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Abstract This study investigated the usability of hybrid sandwich structures as facade panels. The explored sandwich structure was made of mineral-glass fibre reinforced polymer (GFRP) skins and a GFRP truss core, fabricated by means of a novel manufacturing method. The compressive and shear specific strengths of the panels were assessed and compared with a few common lightweight structures to verify that the manufactured truss core had comparable values. Three-point bending tests indicated that the polyurethane foam used (required for the manufacturing process) had negligible mechanical contribution. Full-scale panels were tested under a distributed load. The tests were simulated using the three-dimensional finite element method to predict the pressure at which mineral cracks appeared in order to avoid their occurrence in the design phase. The simulation results exhibited good agreement with experimental data, and the model was validated in terms of deflection and strain responses. The occurrence of cracks and their propagation were numerically reproduced using the concrete-damage plasticity model. The link between the connector and crack positions in the mineral skin was highlighted in this study. [ABSTRACT FROM AUTHOR]

Abstract Estimation of the remaining useful life (RUL) based on the elastic strain energy density using the non-contacting and full-field capabilities of Thermoelastic Stress Analysis (TSA) was applied to E-glass fiber-reinforced polymers (GFRPs) subjected to high-cycle fatigue loading conditions. A quantitative prediction was successfully attained during the material's intermediate and final fatigue life phases. The initial state of the specimen was used as the reference data for defining a damage parameter that enabled the detection of visually imperceptible subsurface cracks. [ABSTRACT FROM AUTHOR]

Highlights • This paper deals with the mechanical response of glued in rods. • It takes into account the diameter of rods, the material of rods and the direction of the grain of the timber. • It gives an overview and presents known design models and technical approvals comparing the different approaches. • Comparison between the experimental results and the main equations of the literature review. • The authors propose one equation for the case where the bars are parallel to the timbers' grain. • In addition, another one for the case where the bars are perpendicular to the timbers' grain. Abstract We address the mechanical response of glued in rods, taking into account parameters such as rod diameter, the material properties of the rods (carbon or glass fibre-reinforced polymer), and the grain orientation of the timber (rods parallel and perpendicular to the timber grain). All the experimental setups employ pull-out tests, where rods are glued in only on one side of the specimen, and these tests are assessed at the premises of the Laboratory for Composite Materials and Composite Structures at the University Claude Bernard Lyon I. In addition, we give an overview and present known design models, technical approvals and regulations, national standards, and guidance papers, comparing the different approaches among them and with the experimental results. Good agreement was shown and further useful results were observed. [ABSTRACT FROM AUTHOR]

This paper aims to present a methodology to predict the anisotropic and non-linear behaviour of glass fibre reinforced plastics using finite element methods. A material model is implemented in order to remedy the need of multiple material definitions, and to control the local plastic behaviour as a function of the fibre orientation. Injection moulding simulations traditionally provide second order orientation tensors, which are considered together with a homogenization scheme to compute local material properties. However, in the present study, fourth order tensors are used in combination with traditional methods to provide more accurate material properties. The elastic and plastic response of the material model is optimized to fit experimental test data, until simulations and experiments overlap. The proposed material model can support design engineers in making more informed decisions, allowing them to create smarter products without the need of excessive safety factors, leading to reduced component weight and environmental impact. [ABSTRACT FROM AUTHOR]

This study investigates the impact behavior of fiber-metal laminates (FMLs) (Carbon FMLs and Glass FMLs), which were fabricated by using high-stiffness steel, carbon prepreg, and glass prepreg through autoclave molding. The mechanical behavior of the FMLs was evaluated by performing tensile, compressive, in-plane shear, and low-velocity impact tests. Drop-weight impact tests were conducted to induce cracking of the FMLs, and the crack initiation along with crack propagation behavior of the different laminate sequences ([0/0], [0/90], [0/90/0], [90/0/90] and [0/90/90/0]) were also studied. The results show that the fabricated FMLs have higher strength and stiffness than conventional FMLs. Their impact strengths increased, and weights decreased simultaneously. The absorption energy was proportional to the crack length that was induced by the low-velocity impact. Moreover, it was found that the fiber orientation mainly affected the direction of crack propagation in the FMLs. This investigation facilitates the design of high-stiffness and lightweight FMLs for automotive parts. [ABSTRACT FROM AUTHOR]

