Durability Of Composite Materials Research Articles

Low-Velocity Impact Analysis in Composite Plates Incorporating Experimental Interlaminar Fracture Toughness

Reliable performance of composite adhesive joints under low-velocity impact is essential for ensuring the structural durability of composite materials in demanding applications. To address this, the study examines the effects of temperature, surface treatment techniques, and bonding processes on interlaminar fracture toughness, aiming to identify optimal conditions that enhance impact resistance. A Taguchi experimental design and analysis of variance (ANOVA) were used to analyze these factors, and experimentally derived toughness values were applied to low-velocity impact simulations to assess delamination behavior. Sanding and co-bonding were identified as the most effective methods for improving fracture toughness. Under the identified optimal conditions, the low-velocity impact analysis showed a delamination area of 319.0 mm2. These findings highlight the importance of parameter optimization in enhancing the structural reliability of composite adhesive joints and provide valuable insights for improving the performance and durability of composite materials, particularly in aerospace and automotive applications.

Impact of drilling parameters on the surface roughness of egg shell filled glass fibre/polyester composites

Abstract Glass fiber-reinforced polymers (GFRPs) are widely used in domestic applications such as doors, windows, and furniture, where drilling is a common machining process. The surface roughness of drilled hole walls is a critical factor, particularly in fastening applications, where smooth finishes are essential. This study explores the influence of drilling parameters on the surface roughness of GFRPs reinforced with different types of eggshell fillers viz.,un-carbonized, carbonized, and hybrid along with an unfilled variant. The research employs a Central Composite Design within the Response Surface Methodology (RSM) framework to investigate the effects of material type, spindle speed, feed rate, and point angle on surface roughness. Material type and point angle were treated as categorical variables, while spindle speed and feed rate were continuous, each with four levels, resulting in 16 experimental runs. The results showed that surface roughness values varied from 3.04 to 4.99μm, depending on the specific combination of drilling parameters. Statistical analysis using Analysis of Variance (ANOVA) confirmed that spindle speed and feed rate significantly impact surface roughness, with roughness increasing at higher speeds and feeds. Notably, the carbonized eggshell-filled GFRP variant achieved the lowest surface roughness. The study also developed a highly accurate regression model, validated through experimental data. The novel use of different variants of eggshell fillers in GFRPs provides a sustainable and effective way to enhance material properties. Further, conducting the drilling studies to observe the outcomes, offers potential industrial applications in the production of high-quality, durable composite materials.

Molecular Dynamics Simulation of Cumulative Microscopic Damage in a Thermosetting Polymer under Cyclic Loading.

To develop durable composite materials, it is crucial to elucidate the correlation between nanoscale damage in thermosetting resins and the degradation of their mechanical properties. This study aims to investigate this correlation by performing cyclic loading tests on the cross-linked structure of diglycidyl ether bisphenol A (DGEBA) and 4,4'-diaminodiphenyl sulfone (44-DDS) using all-atom molecular dynamics (MD) simulations. To accurately represent the nanoscale damage in MD simulations, a bond dissociation algorithm based on interatomic distance criteria is applied, and three characteristics are used to quantify the microscopic damage: stress-strain curves, entropy generation, and the formation of voids. As a result, the number of covalent bond dissociations increases with both the cyclic loading and its amplitude, resulting in higher entropy generation and void formation, causing the material to exhibit inelastic behavior. Furthermore, our findings indicate the occurrence of a microscopic degradation process in the cross-linked polymer: Initially, covalent bonds align with the direction of the applied load. Subsequently, tensioned covalent bonds sequentially break, resulting in significant void formation. Consequently, the stress-strain curves exhibit nonlinear and inelastic behavior. Although our MD simulations employ straightforward criteria for covalent bond dissociation, they unveil a distinct correlation between the number of bond dissociations and microscale damage. Enhancing the algorithm holds promise for yielding more precise predictions of material degradation processes.

Challenges and Future Recommendations for Lightning Strike Damage Assessments of Composites: Laboratory Testing and Predictive Modeling.

Lightning strike events pose significant challenges to the structural integrity and performance of composite materials, particularly in aerospace, wind turbine blade, and infrastructure applications. Through a meticulous examination of the state-of-the-art methodologies of laboratory testing and damage predictive modeling, this review elucidates the role of simulated lightning strike tests in providing inputs required for damage modeling and experimental data for model validations. In addition, this review provides a holistic understanding of what is there, what are current issues, and what is still missing in both lightning strike testing and modeling to enable a robust and high-fidelity predictive capability, and challenges and future recommendations are also presented. The insights gleaned from this review are poised to catalyze advancements in the safety, reliability, and durability of composite materials under lightning strike conditions, as well as to facilitate the development of innovative lightning damage mitigation strategies.

