Glass Fiber Specimens Research Articles

Durability test study of laminated specimens for large glass fiber protective structures in seawater

The mechanical properties of glass fiber composite structures prepared by vacuum forming manufacturing process are influenced by various factors and have a certain degree of dispersion, resulting in unclear durability characteristics when applied in corrosive seawater engineering. Firstly, a variety of resin materials for underwater protective structures are tested for seawater degradation, and excellent resins that can still ensure the structural load-bearing capacity and stability after immersion are selected. Secondly, based on relevant standards and specifications, the article conducted seawater immersion aging tests at room temperature and accelerated seawater immersion aging tests at 60°C on glass fiber specimens of 430 epoxy bisphenol vinyl resin and 1967 polycyclic pentadiene resin. Finally, the degradation characteristics of strength, modulus, and impact toughness of the specimens were obtained through a series of mechanical property tests, such as bending, compression, shear and impact, under different aging time periods in room temperature and 60°C seawaters, respectively. The article summarizes the differences in the durability and mechanical properties degradation of large glass fiber protective structures with different resins during seawater immersion.

Microscopic mechanism analysis and failure criterion study of glass fiber recycled concrete under three‐dimensional compressive stress state

AbstractThis study aims to address the complex stress state commonly observed in concrete structures in practical engineering, as well as the challenges posed by resource scarcity and environmental pollution. To achieve this, a total of 168 cylinder specimens of glass fiber recycled coarse aggregate concrete (GFRAC) were designed for conventional triaxial compression tests. The analysis of the test results reveals that the application of lateral restraint force induces a shift in the failure mode of GFRAC from longitudinal splitting failure to plastic deformation failure, occurring either in the middle or at the end of the specimen. The lateral constraint force can effectively improve the stress and strain at the peak point of GFRAC and the modulus of elasticity of the specimen. The glass fiber increases the peak stress of the specimen, and the maximum growth rate is 20%. On the contrary, the glass fiber reduces the peak strain, and the maximum reduction is 49.66%. Increasing the replacement rate of recycled coarse aggregate will lead to a decrease in peak stress, with a maximum decrease of 19.17%. Glass fiber (GF) limits the appearance and propagation of cracks by bridging, pulling out or breaking. Finally, three different failure criteria are used to analyze the triaxial compression state of GFRAC from a macro perspective.

Visualizing pseudo‐ductility in carbon/glass fiber hybrid composites manufactured using infusible thermoplastic Elium® resin

AbstractIn this study, two different type of glass and carbon fiber hybrid laminates were manufactured using a low‐viscosity thermoplastic resin that is, Elium®. A detailed microstructure visualization study was conducted using X‐ray computed tomography (XCT) analysis. The viscoelastic properties were examined through dynamic mechanical analysis. The mechanical performance was investigated through flexural and tensile tests along with a fractographic study using optical and scanning electron microscopy. The XCT analysis revealed a weak interface between the Elium® resin and the glass fabric, with glass fiber specimens exhibiting a void content of 1.24%, in contrast to the carbon fiber specimens which showed void content of only 0.28%. Therefore, adding glass fabric layers in the hybrid laminates increased the void content, which had a negative impact on the overall mechanical performance. The average flexural strength of the hybrid specimen having G2C4G2 stacking sequence was observed to be 254% higher than pure GFRPC specimens. Similarly, the tensile strength and Young's modulus of the same hybrid specimen showed 155% and 380% increases, respectively, compared to the GFRPC specimens. This increase was primarily due to higher stiffness of the carbon fibers and their better fiber – matrix interface. Whereas the tensile strain of the hybrid specimen having G3C2G3 stacking sequence was 37% higher than that of the CFRPC specimens. The SEM images highlighted fiber fracture and brittle failure modes in the carbon fiber specimens, in contrast to fiber pullout, interfacial failure, poor fiber‐matrix bonding and ductile failure modes in the glass fiber specimens.

