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Mechanical performances of polymerized cyclic butylene terephthalate (pCBT) matrix, glass fiber reinforced pCBT (GF/pCBT), and nano-silica modified glass fiber/pCBT composites (nano-GF/pCBT) in hygrothermal condition were investigated. All the materials were aged in hygrothermal environments for up to three months, and then theirmechanical strength degeneration ratio (SDR)was calculated. To study the aging effect of temperature, specimens with and without nano-silica modification were tested in temperatures ranging from 298 to 500 K. Differential scanning calorimeter (DSC) test, dynamic mechanical analysis (DMA), and fiber pull-out test were adopted to complement the experimental results. It is found that all the SDR-time curves follow the linear relationship in hygrothermal environment, while SDR-temperature curves follow a bilinear relationship due to the effect of glass transition temperature (Tg) of the matrix. Fibersmodified by coating nano-silica on the surface could decrease SDR of the composites. This is due to the fact that the fillers on the fiber surface could resist the movement of pCBT molecular chain and diffusion of water molecules in aging conditions. The fiber pull-out test verifies that the interface strength between fiber and matrix is enhanced by the modification. [ABSTRACT FROM AUTHOR]

The main objective of this study is to investigate the functional failure of Glass fiber Reinforced Polyester (GRP) pipes subjected to hydrostatic internal pressure implementing stochastic approach. In this regard, a progressive damage modeling is developed to evaluate the pressure at which weepage takes place throughout the pipe wall thickness. The functional failure implies on a certain pressure that the fluid finds a path through the pipe wall thickness as a consequence of weepage phenomenon. Fiber volume fraction and winding angles in cross plies are considered as the random parameters representing the most important uncertain parameters of filament winding production process. Sufficient numbers of samples are generated using Monte-Carlo technique on the basis of defined convergence criterion. The influence of random behavior of these parameters on the both first-ply-failure and functional failure of GRP pipes are analyzed in an integrated procedure. The results demonstrate that the effect of fiber volume fraction variation on the functional failure pressure is more crucial than that of winding angle variation. Finally, statistical analysis of obtained results is presented on obtained results from stochastic analysis in the form of Weibull probability density function. [ABSTRACT FROM AUTHOR]

Glass fiber composites (GFRP) are common in civil engineering projects, but not in marine structures. One reason is that seawater effects degrade GFRP composites mechanical properties and interlaminar shear strength (ILSS). Here, influence of seawater environment is studied to determine the best composite materials for marine civil engineer applications, studying the influence of several factors in their mechanical properties. This is to determine safety factors to use in the design of structural calculations for marine applications. Glass/epoxy composites are the safest materials to use in marine civil structures as mechanical properties degradation becomes stabilized after moisture saturation level. UV and water cyclic analysis must be done to determine affection to transversal strength. Only vinylester GFRP has problems with biodegradation. GFRP fatigue performance is not influenced by seawater environment. [ABSTRACT FROM AUTHOR]

In this paper, a macro phenomenological fatigue model is developed for the off-axis fatigue behavior of glass fiber reinforced polymer (GFRP) composite laminates. The residual stiffness method and strain failure criterion are used to characterize the brittle nature of fatigue damage evolution. This allows one to obtain a practical form of multiaxial fatigue model that takes into account of the non-linear effects of fiber orientation dependence, stress ratio dependence as well as the effect of loading frequency on the fatigue behavior of composite laminates. Parameters of the model are fitted out according to relative fatigue experiment data with specific lay-up under certain stress ratio and loading frequency. Fatigue life predictions are verified by different stress ratios and loading frequencies, and the results of the model show a good agreement with experimental data. [ABSTRACT FROM AUTHOR]

Highlights: [•] FRP with and without fly ash filler were prepared. [•] Mechanical properties of composites were analyzed. [•] Mixture Design Method was used to model the system. [•] Experimental and mathematical model results were compared. [ABSTRACT FROM AUTHOR]

Highlights: [•] We completed natural fiber material selection using AHP method. [•] New product design specifications for parking brake lever was developed. [•] Kenaf bast fiber is the best natural fiber for hybrid polymer composites. [•] Overall AHP consistency ratio obtained is less than 0.10. [•] Validation of the results was made using sensitivity analysis. [ABSTRACT FROM AUTHOR]