Increased durability of glass composites

Composite materials based on cement binders are currently among the widely used for the construction of transport structures. In accordance with regulatory requirements, concrete for transport construction must have improved physical, mechanical and operational properties. One of the areas that makes it possible to obtain materials with improved properties is the use of various fillers, including waste from industrial enterprises. Among the variety of man-made waste, a significant part is broken glass, which is an effective secondary resource and can be used in the construction industry to produce binders, fillers, composites and structures based on them. The article presents the results of research aimed at increasing the durability of composite materials based on cement binders filled with cullet. Effective additives have been proposed to reduce the reactivity of broken glass with binders. Processing of experimental data was carried out using experimental planning methods. The study of the experimental design showed that it is possible to reduce the number of factors previously involved in the formation of the experimental planning matrix. It was established that the reduction in the number of factors is carried out with a confidence probability of at least 0,95. Experimental studies were carried out on the biological resistance of composites filled with broken glass and their components under the influence of filamentous fungi. It has been established that pre-treatment of the filler surface with a 1, 3, 5 % solution of potassium permanganate helps impart fungicidal properties to the composites, and treatment with a 7,5 % solution makes it possible to obtain filled materials with fungicidal properties.

Fast and accurate prediction of cure quality and mechanical performance in fiber‐reinforced polymer composite using dielectric variables and machine learning

AbstractFiber‐reinforced polymer (FRP) composites are widely used in the aerospace and automotive industries due to their high strength‐to‐weight ratio. However, the manufacturing process of FRP composites is intricate, requiring precise control over multiple parameters, which can be challenging. To ensure top‐notch product quality and bolster confidence in the durability of composite materials, it requires a uniform curing evaluation technique and a predictive strength model. This study presents a rapid nondestructive quality inspection technique for composites, involving three distinct studies that employ machine learning techniques in combination with the frequency‐dependent dielectric response of materials. The first study introduces a nondestructive method for swiftly inspecting the cure state (degree of cure) of composite samples. This technique combines broadband dielectric spectroscopy with supervised machine learning algorithms, particularly support vector machines. The second study employs advanced artificial neural networks like multi‐layer perceptron to predict the tensile strength, a measure of mechanical performance, of composite materials. The results demonstrate an accurate classification of the curing state with 96.7% accuracy and a prediction of tensile strength with 87.5% accuracy. The final study explores the application of machine learning in quality monitoring of prepreg (raw materials for FRP) aging at room temperature.Highlights Integration of machine learning with frequency‐dependent dielectric measurement offers efficient method for inspecting and monitoring the curing state and mechanical performance of composite materials. Machine learning and frequency‐dependent dielectric response used to accurately assess the curing state of fiber‐reinforced polymer composites with 96.7% accuracy, which saves the time and effort and also reduces the need for destructive testing. Advanced artificial neural networks, specifically multi‐layer perceptron, employed to predict mechanical performance of composite materials with 87.5% accuracy, enhancing confidence in product reliability. Novel dielectric measurement technique integrated with machine learning algorithms enables prepreg age monitoring at room temperature.

Investigation on Composites Reinforced with Multi-Layer Carbon Fiber and Silicone Rubber Against Impact test and Shoot Strength.

The aim of this study is to examine the durability of composite materials reinforced with carbon fiber and the effects of silicone rubber on the composites' tensile strength, bending, firing, impact, and density. The silicon fiber was mixed with resin using a magnetic stirrer at 250 rpm, with a temperature of 40o C for 30 minutes. Furthermore, the composite production process was carried out using a vacuum infusion method with carbon fiber sheet variations of 6, 8, and 10. Tensile strength shows a proportional increase with the number of carbon fiber layers. Flexural strength indicates the opposite. The impact test was conducted in accordance with the ASTM E 23 standard, the firing test was performed using a 9x19 mm caliber bullet with a distance of 10 m, and the density was found by employing ASTM 792-13. The greatest density was 1,274 grams/cm3, and it was gotten from the sample with 10 fiber layers. Following this, the results of the impact test (Izod) showed that the specimen with 6 layers of carbon fiber had the highest impact strength of 0.040 Joule/mm. While the shoot test results indicated that the composite with 6 layers of carbon had smaller shot holes. There was no significant absorption in the water absorption test.

