Glass Composite Systems Research Articles

Influence of adhesive stiffness on the post-cracking behaviour of CFRP-reinforced structural glass beams

Reinforcement strategies have been developed to prevent catastrophic failures of glass structures after cracking. In this context, the composite action between glass and reinforcement plays a crucial role in the post-cracking performance of glass composite systems. Hence, this paper presents an experimental and numerical investigation on glass-CFRP composite beams manufactured using three different adhesives, with high, intermediate and low stiffness. The experimental programme comprised (i) mechanical characterization tests, (ii) tensile tests on double-lap joints and (iii) flexural tests on composite beams. Moreover, numerical simulations were carried out aiming at providing reliable numerical tools for the design of glass structural elements. Bending tests have shown that it is possible to obtain ductile failure modes in glass elements reinforced with CFRP laminates, sometimes attaining or surpassing the cracking load during the post-cracking phase, depending on the type of adhesive. On the other hand, glass-CFRP composite beams manufactured with stiff, moderate and flexible adhesives were well simulated (i) neglecting the physical existence of the adhesive layer, (ii) assuming the linear elastic behaviour of the adhesive, and (iii) modelling the bond behaviour of the adhesive joint, respectively.

Influence of Friction on the Behavior and Performance of Prefabricated Timber–Bearing Glass Composite Systems

The basic concept of seismic building design is to ensure the ductility and sufficient energy dissipation of the entire system. The combination of wood and bearing glass represents a design in which each material transmits the load, and with the mutual and simultaneous interaction of the constituent elements, it is also earthquake resistant. Such a system has been developed so that the glass directly relies on the wooden frame, which allows the load to be transferred by contact and the friction force between the two of materials. Within the seismic load, friction between glass and wood is an important factor that affects both the behavior and performance of a wood–glass composite system. The set-up system consists of a single specimen of laminated or insulating glass embedded between two CLT elements. The friction force was determined at the CLT–glass contact surface for a certain lateral pressure, i.e., normal force. Friction depends on the way the elements (especially glass) are processed, as well as on the lateral load introduced into the system. Conducted experimental research was accompanied by numerical analyses. Experimental research was confirmed by numerical simulations.

Nanostructured Glass Composite for Self‐Calibrated Radiation Dose Rate Detection

AbstractThe wide applications of ionizing radiation in various important technologies such as 3D industrial tomography, mammography, and small‐animal micro‐CT with low energy X‐ray have increased the demand for precise radiation measurement. Detection technologies have undergone remarkable progress, but most of them strictly rely on the complicate calibration process, thus remarkably limiting their applications. Here, a nanostructured glass composite system for self‐calibrated radiation dose rate detection (at 40 keV X‐ray) is described. Results show that the in situ precipitation of LiGa5O8 nano‐domains from glass composite results in unique emission centers at ≈496 and ≈718 nm with distinct ionizing radiation response. Subsequently, the radiation level is directly assessed by comparing the radiative transition ratio of these two centers. The nanostructured glass composite can also be constructed into fiber, which exhibits perfect core‐clad configuration and maintains excellent optical activity. The novel principle device with self‐calibrated function is successfully constructed, and the application for online radiation monitoring is demonstrated. The results not only provide an alternative opportunity for developing the next generation of ionizing radiation detection system, but also suggest a powerful pathway for the creation of new optical function through nanocrystallization of glass.

Impact and mechanical properties of different composite systems modified with multi-walled carbon nanotubes

Kevlar and glass fiber composites have distinguished mechanical properties such as specific strength and stiffness, resistance to impact loading, and tailoring the overall properties to meet the needs of a specific application. Enhancing their mechanical properties via incorporation of carbon nanotubes (CNTs) into their polymer matrices and proper characterization are very important for automotive and aerospace applications, which is the main objective of this study. This article presents an experimental study on manufacturing and mechanical characterization of six different materials. The tested materials include: CNT-nanocomposites, Kevlar fiber reinforce epoxy (KFRE) and glass fiber reinforced epoxy (GFRE) composites modified with CNTs. The CNTs were ultrasonically dispersed into the epoxy resin at 30% sonication amplitude (225 W) for 30 min to avoid their damage. The results were compared with the control materials (without CNTs). The mechanical tests are drop weight impact, tension, and in-plane shear. All the tests were performed according to ASTMs using computerized testing machines at room temperature. Results from the experimental study showed that the incorporation of the CNTs into the epoxy resin improves their tensile and shear strengths by 11% and 22.2%, respectively. In addition, the tensile and shear moduli of the CNT-nanocomposite were improved respectively by 68.7% and 29%. The absorbed energy and maximum contact force of the CNT-nanocomposite were improved by 11.4% and 9.5%, respectively. The tensile strength of the GFRE/CNT and KFRE/CNT composites showed improvements of 15.3% and 19.6%, respectively. The improvements in the tensile and shear moduli of GFRE/CNT and KFRE/CNT composites are in the range of 15–20%. The CNTs have marginal effects on the impact properties of the modified composite laminates. The tensile properties of the Kevlar composite systems (with and without CNTs) are higher than those of the glass composite systems and vice versa for the shear moduli and the absorbed energies.

