Mechanical Behavior Of Composite Materials Research Articles

Numerical and experimental investigation of quasi-static indentation response of PVC foam sandwich and GFRP laminated composites

AbstractComposite materials are vulnerable to impacts that may occur during their use. Such transverse loads represent a significant threat to these materials because they can cause damage that is difficult to detect. Thus, understanding the mechanical behavior of composite materials during impacts is crucial for improving their damage resistance. Therefore, this study investigates the response of two commonly used composite panels in maritime transportation—a PVC core sandwich composite and a laminated GFRP composite—under quasi-static indentation (QSI). Using numerical simulations with Abaqus/Explicit, this investigation aims to anticipate mechanical characteristics and damage patterns during low-velocity impact. Results show a strong correlation between numerical and experimental data. The force-displacement curves aid in understanding damage sequences, with predicted maximum loads at 1.43% and 6.45% accuracy for laminated and sandwich composites. Both exhibit significant damage, including permanent indentation, matrix cracks, fiber fractures, and prevalent delamination around the impact point.

Effect of Graphene Particle Diameter on Mechanical Properties of Graphene Composite Material

In order to improve the mechanical properties of alloys and broaden their application fields, high-performance metal matric composites have received more and more attention. Graphene has excellent mechanical properties and is often used as a reinforcing phase for various composite materials. However, as the reinforcing phase of the composite, the number, shape, and size of graphene have a significant effect on the overall mechanical properties of the composites. Therefore, the influence of graphene particle diameter on the mechanical properties of graphene particle reinforced metal matrix composites was studied in this paper. By establishing a series of finite element models, we simulated the mechanical behaviour of composite materials under static tension loading. The relationship between graphene particle diameter and material mechanical properties is revealed.

Prediction of the mechanical behavior of composite materials based on image processing analysis and multi-scale finite element method

Prediction of the mechanical behavior of composite materials based on image processing analysis and multi-scale finite element method

Mechanical behaviour of composite materials including waste rubber chips: experimental and numerical investigations

ABSTRACT Converting scrap tires to a useful form is becoming an acceptable technique for a broad range of applications. This study focuses on the mechanical characterisation of composites containing a high amount of waste tire rubber which are reinforced with different content of aluminium powder. Therefore, a set of experimental test is performed to highlight the effect of metallic fillers reinforcement on the mechanical response of elaborated composites under static and quasi-static tests. Results of this study reveal the high improvement of material properties for the elastomeric matrix reinforced with metallic fillers. In fact, the ultimate strength of composite material has increased to 1.8 MPa for a high reinforcement content. In the second part, a modified visco-hyperelastic model is developed on the basis of experimental results which demonstrate the prominence of the strain-rate-dependent behaviour consideration. Coupled with the Prony’s series approximation, the Mooney Rivlin model is actually applied to refine the strain energy potential in order to examine the mechanical behaviour of the composite material under different loadings conditions. Finally, the good concurrence between the numerical and experimental results highlights the impressive efficacy of the proposed model in accurately predicting the mechanical characteristics of the materials under investigation.

Physical-Mechanical Properties of Light Bark Boards Bound with Casein Adhesives

Based on the background of the limited availability of raw materials in the forestry and timber industry, increased attention applies to sawmill by-products and their potential for future applications. Within the present research, the suitability of a natural binder based on different casein sources, superficially lean curd with different lime ratios, for the production of bark insulation panels from larch bark (Larix decidua) in fraction 12.5–4.0 mm with densities below 500 kg/m³ were discussed and physical and mechanical properties evaluated. In order to obtain a benchmark, control boards bound with powdery casein and urea-formaldehyde resin were fabricated. The evaluation of physical-mechanical characteristics indicated the lean curd panels to be competitive with the references and commercially available insulation materials, whereby higher values could be achieved consistently with a lower lime content of 20% compared to 31%. The best moisture resistance and water absorption were observed with a lime ratio of 31%, whilst thickness swelling and mechanical characteristics were best with a lime content of 20%. Particularly with regard to mechanical properties, panels containing a low proportion of lime in the lean curd blends delivered convincing results, e.g., with an average IB of 0.19 N/mm2, MOR of 1.43 N/mm2 and C of 1.70 N/mm2. In terms of thickness swelling, lean curd adhesives generated unsurpassed values of approximately 11% compared to the casein and urea-formaldehyde references. Additionally, as described in the relevant literature, a considerable influence of density on the mechanical behavior of composite materials was observed. Partly, the lime content significantly influenced the panel properties. The study proved that natural binders based on lean curd and lime are suitable for the production of bark insulation boards and represent a serious alternative to synthetic, oil-based adhesive systems. The results are promising with regard to the market situation due to the availability and pricing of raw materials and technical requirements and demonstrated great potential for further research efforts.