Degradation of Polyester Composite Reinforced E-Glass Fiber with Calcium Carbonate Filler in Seawater

This research is concerned with composite materials that use CaCO3 as a reinforcing material in construction, especially subsea panels and buildings. Composite materials are solids composed of two or more materials that have their own properties and improve their properties when combined. In this experiment, glass fiber and CaCO3 were mixed in a certain composition and tested to evaluate the water absorption and mechanical strength of the composite. The results show that increasing temperature can increase water absorption, while the addition of CaCO3 has a significant effect on water absorption due to its hydrophilic properties. Water absorption in polyester composites is influenced by aging temperature and Calcium Carbonate powder filler, affecting tensile and bending strength. As aging temperature increases, mechanical strength decreases, composite having the highest tensile strength. Bending tests show debonding and splitting fault patterns due to glass fiber arrangement. With a deeper understanding of how CaCO3 affects composite materials under various conditions, this research can provide valuable insights for developing more durable composite materials suitable for construction applications, especially in corrosive environments such as subsea buildings.In this research, it proposes theoretically model to controlling on half-wave voltage of modulator, in which it uses studying the factor of effective of refractive index difference, this using analysis distribution of refractive index for LN material before and after voltage is applied (i.e., with and without applied voltage), and uses analysis a factor of propagation constant difference ??, before and after voltage is applied where it depends on the wavelength, these leads to it controls on the half-wave voltage V? using a reduction half-wave voltage up to 1V. Also, it achieves an excellent solution for solve the fundamental optical mode with effective factor is neff. Finally, the modulator with an effect effective refractive index difference have lower applied voltage up to 10V, and with an effective propagation constant difference the operating voltage is from value of 20V.

Feasibility of bolted connectors in hybrid FRP-steel structures

Due to the low weight and excellent durability of composite materials, Fibre Reinforced Polymer (FRP) decks mounted on steel superstructures are becoming increasingly common in engineering practice. Bolted joints are generally used to facilitate connections between an FRP deck and steel girders in road bridges. The connections are subjected to both high magnitude static forces as well as fatigue loading due to overpassing vehicles. With ever increasing traffic on both road and railway bridges, fatigue performance is of critical concern. Bolted FRP joints have been extensively researched in the past under static loading, but less is known about the fatigue and creep behaviour of such joints. Furthermore, little research exists on non-pultruded FRP profiles connected using bolted connections. Therefore, the objective of this research is to investigate connectors’ feasibility by means of static, fatigue and creep experiments on four different types of bolted joints comprising mechanical connectors and injection techniques. The study focuses on application in vacuum infused GFRP panels with integrated webs made of multi-directional laminates) connected to steel bridge superstructures. In addition, experimental results are used to validate Finite Element Analyses (FEA). Based on the obtained results, the novel injected steel-reinforced resin (iSRR) connector shows promising potential in hybrid steel-FRP bridges where good fatigue endurance of the connection, are required.

Application of Variational Methods for the Development of Optimal Multiparametric Models of Durability of Composite Materials and Structures under the Influence of Extreme Environmental Factors

The increasing use of composites in such modern fields as aviation and space technology, shipbuilding, oil and gas industry, etc., determines the importance and relevance of developing effective high-precision methods for long-term forecasting of the defining characteristics of composite materials and structures made of them (residual life, strength, reliability, durability). A study of the promising possibilities of applying modern provisions of the kinetic theory of strength to develop optimal models of durability of composite materials and structures made of them under the influence of extreme environmental factors has been carried out. Based on the application and development of mathematical and computer modelling methods, effective methods for predicting the defining characteristics (residual life, strength) have been developed.

Preface to the theme issue 'Durability and ageing of composite materials'.

The issue focuses on ageing and durability of composite materials for industrial applications. Ageing and durability are two fundamental topics within the context of design and optimization of materials and structures: ageing may induce degradation and leads to premature failure. Therefore, understanding the main ageing mechanisms is of paramount importance for predicting material durability. These topics are still barely studied systematically and the main related issues are debated within mechanical, chemical, and solid-state physics research communities. This issue aims to update the current research state of the art, clarifying the interplay between chemical and physical mechanisms involved in degradation processes, and providing test protocols and design rules that account for ageing and durability. This article is part of the theme issue 'Ageing and durability of composite materials'.

