Polymer Matrix Laminates Research Articles

Sensor-Enhanced Thick Laminated Composite Beams: Manufacturing, Testing, and Numerical Analysis.

This study investigates the manufacturing, testing, and analysis of ultra-thick laminated polymer matrix composite (PMC) beams with the aim of developing high-performance PMC leaf springs for automotive applications. An innovative aspect of this study is the integration of Fiber Bragg Grating (FBG) sensors and thermocouples (TCs) to monitor residual strain and exothermic reactions in composite structures during curing and post-curing manufacturing cycles. Additionally, the Calibration Coefficients (CCs) are calculated using Strain Gauge measurement results under static three-point bending tests. A major part of the study focuses on developing a properly correlated Finite Element (FE) model with large deflection (LD) effects using geometrical nonlinear analysis (GNA) to understand the deformation behavior of ultra thick composite beam (ComBeam) samples, advancing the understanding of large deformation behavior and filling critical research gaps in composite materials. This model will help assess the internal strain distribution, which is verified by correlating data from FBG sensors, Strain Gauges (SGs), and FE analysis. In addition, this research focuses on the application of FBG sensors in structural health monitoring (SHM) in fatigue tests under three-point bending with the support of load-deflection sensors: a new approach for composites at this scale. This study revealed that the fatigue performance of ComBeam samples drastically decreased with increasing displacement ranges, even at the same maximum level, underscoring the potential of FBG sensors to enhance SHM capabilities linked to smart maintenance.

Ramie Fiber Woven Composite: The Effect of Number of Layers of Woven Fibers on the Thrust Force in the Drilling Process

Composite material is a combination of two or more materials to obtain better properties and capabilities of the constituent materials. Applications for the use of composites can now be found in industrial equipment to household appliances. To produce these products required machining process. The aim of the study was to determine the effect of the number of layers of woven fiber and the diameter of the drill bit on the thrust of the ramie woven fiber composite in the machining process. The research method was based on ASTM D 5766/D 5766M-02 (Standard Test Method for Tensile Strength Open Hole Laminated Polymer Matrix Composites), the method of making composite material specimens using the hand lay-up method, and the drilling process was carried out with various machining parameters such as composite thickness with variations of 3 layers, 4 layers, 5 layers, and without layers (0 layers). The maximum thrust value obtained was 153.54 ± 3.3 N, with 5 layers of hemp fiber reinforcement, the highest feed rate was 0.15 mm/rev, and the lowest spindle speed was 88 rpm, while the minimum thrust value was 29.52. ± 3.12 N with 0 layers of ramie fiber reinforcement, and the lowest feed rate is 0.05 mm/rev with the highest spindle speed of 1500 rpm.

Effect of Heating and Cooling of Aluminium-Based Fibre-Metal Laminates on Their Tensile Strength

The widespread use of composite materials in the construction of machines encourages to better understand their properties and the impact of various external factors on these properties. Fibre metal laminates (FMLs) consist of alternating layers of metal and a polymer matrix laminate reinforced with continuous fibres. The aim of this work was to investigate the effect of cyclical temperature changes and thermal shocks (heating the sample to a high temperature in a short time) on the strength properties of FMLs from AW-1050A aluminium sheet, glass fibre fabric and carbon fibre fabric. The research concerns the determination of how cyclical temperature changes affect the tensile strengths properties of FMLs. The results indicate a small effect of the cycles on the tensile strength of the composites. The composites with glass fibre reinforced laminate also showed high resistance to delamination, moreover, the samples did not delaminate even after they were broken. The carbon fibre reinforced laminate composites showed a tendency to delaminate after heat treatment.

Enhancement of the interlaminar performance of silica/phenolic laminates after high-temperature pyrolysis using a boron carbide/silicon carbide fibre z-pin

The interlaminar strength of polymer matrix laminates significantly affects their performance. Z-pinning is an effective method for improving the interlaminar performance of laminates. However, it remains a challenge to improve the interlaminar performance of polymer matrix laminates at high temperatures. In this study, the interlaminar performance of silica/phenolic laminate after high-temperature pyrolysis was enhanced by using a boron carbide/silicon carbide fibre (B4C/SiCf) composite pin. Experimental results revealed that the in-plane interlaminar shear strength (ILSS) of the pyrolyzed B4C/SiCf z-pinned laminates was above 3.0 MPa, which was 110% higher than that of the unpinned laminate. In addition, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis revealed that the combined effect of B4C and SiC fibres in the pin on the interlaminar performance of the laminate at high temperatures due to the enhancement in the interlaminar strength of the composite. Furthermore, the ILSS of the laminate increased when the z-pin content of the B4C/SiCf pins increased; however, when the content of the z-pin further increased, the vertical interlayer direction would happen the brittle fracture.

