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Fiber-reinforced polymer (FRP) is a composite material made of a polymer matrix reinforced with fibers. Hybrid composites are referred to as high-performance FRP materials used in safety-critical structural applications. Generally, FRP composite laminates are very weak in their out-of-plane properties, to address this issue unidirectional (UD) Glass laminates are prepared by modifying the matrix using plasma-treated multi-walled carbon nanotubes (MWCNTs) in epoxy matrix and compared fracture toughness characteristics with low-cost micro fillers like Aluminum oxide (Al2O3) and Sodium Carbonate (Na2CO3). These Nano and Micro fillers are loaded with 0.5wt%, 1wt% and 2wt% in the epoxy matrix while making FRP laminates. Adding these fillers into the epoxy matrix was caused a significant increase in the out-of-plane load-bearing capacity of the composites as compared to plain Glass epoxy laminates. Thus, the fracture toughness was enhanced by 20-26% and 14-17% under mode I and mode II loading respectively. Further, a Scanning electron microscopic analysis was also done on delaminated glass laminates to understand the failure mechanisms. [ABSTRACT FROM AUTHOR]

The present study involves frequency-driven exploration of bi-directional, industry-driven, laminated composite glass/epoxy beams by experimental and finite element analysis. The experimental vibration responses were ensured through a vibration first Fourier transform (FFT) analyzer. The finite element predictions were made using MATLAB platform by developing a programmable computer code accounting for shear deformation. The results conclude that the free-vibration finite element predictions for glass/epoxy beams are sensitive to effects of different boundary conditions and span-to-thickness ratios. The present study will assist in our understanding of modal behaviour towards design and service of laminated beams in the frequency domain and can serve as experimental benchmark results. [ABSTRACT FROM AUTHOR]

This study focuses on developing and implementing Mamdani hybrid fuzzy logic inference system (FIS) for transverse crack detection and fault diagnosis in a woven fiber laminated glass/epoxy composite beam using different vibration modes of natural frequencies. The shifting of vibration is attributed to the implication of cracks. These vibration signatures are fuzzified through hybrid fuzzy sets (triangular, trapezoidal, Gaussian) and scaled to crack location and depth using the fuzzy rules and defuzzification process. The vibration signatures are recorded using ABAQUS finite element (FE) simulation software for a fixed beam and are fed as input parameters to the developed FIS for computing the desired outputs. The realization for crack depth and position is experimentally verified through a Fast Fourier Transform (FFT) analyzer. The experimental results with simulated data show that fuzzy logic application detects crack positions and depth accurately at different levels. It is concluded that the hybrid FIS bears a close resemblance to the experimental analysis and also stands out as an effective method for crack detection in LCB over other standalone methods. The current method can be used as a cost-effective non-destructive technique for health monitoring and fault diagnosis of composite beam structures in any practical field. [ABSTRACT FROM AUTHOR]

Composite material has attractive applications in electronic devices; glass fiber/copper reinforced epoxy is one completive material in Micro–Electro–Mechanical-Systems (MEMS). Upon operation, mechanical vibration arises from the electrical current fluctuations causing damage and consequently affect its performance. On the other hand, size effect in the strength of a material is referred to as a decrease in the nominal strength of a scaled open hole structure. Therefore, this work aims to study the scaling phenomenon concerning dynamic and vibration for a composite structure used in MEMS devices. At this end, a matrix of specimens with 2, 4, 6, 8, 10, and 12 mm diameter circular holes of copper/laminated glass fiber reinforced epoxy plated have subjected to simple vibration test modal analysis using the free-fallen hammer. A simple finite element model is built to obtain different shape modes which revealed the different mode shapes and Mises stress effect regions, moreover the frequency factor at each mode. The response of the material to free vibration has given different trends with holes. With increasing specimen size, the natural frequencies increase, this is opposite results when increasing the static load. The Finite element results are in good agreement with the published ones. The cantilever boundary condition is reported to be the most satisfied for the lower two modes. [ABSTRACT FROM AUTHOR]

In this study, a multi-parameter analysis, using Taguchi method for design of experiments, has been conducted to investigate the optimum curing conditions for GNPs/E-glass fabric/epoxy laminated nanocomposites. The independent variables in the L25 Taguchi orthogonal array were heating rate, curing temperature and curing time, addressing five levels each. Tensile and 3-point bending tests were performed for each experiment number (run number) of the Taguchi L25. The analysis shown that the most significant parameter for tensile strength is the time and for flexural strength is the temperature. Also, it shown that the optimum performance was obtained for temperature values greater than the glass transition temperature Tg. [ABSTRACT FROM AUTHOR]