Fatigue of hybrid fibre-reinforced plastics.

Understanding the fatigue behaviour of hybrid fibre-reinforced plastics is desirable for exploiting their features in safe, durable and reliable industrial components. The fatigue performance of hybrid composites has not been extensively investigated yet. The paper presents an overview of the available knowledge on the fatigue of hybrid fibre-reinforced plastics, and, more specifically, reports the fatigue behaviour of a quasi-isotropic pseudo-ductile all-carbon fibre interlayer hybrid composite by experimental measurements and observations, with emphasis on the damage development. The fatigue conditions are tension-tension stress- and strain-controlled cyclic loading. The results include fatigue life for different maximum stress and strain levels, stiffness evolution and damage observations by X-ray micro-computed tomography. The studied hybrid all-carbon fibre quasi-isotropic composite exhibits pseudo-ductility in quasi-static testing. For stress-controlled fatigue, the fatigue load over the limit of elastic response is not sustained. Contrary to that, the composite retains its load-carrying ability in the pseudo-ductile regime for a strain-controlled regime, albeit with lowered stiffness. This article is part of the theme issue 'Ageing and durability of composite materials'.

Modelling changes in glass transition temperature in polymer matrices exposed tolow molecular weight penetrants.

Polymer matrices, when placed in contact with a fluid phase made of low molecular weight compounds, undergo a depression of their glass transition temperature (Tg) determined by the absorption of these compounds and the associated plasticization phenomena. Frequently, this effect is coupled with the mechanical action of the compressive stress exerted by the pressure of the fluid phase that, in contrast, promotes an increase in the Tg. This issue is relevant for technological and structural applications of composites with high-performance glassy polymer matrices, due to their significant impact on mechanical properties. We propose an approach to model and predict rubbery-glassy states maps of polymer-penetrant mixtures as a function of pressure and temperature based on the Gibbs-Di Marzio criterion. This criterion establishes that a 'thermodynamic' glass transition does occur when the configurational entropy of the system vanishes. Although questioned and criticized, this criterion constitutes a good practical approach to analyse changes of Tg and, in some way, reflects the idea of an 'entropy catastrophe' occurring at the glass transition. Several polymer-penetrant systems have been analysed modelling configurational entropy by means of the Non-Random Hydrogen Bond lattice fluid theory, able to cope with possible non-random mixing and occurrence of strong interactions. This article is part of the theme issue 'Ageing and durability of composite materials'.

Global-local multi-field models for the stress analysis of laminated structures.

The present paper presents an innovative numerical model for predicting stress concentrations in composite materials in a multi-physics context. The numerical approach is based on the Carrera unified formulation, a numerical tool able to handle any kinematic model using a unified and compact notation. A general formulation for one-, two- and three-dimensional higher-order models has been presented. Equivalent single-layer and layer-wise models have been considered since theyare the most effective in the analysis of composite materials. A hygro-thermo-elastic multi-physics formulation has been considered. The model has been used to investigate stress concentrations considering different configurations. Mechanical, thermal and hygroscopic loads have been considered. An innovative global-local analysis technique has been used to reduce the computational cost preserving the accuracy of the solution. This article is part of the theme issue 'Ageing and durability of composite materials'.

A peridynamic approach to simulating fatigue crack propagation in composite materials.

In this article, a numerical tool is proposed in the framework of bond-based peridynamics to simulate fatigue crack propagation in composite materials and structures. The cycle-dependent damage-cumulative model derived from Peerlings' law and applied to a bilinear constitutive law is used to evaluate the fatigue degradation of the bond stiffness. Several benchmark cases are studied to validate the proposed approach. Finally, static and fatigue crack propagations in composite systems with single or multi-inclusions are simulated to illustrate the capabilities and characteristics of the developed approach. This article is part of the theme issue 'Ageing and durability of composite materials'.

Characterizing and predicting the relationship between translaminar fracture toughness and pull-out length distributions under distinct temperatures.