Vol4 num4-11 Biaxial testing on CFRP laminates cruciform specimens under compressive loads

A numerical and experimental study is performed on biaxial tests with cruciform specimens in which at least one direction is under compression. Continuous carbon fibre reinforced polymer matrix laminates are studied in angle-ply sequences. The high complexity of the biaxial test is analysed, highlighting the non-linear behavior of the material with pseudo-ductile response. In addition, the presence of compression loads lead to tests in which it is necessary to avoid instabilities in order to obtain adequate results. The numerical simulations based on the Finite Element Method allow to study of the initiation and evolution of the damage in the laminate. The combination of numerical techniques with experimental results, obtained by means of the test instrumentation with strain gauges and Digital Image Correlation, allows to perform a complete characterization of the behaviour of the material in order to achieve less conservative designs of composite structures.

Pseudo-ductility under tensile and compressive loading in ±45º laminates

This work focuses on analyzing the uniaxial response of carbon fiber reinforced polymer matrix laminates with the configurations [±45]2S under tension and [±45]4S under compression. These present non-linear stress-strain evolutions that allow them to withstand large deformations before losing their load-carrying capacity. Both responses are characterized by a first linear stage, followed by a plateau in which the strain grows without increasing the stress level, and finally by a re-stiffening phase. But there are quantitative differences that lead to different failure patterns, which are explained with the help of the state of stress in the plane of maximum shear stress. For a better understanding of the process, tensile load-unload-reload tests are performed to verify if the energy recovered in each cycle could be related to the loss of the apparent stiffness. During the first two stages of the mechanical response, the laminate suffers a progressive damage with a reduction in stiffness related to the dissipated energy, but this pattern is not repeated in the last stage of strain hardening. Based on the experience of other authors, it is assumed that the re-stiffening stage follows a different pattern due to possible microstructural changes in the matrix during the plateau. These are promoted by a narrowing process under tensile loads and a local widening of the test zone under compression. The dimensional changes perpendicular to the load direction are observed thanks to the strain fields obtained by Digital Image Correlation.

Sound insulation of a novel laminated polymer matrix composite containing metallic hollow spheres based on phononic crystal structure design

AbstractAs a noval functional material designed and prepared artificially, one‐dimensional phononic crystal has a great prospect in the field of noise reduction. In this study, a novel one‐dimensional phononic crystal metamaterial based on the metallic hollow spheres (MHS)/polymer matrix laminated composites was designed and prepared. The result of impedance tube test shows that the laminated composite has excellent sound insulation performance. The incident direction of sound waves has little effect on the sound insulation performance of the laminated composites. The average sound insulation of MHSP/SR‐LC (MHSP side) was 44.4% higher than that of SR and 272.0% higher than that of PU. After analysis, it can be found that the average sound insulation of laminated composites increases with the acoustic impedance increasing, but the equivalent mass density and equivalent bulk modulus have little effect on it. The metallic hollow spheres can increase the sound energy loss by extending the transmission path of sound waves, andit can also improve the sound insulation by changing the density, elastic, and hardness of SR and PU matrix to increase the resonance strength of the spring‐mass oscillator. This work may open up new possibilities for the development of novel acoustic materials applied in noise control.

An Assessment of ASTM E1922 for Measuring the Translaminar Fracture Toughness of Laminated Polymer Matrix Composite Materials.

The main objective of this work is to predict the exact value of the fracture toughness (KQ) of fiber-reinforced polymer (FRP). The drawback of the American Society for Testing Materials (ASTM) E1922 specimen is the lack of intact fibers behind the crack-tip as in the real case, i.e., through-thickness cracked (TTC) specimen. The novelty of this research is to overcome this deficiency by suggesting unprecedented cracked specimens, i.e., matrix cracked (MC) specimens. This MC exists in the matrix (epoxy) without cutting the glass fibers behind the crack-tip in the unidirectional laminated composite. Two different cracked specimen geometries according to ASTM E1922 and ASTM D3039 were tested. 3-D FEA was adopted to predict the damage failure and geometry correction factor of cracked specimens. The results of the TTC ASTM E1922 specimen showed that the crack initiated perpendicular to the fiber direction up to 1 mm. Failure then occurred due to crack propagation parallel to the fiber direction, i.e., notch insensitivity. As expected, the KQ of the MC ASTM D3039 specimen is higher than that of the TTC ASTM D3039 specimen. The KQ of the MC specimen with two layers is about 1.3 times that of the MC specimen with one layer.

