numerically investigated, examining the effect of impact angle. A plastic continuum damage model, introducing the cohesive interface to describe delamination damage, was established and was validated by available experimental data. Impact histories, progressive deformation, [...] Read more.

The low-velocity impact behavior of carbon-epoxy cross-ply composites was numerically investigated, examining the effect of impact angle. A plastic continuum damage model, introducing the cohesive interface to describe delamination damage, was established and was validated by available experimental data. Impact histories, progressive deformation, stress transfer, and impact damage are respectively discussed. The results show that an increase in impact angle intensifies the action of tangential force, and gradually transfers energy absorption from normal plastic deformation to tangential deformation and friction, which dissipates more energy through relatively longer contact duration and larger impactor displacement. The delamination damage to upper layers is more affected by tangential loads, intensifying with the increase of the impact angle, and the damage area to the top interface is increased by 132.1% from 0° impact to 60° impact. Meanwhile, the delamination damage to lower layers is mainly determined by normal loads, weakening with the increasing impact angle overall, and the damage area of the lowest interface decreases by 36.6% from 0° impact to 60° impact. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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13 pages, 4987 KiB

Open AccessArticle

Experimental Study on the Effect of Gradient Interface on the Mechanical Properties of Cu/WC_P Functionally Gradient Materials Using Digital Image Correlation Technique

by Hai Yu, Yunpeng Liu, Yunxiang Hu and Mingyang Ta

Materials 2022, 15(11), 4004; https://doi.org/10.3390/ma15114004 - 4 Jun 2022

Cited by 1 | Viewed by 1507

Abstract

In order to investigate the effect of gradient interface on the mechanical properties of Cu/WC_P functional gradient materials, digital image correlation technique was used to analyze the mechanical characteristics of laminated Cu/WC_P functional gradient material under tension load in the layer [...] Read more.

In order to investigate the effect of gradient interface on the mechanical properties of Cu/WC_P functional gradient materials, digital image correlation technique was used to analyze the mechanical characteristics of laminated Cu/WC_P functional gradient material under tension load in the layer direction. In this paper, the deformation information of the specimens is obtained by the digital image correlation method. In order to obtain high-precision measurement results, speckle patterns with small spots and uniform distribution are prepared on the specimen surface by using small sample speckle preparation technology. The tensile experimental results showed that the incorporation of WC particles significantly improved the stiffness and strength of Cu/WC_P composites. Meanwhile, the plastic strain and plastic strain rate are non-uniform in each layer of the five-layer Cu/WC_P functional gradient material under the tension load along the layer direction. The plastic strain and plastic strain rate in each layer gradually increase along with the decreasing direction of WC content. It is found, from the analysis of experimental results, the existence of the gradient interface has an obvious inhibitory effect on the increase in plastic strain rate along the decreasing direction of WC content, and the specimen fracture location also has a certain relationship with the plastic strain rate, which reflects the important influence of the gradient interface on the mechanical properties of Cu/WC_P functional gradient materials. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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14 pages, 5269 KiB

Open AccessArticle

Study of the Influence of the Type of Aging on the Behavior of Delamination of Adhesive Joints in Carbon-Fiber-Reinforced Epoxy Composites

by Paula Vigón, Antonio Argüelles, Victoria Mollón, Miguel Lozano, Jorge Bonhomme and Jaime Viña

Materials 2022, 15(10), 3669; https://doi.org/10.3390/ma15103669 - 20 May 2022

Cited by 4 | Viewed by 1465

Abstract

This study analyzes the behavior under the static delamination and mode-I fracture stress of adhesive joints made on the same composite material with an epoxy matrix and unidirectional carbon fiber reinforcement and two types of adhesives, one epoxy and the other acrylic. Standard [...] Read more.

This study analyzes the behavior under the static delamination and mode-I fracture stress of adhesive joints made on the same composite material with an epoxy matrix and unidirectional carbon fiber reinforcement and two types of adhesives, one epoxy and the other acrylic. Standard DCB tests (for mode-I fracture) were used to quantify the influence on the interlaminar fracture toughness of the type of adhesive used. Both materials were subjected to two different degradation processes, one hygrothermal and the other in a salt-fog chamber. After aging, the mode-I fracture has been evaluated for both materials. From the experimental results obtained, it can be deduced for the epoxy adhesive that exposure to the hygrothermal environment used moderately modifies its behavior against delamination, while its exposure to the saline environment produces a significant loss of its resistance to delamination. For the acrylic adhesive, the hygrothermal exposure causes an improvement in its delamination behavior for all the exposure periods considered, while the saline environment slightly modifies its behavior. There is, therefore, a clear influence of the type of aging on the fracture behavior of both adhesives. Full article

(This article belongs to the Special Issue Mechanical Behavior of Composite Materials II)

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