Contribution to the Microstructural Study of a Composite Material Based on Carbon Fibers for Use in Orthopedic Prostheses

The use of a carbon fiber composite material to make external prostheses in the form of a femoral socket was the subject of this laboratory study. According to the prior bibliographical studies, this material adapts well to this type of prosthesis. The objective of this research is to study its microscopic structure, in order to verify the good wetting of the fibers by the resin, the good cohesion and molding by infusion. The morphological study of the facies of the parallelepiped-shaped specimens was carried out after cuts perpendicular to the axis of the fiber strands, parallel according to the width and thickness of the specimen. This study was carried out using a scanning electron microscope (SEM), in order to determine, thanks to the typical microstructure of the composite, the various degradations, which appear as a result of the effect of static tension. The laminate used is based on three layers of carbon taffeta fabric and an orthocrylic resin. Tensile tests have been carried out at a speed of 1mm/min with a Zwick/Roell machine with a load cell of 50 kN. This speed was chosen to allow a comparative study with glass fiber specimens, which have been used previously for the production of prostheses, before those made of carbon. The microscopic study allowed to identify the four types of degradation; Matrix fracture, which manifested itself as fault lines, in preferred directions of different sizes. This contributed to interlaminar delamination. The decohesion that contributes to delamination in a different way from that of matrix breakage is visible at different levels. Interlaminar delamination results from the combined effect of matrix breakdown and decohesion and manifests itself as uneven strata. Fiber breakage was manifested by shearing. This study allowed to observing a degradation of the material imposed by static traction. As for the material used in orthopaedics, it has retained good cohesion and meets the requirements of prostheses, despite the defects detected by the microscopic study.

Flexural tests and analysis of notched specimens of glass fiber reinforced composite

Fracture of notched Specimens of laminar glass fiber reinforced composite is quasi-brittle and with noticeable delamination crack growth around the notch tip, as indicated by the non-linear load–deflection curve close to the peak fracture load. In order to analyze the fracture performance of the composite with highly heterogeneous and anisotropic microstructures, the boundary effect model (BEM) considering the composite layered structures and damage along and perpendicular to the notch was adopted in this study. Around 90 notched three-point bending specimens with the span from 40 to 90 mm, plate thickness around 10 mm, the initial notch depth from 3 to 6 mm were tested and the maximum load Pmax values were recorded. The average fiber ply or layer thickness Cch was the characteristic microstructure modelled by BEM for both the crack-tip damage zone length (crack-bridging) and width (delamination). Both the tensile strength ft and fracture toughness KIC were determined from the notched bending tests. Direct tensile tests were also conducted and the measured tensile strength ft was close to the measurement from the three-point bending tests with the relative error < 6 %.

Experimental investigation on the mechanical behavior and damage of 3D printed composites under three-point bending

Three-dimensional (3D) printing has been triumphantly applied for the manufacture of various composite components. In this work, acoustic emission (AE), X-ray micro-computed tomography (Micro-CT) are used in conjunction with digital image correlation (DIC) measurement to investigate the mechanical behaviors of 3D printed continuous fiber reinforced composites under three-point bending test. Meanwhile, several mechanical experiments are carried out to study the flexural properties of three kinds of composite specimens, among which the specimens with larger glass fiber content exhibit more superior mechanical properties. Furthermore, AE response characterizations and microscopic damage morphology are also examined. In consequence, the complementary nondestructive testing (NDT) technology combining AE, DIC, and Micro CT is successfully applied to evaluate the mechanical behaviors of 3D printed composites, and the flexural deformation and damage are comparatively investigated for different composite specimens. The cross-validation results of cluster analysis (k-means), K-Nearest Neighbor (KNN) and principal component analysis (PCA) show that AE parameters including frequency, amplitude, and RA value (rise time divided by peak amplitude) are closely associated with the damage process of different specimens. The results show that the PCA can confirm the selected K-means cluster analysis parameters (peak frequency and peak amplitude) and the dimensionality reduction effects of 20% glass fiber specimens have the best results, indicating that the proportion of the principal components extracted can represent the original parameters is 81%. It was also confirmed that the supervised learning KNN algorithm corresponding to different damage patterns can verify the unsupervised learning k-means cluster. Correspondingly, the strain fields characterized by DIC are reasonably matched with the AE signal responses. In addition, the critical damage and delamination mechanisms of the 3D printed continuous fiber reinforced composites are clearly revealed by Micro-CT characterization.