Characterization of microcracking of NCF composites under accelerated hygrothermal cycles: Influence of the stitching yarn and the style of biaxial NCF

In this paper, an analysis of the evolution of microcracking of Non-Crimp Fabric (NCF) polymer matrix laminates under hygrothermal loading is presented. These composites are reinforced with biaxial NCF styles ([+45/-45], [0/90], etc.) and manufactured by Liquid Resin Infusion (LRI). The samples are subjected to accelerated hygrothermal cycles that cause microcracks in specific resin-rich areas (RRA). Three types of microcracks were found to occur in the heterogeneous morphology of NCF. An experimental method based on 2D microscopic observations was adapted for the characterization of microcracking in several NCF laminates. 3D tomographic X–ray observations were performed to investigate the propagation and location of microcracks in the NCF volume. The influence of humidity on microcracking was investigated. The impact of several parameters on microcracking was discussed, in particular the stitching yarn size and styles of biaxial NCF used in laminates.

Mechanical Lock Joint for Effective In-Plane Application of Concentrated Loads to Thin Polymer Matrix Laminates.

Means of in-plane loading of thin laminates with concentrated loads are of high practical importance. The purpose of this work was to investigate experimentally and numerically the mechanism of load transfer, load capacity, damage and associated failure modes of a specific, mechanical lock joint intended for in-plane loading of thin laminate plates with concentrated loads. The experimental investigations were carried out with the digital image corelation (DIC) and computed tomography (CT), and numerical ones with the help of a non-linear FE modelling, accounting for progressive damage. For this purpose, a special algorithm was developed accounting for a continuous degradation of the stiffness moduli of the laminate with strains according to the custom defined degradation law. Due to the specific design, the joint loaded a laminate plate with its front and rear parts, unlike a typical bolt joint transferring a load only by contact pressure developed at the front side of a bolt. Due to this feature, the load capacity of the joint was almost two times higher than that of a typical bolt joint of the same relevant dimensions.

Carbon fibre damage during 3D printing of polymer matrix laminates using the FDM process

Fused deposition modelling (FDM) is an additive manufacturing process used for the 3D printing of continuous fibre-polymer laminates. However, the mechanical properties of laminates printed using the FDM process are often relatively low. The damage caused to continuous carbon fibres during different stages of the FDM process from the initial feedstock material to the final 3D printed material is investigated to determine the causes of the properties decay. The effect of the process stages on the damage and mechanical properties of a continuous carbon fibre/polyamide filament material is determined. Fibre damage occurs at multiple stages of the FDM process, although most damage occurs in the final stages when the FDM filament is extruded through the printer nozzle and then printed. The average strength of carbon fibres within the FDM filament evaluated in this study is reduced ~33% by the FDM process. The tensile strength and compression kinking stress of the 3D printed filament material are reduced by ~60% and ~25%, respectively. The causes of the damage and the resultant reductions to the mechanical properties of the FDM filament during 3D printing are identified.

Is the Viscoelastic Sheet for Slamming Impact Ready to Be Used on Glass Fiber Reinforced Plastic Planning Hull?

Planing hull vessel built with polymer matrix laminates and fiberglass reinforcements (GFRP) suffer structural damage due to the phenomenon of slamming during navigation, due to the impact of the boat hull on the free surface of the water at high speed. A modification in the manufacture of the laminates for these fast boats is proposed, consisting of the insertion of an additional layer of a hybrid material, formed by elastomer encapsulated in an ABS polymer cell. Using GFRP specimens made from pre-impregnated material and reproducing the characteristic impacts of slamming, it is possible to compare the modified material with the introduction of the viscoelastic layers with the response under the same conditions as the unmodified laminates. Additionally, the panels have been tested using impacts due to weight drop at different energies, which allow determining the material damage threshold as a function of the energy absorbed, and to establish a comparison with the GFRP panels modified by observation in fluorescent light. It is verified that the proposal to reduce the effect of these impacts on the generation of damage to the material and its progression throughout the service life of the vessel is effective.

