Polymer Composite Laminates Research Articles

Fractographic analysis of fiber‐reinforced polymer laminate composites for marine applications: A comprehensive review

AbstractIn the past decade, polymer‐based glass fiber‐reinforced laminate composites have gained significant popularity in various mass transit applications, including marine, aircraft, and automotive industries. However, it is crucial to consider the degradation and potential failure of these materials, especially in mass transit networks. To address this concern, fractographic analysis has emerged as a valuable approach for investigating fracture surfaces, extracting vital information, and facilitating the development of new materials. Furthermore, it sheds light on the underlying physical mechanisms that contribute to composite failure. This paper primarily focuses on examining flaws, failure modes, and performing fractography analysis on fiber‐reinforced polymer (FRP) laminate composites subjected to various loading conditions such as tension, compression, flexure, impact, shear, and fracture. Fractography, as an indispensable method, plays a pivotal role in the comprehensive development of composite structures and has become a reliable tool for composite engineers. The outcomes of this study are expected to serve as a foundation for identifying areas that require further investigation in terms of fracture analysis and failure modes specific to FRP composite materials, particularly those used in marine applications.Highlights Introduction to FRP laminate composites in marine structures. Concise analysis of failure modes in FRP laminate composites. SEM fractography review of FRP laminate composites under varied loading conditions. Comprehensive study on tensile, flexural, impact, compression, shear, and fracture toughness failure modes. Summarization of identified defects in FRP composites.

Effect of stacking order on the properties of hybrid palm sheath/polyester fiber felt‐reinforced polymer composite laminates

AbstractNatural fiber‐reinforced composites exhibit excellent mechanical properties. However, achieving a balance between excellent mechanical properties and optimal acoustic performance remains a challenge. In this study, four composite laminates with different stacking orders were fabricated using polyester fiber mats (WFs) and palm sheaths (WPs) through a hot‐press process. Moreover, the effects of different stacking orders on the mechanical and acoustic properties of the composite were investigated. The results revealed that the incorporation of polyester fiber felts and the modification of the layup sequence of WP and polyester fiber felts significantly improved the mechanical and acoustic properties of the composites. Scanning electron microscopy images revealed a strong bonding between palm fibers and polyester fibers at the epoxy resin interface. Compared with pure palm fiber composites, the alternately stacked palm fibers and polyester fibers (WP/WP/WF/WP/WF) exhibited the highest mechanical properties, with a significant enhancement of 142.67% and 16.90% in flexural and tensile strengths, respectively. Additionally, the peak absorption coefficient of polyester fiber felts, positioned in the surface layer of the composite material, within the 2580–3400 Hz frequency band significantly increased from 0.07 to 0.44. Therefore, this study indicates that modifying the stacking order improves the mechanical and acoustic properties of the composites, making them suitable for use in acoustic engineering materials for buildings and decorative panels for furniture, including perforated panels and acoustic screens.Highlights The fabric‐like textured structure significantly enhanced the overall performance of the composites. The stacking order significantly influenced the overall properties of the composite. Alternately stacked polyester fiber felts and palm fibers exhibited excellent mechanical performance. The polyester fiber felts positioned on the surface layer of the composites exhibited superior mechanical performance. A laminate with “green” attributes and good acoustic properties was fabricated.

Fracture Behavior of Sandwich-Structured Fe-Based Amorphous Alloy Strip and ABS Polymer Composite Laminates

Fracture Behavior of Sandwich-Structured Fe-Based Amorphous Alloy Strip and ABS Polymer Composite Laminates

Theoretical Analysis of the Buckling Behaviors of Inhomogeneous Shape Memory Polymer Composite Laminates Considering Prestrains

Theoretical Analysis of the Buckling Behaviors of Inhomogeneous Shape Memory Polymer Composite Laminates Considering Prestrains

A hierarchically modified fibre-reinforced polymer composite laminate with graphene nanotube coatings operating as an efficient thermoelectric generator

SWCNT-p-type TE films on GF with a power factor of 96 μW m−1 K−2. SWCNT-n-type TE films on GF with a power factor of 82 μW m−1 K−2. The GFRP–OTEG exhibited: VOC = 1.01 V, ISC = 850 μA, Pmax = 215 μW.