Prediction of Mechanical, Thermal and Electrical Properties of Wool/Glass Fiber based Hybrid Composites

The mechanical, thermal and electrical properties of wool and glass fiber-reinforced epoxy-based hybrid composites were investigated experimentally. Three different types of the composite material were manufactured. The first type was plain woven glass fiber reinforced epoxy with 50% volume fraction. The second type consisted of natural fiber (Wool) reinforced epoxy with 50% volume fraction. The third type was hybrid natural wool and plain woven glass fiber reinforced epoxy with 50% volume fraction (25% fiber + 25% wool).The results showed that the hybrid composite specimens have higher values of the tensile strength, modulus of elasticity and flexural strength compared with the wool specimens, while these values are less than that for glass fiber specimens. The values of the thermal conductivity and electrical conductivity are arranged in an ascending order as follows: wool/epoxy, wool-glass/epoxy, and glass/epoxy composites.

Experimental evaluation of static and dynamic properties of low styrene emission vinylester laminates reinforced by natural fibres

The aim of this experimental investigation is to perform a thorough analysis in terms of mechanical properties of thermoset composites built with an eco-friendly resin and reinforced by natural fibres. Flax and basalt were the reinforcements selected, being applied both in single and hybrid layouts with a low-styrene emission (LSE) vinylester matrix, and glass synthetic fibre composites were also studied for comparison purposes. Tensile, flexural and low-velocity impact tests were carried out according to their respective ASTM standards, showing that basalt and flax laminates are respectively the strongest and the weakest materials analysed, where the hybrid composition offers similar tensile and flexural moduli to glass, being 30% stronger in tension and 10% in bending. Impact tests performed at a same shock energy of 30.6 J perforated glass fiber specimens, while small indentations were noticed in naturally reinforced coupons characterized by fiber tensile breakage and matrix compressive failure regions.

A study on the crushing behavior of basalt fiber reinforced composite structures

The crushing behavior and energy absorption capacity of basalt fiber reinforced hollow square structure composites are studied under axial compression. Using the hand layup technique, basalt fiber reinforced composites were fabricated using general purpose (GP) polyester resin with the help of wooden square shaped mould of varying height (100 mm, 150 mm and 200 mm). For comparison, similar specimens of glass fiber reinforced polymer composites were also fabricated and tested. Axial compression load is applied over the top end of the specimen with cross head speed as 2 mm/min using Universal Testing Machine (UTM). From the experimental results, the load-deformation characteristics of both glass fiber and basalt fiber composites were investigated. Crashworthiness and mode of collapse for the composites were determined from load-deformation curve, and they were then compared to each other in terms of their crushing behaviors.

Micro-Hardness of Irradiated Polyamide

The influence of beta radiation on the changes in the structure and selected properties (mechanical and thermal) was proved. Using high doses of beta radiation for glass fiber filled polyamide (PA) and its influence on the changes of micromechanical properties of surface layer has not been studied in detail so far. The specimens of glass fiber filled PA were made by injection moulding technology and irradiated by low doses of beta radiation (0, 132, 165 and 198 kGy). The changes in the microstructure and micromechanical properties of surface layer were evaluated using WAXS and instrumented microhardness test. The results of the measurements showed change some in micromechanical properties (indentation hardness) when high doses of beta radiation are used.

Mechanical Property Testing of Woven Roven Glass Fiber Specimen and Structural Analysis of a Composite Leaf Spring

A Composite material has been fabricated by laying epoxy resin over woven roven fiber mat and carbon fiber combination and its mechanical properties were attained in the Material testing Laboratory. Based on the material properties achieved, A multi-leaf steel spring used in the rear suspension system of light vehicles is designed and analyzed using ANSYS software. The finite element results showing stresses and deflections, verified the existing analytical and experimental solutions. Using the results of the steel leaf spring, a composite one made from Woven glass fiber with epoxy resin was designed and optimized using ANSYS. Main consideration was given to the optimization of the spring geometry. The objective is to obtain a spring with minimum weight that is capable of carrying given static external forces without failure. The design constraints were stresses and displacements. The results show that an optimum spring width decreases hyperbolically and the thickness increases linearly from the spring eyes towards the axle seat. Compared to the steel spring, the optimized composite spring has stresses that are much lower, the natural frequency is higher and the spring weight without eye units is lower and the cost of the composite leaf spring that has been fabricated is comparatively less.