Modeling fatigue life of composite laminates: A statistical micro-mechanics approach

Modeling the stiffness degradation associated with intra-laminar damage is an essential aspect of many fatigue models for laminated polymer matrix composites. The present paper therefore investigates the effect of intra-laminar micro-cracks on the effective stiffness of unidirectional plies. Following a brief review of the damage mechanisms observed in laminates under fatigue loading as well as current approaches for fatigue modeling, a Monte-Carlo algorithm is employed to generate random arrangements of unidirectional carbon fibers embedded in a polymer matrix. The cross sections of these geometries are tessellated by means of Voronoi-cells and Delaunay-triangles to create potential crack paths and meshed using finite volume elements. The finite element models are then subjected to cyclic transverse strain via periodic boundary conditions. A multi-axial fatigue life criterion formulated on the micro-scale is used to model the damage process of the material in a simplified manner. For each simulated state, the effective stiffness properties of the composite are determined. Material behavior is then statistically analyzed for samples of random fiber arrangements containing different numbers of fibers. In general, the effective material behavior is monoclinic showing coupling between out of plane shear and transverse normal deformation. In the initial undamaged state, some but not all engineering stiffness parameters can be assumed to follow a normal distribution. As expected, a statistical size effect on the fatigue life to crack initiation can be demonstrated. For increasing severity of the simulated damage, a linear correlation is observed between most of the primary engineering stiffness parameters such as the elastic and shear moduli while this is not the case for many of the normal-shear coupling parameters.

Buckypaper embedded self-sensing composite for real-time fatigue damage diagnosis and prognosis

In this study, buckypaper (BP) membranes have been used to introduce self-sensing capability in glass fiber reinforced polymer matrix (GFRP) laminates by embedding them in the interlaminar region of the laminates. Piezoresistive characterization studies were conducted by subjecting the self-sensing GFRP (SGFRP) specimens to cyclic loading and high sensitivity to strain was observed. A measurement model for real-time quantification of fatigue crack, developed using in-situ resistance measurements obtained under fatigue loading, was used to quantify fatigue crack length in real time. The fatigue crack growth rates and the nature of crack propagation in baseline and SGFRP specimens were compared. The results show that the introduction of BP reduced the average crack growth rate by an order of magnitude as a result of crack tip blunting during fatigue, while facilitating real time strain sensing and damage quantification. A fully probabilistic prognosis methodology was also developed by combining the in-situ measurement model with a machine learning based prognosis model to accurately predict the real-time fatigue crack propagation using sequential Bayesian techniques.

Influence of low-velocity impact-induced delamination on electrical resistance in carbon fiber-reinforced composite laminates

In this paper, experiments have been performed and finite element models have been developed for studying the influence of low-velocity impact damage on the four-probe electrical resistance of carbon fiber-reinforced polymer matrix laminates. Sixteen-ply and 32-ply AS4/3501-6 laminates with quasi-isotropic layup were analyzed. Electrical resistance was evaluated using a four-step procedure. First, finite element models were created in Abaqus Finite Element Analysis (FEA) for simulating low-velocity impact using a quasi-static loading approach. Second, matrix rupture in the inside plies was evaluated, and delamination analysis was performed at the corresponding interfaces to determine delamination patterns. Third, four-probe electrical finite element models were developed in Abaqus FEA for specimens before and after impact using the concept of effective conducting thickness and the delamination patterns obtained from the delamination analysis. Effects of the low-velocity impact delamination on four-probe top and oblique electrical resistance were studied. Electrical resistance predictions were compared to the experimental data. Both top and oblique resistance planes were sensitive to presence of delamination with the oblique resistance measurement being more sensitive as compared to the top resistance measurement. In addition, the resistance of the 16-ply specimens was more greatly affected by the delamination compared to the 32-ply specimens. The proposed analysis can be utilized for design of carbon fiber-reinforced polymer matrix composites with optimized damage sensing capabilities.

Properties of thermally recycled basalt fibres and basalt fibre composites

The reduction to the tensile failure stress caused by high-temperature incineration of basalt fibres is investigated. The failure stress of single basalt fibres and tows decreases rapidly with increasing temperature when heated above ~ 250 °C, and at temperatures typically used for incineration of waste composite materials (450–600 °C) the fibre strength is reduced by more than 65%. Strength testing of single basalt fibres with sub-micron notches produced by focussed ion beam milling indicates the reduction in fracture stress is caused by thermally activated surface flaw growth. Following thermal treatment, the recycled basalt fibres were used to produce polymer matrix laminates. The tensile failure stress of laminates containing recycled basalt fibres was much lower than the original strength due to fibre weakening and the absence of fibre sizing needed to promote bonding to the polymer matrix.

