Mechanical Behavior Of Composites Research Articles

Scale modeling of thermo-structural fire tests of multi-orientation wood laminates

The stacking sequence of laminated wood significantly impacts the composite mechanical behavior of the material, especially when scaling down thermo-mechanical tests on plywood. In previous research, we developed a scaling methodology for thermo-structural tests on samples with similar cross sections, however this paper focused on testing plywood samples with different stacking sequences between the scales. Plywood samples at ½-scale and ¼-scale were subjected to combined bending and thermal loading, with the loading scaled to have the same initial static bending stresses. While the ¼-scale 4-layer [0°/90°]s laminate and the ½-scale 8-layer [0°/90°/90°/0°]s laminate had an equal number of 0° and 90° layers, as the char front progresses, the sections behave differently. Thus, modeling becomes essential to extrapolating the data from the smaller ¼-scale test to predict the behavior of the larger ½-scale test. Reduced cross-sectional area models (RCAM) incorporating classical laminated plate theory were used to predict the mechanical response of the composite samples as the char front increased. Three methods were proposed for calibrating the RCAM models: Fourier number scaling, from detailed kinetics-based pyrolysis GPyro models, and fitting to data from fire exposure thermal response tests. The models calibrated with the experimental char measurements produced the most accurate predictions. The experimental char models validated to predict the behavior of the ¼-scale tests within 2.5%, were then able to predict the ½-scale test behavior within 4.5%.

A printable shear stiffening composite with enhanced fracture toughness and impact resistance for intelligent wearable applications

The continuous advancement in shear stiffening materials has sparked innovation in the field of flexible wearable devices. However, conventional preparation techniques for these materials have drawbacks such as limited toughness and lack of structural design. Herein, we propose a convenient fabrication method for shear stiffening elastomer (SSE) composite using a direct-ink-writing (DIW) assisted manufacturing technique. The influence of SSE structural design strategy on the mechanical behavior of composite is comprehensively investigated using crack propagation and dynamic impact experiments. Benefiting from the mechanically complementary effect of two-phase materials, coupled with robust interfacial adhesion, the composite with a densely arranged rectangular SSE structure exhibits high fracture toughness (2776.10 J⋅m−2) and impact force dissipation (61.78 %). Further, by integrating the printable composite with deep learning-based wireless sensing modules, a wearable elbow pad with attractive man–machine interaction is developed, which verifies the broad application prospect of this composite in intelligent protection.

Tribological and Mechanical Performance Evaluation of Hybrid Reinforced Copper Composites

The powder metallurgy technique is utilized in this study to produce Cu matrix hybrid composites with ZrO2 reinforcements and graphite additives. This study compares composites' microstructural (theoretical, experimental, and relative density, phase morphology, type, chemical content), mechanical (microhardness), and tribological behavior (wear and friction) with 5, 10, and 15 wt% reinforcement, together with and without the effect of 2 wt% graphite additives. The hardness of the composites increased as the amount of ZrO2 increased with the addition of graphite. The wear resistance of ZrO2-doped copper samples was improved between 1.32 and 4.84 times better than that of copper without reinforcement.

A novel FFT framework with coupled non-local elastic-plastic damage model for the thermomechanical failure analysis of UD-CF/PEEK composites

A novel FFT-based computational framework for coupling non-local elastic-plastic damage model is proposed in this paper, which is employed to accurately simulate the transverse tensile behaviors of unidirectional (UD) CF/PEEK composite materials under different temperatures. To address the distinct material properties exhibited by different microscopic constituents within the composite, two approaches are employed: (i) an integral-type regularized traction-separation damage model is applied to the interphase debonding, and (ii) an implicit gradient regularization technique for Lemaitre-type damage (matrix cracking) of the PEEK. By coupling the non-local damage model capable of accurately characterizing different failure modes within composites with an FFT computational framework, accurate predictions of the transverse tensile performance of UD-CF/PEEK composites at different temperature conditions can be achieved. Furthermore, the influence of non-local feature parameters and interphase mechanical properties on the composite's mechanical behavior is thoroughly discussed. Comparisons with experimental results affirm the accurate prediction of the transverse tensile behavior of UD-CF/PEEK composites through the proposed computational framework. Ultimately, based on this framework, the transverse tensile modulus and strength of UD-CF/PEEK composites, considering different fiber volume fractions and temperatures, are predicted, successfully demonstrating the effectiveness and applicability of the proposed approach in forecasting the mechanical behavior of composites.