The present investigation deals with an experimental analysis of punching process of Glass Fiber Reinforced Plastics (GFRP) sheets. The process has the potential to dramatically reduce the cycle time; thus, it can be used for industrial applications where large numbers of holes are needed. However, the laminate damage represents the major concern for the employment of hole punching. Thus, a campaign of experimental tests was conducted on thin laminates with varying the punch-die clearance. In addition, drilled holes were performed in order to compare the quality and strength of the holes performed by drilling and punching processes. To assess the influence of the process parameters on the holes quality, mechanical characterization was performed by means of tensile test with central hole and bearing test. Moreover, morphological analysis was conducted to determine the quality of the punched hole and the extension of the delaminated region. According to the achieved results, the damage produced by punching process, especially when small clearances were used, is limited and comparable to that produced by drilling process. [ABSTRACT FROM AUTHOR]

An experimental investigation is presented into the explosive blast response of fibre-reinforced polymer laminates used in naval ship structures. Blast tests using plastic explosive charges were performed in air on square target plates made of carbon-polyester, glass-polyester, carbon-vinyl ester or glass-vinyl ester laminates, which are composite materials used in naval ships. The laminates were dynamically loaded by shock waves of increasing pressure and impulse, and the deformation, damage and residual mechanical properties were determined. The amount of blast-induced damage and the post-blast mechanical properties depend on both the fibre reinforcement and polymer matrix. E-glass laminates have higher resistance to blast-induced delamination cracking and tow rupture than carbon fibre composites. Furthermore, glass or carbon fibre laminates with a vinyl ester matrix have superior blast damage resistance compared to composites with a polyester matrix. The higher damage resistance is attributed to the higher flexural strain energy capacity and interlaminar fracture toughness properties of laminates containing glass fibres or vinyl ester matrix. [ABSTRACT FROM AUTHOR]

This work presents an experimental and a numerical studies on the effect of the phenomenon of porosity on the mechanical properties of Glass Fiber Reinforced Polymer (GFRP). In a first part, material elaboration, as well as its characterization using a three-point bending test to extract the basic mechanical properties of the material, is considered. In a second part, a finite element model is created to simulate the problem of air bubbles broadly. Several cases of different shapes and sizes are simulated. The results show a significant effect on the reduction of load in both tensile and bending cases as the size of the bubbles increases. Furthermore, the second part includes the application of the Artificial Neural Network-Enhanced Jaya Algorithm (ANN-E JAYA) to predict the reduction of the tensile load as a function of different crack lengths obtained from an Extended Finite Element Method (XFEM) model. Next, to verify the accuracy of provided application , a comparison is made with two other applications such as Artificial Neural Network-Jaya Algorithm (ANN-JAYA) and Artificial Neural Network-Particle Swarm Optimization (ANN-PSO). The results of the three algorithms show good convergence, with a slight increase in accuracy for ANN-E JAYA. MATLAB code and data used in this article can be found at https://github.com/Samir-Khatir/GFRP-ANN-E-JAYA.git. [ABSTRACT FROM AUTHOR]

This work presents an experimental and a numerical studies on the effect of the phenomenon of porosity on the mechanical properties of Glass Fiber Reinforced Polymer (GFRP). In a first part, material elaboration, as well as its characterization using a three-point bending test to extract the basic mechanical properties of the material, is considered. In a second part, a finite element model is created to simulate the problem of air bubbles broadly. Several cases of different shapes and sizes are simulated. The results show a significant effect on the reduction of load in both tensile and bending cases as the size of the bubbles increases. Furthermore, the second part includes the application of the Artificial Neural Network-Enhanced Jaya Algorithm (ANN-E JAYA) to predict the reduction of the tensile load as a function of different crack lengths obtained from an Extended Finite Element Method (XFEM) model. Next, to verify the accuracy of provided application , a comparison is made with two other applications such as Artificial Neural Network-Jaya Algorithm (ANN-JAYA) and Artificial Neural Network-Particle Swarm Optimization (ANN-PSO). The results of the three algorithms show good convergence, with a slight increase in accuracy for ANN-E JAYA. MATLAB code and data used in this article can be found at https://github.com/Samir-Khatir/GFRP-ANN-E-JAYA.git. [ABSTRACT FROM AUTHOR]