Effect of Alternating Hybridisation of Fibres on the Physico - Mechanical Behaviour of Composite Materials

Abstract The performance/weight ratio of fiber reinforced polymer matrix composites makes them the material of choice for structural applications in many fields such as aerospace, aeronautics, automotive and civil engineering...etc. In polymer matrix composites, the fibers used as reinforcement are mainly synthetic fibers such as carbon and/or glass fibers. To ensure the low cost of using fiber-reinforced materials in motor vehicles, it is proposed to selectively incorporate carbon fibers to enhance glass fiber composites along the roadway, and to enhance glass fiber composites along the main load path. For this purpose, we conducted a behavioral study of hybrid epoxy thermoset polymer matrix laminates to highlight the influence of alternate hybridization of glass and carbon fibers on the physical-mechanical behavior of the materials.The results obtained show that the alternated hybridation of the fibers has a significant influence on the tensile properties; and it affected the density, hardness and flexural properties significantly.

Growth and Mechanical Characterization of Mycelium-Based Composites towards Future Bioremediation and Food Production in the Material Manufacturing Cycle.

Today’s architectural and agricultural practices negatively impact the planet. Mycelium-based composites are widely researched with the aim of producing sustainable building materials by upcycling organic byproducts. To go further, this study analyzed the growth process and tested the mechanical behavior of composite materials grown from fungal species used in bioremediation. Agricultural waste containing high levels of fertilizers serves as the substrate for mycelium growth to reduce chemical dispersal in the environment. Compression and three-point bending tests were conducted to evaluate the effects of the following variables on the mechanical behavior of mycelium-based materials: substrate particle size (with or without micro-particles), fungal species (Pleurotus ostreatus and Coprinus comatus), and post-growth treatment (dried, baked, compacted then dried, and compacted then baked). Overall, the density of the material positively correlated with its Young’s and elastic moduli, showing higher moduli for composites made from substrate with micro-particles and for compacted composites. Compacted then baked composites grown on the substrate with micro-particles provided the highest elastic moduli in compression and flexural testing. In conclusion, this study provides valuable insight into the selection of substrate particle size, fungal species, and post-growth treatment for various applications with a focus on material manufacturing, food production, and bioremediation.

Resin-Rich Volumes (RRV) and the Performance of Fibre-Reinforced Composites: A Review

This review considers the influence of resin-rich volumes (RRV) on the static and dynamic mechanical and physical behaviour of fibre-reinforced composites. The formation, shape and size, and measurement of RRV in composites, depending upon different fabric architectures and manufacturing processes, is discussed. The majority of studies show a negative effect of RRV on the mechanical behaviour of composite materials. The main factors that cause RRV are (a) the clustering of fibres as bundles in textiles, (b) the stacking sequence, (c) the consolidation characteristics of the reinforcement, (d) the resin flow characteristics as a function of temperature, and (e) the composite manufacturing process and cure cycle. RRV are stress concentrations that lead to a disproportionate decrease in composite strength. Those who are considering moving from autoclave consolidation to out-of-autoclave (OOA) processes should be cautious of the potential effects of this change.

A methodology for determining the local mechanical properties of model atomistic glassy polymeric nanostructured materials