Fatigue damage mechanisms and evolution of residual tensile strength in CFRP Composites: Stacking sequence effect

This study explores the effect of fiber orientation on the fatigue resistance of carbon fiber reinforced polymer composite laminates. First, fatigue damage mechanisms of composite laminates with different stacking sequences at various stress levels are analyzed by utilizing digital image correlation (DIC) and scanning electron microscope (SEM) techniques. The findings highlight that the fiber orientation of the laminate has a significant effect on the fatigue life of the specimens. Prior to final fatigue failure, laminates with 0° fiber orientation experience only a 30 % reduction, while laminates with ± 45° fiber orientation show up to 93 % stiffness reduction. The fracture modes of laminates with a 0° fiber orientation vary depending on stress levels. Microscopic observations confirm that in the case of laminates with ± 45° fiber orientations under compressive loading, fiber flexion, and delamination are the predominant failure mechanisms. Further, the post-fatigue tensile tests reveal that the residual tensile strength of the laminates with ± 45° fiber orientations increases by 6.3 % after 15 % of the total cycles (7.2 × 104) at a 30 % stress level. The contribution of this study provides vital insights into the structural design of laminates and offers a pathway for improving their fatigue performance.

Study of the dynamic response and damage evolution of carbon fiber/ultra-thin stainless-steel strip fiber metal laminates under low-velocity impact

Two configurations of carbon fiber/ultra-thin stainless-steel strip fiber metal laminates (CUSFML) with differing metal volume contents (35.3% and 18.2%) and carbon fiber-reinforced polymer (CFRP) composite laminates were selected for tests. The impact response and the effect of metal volume content on the impact resistance of CUSFML were assessed via experiment and FEM. Inducing damage by drop-weight test within the impact energy range of 18.60–46.23 J, two types of CUSFML and CFRP composite laminates were compared. In particular, the bearing capacity, impact deflection, failure modes, and energy dissipation were considered. The impact modeling using the VUMAT subroutine refines the relationship between energy-dissipating mechanism and damage evolution. The results indicate that CUSFML are characterized by higher impact resistance than CFRP composite laminates under low-velocity impact. The effect of metal volume content on the impact resistance increases gradually with impact energy increasing. Under 46.23 J impact, the CUSFML with higher metal volume content exhibits more concentrated damaged area with severe penetration failure, which is more dominated by metal failure features with a higher proportion of plastic energy dissipation. For CUSFML with lower metal volume content, extensive delamination and damage expansion occurs under the dominance of fiber damage behaviors.

Resin pressure monitoring method and variation in autoclave processing of polymer composite laminates using capillary sensors

Resin pressure monitoring method and variation in autoclave processing of polymer composite laminates using capillary sensors

Hybrid effects and failure mechanisms of carbon/Kevlar fiber composite laminates under the bending-after-impact loading

The hybrid fiber design concept is widely used in the aerospace industry to improve the mechanical properties (stiffness, strength, elongation, energy absorption ability) of composite laminates. In the present work, an experimental method was employed to investigate the hybrid effects on the failure mechanism of carbon-Kevlar hybrid fiber-reinforced polymer (HFRP) composite laminates under bending-after-impact (BAI) loading conditions. Carbon/Kevlar FRP specimens with five different hybrid ratios and three different stacking sequences were designed and fabricated by the compression molding method. A series of three-point bending (3 PB) tests and BAI tests were conducted to characterize the degradation of the residual flexural properties of the laminates under low-energy impacts. Among the laminates designed with different hybrid ratios, the [K3C3] structure combined the advantages of the high strength of carbon fibers and the high toughness of Kevlar fibers; thus, it exhibited excellent residual bending properties. Among the laminates designed with different stacking sequences, the outermost Kevlar fiber layer in the [KCC]S structure effectively protected the inner carbon fiber layers on the compressed and stretched sides; thus, it yielded excellent residual flexural properties.

