Search

The drilling of composite structure leads to its damage, near the peripheral areas of the drilled hole, due to the laminar structure of the composites. The goodness of a drilling process can be evaluated by measuring the extent of the damage caused by it. In the present study, lock-in thermography non-destructive inspection method is proposed to characterise the drilling damages in glass fiber–reinforced polymer panel. A semi-automated image processing methodology is proposed to calculate damage parameters, namely delamination area and size, and delamination factor. The effect of excitation frequency on the damage characterisation is studied to decide the optimum frequency range to measure the damage parameters through signal-to-noise ratio and damage visibility. The damage parameters are measured at optimum frequency. The study showed that the lock-in thermography technique has the potential to characterise drilling damage. [ABSTRACT FROM AUTHOR]

This study looks at the mechanical and free vibration properties of glass laminated with functionalized aluminium reinforced epoxy. NaOH, K2Cr2O7, Fe2(SO4)3. XH2O, and C8H18O3Si were employed to functionalize aluminum. The flexural, impact, and shear strengths, as well as their failures, were investigated using electron microscope images. The impulsive hammer approach was applied to investigate laminate vibration behaviour. The results showed that the flexural strength (623.83 MPa), impact strength (76.41 J/mm2), and shear strength (55.31 MPa) of C8H18O3Si functionalized laminates outperformed those of other functionalized laminates. The improvement of mechanical properties was due to the change in interfacial adhesion. This is dependent on the functionalization of aluminium used in stacked laminates. Moreover, C8H18O3Si functionalized laminates exhibit a higher natural frequency and higher damping than other functionalized laminates. This natural frequency and damping are enhanced due to the strong mechanical interlocking between polymer and metal adhesion. It was noted that the same laminates have higher toughness than other laminates because of the high impact energy obtained. [ABSTRACT FROM AUTHOR]

This study was motivated by the need for a mechanistic-empirical (ME) design method applicable to asphalt pavements after mill-and-overlay repairs that include reinforcing grids; the focus was solely on the mechanistic component. A new model, based on layered theory, was developed – coupling in one single framework the following features: elastic layers for representing subgrade and unbound layers, fragmented layers for representing existing aged and densely cracked asphalt concrete (AC), imperfect bonding conditions for representing any differential slippage between adjoining layers, thermo-viscoelastic layer properties for representing new AC, and moving loads for representing traffic conditions. Grid effects were modelled as a combination of three contributions: the presence of an additional thin high-modulus elastic layer within the pavement system, the influence of a grid on interlayer bonding between layer above and below it, and the influence of a grid on the properties of the surrounding AC. These contributions require new grid-related modelling inputs that are physically meaningful and generic – not limited to any specific product. A secondary objective of the work was to generate some initial intuition on the mechanistic effects of interlayer grids. Accordingly, the new model was demonstrated in a parametric investigation covering a synthetic milled-and-overlaid structure with and without reinforcement. Findings from this demonstration provided an initial validation for the new model, given the conformity to findings from experimental studies. Overall, the new model is deemed a candidate computational engine for a ME design applicable to new and rehabilitated asphalt pavement systems. Furthermore, it can serve as an analysis tool to guide manufacturers on improving their products or showcasing existing capabilities in a quantified manner. Lastly, the new model can support the design of experimental setups for assessing grid effects within asphalt pavement systems, and therefore ensure the collection of usable measurements for subsequent mechanistic interpretation. [ABSTRACT FROM AUTHOR]

The Finite Strip Method (FSM) was employed to study the buckling behavior of laminated glass fiber-reinforced polymer (GFRP) stiffened plates with different boundary conditions under axial compression. The theoretical formulation was established based on the first-order shear deformation theory (FSDT) for the thin plate and the stiffener. In this formulation, the stiffeners are not required to be placed on the nodal lines. This feature is considered useful in modeling the stiffened plates in which the stiffener elements are placed arbitrarily in complex planforms. Experimental, numerical and analytical studies were conducted to investigate the effects of the plate width-to-thickness ratio, the stiffener thickness-to-width ratio, dimensions, angle, eccentricity, torsional stiffness and geometric configuration of stiffeners on axial buckling capacity. Furthermore, the obtained results of the analytical method were compared with experimental results and ANSYS code to show its accuracy and convergence. The advantages of the present are that number of elements is much less and the mesh refinement process is much more convenient than commercial finite element software and traditional finite element method (FEM). Therefore, time consumed for analysis is less than the codes which work based on the finite element method. [ABSTRACT FROM AUTHOR]