We propose a methodology for calculating the distribution of the mechanical properties in model atomistic polymer-based nanostructured systems. The use of atomistic simulations is key in unravelling the fundamental mechanical behavior of composite materials. Most simulations involving the mechanical properties of polymer nanocomposites (PNCs) concern their global (average) properties, which are typically extracted by applying macroscopic strain on the boundaries of the simulation box and calculating the total (global) stress by invoking the Virial formalism over all atoms within the simulation box; thus, extracting the pertinent mechanical properties from the corresponding stress-strain relation.However, in order to probe the distribution of mechanical properties within heterogeneous multi-component polymer-based systems, a detailed computation of stress and strain fields within specific sub-domains is necessary. For example, it is well known for multi-component nanostructured systems, such as PNCs, that the mechanical behavior of the polymer/nanofiller interphases, or interfaces, is crucial for determining the global mechanical properties of the composite materials. Here we propose a new methodology to probe the distribution of mechanical properties by directly computing the (local) stress and strain at the atomic level, and averaging over user-defined subdomains. The workflow of our computational method possesses the following features:•Calculating the stress and strain per atom (or per particle) for nanostructured microscopic (here atomistic) model configurations, under an imposed applied deformation.•Averaging the local, per-atom defined, stress and strain on user-defined subdomains within the nanostructured model system.•Predicting the mechanical properties within the specific subdomains, focusing on polymer/solid interphases.

Dynamic mechanical behavior of composite materials reinforced by graphene and huntite minerals

Abstract The aim of this study is to investigate the dynamic mechanical properties of composite materials reinforced by mineral experimentally. Graphene and huntite minerals were added to epoxy resin at different weight ratios (wt.-%) as 0.5 weight percent, 1 weight percent and 3 weight percent, to examine the effect of mineral types and percentages on the resulting dynamic mechanical properties. In addition, the effect of non-layered huntite unlike graphene, with a nano-sized grain structure, was investigated. Thus, glass transition temperature (Tg), storage modulus (E’), loss modulus (E”) and damping ratio (tan δ) values were determined and compared. Moreover, a tensile test was performed in order to explain the relation between stress and strain. It was seen that adding different minerals caused different results according to types and proportions. In general, adding minerals to the pure resin increased the storage modulus and loss modulus, whereas the damping ratio (tan δ) decreased compared to the pure resin.

Improvement of the Mechanical Behavior of Composite Materials with Different Binders Based on Local Plant Fibers Alfa and Diss

Abstract Concerned about the environmental and economic impact, composite materials are increasingly used in the construction sector. Indeed, the use of plant fibers as reinforcement in construction materials have been the subject of several researches in recent years; the main motivation is the weight gain combined with high mechanical characteristics. The objective of this research concerns the study of the physicomechanical properties of composite materials with cement and clay matrices reinforced with Alfa and Diss fibers with dimensions ranging from 2 to 8 cm. This involves evaluating the performance of these materials according to the formulation, for a volume ratio (Alfa or Diss / Matrix fibers equal to 4), using dry fibers and pre-wetted fibers. The study of the mechanical properties showed a drop of the performance for both compression and bending strength compared to the reference material without adding fibers (cement or clay paste). It should be noted that the best mechanical performance is obtained for the case of composites materials with cementitious matrix with pre-wetted fibers. On the other hand, in the case of composites with clayey matrices, pre-wetting does not improve the mechanical characteristics. It is also noted that the best dimensions of fibers which improve the mechanical characteristics in bending are generally 6 cm for composites with a clay matrix and between 2 and 4 cm for cementitious composites. In all cases, the fibers in composite materials with cement or clay matrix create a bridging effect, making it possible to limit the progression of cracks during loading. This phenomenon gives to the various composite materials a ductile behavior.

Synthesis and mechanical behavior of composite material reinforced with Guadua fiber and with a polyurethane or polyester matrix

A reactive hot-melt resin (polyurethane) was used to manufacture Guadua composites with a certain flexibility, high processing speed, good initial rigidity, and high temperature performance. These composites can support a moderate tensile stress, allow for large strains at low stresses, and have a low density and a working temperature range of -40 °C and 110 °C. During the flexural test, bamboo composites with reactive polyurethane matrix do not break or fail during the test. A polyurethane-based reactive hot-melt resin was characterized by tensile tests, Shore hardness tests, differential scanning calorimetry, and thermogravimetry. Besides, a composite material was made with Guadua fiber and polyester matrix, which had a greater strength in the test of tension and flexion, although it had a lower percentage of elongation than the composite material with reactive polyurethane. Guadua fiber can increase the strength by 266% of polyurethane matrix and 228% of polyester matrix.