Integrated composite electrothermal de-icing system based on ultra-thin flexible heating film

Icing is a serious threat to the flight safety of aircraft. Lightweight and efficient electrothermal de-icing systems for carbon fiber reinforced polymer components are expected to contribute to the lightweighting and electrification of aircraft. This study presents the development and test of a novel, integrated, multifunctional composite electrothermal ice protection system. The system achieves this by incorporating a carbon-based ultra-thin flexible heating film into a carbon fiber-reinforced polymer composite laminate. T700 and M40 carbon fiber prepregs were used. The system composition and configuration were designed based on the anisotropic mechanical and thermal properties of the carbon fiber-reinforced polymer composite. The effects of ply stacking sequence, presence of insulation layer, ply angle, heating area, and prepreg type on thermal response and de-icing performance were investigated. Thermal response experiments were carried out in both room temperature and low temperature environments. A one-dimensional thermal response analysis model was developed for a representative heating structure. Comparative de-icing experiments were conducted on different samples in a low-temperature test chamber. A numerical model, based on the modified enthalpy-porosity method, was developed to simulate the de-icing process, and showed good agreement with the experimental results. Experiments and numerical calculations show that the arrangement of the heater close to the deicing surface improves the performance of the electrothermal deicing system while maintaining the overall mechanical properties of the multi-layer structure. While the insulation layer helps marginally with heat loss during de-icing, it significantly increases the system’s thermal inertia, which delays the de-icing’s start. It is recommended to minimize or eliminate insulation layer thickness. Rapid de-icing effects, combined with energy conservation, can be achieved through a short-term, high-power heating strategy.

Mode I fracture toughness determination and environmental durability evaluation of adhesive bonds by wedge test

This paper presents a study of a method for determining the fracture toughness of adhesive bonds under Mode I loading using the wedge test. The slope of adhesively bonded specimen arms at loading points was used to provide an effective crack length for the wedge test specimen. A simple expression was derived based on beam theory for the Mode I energy release rate. Finite element analyses were conducted on wedge specimens with a range of material and geometrical properties. Good agreement was found between the energy release rates from the beam theory-based expression and the virtual crack closure technique (VCCT). A comparison of various energy release rate expressions showed that the present expression was more accurate than the other expressions available in the literature. The results of this study suggest that the environmental durability of adhesive bonds with composite adherends as well as metallic adherends can be assessed in terms of their fracture toughness using the present method. Experiments under hot and humid conditions were performed on wedge specimens with adherends made of carbon fiber reinforced polymer (CFRP) composite laminate and titanium alloy, and the fracture toughness results were obtained.

Agro-waste-based polymeric composite laminates for aerospace cabin interior and identification of their optimal configuration

Agro-waste-based polymeric composite laminates for aerospace cabin interior and identification of their optimal configuration

SEISMIC performance of RC square columns strengthened by bidirectional basalt-fiber-reinforced polymer (BFRP) composite laminates with fan-shaped anchors

For seismic retrofitting of existing reinforced concrete (RC) structures, multiple strengthening demands may be required simultaneously including shear, flexural, and axial strength, as well as ductility. However, satisfying such multiple demands using conventional materials and strengthening systems may be challenging. As compared to commonly used unidirectional fibers reinforced polymers (FRP) composites laminates, bidirectional FRP laminates offer an effective methodology for providing strength and ductility in different directions. In this study, seven reinforced concrete (RC) columns specimens confined by bi-directional basalt-fiber-reinforced polymer (BFRP) composite jackets at plastic hinge regions with and without fan-shaped composite anchors are evaluated. All specimens are subjected to low-frequency full-reversal cyclic lateral loadings up to failure. Several design parameters are assessed to identify its impact on the behavior of confined columns that include: (i) composite laminate types, (ii) number of plies, (iii) strengthening scheme, and (iv) presence of anchorages. Service and ultimate seismic performance of each specimen including failure modes, rupture strain, and ductility are described and investigated. Experimental results indicated that ultimate failure mode changes from a shear failure, in the case of unidirectional composite jacket, to a combined flexure/shear failure mode when bidirectional [0°/90°] composite jackets are utilized. However, results indicated that the circumferential (hoop) fibers of a bidirectional composite jacket have lower ultimate hoop strain as compared to those obtained for columns with unidirectional composite jackets. Results also showed that the use of composite anchors effectively improved working strain of longitudinal fibers [0°], especially for columns with bidirectional composite jackets. In this case, tensile strain increased by 1.5 times as compared to specimens without composite anchors. Furthermore, the presence of anchors improved flexural capacity of confined columns. In addition, an analytical model to predict flexural capacity of RC columns confined with bidirectional laminates with anchors is proposed, which was verified using experimental results. Results of this study indicated that the use of bidirectional FRP composites laminates jackets with fan-shaped anchor enhanced both strength and ductility of RC columns.