Two types of laminate composites made of glass fibre/epoxy matrix (EPO_FV) and glass fibre/epoxy modified tri-block copolymer (Nanostrength) matrix (EPONS_FV) were manufactured by compression moulding. Some AFM investigations have been done to identify the Nanostrength dispersion in the epoxy matrix and some DMA analyses have been performed, at different frequencies, to understand the frequency or the strain rate sensitivity of both composites. Compared to EPO_FV, EPONS_FV exhibits a significant frequency/strain rate sensitivity. Impact resistance of the composite was investigated by means of low velocity impact tests. The low velocity impact results indicate that the addition of Nanostrength leads to the improved impact resistance and an increase in absorbed energy, especially at high impact energy level. SEM observations, performed on ion polished samples, reveal the presence of micro-cracks for both composites. Micro-cracks consist of a coalescence of fibre matrix de-bonding. It was also observed that EPONS_FV contains a lower density of micro-cracks compared to EPO_FV, confirming the fact that the composite with Nanostrength absorbs more energy by Nanostrength micelles cavitation. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this work is the study of the mechanical behaviour in 3-point bending, in static and fatigue mode, of two different composite sandwiches laminate foam with unidirectional reinforcements and crossed SMS [04] and SMS [0/902/0]. These two sandwich composites were developed in laboratory. The specimens are made of fiberglass and epoxy resin for skins and PVC foam for the core. The tests in the static mode permitted the determination of the mechanical characteristics necessary to the fatigue tests and the mechanical behaviour of the materials. The fatigue tests made in controlled force gave curves which inform about the lifetimes of the materials. The observations of the fracture surfaces revealed the different modes of damages causing the material fracture. The lifetimes are characterized by the Wöhler curves. This study evidenced the influence of the reinforcement orientation on endurance of the studied material. [Copyright &y& Elsevier]

This article describes further development of a novel Non Destructive Evaluation (NDE) approach described in one of our previous papers. Here these sensors have been used for the first time as a Piecewise Continuous System (PCS), which means that they are not only capable of following the deformation pattern but can also detect distinctive fracture events. In order to characterize the simultaneous compression and traction response of these sensors, multilayer glass laminate composite samples were prepared for 3-point bending tests. The laminate sample consisted of five layers of plain woven glass fabrics placed one over another. The sensors were placed at two strategic locations during the lay-up process so as to follow traction and compression separately. The reinforcements were then impregnated in epoxy resin and later subjected to 3-point bending tests. An appropriate data treatment and recording device has also been developed and used for simultaneous data acquisition from the two sensors. The results obtained, under standard testing conditions have shown that our textile fibrous sensors can not only be used for simultaneous detection of compression and traction in composite parts for on-line structural health monitoring but their sensitivity and carefully chosen location inside the composite ensures that each fracture event is indicated in real time by the output signal of the sensor. [ABSTRACT FROM AUTHOR]

Traditional epoxy resin (EP) materials have difficulty to meet the performance requirements in the increasingly complex operating environment of the electrical and electronic industry. Therefore, it is necessary to study the design and development of new epoxy composites. At present, fluorinated epoxy resin (F-EP) is widely used, but its thermal and mechanical properties cannot meet the demand. In this paper, fluorinated epoxy resin was modified by ordered filling of fluorinated graphene oxide (FGO). The effect of FGO interlayer spacing on the thermal and mechanical properties of the composite was studied by molecular dynamics (MD) simulation. It is found that FGO with ordered filling can significantly improve the thermal and mechanical properties of F-EP, and the modification effect is better than that of FGO with disordered filling. When the interlayer spacing of FGO is about 9 Å, the elastic modulus, glass transition temperature, thermal expansion coefficient, and thermal conductivity of FGO are improved with best effect. Furthermore, we calculated the micro parameters of different systems, and analyzed the influencing mechanism of ordered filling and FGO layer spacing on the properties of F-EP. It is considered that FGO can bind the F-EP molecules on both sides of the nanosheets, reducing the movement ability of the molecular segments of the materials, so as to achieve the enhancement effect. The results can provide new ideas for the development of high-performance epoxy nanocomposites. [ABSTRACT FROM AUTHOR]