Effect of Time-Real Marine Environment Exposure on the Mechanical Behavior of FRP Composites

Fiber reinforced polymer (FRP) composites coupons were exposed to real sea environment to assess the influence on the mechanical behavior of composite materials used in the construction of marine structures. Real-life sea environment conditions were opted for instead of the more common simulated and laboratory versions of seawater in the attempt to obtain more realistic structural modeling environmental input design parameters for marine structures. Exposure was performed over prolonged time span instead of the usual accelerated tests. Epoxy and polyester resins, reinforced with glass fibers in three fiber layout configurations, were used to manufacture standardized tensile testing coupons. Mass changes due to seawater absorption, microorganism growth, changes in tensile strength (standard tensile tests), and surface morphology of the coupons were evaluated after 6- and 12-month long periods of submersion in the sea in the Rijeka bay, Croatia. All specimens showed mass increase due to water absorption and growth of attached algae and sea microorganisms. Various levels of reduction in tensile strength, depending on the fiber layout configurations, were observed. Significant changes in the matrix material structure were noticed, effectively producing “voids”. Based on these results, sustainability of FRP composites in marine environment is addressed and discussed.

Constitutive Model for Fibre Reinforced Cemented Silty Sand

ABSTRACT In this study, a modified version of Severn–Trent constitutive model was used to simulate the mechanical behaviour of composite materials under drained and undrained triaxial compression loading conditions. Two additional parameters obtained from the laboratory tests were added to the standard Severn–Trent model to simulate the stress-strain behaviour of cement and fibre-reinforced Toyoura silty sand. The model parameters were derived based on the experimental results performed, parametric study, trial and error and by comparison with previous research studies. The comparisons covered ranges of material from 0% to 3% fibre, 0% to 3% cement, 20% to 60% relative densities, and silt contents of up to 75%. The experimental results and model simulations were compared in terms of deviatoric stress versus axial strain, volumetric strain versus axial strain, and stress path behaviour. A close agreement of model simulations with the experimental results is observed for many of the tests performed on pure Toyoura sand, cemented, fibre, and fibre-reinforced cemented Toyoura silty sand. The extracted parameters are used to predict the response of those experiments until a reasonable (e.g. ± 5–10% peak strength) comparison is obtained.

A multifield continuum model for the description of the response of microporous/microcracked composite materials

The description of the mechanical behavior of composite materials is an open challenge in engineering. The focus of this work is on micro-cracked/micro-porous composites, made of stiff grains embedded in a cracked or porous deformable matrix. Grains interact between each other and with cracks or pores localized at the interfaces, which reduce the contact area between grains. Pores’ interaction is also taken into account. We apply a two-scale modeling strategy based on a discrete to scale-dependent (non-classical) continuum equivalence procedure. The constitutive relationships of the resulting microcontinuum, identified by requiring equivalence, in terms of virtual work, between discrete and continuum non-local descriptions of the reference material, take directly into account the material internal structure, and, in particular, material internal lengths. Field and boundary conditions of the equivalent continuum are also derived based on work equivalence between internal and external actions. The response of the obtained one-dimensional equivalent model and of a finite element model of a bar with pores are compared. A good match was obtained in a wide range of pore densities.

Enhanced computational homogenization techniques for modelling size effects in polymer composites

Several experimental investigations corroborate nanosized inclusions as being much more efficient reinforcements for strengthening polymers as compared to their microsized counterparts. The inadequacy of the standard first-order computational homogenization scheme, by virtue of lack of the requisite length scale to model such size effects, necessitates enhancements to the standard scheme. In this work, a thorough assessment of one such extension based on the idea of interface energetics is conducted. Systematic numerical experimentation and analysis demonstrate the limitation of the aforementioned approach in modeling mechanical behavior of composite materials where the filler material is much stiffer than the matrix. An alternative approach based on the idea of continuously graded interphases is introduced. Comprehensive evaluation of this technique by means of representative numerical examples reveals it to be the appropriate one for modeling nano-composite materials with different filler-matrix stiffness combinations.

Piezo-Resistive Properties of Bio-Based Sensor Yarn Made with Sisal Fibre.