Dynamic Mechanical and Flexural Characteristics of Glass-Carbon Hybrid Composites

This paper deals with the fabrication of test specimens of Glass fiber reinforced plastic (GFRP), Carbon fiber reinforced plastic (CFRP), Glass-Carbon fiber reinforced plastic (G-CFRP) and Carbon glass fiber reinforced plastic (C-GFRP) by using hand layup method. The low velocity point load setup was fabricated and fixed in the milling machine by using cam pointer arrangement. The specimens have been subjected to the low velocity point load for specific duration by exposure time such as 0,15,30,45 and 60 minutes. Then impact and DMA tests are also carried out for the above specimens. From the DMA test results it was found that the storage modulus and loss factor of GFRP specimen are high compared with others. Izod impact test result shows that impact strength of G-CFRP specimen is high. The flexural results reveals that among the four types of laminates CFRP gives higher order of flexural strength and modulus compared to the others

Development of an artificial neural network processing technique for the analysis of damage evolution in pultruded composites with acoustic emission

Acoustic Emission (AE) is a promising technique for the damage detection and the real-time structural monitoring of composite lightweight structures; however data interpretation and discrimination among failure modes from AE data is difficult to be carried out without proper data processing techniques. In this paper, a neural-network based classification of AE signals from tensile tests of pultruded glass-fiber specimens is proposed. A self-organizing map is trained with AE data from one specimen; then the map is clustered with the k-means algorithm. The optimal number of clusters is chosen by a voting procedure that takes into account a number of quality indexes; then the clustered neural network is used to classify AE data from other specimen. Results have shown that the classifier built from a smooth specimen was able to correctly classify other specimens with the same and with a different material layup, and is capable of recognizing signals from notched specimens, thus providing interesting and encouraging indications in view of the application on real structures.

Quantification of defects in composites and rubber materials using active thermography

Active (lock-in and pulsed) thermography technique is used to quantify defect features in specimens of glass fiber reinforced polymer, high density rubber, low density rubber and aluminum bonded low density rubber with artificially produced defects. The relationship between phase contrast and thermal contrast with defect features are examined. Using lock-in approach, the optimal frequencies for different specimens are determined experimentally. It is observed that with increasing defect depth, the phase contrast increases while the thermal contrast decreases. Defects with radius to depth ratio greater than 1.0 are found to be discernible. The phase difference between sound and defective region as a function of square root of excitation frequency for glass fiber reinforced polymer specimen is found to be in good agreement with the predictions of Bennet and Patty model [1]. Further, using pulsed thermography, the defects depth could be measured accurately for glass fiber reinforced polymer specimen from the thermal contrast using the analytical approach of Balageas et al. [2].

G030086 ガラス繊維強化プラスチックの強度に及ぼすタンク内キャビテーションの影響

This work investigates influence of cavitation m the tank on mechanical behavior of fiber reinforced polymers R-134a used as pressure-liquefied gas at 273 K was boiled by instantaneous depressurization. A compressor was used to re-liquefy boil-off gas and to achieve a cyclic liquid-vapor condition. Specimens of glass fiber reinforced polymers (GFRP) were immersed in the cyclic condition. After laser immersion, scanning laser micrographs showed microcrack development short-beam three-point bending tests were performed m accordance with JIS K 7057 to evaluate the influence of the boiling condition on interlaminar shear strength of GFRP.

THE EXAMINATION OF WELD LINE PROPERTIES IN INJECTION MOLDED PP AND PP COMPOSITES

In this study, the effect of weld lines occurred in injection moulded components on mechanical behaviours of PP and PP with 30% glass fiber (GF) materials has been investigated. Two types of specimens were produced; with and without weld line by using single gate and double gate moulds. The range of process temperatures was varied depending on the type of material. The mold was designed to achieve homogenous cooling with the help of Moldflow software. The bending and tensile tests were carried out on the specimens. Tensile strength of the PP and PP+30%GF specimens with weld line decreased by 11.04 and 52.81 % respectively compared to those without weld line. Bending strength of the specimens with weld line decreased by 23.88 and 41.14% for PP and PP+30%GF samples respectively. It was seen that the process temperature is an important parameter affecting weld line property and low temperatures should not be preferred. PP+30%GF samples with weld line is of higher strength than the unreinforced PP counterpart. The tensile and bending strength of PP+30%GF samples with weld line increased 40.65 % and 102.65 % respectively.