An experimental study on the role of fiber distribution in hybrid composite mechanical behavior

An experimental study on the role of fiber distribution in hybrid composite mechanical behavior

Study of the influence of PPS, PAEK, and PEEK thermoplastic matrices on the static mechanical behavior of carbon fiber‐reinforced composites

AbstractThe growing use of poly(phenylene sulfide) (PPS), poly(aryl ether ketone) (PAEK), and poly(ether ether ketone) (PEEK) polymers reinforced with carbon fiber (CF) aims to meet the increasing demand for structural thermoplastic composites in applications that require excellent mechanical properties and thermal stability at higher temperatures (for example, above 120°C). The present work studied the influence of semicrystalline thermoplastic matrices of PPS, PAEK, and PEEK on the static mechanical behavior of CF‐reinforced composites through tensile tests and fractographic analysis of the respective fracture surfaces. The results of mechanical tests showed that the matrix influenced the static properties of the composites, mainly in stiffness, highlighting the CF/PEEK composite with the highest stiffness (42.3 ± 0.5 GPa) and the CF/PPS with the lowest standard deviation in tensile strength (599 ± 12 MPa). The fractographic analyses showed the good quality of the laminates, which presented an excellent matrix‐reinforcement interface, without fiber detachment or pulling out after mechanical tests, guaranteeing the transfer of efforts from the matrix to the reinforcement.Highlights Static mechanical behavior of structural composites with thermoplastic matrix. Static tensile tests of CF/PPS, CF/PEEK, and CF/PAEK composites were performed. Influence of semicrystalline matrices on the mechanical behavior of composites. Mechanical behavior of CF‐reinforced composites with PEEK, PAEK, and PPS. Fractographic analyses of the fracture surfaces of thermoplastic composites.

Hygrothermal exposure and residual strength after cyclic loading on epoxy composites reinforced with sisal fibers

The fatigue behavior of epoxy/sisal composites with hygrothermal exposure was investigated. However, their mechanical characterization under cyclic loading associated with aging from hygrothermal exposure is necessary to expand their use in consumer goods and automotive parts. This work used untreated and NaOH-treated sisal fibers (30% in volume) to reinforce epoxy composites in unidirectional and cross-ply orientations. The composites were submitted to cyclic loading tests before and after hygrothermal exposure and submitted to hot water absorption test, tensile strength, residual tensile strength, and scanning electron microscopy (SEM) analyses. The results show that unidirectional NaOH-treated sisal/epoxy composites outperformed the untreated composites, with approximately 40% less water absorption after the hygrothermal exposure and a 1.4 times improvement in tensile strength. This performance enhancement resulted from the efficient transfer of stresses between the components, stemming from adhesion between the fibers and the epoxy matrix. The tensile strength of unidirectional treated sisal composites showed a minor decrease following cyclic loading (approximately 6%), in contrast to the untreated composites, which experienced a significant decline of 20%. As a result, the treated sisal improved the composites mechanical behavior compared to the untreated ones, which underwent a more significant loss due to weaker interactions between the fibers and the matrix. The SEM images showed that the fiber/matrix interface played a central role in the composites' performance in all tests. Overall, this study highlights the potential of unidirectional NaOH-treated sisal/epoxy composites, an environmentally friendly material, for applications subjected to cyclic loading and hygrothermal exposure.

EVALUATION OF MECHANICAL BEHAVIOUR AND EFFECT OF PARTICLE SIZE ON LM26/Gr METAL MATRIX COMPOSITE

In automotive industries, Aluminium cast alloy (LM26) is well-renowned material in the fabrication of pistons for both diesel and petrol engines for its superior casting and mechanical properties. However, diminishing strength at higher temperatures drives metal matrix composites in cast alloys. The present study focused on the impact of naturally available ceramic particles Garnet on the microstructure and mechanical properties of Aluminium cast alloy (LM26). Samples were fabricated with varied Garnet (Wt. % of 3, 6, 9, and 12) by dual step stir casting technique. Two different particle sizes (400µm and 250µm) were incorporated to determine the effect of particle size on composite mechanical behaviour. Scanning electron microscope images unveiled the dissemination of ceramic particles inside the cast alloy matrix. It was found that ultimate tensile strength, yield strength, and impact strength were increased up to a certain Garnet percentage and started diminishing with the rise in particulate fraction for both particle sizes. However, the increase in hardness value indicates the brittleness of Metal matrix composite with the increase in ceramic reinforcement. Validation of Experimental results with theoretical values was also discussed.