Analysis of unidirectional polyethylene-glass fiber-reinforced phenolic polymer composite laminate

Analysis of unidirectional polyethylene-glass fiber-reinforced phenolic polymer composite laminate

Polysulfone nanofiber-modified composite laminates: Investigation of mode-I fatigue behavior and damage mechanisms

In this study, the fatigue properties of carbon fiber-reinforced polymer (CFRP) composite laminates were investigated, specifically focusing on the incorporation of 100-µm polysulfone (PSU) nanofibers as an interleaving material. The PSU nanofibers were produced using the electrospinning technique. Both quasi-static and fatigue tests were conducted on both the reference specimens and the modified specimens to evaluate their mode-I performance. The results revealed an 85% increase in fracture toughness (GIC) under quasi-static testing. The fatigue plots revealed a noteworthy reduction in the fatigue crack growth rate (da/dN) for the modified specimens due to new toughening mechanisms. Scanning electron microscopy (SEM) demonstrated that, the PSU nanofiber became melted and distributed in the interface, leading to phase separation and a sea-island structure. The presence of PSU microspheres caused crack deflection during delamination, which resulted in increased fracture and fatigue resistance.

Linear and Nonlinear Free Vibration and Optimal Design of Bio-Inspired Helicoidal CFRPC Laminated Plates

Bio-inspired helicoidal carbon fiber reinforced polymer composite (CFRPC) laminates stacked with Bouligand configurations are considered to own great potential in engineering fields. The optimization design of helicoidal layups with single-form and combination-form of linear and nonlinear helicoidal arrangements is carried out using ABAQUS and Isight. Two single-objective optimizations and one multi-objective optimization of maximum fundamental frequency and the difference among the first four adjacent vibration frequencies of helicoidal CFRPC laminated plates are performed and the nonlinear free vibration characteristics of optimal ones are investigated for the first time. Numerical studies are carried out for 16-ply symmetrical rectangular helicoidal laminated plates under two different boundary conditions compared with quasi-isotropic counterparts. The results show that the combination-form helicoidal layup sequences can improve the linear vibration characteristics of CFRPC laminated plates. The plates stacked with the combination form of nonlinear Fibonacci and linear patterns are expected to provide better vibration characteristics.

USING ADDITIVE RATIO ASSESSMENT AND ARTIFICIAL BEE COLONY (ARAS-ABC) OPTIMIZATION ALGORITHM DURING DRILLING OF CARBON NANOMATERIAL/ GLASS FIBER-REINFORCED POLYMER LAMINATED COMPOSITES

In manufacturing industries, polymers are widely used due to their exceptional physiochemical and mechanical characteristics. It consists of high strength, low weight, corrosive resistivity, and ease of fabrication. Glass fiber is more cost-effective and easily available than other fibers such as carbon, aramid and kevlar. The most challenging issue for the manufacturer in the laminated polymer is the non-homogeneity and anisotropic behavior. This nature also hinders the machining performance of laminated polymer composites, which are entirely different from metals and their alloys. The supplements of nanomaterials enhanced the physiomechanical properties and the machining efficiency of fiber laminates. This work highlights the machining (drilling) aspect of glass fiber-reinforced polymer composites modified by multiwall carbon nanotube (MWCNT). The effect of drilling factors such as spindle speed ([Formula: see text]), feed rate ([Formula: see text]), and MWCNT weight percent (wt.%) on machining responses such as Thrust force (Th), Torque ([Formula: see text]), and Surface roughness (SR) has been investigated. The drilling operations were conducted using the 5 mm diameter TiAN (Sic coated) according to the response surface methodology (RSM) design. The process constraints were controlled by the hybrid module of additive ratio assessment (ARAS) and the Artificial Bee Colony (ABC) algorithm. The nature-inspired principles of the bee are used to optimize the objective function. The multiple responses were aggregated using the ARAS method, and its objective function is fed into the ABC algorithm. It was remarked that the hybrid ARAS-ABC is more capable than the traditional ARAS, with an overall improvement of 7.33% in assessment values. The scanning electron microscopy (SEM) test confirms the feasibility of the proposed hybrid (ARAS-ABC) module to achieve a favorable machining environment while drilling modified nanocomposites.