Natural fibers are gaining much interest in composite materials because of their potential to replace conventional glass fibers. In particular, unidirectional flax fiber composites have shown excellent mechanical properties with different thermoset matrices. However, few data are available when they are made with a biodegradable thermoplastic matrix. This paper compares the mechanical properties of two types of unidirectional flax composites using polylactic acid as the matrix: one made with layers of aligned flax rovings alone and the other containing an additional paper layer fabricated using paper making techniques. The results show that specific tensile properties of the flax/PLA (252 MPa·cm 3 ·g −1 ) and flax-paper/PLA (217 MPa·cm 3 ·g −1 ) composites are similar to those made using woven glass fabrics impregnated with epoxy (227–278 MPa·cm 3 ·g −1 ). Very high impact strength (600 J/m) was also obtained for UD flax-paper composites compared to unreinforced resin (15 J/m). Together these mechanical properties are promising for industrial applications of this new reinforcement. [ABSTRACT FROM AUTHOR]

Laminate composites made of glass fibre/epoxy resin filled with acrylic tri-bloc copolymers (Nanostrength) have been successfully manufactured. Microstructure, thermomechanical properties and impact resistance have been investigated and compared with those of a glass fibre/epoxy resin system. Dynamic mechanical analysis (DMA) tests have been conducted to determine the effect of Nanostrength on storage, loss modulus and glass transition temperature. A drop weight tower was used to perform low-velocity impact tests on laminate composites. Addition of Nanostrength to the epoxy matrix led to an increase in both strength and impact resistance of the composite. Moreover, a moderate decrease of storage modulus and glass transition temperature was observed. [ABSTRACT FROM AUTHOR]

Abstract: This paper shows the influence of interphase areas in a UD glass fibre/epoxy composite on water diffusion process and mechanical properties thanks to experimental, analytical and numerical analysis. The interphase is first characterized in terms of molecular mobility by micro-thermal analysis and in terms of mechanical properties by force measurements with atomic force microscopy. The measurements show an increase in elastic modulus and in glass transition temperature around each fibre. Optical microscopy reveals an important heterogeneity of fibre distribution inside the matrix with many contacts between fibres. A realistic microstructure including the interphase size (defined by μTA) and fibre distribution has then been considered to model the composite accurately. Diffusion parameters resulting from water absorption measurements on both the resin and the composite were also used in the finite element analysis. The comparison between experimental data, analytical and finite element models shows that the water diffusion coefficient is about five times higher in the interphase area than in the matrix whereas the gradient in modulus around the fibres barely modify the composite mechanical response. [Copyright &y& Elsevier]

Abstract: The behavior of single bricks and small masonry pillars strengthened by means of fabric reinforced cementitious matrix systems made with glass-fiber grids is discussed both from an experimental and numerical standpoint. A standard Push–pull double lap test is performed on three different series of experimental set-ups for reinforced single bricks and on masonry pillars, evaluating the role played by the anchorage length on the overall behavior of the strengthened system. Standard Italian bricks with very good mechanical properties are used, in order to evaluate the ultimate strength of the grid for delamination within the mortar. The masonry pillar is built with 3 bricks spaced out by two thick mortar joints. When dealing with the single bricks, three different anchorage lengths were tested, equal to 5, 10 and 15cm, in order to evaluate the reduction of the ultimate strength induced by an insufficient anchorage. To suitably interpret experimental results, both a newly developed analytical–numerical approach and a recently presented 3D FEM model were utilized to have an insight into experimental results. In the analytical–numerical approach only the glass-fiber grid was considered and modeled by means of 1D Finite Elements interacting with the surrounding mortar by means of interfaces exhibiting a non-linear stress–slip behavior deduced from experimental data. The 3D model uses 8-noded rigid elements interconnected by inelastic interfaces exhibiting softening. The incremental non-linear problem is solved by means of a robust Sequential Quadratic Programming routine already tested on medium and large scale examples with softening materials. The grid is modeled through non-linear truss elements, interacting with surrounding mortar by means of non-linear interfacial tangential stresses. Stress–slip behavior of the interface between the mortar and the textile is deduced through ad hoc experimentation conducted on a mortar specimen reinforced with a single yarn and subjected to a standard tensile test. Good agreement was found between experimental evidences and numerical simulations, meaning that the combined approach proposed may be considered as reference for design considerations. [Copyright &y& Elsevier]