In this work, a sensor yarn based on a natural sisal yarn containing a non-electro-conductive core impregnated with PVA polymer and coated by PEDOT:PSS polymer as an electro-conductive sheath was investigated. The main objectives include the development of this new sensor yarn as a first step. Then, we look towards the insertion of this sensor yarn into different woven structures followed by the monitoring of the mechanical behaviour of composite materials made with these fibrous reinforcements. The combined effect of the structural geometry and the number of PEDOT:PSS coating layers on the properties of the sensor yarns was investigated. It was found that the number of PEDOT:PSS coating layers could strongly influence the electromechanical behaviours of the sensor yarns. Different methods of characterization were employed on strain-sensor yarns with two and four coating layers of PEDOT:PSS. The piezo-resistive strain-sensor properties of these selected coating layers were evaluated. Cyclic stretching-releasing tests were also performed to investigate the dynamic strain-sensing behavior. The obtained results indicated that gauge factor values can be extracted in three strain regions for two and four coating layers, respectively. Moreover, these strain-sensor yarns showed accurate and stable sensor responses under cyclic conditions. Furthers works are in progress to investigate the mechanism behind these first results of these sisal fibre-based sensors.

End-to-end deep learning method to predict complete strain and stress tensors for complex hierarchical composite microstructures

Due to the high demand for materials with superior mechanical properties and diverse functions, designing composite materials is an integral part in materials development. However, due to the heterogeneity and complexity of composites, measurements of properties and designs of optimal structures are often experimentally or computationally intractable. Here we report complete strain and stress tensors predictions given input composite geometries, based on a deep learning approach. The model not only predicts all strain and stress tensor components accurately, but also observes rigorous continuum mechanical principles. Furthermore, through tuning data statistics, the model performance is enhanced even with a small amount of data in terms of handling material microstructures with varying constituent ratios and hierarchical geometries. The method vastly improves the efficiency of predicting comprehensive mechanical behaviors of composite materials and provides a powerful tool for design problems such as multifunctional composites design and hierarchical structures optimization.

Machine learning based multiscale calibration of mesoscopic constitutive models for composite materials: application to brain white matter

A modular pipeline for improving the constitutive modelling of composite materials is proposed.The method is leveraged here for the development of subject-specific spatially-varying brain white matter mechanical properties. For this application, white matter microstructural information is extracted from diffusion magnetic resonance imaging (dMRI) scans, and used to generate hundreds of representative volume elements (RVEs) with randomly distributed fibre properties. By automatically running finite element analyses on these RVEs, stress-strain curves corresponding to multiple RVE-specific loading cases are produced. A mesoscopic constitutive model homogenising the RVEs’ behaviour is then calibrated for each RVE, producing a library of calibrated parameters against each set of RVE microstructural characteristics. Finally, a machine learning layer is implemented to predict the constitutive model parameters directly from any new microstructure. The results show that the methodology can predict calibrated mesoscopic material properties with high accuracy. More generally, the overall framework allows for the efficient simulation of the spatially-varying mechanical behaviour of composite materials when experimentally measured location-specific fibre geometrical characteristics are provided.

Effects of Thermal Residual Stresses on Tensile and Interlaminar Shear Behaviors of GLARE Laminates

The residual stresses caused by curing, forming and machining process significantly affect the mechanical behaviors of composite materials, especially for super hybrid structure like GLARE (glass fiber reinforced aluminum laminates). In this work, the curing thermal residual stresses characteristics of GLARE and corresponding effects on tensile and interlaminar shear behaviors were investigated. Firstly, the characteristics of residual stresses were described by a finite element (FE) model and verified by layer removal method. Then, thermal residual stresses were incorporated into FE mechanical behavior prediction models in the form of predefined field to analyze the effects on tensile and interlaminar shear behaviors. The corresponding simulation conclusions were consistent with the experimental observations. The results indicated that there were about 40 MPa tensile residual stress in aluminum layers and 70 MPa compressive residual stress in GFRP (glass fiber reinforced polymer) layers of GLARE. Residual stresses had obvious reduction effect on the yield strength of GLARE, and the prediction accuracy was hence improved by 9%. Moreover, the failure mode of tensile tests was hardly affected by the residual stresses, but the tensile strength and the initial damage loads were reduced slightly. In interlaminar shear tests, the peak load and initial damage load were reduced by the residual stresses in the adhesive layers of GLARE, and the interlaminar shear strength was slightly influenced. An edge failure mode caused by edge effect was observed during the propagation of the delamination cracks, which was verified by interlaminar shear finite element models and SEM (scanning electron microscope) images.