A Review on Acoustic Emission Testing for Structural Health Monitoring of Polymer-Based Composites.

Acoustic emission (AE) has received increased interest as a structural health monitoring (SHM) technique for various materials, including laminated polymer composites. Piezoelectric sensors, including PZT (piezoelectric ceramic) and PVDF (piezoelectric polymer), can monitor AE in materials. The thickness of the piezoelectric sensors (as low as 28 µm-PVDF) allows embedding the sensors within the laminated composite, creating a smart material. Incorporating piezoelectric sensors within composites has several benefits but presents numerous difficulties and challenges. This paper provides an overview of acoustic emission testing, concluding with a discussion on embedding piezoelectric AE sensors within fibre-polymer composites. Various aspects are covered, including the underlying AE principles in fibre-based composites, factors that influence the reliability and accuracy of AE measurements, methods to artificially induce acoustic emission, and the correlation between AE events and damage in polymer composites.

Deep reinforcement learning for stacking sequence optimization of composite laminates

Fiber reinforced polymer (FRP) composite laminates are increasingly used in a wide range of safety–critical products due to their excellent material properties. The stacking sequence of FRP composite laminates plays a critical role in the resulting part’s mechanical properties. Despite this, composite engineers still commonly fabricate parts with “classic” ply layups (e.g. four ply laminate with fiber orientation angles: [-45/0/45/90°]), which may have sub-optimal mechanical performance in the expected loading/use cases. Finding the composite stacking sequence that achieves the best material and mechanical properties possible is a challenging optimization problem characterized by the large domain space involved in solving an inverse design problem. This paper introduces a novel approach to optimizing stacking sequence for composite plate stiffness by applying off-policy deep reinforcement learning (DRL). We formulate the problem as a sequential decision making process. The state of the system is based on the stiffness of the composite for the currently selected stacking sequence and the action is to select a new stacking sequence using our reward function, formulated as the offset, normalized stiffness modulus. We compare our DRL model to two classical stacking sequences, a randomized baseline model, and a competitive genetic algorithm (NSGA-II). For maximizing longitudinal composite plate stiffness, the DRL model finds the optimum solution for all ply thicknesses and the genetic algorithm comes within 0.5% of the optimum. The DRL model determines the optimum stacking sequence significantly faster and is less sensitive to parameter tuning. The DRL model and the genetic algorithm both outperform the random baseline algorithm by over 5.7 standard deviations in the most conservative case. This research demonstrates the ability of DRL to effectively and efficiently optimize composite laminate stacking sequence.

Experimental study of the interfacial micromechanics of multifunctional unidirectional carbon fiber reinforced polymer composite laminates with copper mesh

The mechanical properties of a unidirectional carbon-fiber reinforced polymer (CFRP) laminate with Cu mesh layers were investigated for use in aerospace applications as a multifunctional structural and electromagnetic interference shielding component. Nanoindentation was used to study the fiber/PEEK and Cu/PEEK interfaces. A data analysis methodology is presented to assess the interfacial strength from plots of hardness and modulus versus distance from fiber/Cu edge. The results indicated that annealing resulted in enhanced adhesion at the fiber/PEEK interface. Additionally, indents near the Cu/PEEK interface indicated poor interfacial adhesion. Bulk mechanical testing was performed to determine the effect of adding Cu mesh layers on the mechanical properties of the laminate. Additional Cu mesh layers decreased the tension, shear, and bending strength/modulus, while the open hole compression strength increased. This indicates that the Cu/PEEK interfaces weaken the laminate and lower the tension, shear, and bending strength by delamination.