Influence of temperature dependent matrix properties on the high-rate impact performance of thin glass fiber reinforced composites

The influence of measurement temperature on the high velocity (>100 m/s) impact performance was investigated for three thermosetting epoxy resin S-2 glass composite systems. These three model resins were chemically similar but have different glass transition temperatures (Tg) and molecular weights between crosslinks (Mc) through the use of different diamine curing agents (Jeffamine® D230, D400, and D2000). Impact performance was quantified by the projectile kinetic energy absorbed (KE50) as calculated from the characteristic ballistic velocity (V50) of the composites during high velocity impact. Among the resin systems, the KE50 remained essentially constant over a broad range of temperatures for each composite set and modestly increased with decreasing Mc. The superficial damage area associated with delamination showed remarkable sigmoidal behavior as a function of the testing temperature relative to the Tg (T-Tg). Damage was high for low T-Tg values (glassy resin) and decreased as the resin traversed its Tg into the rubbery region. These damage area trends were found to depend on the resin Mc, with higher Mc values resulting in lower overall damage area and a lower inflection point temperature. High speed videography of the back surface of the samples showed that lower damage areas correlated with an increased back face deflection, which enabled energy absorption with relatively less delamination. Composite mechanical tests were performed to validate the impact performance and explain the deformation mechanisms observed during impact energy dissipation. Our results illustrate the critical importance of the resin architecture and temperature-dependent viscoelastic behavior on the impact properties of composites for impact-resistance applications.

Sintering densification behaviors and crystallization characteristics of glass–ceramics formed by two types of CaO–B2O3–SiO2 glass

The sintering densification behaviors and crystallization characteristics of CBS glass have been investigated systematically, and a new CBS glass composite system containing two types of CBS glass is reported. The results demonstrated that the sintering densification characteristic of single CBS glass and CBS composite could be divided into two stages: the fast and slow densification stage. The temperature range of the fast densification stage of single CBS glass is quite narrow (680–710 °C), while CBS composite gets a wider one (680–730 °C). In result, more moderate sintering densification process, which benefits the co-firing compatibility with electrode materials, is obtained in CBS composite. The major crystalline phases of the CBS glass and CBS composite were CaSiO3 and CaB2O4. CBS glass sintered at 910 °C for 10 min exhibited excellent microwave dielectric properties of dielectric constant value of 6.4 and quality factor value of 11,110 GHz, while CBS composite showed dielectric properties of dielectric constant value of 6.1 and quality factor value of 10,640 GHz, which meets the requirements for LTCC applications.

Comparison of nanoscale and microscale bioactive glass on the properties of P(3HB)/Bioglass ® composites

This study compares the effects of introducing micro (m-BG) and nanoscale (n-BG) bioactive glass particles on the various properties (thermal, mechanical and microstructural) of poly(3hydroxybutyrate) (P(3HB))/bioactive glass composite systems. P(3HB)/bioactive glass composite films with three different concentrations of m-BG and n-BG (10, 20 and 30 wt%, respectively) were prepared by a solvent casting technique. The addition of n-BG particles had a significant stiffening effect on the composites, modulus when compared with m-BG. However, there were no significant differences in the thermal properties of the composites due to the addition of n-BG and m-BG particles. The systematic addition of n-BG particles induced a nanostructured topography on the surface of the composites, which was not visible by SEM in m-BG composites. This surface effect induced by n-BG particles considerably improved the total protein adsorption on the n-BG composites compared to the unfilled polymer and the m-BG composites. A short term in vitro degradation (30 days) study in simulated body fluid (SBF) showed a high level of bioactivity as well as higher water absorption for the P(3HB)/n-BG composites. Furthermore, a cell proliferation study using MG-63 cells demonstrated the good biocompatibility of both types of P(3HB)/bioactive glass composite systems. The results of this investigation confirm that the addition of nanosized bioactive glass particles had a more significant effect on the mechanical and structural properties of a composite system in comparison with microparticles, as well as enhancing protein adsorption, two desirable effects for the application of the composites in tissue engineering.

A study on the effect of the type and content of filler in epoxy–glass composite system on the friction and slide wear characteristics

The comparative performance of glass–epoxy (G–E) composites, having rubber in one instance and graphite of two differing levels in epoxy matrix resin in the other, during sliding in pin-on-disc type set up under varying load and sliding velocities is reported in this investigation. Besides conventional weighing, determination of coefficient of friction ( μ) and examination of the worn surface features by scanning electron microscope (SEM) were undertaken to have an overall picture of the tribological behaviour of the filled composites. For increased load and sliding velocity situations, higher wear loss was recorded. In case of rubber-bearing samples, the coefficient of friction values show an increasing trend with a rise in load and a decrease in their values for increase in velocity. The coefficient of friction increases with increase in load for a fixed velocity in higher graphite bearing samples. However, G–E composite having either lower or higher amount of graphite shows, respectively, either a decrease or increase in coefficient of friction with an increase in sliding velocity for a fixed load. Thus, the higher graphite bearing G–E composite records lower coefficient of friction for any combination of load and velocity. These are explained on the basis of frictional drag forces and formation of graphite film on the surface. Some of these deductions are supplemented by SEM observations.