Fractographic analysis of composite joints under cryogenic conditions

Fiber-reinforced polymer matrix composites are often alternative materials for aerospace structures applications where high strength and stiffness at low weight are mandatory design requirements. However, there are still open issues related to thermal effects on composite parts' mechanical properties and fracture behavior, particularly under cryogenic conditions. This work aims to investigate the fracture aspects of carbon fiber composite joints made with co-curing, co-bonding, and secondary bonding technologies when subjected to cryogenic conditions. A detailed study was carried out on their mechanical performance under Mode I and Mixed Mode I/II loading by performing interlaminar fracture tests at −54 °C. Microscopy techniques were applied to better understand the failure mechanisms observed for each bonding technology. The manufacturing process has a direct influence on the crack propagation of the laminates at cryogenic temperature. The post-cure process results in a brittle behaviour for CB and SB composite joints tested at cryogenic temperature leading to significant reductions in the fracture toughness values. The CC composite joints exhibited a tougher behaviour in comparison to CB and SB composite joints. This is mainly due to the fact that these joints are not post-cured and the presence of an interlayer that delays crack propagation.

Mechanical and microstructure behaviour of WSC/SiC/Al composites synthesized with and without ultrasonic treatment

In this research, aluminium composites were fabricated using two alternative casting methods namely, traditional stir casting and ultrasonic-aided stir casting technique. The aluminium composites were manufactured by reinforcing them with three different concentrations of waste spent catalyst and silicon carbide (0.5, 1.0, and 1.5 wt-%), respectively. The microstructural and mechanical behaviour of aluminium composites synthesised using both methods were studied and compared. The microstructure of the aluminium composite obtained by the stir casting technique with ultrasonic treatment resulted in a homogeneous dispersion of reinforcement particles and grain size refinement. Moreover, the overall test results showed that the ultrasonic-aided stir-casting technique improves the microstructure and mechanical behaviour of the composites when compared to the traditional stir-casting approach.

Preparation and characterization of Al8011 TiO2 and nano Graphene hybrid composite mechanical and wear behavior

Aluminum Metal Matrix Composite (AMMC) materials are advantageous in a wide range of engineering applications, most notably due to their lightweight strength, among other factors. The present research focuses on determining the mechanical and wear behavior of Aluminum 8011 (Al8011) reinforced with (30 µm particle size) Graphite (Gr) by 3% by weight fraction and titanium oxide (TiO2) 5%, 10% and 15% weight. Stir casting was chosen as the cheapest approach in this investigation because it was readily available and cost-effective. Distinct samples of the newly developed composites were used in conjunction with a control sample of the aluminum alloy base material. Al8011 reinforced with (Gr) and TiO2 is being investigated in order to better understand how these materials interact with one another when heat treated and without treatment. With increasing TiO2 and Gr content, the hardness improved as well as the hardness up to specific limitations; the microstructure shows the compounds distribution uniformity for Al8011 with 10% TiO2 and 2% wt Gr. The hardness also improved with the same compositions, according to the test findings (10% TiO2 and it was identified that the heat treatment created a strong bond between the compound reinforcement. The wear resistance also increaseswith the hardness.

Fabrication and finite element simulation of aluminum/carbon nanotubes sheet reinforced with Thermal Chemical Vapor Deposition (TCVD)

This study aims to grow the carbon nanotubes (CNTs) on the aluminum substrate (sheet) using Thermal Chemical Vapor Deposition (TCVD) so that the aluminum sheets can be clad together. Besides, finite element simulation (FEM) was used to evaluate the damage progression, and fracture initiation in AL-CNT composites. AL-CNT Representative Volume Element (RVE) was studied to numerically get an appropriate micro-scale Al-CNT composite simulation. To forecast the statistical connection between material microstructure and effective constitutive properties, the RVE approach was developed. AL/CNT RVE models were studied to determine the most effective carbon nanotube weight percentage as a contender to reinforce the aluminum matrix. The experimental technique was then used to investigate the results found in the RVE models. According to the experimental procedure, AL/CNT shows the maximum mechanical strength and material behavior in the CNT weight percentage reported by the RVE model analysis. Furthermore, regarding the importance of continuum mechanical simulation of microstructural damage processes in the ductile fracture mechanics research, the effect of stress triaxiality ratios, such as the ratio of mean stress to equivalent stress, on the damage growth rate was studied. The experimental results show that the composite mechanical behavior is appropriate at each CNT weight percentage simulations were conducted, and the results were compared to the numerical and experimental approaches in the literature, yielding satisfactory agreements. Based on the experimental findings, ultimate strength and young modulus of AL-5 wt.% CNT are 239 MPa and 73 GPa respectively. By adding more CNT concentration, CNT agglomerations are appeared inside the samples based on SEM. Therefore AL-5 wt.% CNT is the final candidate with the best physical properties.