The translaminar fracture toughness reflects the damage tolerance of a fibre-reinforced composite under longitudinal tension, which often governs the final failure of structures. One of the main energy-dissipation mechanisms that contributes to the translaminar toughness of composites is the fibre pull-out process. The present study aims to quantify and model the statistical distribution of fibre pull-out lengths formed on the translaminar fracture surface of composites, for the first time in the literature; this is done under different temperatures, so that the relationship between pull-out length distributions, micromechanical properties and the translaminar fracture toughness can be established. The fracture surfaces of cross-ply compact tension specimens tested under three different temperatures have been scanned through X-ray computed tomography to quantify the extent of fibre pull-out on the fracture surfaces; the distribution of pull-out lengths showed alarger average and larger variability with an increase in temperature, which also lead to an increase in translaminar fracture toughness. A similar trend has been captured by the proposed analytical model, which predicts the pull-out length distribution based on the analysis of quasi-fractal idealizations of the fracture surface, yielding an overall accuracy of more than 85%. This article is part of the theme issue 'Ageing and durability of composite materials'.

Characterization and modelling of the hygro-viscoelastic behaviour ofpolymer-based composites used in marine environment.

This paper presents results from a study of the long-term behaviour of carbon/epoxy composites. The interactions between ageing in water and constant mechanical loads are described, first experimentally then using a simple modelling approach. An identification procedure for the model is carried out and test/model comparisons are discussed. The results show that a four-parameter Burgers model can provide a good fit of the experimental data. The analysis of the results indicates the impact of water diffusion on the viscoelastic behaviour with larger strains for both creep and recovery phases. Those changes tend to appear at the early stage of the moisture diffusion process and stabilize quite quickly. This article is part of the theme issue 'Ageing and durability of composite materials'.

Multi-Response Modelling and Optimisation of Mechanical Properties of Al-Si Alloy Using Mixture Design of Experiment Approach

The research aims to produce, model, and optimise the mechanical properties of novel composite material through a structured multidisciplinary approach. The primary objective is to combine materials science, mechanical engineering, and statistical concepts to ensure Design for Manufacturability (DFM) from the industrial perspective. More specifically, the article is intended to determine the optimal mixture components and predictive model of Al-Si alloy with Al2O3 by accommodating multi-responses that enable DFM. The study adopted ASTM standards to prepare and test the novel composite material. Additionally, the Mixture Design of Experiment (DOE) approach was used to design the experimentation and subsequent analysis. In addition, microstructural images, Cox Response Trace plot, and Response Optimiser plot are effectively utilised to draw robust inferences. For multi-response modelling and optimisation, the composite material’s mechanical properties, like impact strength, hardness, density, and tensile strength, are considered. The study determines that innovative composite material will yield better results when Al-Alloy is 94.65 wt% and Al2O3 is 5.35 wt% from a multi-responses perspective. Further, it provides predictive models with a high level of predictability. Besides, the research shows that novel composite material has better mechanical properties from a practical perspective. The article not only provides the mechanical properties of a new class of material but also shows the effective utilisation of material science and statistical concepts to develop the novel material in a structured manner. This composite material can be used as a replacement for various parts of automobiles and aircraft. Additionally, researchers can use the article’s modelling and optimisation approach as a paradigm to create durable composite materials.

Damage Analysis of Hybrid Composites Under Multi-Impact Loads: An Experimental and Numerical Study

Laminated composite structures are subjected to impact damage during maintenance and manufacturing operations and their life service. Driven by the necessity to value damage tolerance and durability of composite materials, an analysis of multi-hit impact is conducted to reproduce the real service conditions. Despite many studies in the literature investigated the properties of composites at low impact velocity, in contrast the behavior of the hybrid configuration, especially at repeated impacts, result still little known. This work presents an experimental and numerical study of the dynamic behavior at the repeated low-velocity impact of a carbon and glass fibers hybrid composite laminate.

Numerical Analysis of A Nonlinear Elastic Composite Leaf Spring

In this study, numerical analysis of a composite spring with a nonlinear elastic force-displacement relationship was performed. Due to the lightness and durability of composite materials, their use in the automotive industry is increasing and production methods allow for a high performance spring design. The behavior of a pair of composite leaf springs working in tandem with the cross-section profiles of the leaf springs to be obtained by using the involute curve of the spur gear pairs under load was examined in detail by numerical method, and the desired behavior was obtained. In the analyzes performed using Ls-Dyna software, samples were produced and many mechanical tests were performed for the determination of material parameters. The results obtained from these tests were used as the required material parameters in numerical analysis. The leaf spring thickness that will give the desired non-linear elastic behavior under 400 N load used in numerical analysis has been determined and successfully targeted force-elongation behavior has been created.