The effects of water aging on the interphase region and interlaminar fracture toughness in polymer–glass composites

Three different unidirectional polymer–glass composite systems involving phenolic and polyester resins were aged for 6 and 11 weeks in tap water and tested in the mode I double cantilever beam (DCB) test. The results showed a dramatic increase in water absorption and a decrease in fracture toughness for phenolic/glass systems. Fractographic analysis revealed interfacial debonding to be dominant failure mechanism, indicating a strong influence of water degradation on fracture toughness results. The interphase region of each system was investigated using the nano-indentation and the nano-scratch techniques before and after aging in water. The nano-indentation test produced a series of indents as small as 30 nm in depth, to detect water degradation of the material properties at the interphase region between the fibre and the matrix. The nano-hardness results indicated interdiffusion in water aged interphase regions. The nano-scratch test was used in conjuction with the nano-indentation test, in order to detect the width of the interphase regions before and after water degradation. It was shown, from the coefficient of friction and the scratch profile depth, that the interphase region width increased and the material properties degraded during water aging. Qualitative links between water degradation of the glass–polymer interphase on a nanometer level and interlaminar fracture toughness are discussed.

Application of analytical transmission electron microscopy to the characterization of interlayers in fibre-reinforced composites with ceramic and glass matrices

The microchemistry of interfaces and corresponding interlayers in different fibre-reinforced ceramic and glass composite systems has been investigated by using a dedicated scanning transmission electron microscope demonstrating the potential applicabilities of such an instrument to this large field of materials science. Energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy were used to determine the materials composition on a nanometre scale. Besides analyses performed in the spot mode of the electron probe the distributions of the elements present in the interface region were measured as line profiles across the relevant interface structure by X-ray spectroscopy with a lateral resolution of about 5 nm, even for the detection of a light element as carbon. Moreover, in the composite systems under investigation the two-dimensional element distribution was also attained by energy-filtered imaging. In addition, first results of energy loss near edge structure analyses are presented indicating variations of the chemical bonding of silicon at the interface in a Nicalon fibre/Duran glass composite.

Photoelastic Measurement of Residual Thermomechanical Stress in SiC-Reinforced Glass Composites

Residual thermomechanical stresses in a Nicalon® SiC/7740 glass composite system were measured directly. Residual stresses for both single-tow and two-dimensional cloth-reinforced samples were completely described via a digital microphotoelastic technique. Normal stresses approaching 4 MPa were observed in this composite system that had a thermal expansion coefficient mismatch of only 1.8%. The advantages of using this direct, full-field technique over other theoretical and composite model approaches are also discussed.

Fracture of glass-fibre reinforced poly(phenylene sulphide)

An extensive study of the fracture behaviour of an injection-moulded PET (polyethylene terephthalate)/glass-composite system has recently been completed [1-8]. The PET matrix is generally considered to be ductile, while PPS (polyphenylene sulphide) is considered brittle. Therefore, for comparative purposes, a study of the brittle PPS matrix reinforced by short glass fibres would be of interest. This is the thrust of the present investigation. A PPS matrix reinforced with 40 wt % E-glass fibres was made by injection molding. The mechanical lifetime data were obtained by stressrupture testing [4, 5]. The microstructure was examined by scanning electron microscopy (SEM). The through-thickness microstructure is shown in Fig. 1. The surface of this SEM micrograph was cut parallel to the mold-fill direction (MFD) and to the thickness of the plaque. Near the surfaces of the plaque, the glass fibres are oriented approximately parallel to the MFD, whereas in the centre the fibres lie more nearly normal to the MFD. Two kinds of compact tension specimens are used: the L specimen is cut so that the fibre axis lies parallel to the loading axis; the T specimen has the fibre axis normal to the stress axis. Thus, in the L configuration, the main crack must run perpendicular to the fibres and in the T configuration, parallel to the fibres. A dead load is applied to the specimen until the specimen fails by part-through failure. The environment is controlled by a corrosion cell, within which the specimen is immersed during the whole lifetime of stress-rupture testing. Two kinds of aggressive environments are used, 10 vol. % HCI solution and 10 wt % NaOH solution, and compared with stress-rupture under air. Data for mechanical lifetime under air, 10% HC1 and 10% NaOH are shown in Fig. 2. Both the L (Fig. 2a) and the T (Fig. 2b) geometries are shown. The curves in Fig. 2 are the 0.25 and 0.75 reliability (R) curves, representing a law of the form [4]