We investigate the mechanical properties of a layered material with interlayer friction. We propose a model that contains lateral elasticity and interlayer friction to obtain the response function both in the Fourier and real spaces. By investigating how the internal deformation is laterally induced due to the applied surface displacement, we find that it is transmitted into the material with an apparent phase difference. We also obtain the effective complex modulus of the layered material and show that it exhibits an intermediate power-law behavior in the low-frequency regime. Our results can be used to estimate the internal deformation of layered materials that exists on various different scales. [ABSTRACT FROM AUTHOR]

Transverse cracking and delamination are two of the most common failure modes in cross-ply composite laminates. The initiation and combination of these two failure mechanisms lead to catastrophic failure modes in composite structures. This paper investigates the impact of the layer thickness and the presence of microtubes on the in situ strength of the 90° layer, the influence of induced delamination on the strength of [0/90n/0] laminates in micro and macro scales is also investigated. In order to model the fiber–matrix debonding and matrix cracking formation in 90° plies, the cohesive zone model and extended finite element method (XFEM) are used. Afterward, to examine the induced delamination formation which originates from the tips of the transverse cracks, cohesive surfaces are placed between adjacent layers. It was shown that by increasing the thickness of a 90° layer, both the strength of the first transverse crack formation and the stress for delamination initiation decrease. On the other hand, the presence of microtubes in the vicinity of the 90° and 0° interfaces leads to an increase in the strength of the 90° ply and postpones delamination initiation. [ABSTRACT FROM AUTHOR]

This paper aims to detect and locate damage in an innovative slab-on-girder pedestrian bridge model using the vibration characteristics determined from a combined experimental–numerical procedure. The innovative slab-girder pedestrian bridge model has a bi-layer composite deck with Glass Fiber Reinforced Polymer as the bottom layer and laminated glass as the top layer to exploit the desirable properties of these two materials. Modal data from experimental tests and numerical analyses of the bridge model under single and multiple damage cases together with the modal flexibility method are used to detect and locate damage in the bridge. Results show that the peaks of the model flexibility plots correctly locate the damage and that their values provide a good indication of damage severity, which depend on the number of damages, damaged member and location of damage. Results show that the early vibration modes of this bridge model are dominant in torsion, different to flexure dominant modes in traditional slab-girder bridges. Nevertheless, the combined experimental-numerical procedure is found to be effective for assessing both single and multiple damages in the innovative bridge model. The adopted procedure will be applicable to similar real bridge structures in future investigations and will contribute to their safety. [ABSTRACT FROM AUTHOR]

The low-velocity impact behavior of single-lap joints was investigated in this study. In single-lap joints, woven carbon fiber reinforced epoxy (CFRE) and plain woven glass fiber reinforced epoxy (GFRE) laminates as well as a hybrid composite laminate (HCGFRE), which is formed by stacking carbon and glass composite laminates, are used as adherends. Araldite 2011 and Araldite 138 M/HV998 epoxy adhesives were used with different mechanical properties for joining similar and dissimilar composite adherends. Low-velocity impact tests were carried out with 40 J impact energy. Reaction force-time and impact energy-time graphs were obtained from the experimental study as impact response. In numerical analyses, the damage approach of composite adherend was modeled using composite stress-based failure model (Mat 59) and adhesives were modeled utilizing a mixed-mode cohesive zone model (Mat 138) that existed in LS-DYNA explicit finite element software. It was seen that the numerical results indicated a similar tendency with the experimental results due to the modeling of the adhesives using the proper cohesive zone model, the application of correct boundary conditions, and the selection of the correct contact type. [ABSTRACT FROM AUTHOR]

To address deficiencies in traditional coating and adhesive processes for installing auto safety glasses, mounting brackets for auto safety glass were formed by the insert injection molding process via employing an insert. Specifically, float glass was used as the insert, Chemlok CH456 and CH489 were utilized as the glass primer, and soft polyvinyl chloride (PVC) was adopted as the material for injection molding. The adhesive force of the mounting brackets was measured, and the adhesive behavior of the mounting brackets was characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results indicated that the adhesive force of the mounting brackets obtained by insert injection molding can be as high as 1027 N. The results showed that the primer located in fracture regions was torn from PVC and the glass. Double-interface adhesion was found between the glass, the primer, and PVC. In particular, the primer and the glass surface formed strong adhesion by mechanical locking, diffusion existed between PVC and the primer, and the diffusion depth was greater than 10 μm. This process greatly shortens the production cycle of the mounting brackets for auto safety glass and greatly improves the adhesive quality of the mounting brackets. [ABSTRACT FROM AUTHOR]