Investigations on interfacial moisture storage and its relation to the mechanical behavior in polymer composites

AbstractMoisture absorption in composites significantly influence the fiber/matrix interface regions and mechanical properties. Hence, it is very important to quantify the moisture storage in interfaces and correlate it to the mechanical behavior. The novelty of this article is that, for the first time, it explores the correlation of moisture absorption parameters with the mechanical behavior of composites. The paper studies four different types of moisture‐soaked composites—glass fiber/epoxy, carbon fiber/epoxy, ZnO nanowire incorporated glass fiber/epoxy, and ZnO nanowire incorporated carbon fiber/epoxy. One‐dimensional hindered diffusion model (1D HDM) was used for the extraction of moisture absorption parameters. The hindrance coefficient (ratio of bound to unbound moisture) of composites was found to increase proportionately with the increase in the volume of interfacial regions. Only in carbon fiber/epoxy composite, it did not increase proportionately due to the relatively larger degradation of interface. This was correlated well with mechanical test responses wherein carbon fiber/epoxy exhibited anomalous failure modes due to relatively larger degradation of interface. Numerical simulations were also carried out to describe the moisture absorption in composites. Numerical simulations of moisture absorption in composites using time‐varying boundary conditions matched very well with experimental as well as 1D HDM results.

Impact of fibre weight on the mechanical properties of chopped luffa cylindrica fibre reinforced polymer composites

ABSTRACT Due to its superior properties such as light weight, biodegradable, low density, readily accessible, low cost, high specific strength etc., natural fibre-reinforced polymer composites have been a wide field of research over the last few years. The effect of the fibre content on the mechanical property and water absorption behaviour of luffa cylindrica fibre-reinforced epoxy composite is studied in this research paper. The surface morphology of tensile fracture specimens is also analysed using FESEM analysis. Four different types of composites were prepared by using hand layup technique with varying fibre content such as 4%, 8%, 12% and 16 wt%. The mechanical behaviours of composites have been analysed, such as tensile strength, flexural strength, impact strength and water absorption properties, respectively. The experimental result shows that the water absorption increases with increase in fibre weight percentage. Similarly mechanical properties increase up to 12% luffa fibre content in a composite. Maximum tensile, flexural and impact strength obtained 19 MPa, 50.2 MPa and 2.3 joule, respectively, in 12 wt% luffa fibre composites. But maximum water absorption was obtained as 10.2% in 16 wt% of luffa fibre composites.

A frictional cohesive zone model for characterizing transverse compression responses of unidirectional fiber-reinforced polymer composites

The Coulomb friction law is incorporated into the traction separation law, so a friction cohesive zone model (FCZM) combining sliding friction, interfacial debonding, and the coupling of the debonding and friction is developed. The proposed interface model is used to describe the interfacial mechanical responses of fiber/resin composite. To verify this model, the finite element model of microdroplet is built, then the calculated results of the finite element model are compared with the microdroplet test. To analyze the effect of interface friction on the macroscopic strength and stiffness of unidirectional composites, the FCZM is applied to representative volume element (RVE), and the mechanical behaviors of composites is simulated by finite element analysis of RVE, then the results are compared with the test in reference [1, 2]. It is found that the interfacial debonding is accelerated and the macroscopic strength is reduced due to the friction.

Investigating the Effect of Low-Temperature Drilling Process on the Mechanical Behavior of CFRP.