The compatibility between the majority of thermoplastic veils (TPVs) and epoxies is typically poor, owing to the inherently low surface energies of thermoplastics. This tends to largely affect the toughening performance of TPVs as interlayer materials of carbon fibre/epoxy composites. The traditional methods for surface activation of thermoplastics, such as corona discharge, plasma treatment and acid etches, are not applicable to TPVs as they could cause significant damage to the thermoplastic fibres with nano-/micro-scale diameters. Herein, a UV-irradiation technique was proposed to active the surfaces of polyphenylene-sulfide (PPS) veils, that effectively improved their adhesion with epoxies. Consequently, the effects of an improved veil/epoxy adhesion on the mode-I and mode-II fracture behaviour and corresponding fracture mechanisms of the interleaved laminates were investigated. It was found that an improved veil/epoxy adhesion significantly enhanced the toughening performance of the PPS veils for the laminates manufactured by resin transfer moulding of non-crimp fabrics, by introducing additional carbon fibre delamination and significant PPS fibre damage during the fracture process. In contrast, the increased level of veil/epoxy adhesion inhibited PPS fibre bridging during the fracture process of the laminates produced from unidirectional prepregs, and caused considerable adverse effects on the fracture performance. Unlabelled Image • A UV-irradiation method was proposed for the surface functionalisation of PPS veils. • The veil/epoxy adhesion had been significantly improved upon the UV-treatment. • The effects of the veil/epoxy adhesion on the fracture behaviour of interleaved laminates were studied. • The toughening performance and mechanisms of the PPS veils were significantly affected by the UV-treatment. [ABSTRACT FROM AUTHOR]

The low velocity impact behavior of basalt/epoxy composites, seen as an eco-friendly replacement of glass-epoxy composites, has not been studied systematically so far. Here, the elastic elasto-plastic properties, strengths, intralaminar and interlaminar fracture energies were determined. The intralaminar energies were determined using compact tension and compression tests. The elasto-plastic properties needed in the plastic potential were determined using off-axis test. These properties are used in Finite Element (FE) code with an elasto-plastic damage model developed earlier to simulate the impact response of cross-ply laminates basalt/epoxy laminates. Low velocity impact (LVI) experiments at 10 J, 20 J and 30 J are performed on these composites. The FE simulation is successful in capturing force, energy, deflection histories and damage zones showing a close match to the experiments. A comparison of impact force history and damage area (ultrasonic C-scan) of basalt-epoxy laminates with glass epoxy laminates having same volume fraction shows nearly similar peak forces but the major axis of the ellipsoidal damage zone was bigger in glass/epoxy laminates. • Mechanical characterization of BUD laminates to evaluate moduli and strengths in tension, compression and shear. • Interlaminar (Mode-I and Mode-II) and Intralaminar fracture toughness properties for BUD laminates. • Cyclic off-axis experiments were performed for evaluating plasticity parameters. • Properties obtained from experiments were used as an input to the CDM constitutive model written in VUMAT. • LVI tests at 10 J, 20 J and 30 J were performed on cross-ply Basalt and glass laminates of similar volume fractions. • Total damage region around impact zone is captured using ultrasonic C-scan and fiber breakage using Micro-CT tomography. [ABSTRACT FROM AUTHOR]

In the present research, a novel dynamic constitutive micromechanical (DCM) model was developed to predict the strain rate dependent mechanical behavior of laminated glass/epoxy composites. The present model is an integration of the generalized strain rate dependent constitutive model as a constitutive model for the neat polymer, the plasticity model of Huang as a micromechanical model, and dynamic progressive failure criteria. This model is able to predict the longitudinal and transverse tensile and in-plane shear behaviors of unidirectional glass/epoxy composites with arbitrary fiber volume fractions at arbitrary strain rates. The present model can also predict the stress-strain behavior of laminated composites with different layups and fiber volume fractions at arbitrary strain rates. A comparison between the results predicted by the present model and the available experimental data showed that the model predicts the strain rate dependent mechanical behavior of glass/epoxy composites with very good accuracy. • A model for the dynamic mechanical behavior of laminated composites was presented. • The present model uses the plasticity model and dynamic progressive failure criteria. • The accuracy of the present model was evaluated by the available experimental data. • The present model is able to consider the effect of layups and fiber volume fraction. • Different failure modes in each ply of the laminated composite were identified. [ABSTRACT FROM AUTHOR]