Abstract: Composites based on poly(etherimide) matrix (PEI) with nanoscale reinforcements (multiwalled carbon nanotubes (MWCNTs)) and multiscale reinforcements (MWCNTs and Glass Fibers (GFs)) are processed by melt blending. For nanocomposite materials, we demonstrate that addition of MWCNTs (i) significantly improve electrical conductivity of PEI matrix, (ii) do not significantly improve the mechanical properties (young and flexural modulus) but strongly degrades the strain at break. In the case of multiscale composite materials PEI_GF_MWCNT, strain at break increases with the nanofiller content, and the electrical properties are the same than that in the case of nanocomposites. TEM observations are performed at the PEI/GF interfaces and clearly show a preferential location and orientation of MWCNTs along and perpendicularly to the GFs which explain the evolution of the strain at break for the multiscale composite materials. [Copyright &y& Elsevier]

Abstract: The kinetics of moisture sorption under immersion in water at room and elevated temperatures and flexural characteristics of dry (conditionally initial) and wet (moistened up to saturation level) composite material were investigated on flat specimens of polyester based glass fiber-reinforced plastic, cut from I-beam pultruded profile. It was found that the coefficients of diffusion and swelling are different in three principal axis of the composite. The former have the largest value in fiber axis direction, but the latter – in transverse to fiber axis direction out of plane of the layers. The observed difference in kinetics of mass gain and change of volume strain for the specimens of various sizes allowed evaluate the volume of pores, filled with water. The large data spread for the specimens, cut from the flanges, was found. Edge specimens have lower density and showed lower elastic and strength characteristics. The material specimens moistened up to saturation level showed the decrease in flexural modulus and strength for 8% and 16.5%, respectively. No effect of sorbed moisture on tensile modulus and strength of the composite (tension along the fiber axis direction) was found. [Copyright &y& Elsevier]

Abstract: Basalt reinforced composites are recently developed materials. These mineral amorphous fibres are a valid alternative to carbon fibres for their lower cost, and to glass fibres for their strength. In order to use basalt reinforced composites for structural applications, it is necessary to perform a mechanical characterisation. With this aim in the present work experimental results of several static and fatigue tests are described. Two polymeric matrices are taken into account, vinylester and epoxy, to assess their influence on the evaluated parameters. In parallel to these mechanical tests, also the thermal answer of the specimens to mechanical loads is evaluated by means of thermography. This experimental technique allows defining the composite local heating during the application of mechanical loads and its behaviour in details. Final discussion on obtained results is proposed focussing the attention on basalt fibre composite behaviour, and comparing mechanical properties of BFRP with other composite materials in glass and carbon fibres. [Copyright &y& Elsevier]

Abstract: In this paper effective medium theory based on Clausius–Mossoti relation was used to predict dielectric properties of multiphase composite system. The composite consisted of E-glass fibers (plain weave S-glass, J.B. Martin) embedded in bisphenol A diglycidylether epoxy matrix (D.E.R. 324, D.O.W. chemicals) with hollow ceramic spherical inclusions (SF 14, P.Q. Corp.) at different volume fractions. In many engineering applications, materials with designed dielectric properties are often sought. An important question in engineering design of a composite material is how the overall properties of the composite depend on those of the individual constituents. Mixing the epoxy resin with hollow ceramic inclusions can effectively reduce dielectric constant of the resin, which is often desirable, rendering composites as good candidates for many applications, especially in telecommunications. Compensation for degradation of mechanical properties of matrix (due to inclusion insertion) is obtained by embedding fibers into the mixture. Measurements of dielectric constant and loss tangent for this multiphase composite system were conducted in the region between 0.1 and 100kHz range using DEA 290 (T.A. Instruments) dielectric analyzer and experimental results are presented. Good correlation between analytical model and experimental results was observed throughout all frequency range of investigation. [Copyright &y& Elsevier]

Abstract: This paper studies the high-velocity impact response of sandwich plates, with E-glass fibre/polyester face-sheets and foam core, using finite-element models developed in ABAQUS/explicit code. The failure of the face-sheets was predicted by implementing Hou failure criteria and a procedure to degrade material properties in a user subroutine (VUMAT). The foam core was modelled as a crushable foam material. The numerical models were validated with experimental data obtained from scientific literature. The contribution of the foam core on the impact behaviour was evaluated by the analysis of the residual velocity, ballistic limit, and damaged area. [Copyright &y& Elsevier]