This paper proposes an innovative pedestrian arch bridge, with a new bi-layer composite deck supported by a steel frame. Bottom and top layers of the bridge deck are composed of glass fibre reinforced polymer (GFRP) plate and laminated glass plate respectively. Structural evaluation of this aesthetically pleasing and lightweight pedestrian bridges is important to avoid excessive vibration. With this in mind, free vibration tests were first carried out on the proposed composite deck and results were used to validate a three-dimensional finite element (FE) model of the composite deck developed in ABAQUS software. Static and free vibration responses of the proposed pedestrian arch bridge with steel frame and composite deck are evaluated by FE analyses. While the static performance of the bridge was found to be satisfactory, the fundamental natural frequency was found to be within human walking frequency which could cause excessive vibration. Hence, further analysis was carried out by changing the cross-sectional areas of the bridge parts to obtain the desired performance of the bridge. Results were compared with recommended values in Bridge Design Code and they ensured that the proposed pedestrian arch bridge will be a safe, aesthetically pleasing and serviceable structure for the pedestrians. [ABSTRACT FROM AUTHOR]

Assuming the interlaminar failure in quasi-isotropic laminates, we evaluated the Mode I interlaminar fracture in asymmetric 0°/45° interlayer. To consider coupling effects caused by stacking sequence, we prepared two types of laminates with 0°/45° interlayer: one is that all coupling components are zero, and the other has non-zero D16 and D26 components. As for comparisons, we used unidirectional laminates and angle-ply laminates in which the midplane consisted of a ± 22.5° interlaminar. The laminates with the 0°/45° or ±22.5° interlayers exhibited higher energy release rates than that of the 0°/0° laminates, owing to significant bridging fibers. It was experimentally confirmed that a failure in asymmetric interlayer, which has non-zero coupling components like typical quasi-isotropic laminates, did not propagate straight along a fiber direction on either side, but was distorted in fan-like shape by coupling effects. [ABSTRACT FROM AUTHOR]

In this work, hybrid composite having linear gradation of carbon and glass fibers (functionally graded hybrid (FGH)) is made and its material properties are compared with classical sandwich hybrid (SH) laminates, i.e., carbon fibers in between glass fibers or vice versa. The performance of FGH composite is evaluated in tensile, compressive, and flexural loadings. Using analytical approach (rule of mixtures), hybrid effect w.r.t. carbon fiber or glass fiber laminates is determined in terms of strength and stiffness. It is observed that failure of FGH specimen is progressive, i.e., layer by layer failure, due to this high ductility is noticed in comparison with SH specimens except in compression. Stiffness and strength of FGH specimens are higher than SH specimens under tension, compression, and flexural. The FGH has shown 7–8% positive hybrid effect in flexural modulus w.r.t. carbon fiber reinforced polymer laminates. In terms of compressive strains, SH and FGH specimens have shown 526% and 380% positive hybrid effect w.r.t. carbon fiber laminates, respectively. Overall FGH is proved better in comparison with classical SH laminates. [ABSTRACT FROM AUTHOR]

Laminated glass (LG) comprises two or more glass plates bonded together with elastomeric interlayer. Automobile and aircraft industries have used LG for years because of its ability to maintain closure of window openings following fracture. In the last decade, the architectural industry began to utilise the potential of LG as the best glazing material for building fenestrations that might experience extreme loadings. Polyvinyl butyral (PVB) interlayer and recently advanced polymer interlayer have relatively small thickness in comparison with that of the glass plates in LG. In addition, the structural properties of the interlayer materials vary radically from those of window glass. These issues make analysis of LG difficult. This article presents a higher order finite element model (FEM) to analyse LG under uniform loading. The formulated model can analyse LG with different glass plate types and different interlayer thicknesses over a wide temperature range. While not as comprehensive as some analytical techniques for LG, this model has the advantage of being able to handle different shapes (rectangular, trapezoidal, triangular, etc.) and boundary conditions. [ABSTRACT FROM AUTHOR]