Comparison of mechanical properties of glass fiber/vinyl ester and carbon fiber/vinyl ester composites

Glass and carbon fiber composite laminates were made by vacuum infusion of vinyl ester resin into biaxially knitted glass and carbon fiber fabrics. The strengths of the glass and carbon fiber specimens in tension, compression, open hole tension, open hole compression, transverse tension, indentation and ballistic impact were compared. The carbon fiber laminates proved mechanically superior under loading conditions where the strength is mainly fiber dominated, i.e. under tensile loading and indentation. The ratio of the carbon fiber laminate strength to the glass fiber laminate strength, for laminates of equal thickness, was similar to the ratio of the fiber tensile strengths. The glass fiber laminates were equally strong or stronger under loading conditions where the strength is mainly resin dominated, i.e. compressive loading and ballistic impact. In the carbon fiber specimens, the failure was in general more localized and the strengths had more scatter than in the glass fiber specimens.

Environmental fatigue behavior and life prediction of unidirectional glass–carbon/epoxy hybrid composites

Unidirectional glass fiber reinforced and glass–carbon fiber reinforced epoxy matrix composite specimens were subjected to tension–tension fatigue in air and in distilled water at 25 °C. While no significant change in fatigue life was observed for both types of specimens tested in air and in water when cyclically tested at 85% of average ultimate tensile strength (UTS), the detrimental effect of water becomes apparent at lower stress levels of 65 and 45% UTS. Compared to specimens tested in air, cyclic loading in water results in shorter fatigue lives for both glass and hybrid specimens. While all of the glass fiber specimens did not survive to 10 6 cycles when cyclically loaded in water, hybrid specimens (with 25% carbon fiber (by volume), 75% glass fiber (by volume), 30% total fiber volume fraction) showed better retention in structural integrity under environmental fatigue, for fatigue lives up to 10 7 cycles, a consequence of the corrosion resistant of carbon fiber. Thus it is shown, by incorporating appropriate amount of carbon fibers in glass fiber composite, a much better performance in fatigue can be achieved for glass–carbon hybrid composite. A simple life prediction model for the hybrid composite is proposed. Model predictions are compared with experiments results from both laminated interply and intermingled intraply hybrid composites. Results suggest that synergistic effect of the reinforcing fibers is critical in governing the fatigue behavior of intraply hybrid composite.

Effects of the CTE and Young’s modulus lateral gradients on the bowing of an optical fiber: analytical and finite element modeling

In the analysis that follows, the mechanical response of an optical glass fiber specimen subjected to a significant change in temperature is modeled. The objective of the analysis is to find out whether small lateral coefficient of thermal expansion ~CTE! and Young’s modulus gradients ~along one of the diameters of the fiber cross section! can contribute appreciably to the observed residual bow ~‘‘curling’’! of the fiber. Although the communication does not contain experimental data, we show that these gradients have enough potential to be one of the contributing factors that could possibly lead to curling. As is known, large ‘‘curls’’ can make automatic splicing of fibers difficult.

Repair of acrylic resin denture base reinforced with glass fiber

Statement of problem. The ultimate goal of any denture repair is to restore the original strength of the denture and to avoid further fracture. Purpose. This study investigated the strength and deflection of repaired acrylic resin joints reinforced with various glass fiber concentrations. Material And Methods. Transverse strength, maximum deflection, and modulus of elasticity of glass fiber-reinforced polymethyl methacrylate acrylic resin were studied with a 3-point load test on 54 intact specimens. Six concentrations of type B glass fiber specimens were prepared (n = 9 per each fiber group). Fractured joint margins were rounded, a 2-mm gap was placed between them, and then they were repaired with autopolymerizing acrylic resin and retested. Results. Transverse strength, maximum deflection, and the stiffness of all joints were significantly lower after the repair. Among the groups tested, the units treated with 1% glass fiber displayed the highest transverse strength before and after repair. Modulus of elasticity of the repaired 1% fiber concentration units was enhanced by approximately 25% over those repaired but untreated with glass fiber (0% fiber). (J Prosthet Dent 1998;80:546-50.)