Abstract: The tensile behavior of adhesively-bonded double-lap joints composed of pultruded glass fiber-reinforced adherends and an epoxy adhesive was investigated under temperatures ranging between −35°C and 60°C. The load–elongation response was influenced primarily by the thermomechanical behavior of the adhesive and much less so by that of the adherends. For temperatures above the adhesive glass transition temperature, strength and stiffness decreased with the former being less affected than the latter. The failure mechanism changed with increasing temperature from fiber-tear to adhesive failure. The crack initiation loads were unaffected as long as the temperature remained below the adhesive glass transition temperature. However, the crack propagation rate was higher at low temperatures. Critical strain energy release rates for crack initiation and propagation consistently rose as temperature increased. Modeling results obtained using existing empirical models and FEA compared well to the experimental data in the examined temperature range. [Copyright &y& Elsevier]

Abstract: The aim of this paper is the fabrication and mechanical testing of entangled sandwich beam specimens and the comparison of their results with standard sandwich specimens with honeycomb and foam as core materials. The entangled sandwich specimens have glass fiber cores and glass woven fabric as skin materials. The tested glass fiber entangled sandwich beams possess low compressive and shear modulus as compared to honeycomb and foam sandwich beams of the same specifications. Although the entangled sandwich beams are heavier than the honeycomb and foam sandwich beams, the vibration tests show that the entangled sandwich beams possess higher damping ratios and low vibratory levels as compared to honeycomb and foam sandwich beams, making them suitable for vibro-acoustic applications where structural strength is of secondary importance, e.g., internal paneling of a helicopter. [Copyright &y& Elsevier]

Abstract: The mechanical performance of the composites which are reinforced with glass knitted fabrics composed of tuck stitches have been investigated. Tensile, compression, impact and compression-after-impact (CAI) tests were performed and the results of the composites reinforced with full cardigan derivative knitted fabrics and 1×1 rib knitted fabrics of glass fibers have been compared. As for a composite material, performance depends not only on the strength of the constituent materials but also on the internal structural geometry of the constituents, it is interesting to study the effects of the tuck stitch which is one of three different types of loops that can be used to build the knitted fabrics and has a different geometry than the other loop types. [Copyright &y& Elsevier]

Computational micromechanics analysis of short fiber reinforced polymer (SFRP) composites is of great significance to provide an understanding of the relationship between microstructures and complex mechanical behaviors of the materials. In this study, an innovative computational framework is proposed for the analysis of SFRP composites considering multiple constituents and different failure modes. Firstly, a unit cell model composed of fiber, matrix and interface is built up to analyze the nonuniform stress distribution around a fiber. Secondly, a reconstruction algorithm is proposed to provide geometrical information of fiber distributions with arbitrary orientation state and a wide range of fiber length and fiber volume fraction. With the help of embedded element method (EEM) and MATLAB script, RVE models embedded with numerous unit cells are established. The predicted properties of the RVE models of short glass fiber reinforced polypropylene (SGFRPP) are verified by an orientation average method and a modified rule of mixture, respectively. The progressive damage procedure of the material is predicted and the damage initiation and evolution are for the first time quantitatively characterized by the extent variables of different failure modes. An in situ microtomography tensile test are performed to prove the feasibility and accuracy of the proposed framework. [ABSTRACT FROM AUTHOR]

The fiber/metal composite technology consolidates the usefulness of metallic materials and fiber reinforced matrix systems. Glass laminate aluminum reinforced epoxy is a hybrid composite containing alternative thin layer of Aluminum (Al) plies and fiber reinforced epoxy. However, the low adhesion between Al thin layer and epoxy limits their application. In this work, we used Al wire meshes to toughen the neat E-glass fiber/epoxy composite. Un-notched and notched tensile and flexural tests were conducted to study the effect of incorporating Al wire meshes at different locations within the specimen thickness instead of the glass fiber plies on the mechanical properties of the produced materials. The results indicated that, incorporating Al mesh as a replacement of glass fibers could tailor the laminates strength, ductility and toughness. As the number of Al mesh layers increased, the specific tensile and flexural strengths decreased. The through-the-thickness position and orientation of Al mesh layer significantly affected the properties of the produced hybrid laminates. The presence of Al mesh at the outer layers highly reduced the tensile and flexural strengths. However, it improved the tensile and flexural strains and reaching an improvement of 54% and 117%, respectively. The energy absorption ability under tensile and flexural tests was highly improved with the addition of Al mesh layers reaching a maximum improvement of 210% and 166%, respectively. The mode I fracture toughness characterized by notched bending test was improved by 25.7% for samples with Al mesh layer replacing the third and sixth glass fiber layers. [ABSTRACT FROM AUTHOR]