Interlaminar and Intralaminar Fracture Behavior of Carbon Fiber Reinforced Polymer Composites

Interlaminar and intralaminar fracture behavior of carbon fiber reinforced composites have been experimentally studied. Unidirectional, woven reinforcement and thermoplastic and thermoset polymer matrix laminates have been characterized using double cantilever beam (DCB) and end notch flexure (ENF) specimens for Mode-I and Mode-II fracture toughness, respectively and compact tension (CT) specimens for intralaminar fracture. AS4/PEEK, AS4/8552 and AGP193PW/8552 laminates have been characterized in this study. The fracture toughness determined from the experimental data could be related to the constituents and reinforcements. It has been observed between the two UD laminates, AS4/PEEK exhibit higher fracture resistance under both interlaminar and intralaminar fracture. Woven reinforcement is found to show higher mode-II interlaminar fracture toughness.

Validated progressive damage analysis of simple polymer matrix composite laminates exhibiting matrix microdamage: Comparing macromechanics and micromechanics

The generalized method of cells micromechanics theory, employing the multi-axial mixed-mode continuum damage mechanics model for the matrix of the composite, is used to predict the evolution of matrix microdamage in un-notched (simple), unidirectional and laminated polymer matrix composites. Matrix microdamage is considered to be the evolution of subscale phenomena (including micro-crack, micro-fissure, micro-void, and shear band growth) that are responsible for all non-linearity in the composite up to the onset of more severe damage mechanisms, such transverse cracking, fiber breakage or delamination. Micromechanics is used to explicitly resolve the constituents of the composite at the microscale (fiber-matrix scale). The micromechanics model is validated against experimental data for numerous different laminate stacking sequences and a previously validated macroscale (e.g, lamina-scale), thermodynamically-based, work potential theory (Schapery theory). The inputs used in the continuum damage model, which was incorporated in the micromechanics theory, were calibrated against the same three experimental stress-strain curves utilized to calculate the inputs for the macroscale model. The agreeable predictions, obtained with the micromechanics model, establishes that both the macro- and micro-models are suitable for progressive damage analysis of laminated composites, considering only matrix microdamage. Moreover, the validated micromechanics theory is utilized to study the effect of fiber volume fraction on the matrix microdamage evolution in the various lay-ups. This demonstrates a key capability of the micromechanics approach that is lacking in the macromechanics method due to the macroscale assumption that the laminae are monolithic, anisotropic materials.

Mechanical Performance of Polymer-Matrix Laminate Reinforced with 3D Fabric during Three-Point Impact Bending

The paper presents the analysis of course and the results of impact 3-point bending tests conducted with use of instrumented Charpy hammer (CEAST RESIL 50 hammer + MC101 registrator + CALKA J computer program) on GFRP laminate specimens cut of the panels manufactured by RTM method on base of classic plain-woven fabric preform and 3D fabric. The specimens of the 3D laminate were cut alternatively along (W direction) and transverse (P direction) to the translaminar interweave strands. It was found that maximum force obtained in the tests is comparable for both the classic and the 3D laminates. Deformability of the 3D (W) specimen is by about 20% higher than those of the classic laminate, whereas it is higher by even 75% for 3D (P). The trend of deformability observed for the tested laminates differs from known trends characteristic for static conditions what confirms different material response mechanisms at low and higher load rate. Failure energy in the classic and in the 3D (W) specimen is on comparable level. However, 3D (P) specimen showed slightly lower summary failure energy than the classic one and almost twice a high failure initiation energy (first effects of failure occur before maksimum load is gained).

Role of in-plane stacking sequence on transverse effective thermal conductivity of unidirectional composite laminates

Laminated polymer matrix carbon fiber composites have poor thermal conductivity in through thickness direction as all the conductive fibers are within the plane. One can increase the through thickness thermal conductivity by introducing conductive fibers in that direction or by modifying the form, direction and architecture of the fiber network. In this paper we conduct a parametric study using finite element analysis to investigate the relation between the local fiber architecture and its effective through-thickness thermal conductivity. The role of the fiber tow orientation, volume fraction and stacking sequence is explored. Unidirectional laminates containing fiber tows aligned in the same direction for all laminae exhibit higher through thickness thermal conductivity than the stacking sequence with other orientations. A conductive coating surface layer enhances the thermal conductivity of laminates independent of fiber orientation configuration. A geometric scalar parameter is proposed to correlate laminate through-thickness thermal conductivity with fiber tow stacking sequence. The influence of different boundary condition types on the through-thickness thermal conductivity is also assessed.