Previous research has found that lower temperature drilling is helpful to improve the hole quality of carbon fiber reinforced polymer (CFRP). However, the influence of the lower temperature drilling process on the mechanical behavior of composites is yet not fully understood. To examine the influence of the lower temperature drilling process on the mechanical behavior of CFRP, the open hole CFRP specimens used for mechanical tests were obtained with three cases: drilling with −25 °C/uncoated carbide drills/(1000 rpm, 0.02 mm/r), 23 °C/coated carbide drills/(4000 rpm, 0.03 mm/r), and 23 °C/uncoated carbide drills/(1000 rpm, 0.02 mm/r), respectively; corresponding, three groups of open-hole specimens are obtained: specimens drilling at low-temperature with low damage, specimens drilling at room-temperature with low damage and specimens drilling at room-temperature with low damage; the mechanical behavior of the three groups specimens were obtained by static tensile, tensile–tensile fatigue cyclic tests and residual tensile strength test. The results have shown that the mechanical properties of specimens with a low-temperature drilling process is lower than those of the specimen with a normal drilling process due to the better drilling quality. The damage accumulation in specimens was increased with the damage degree of the original hole, the greater the damage degree, the worse the mechanical properties.

Investigation of Compression properties on E-Glass fiber reinforced polymer matrix composites used for micro wind turbine blades

The main goal of this work is to understand the mechanical behaviour of composites to compression loads. A unidirectional (UD) fabric of E-glass fiber is the most common reinforcement in composite structural applications which exhibits excellent strength, modulus, resistance to water degradation and corrosive environments, durability, good and a quantitative and qualitative analysis is conducted on this model and the results are validated. An experimental test sample made of the E- Glass/Epoxy-resin composite is subjected to uniaxial compression test. The experimental results are validated with the multiscale mechanical model built. The FEA (Finite Element Analysis) is being utilized and the results obtained are validated through experimental approach. With such validated numerical model, application in micro wind turbine blade would result in faster prototype development. Keywords: Compressive strength, Composite material, Micro wind turbine, E-Glass fiber, FEA, Orthotropic Material, Numerical methods, Macrostructure, Microstructure.

Influence of B4C on mechanical properties of AZ91 magnesium matrix composites

In this research, the impact of Boron Carbide on AZ91 Magnesium alloy composite mechanical and tribological behaviour. AZ91 Magnesium Alloy Particulate-reinforced composites were made by mounting the wetting problem between B4C and liquid magnesium metal. K2TiF6 was added as a flux. Subsequently, T6 thermal treatment was conducted for the magnesium B4C composites thus produced. The magnesium alloy matrix AZ91 composite was tested for hardness, compression and flexural strength. The results of testing showed a greater hardness of the composites compared to the base alloy due to the increased ceramic phase.

Effect of Fibre Types on the Tensile Behaviour of Engineered Cementitious Composites

Engineered cementitious composite (ECC) is a group of ultra-ductile fibre-reinforced cementitious composites, characterised by high ductility and moderate content of short discontinuous fibre. The unique tensile strain-hardening behaviour of ECC results from a deliberate design based on the understanding of micromechanics between fibre, matrix, and fibre–matrix interface. To investigate the effect of fibre properties on the tensile behaviour of ECCs is, therefore, the key to understanding the composite mechanical behaviour of ECCs. This paper presents a study on the fibre-bridging behaviour and composite mechanical properties of ECCs with three types of fibres, including oil-coated polyvinyl alcohol (PVA) fibre, untreated PVA fibre, and polypropylene (PP) fibre. The experimental result reveals that various fibres with different properties result in difference in the fibre-bridging behaviour and composite mechanical properties of ECCs. The difference in the composite mechanical properties of ECCs with different fibres was interpreted by analysing the fibre-bridging behaviour.

Polyurethane electrospun membranes with hydroxyapatite‐vancomycin for potential application in bone tissue engineering and drug delivery

AbstractThe purpose of this study is to evaluate the drug delivery behavior and other properties of electrospun composite membranes for potential use in tissue engineering. Tecoflex® (PU1), and a lab‐made polyurethane (PU2) were studied. They were mixed with nano‐hydroxyapatite (PU1‐nHA and PU2‐nHA) and vancomycin (PU1‐VA and PU2‐VA) or mixed with both, nHA and VA (PU1‐nHA‐VA and PU2‐nHA‐VA). Scanning electron microscopy showed a porous structure in all the electrospun membranes with smooth fibers in PU1 and its composites with sizes in the range of 0.6–0.9 μm and nanoparticles of HA, both, adhered and embedded on the PU fibers were observed. nHA and VA affected the thermal and mechanical behavior of composites. Elastic modulus, cytotoxicity, and kinetic release were affected by the PU and nHA. Cell viability up to 75% showed that all membrane extracts are not cytotoxic while microbial inhibition activity was observed in PU1‐VA, PU1‐nHA‐VA, and PU2‐VA.