Abstract: Drilling induced damage in fiber reinforced plastic laminates results in high rate of parts rejection and also affects the in-service performance of the composite products with drilled holes. The tensile testing of composite laminates with drilled holes is necessary to render them satisfactory for application. The present research endeavor is an attempt to develop a generic finite element model in order to investigate to failure of uni-directional glass fiber reinforced plastics (UD-GFRP) composite laminates with drilled hole under uni-axial tensile testing. The results have been compared with the experimental work done earlier and are found to be in good agreement. [Copyright &y& Elsevier]

Abstract: The drilling of fiber reinforced plastics (FRP) often results in damage around the drilled hole. The drilling induced damage often serves to impair the long-term performance of the composite products with drilled holes. The present research investigation focuses on developing a predictive model for the residual tensile strength of uni-directional glass fiber reinforced plastic (UD-GFRP) laminates with drilled hole which has not been developed worldwide till now. Artificial neural network (ANN) predictive approach has been used. The drill point geometry, the feed rate and the spindle speed have been used as the input variables and the residual tensile strength as the output. The results of the predictive model are in close agreement with the training and the testing data. [Copyright &y& Elsevier]

Abstract: The use of adhesive joints has gained good acceptance in the automotive and aerospace industries in recent years, particularly for joining glass fiber reinforced plastics (GFRP) to metals. Such joints will be subjected to short duration dynamic loads in service. The present study focuses on the evaluation of the shear strength of adhesive joints prepared using four different commercial adhesives at loading rates in the range of 0.6–1.2MPa/μs. The adhesives used were Araldite 2014, Araldite 2011, Epibond 1590 and A/B Loctite 324. Joints were prepared with two different adherent combinations; aluminum–aluminum and aluminum–GFRP. The results of the study indicated that, depending on the adhesive and adherent combination, the dynamic strength was 2–4 times the static strength. Among the four adhesives, Epibond 1590 exhibited the highest rate sensitivity whereas Loctite 324 exhibited the least. Further it was also observed that the dynamic strength was not sensitive to the adherent combination whenever the failure was predominantly within the adhesive layer. [Copyright &y& Elsevier]

Abstract: The bending fatigue behaviors were investigated in glass fiber-reinforced polyester composite plates, made from woven-roving with four different weights, 800, 500, 300, and 200g/m2, random distributed glass-mat with two different weights 225, and 450g/m2 and polyester resin. The plates which have fiber volume ratio V f ≅44% and obtained by using resin transfer moulding (RTM) method were cut down in directions of [0/90°] and [±45°]. Thus, eight different fiber-glass structures were obtained. These samples were tested in a computer aided fatigue apparatus which have fixed stress control and fatigue stress ratio [R =−1]. Two-parameter Weibull distribution function was used to analysis statistically the fatigue life results of composite samples. Weibull graphics were plotted for each sample using fatigue data. Then, S–N curves were drawn for different reliability levels (R =0.99, R =0.50, R =0.368, R =0.10) using these data. These S–N curves were introduced for the identification of the first failure time as reliability and safety limits for the benefit of designers. The probabilities of survival graphics were obtained for several stress and fatigue life levels. Besides, it was occurred that RTM conditions like fiber direction, resin permeability and full infiltration of fibers are very important when composites (GFRP) have been used for along time under dynamic loads by looking at test results in this study. [Copyright &y& Elsevier]

Abstract: A failure investigation was performed to determine the failure mode and bearing strength of mechanically fastened bolted-joints in glass fiber reinforced epoxy laminated composite plates, experimentally. Two different geometrical parameters those are the edge distance-to-hole diameter ratio (E/D) and plate width-to-hole diameter ratio (W/D) were considered. For this purpose, E/D ratio was selected from 1 to 5, whereas W/D ratio was chosen from 2 to 5. Due to determining material parameters effect, laminated plates were stacked as three different group which are [0°/0°/45°/−45°]s, [0°/0°/45°/45°]s and [0°/0°/30°/30°]s, symmetrically. In addition, the preload moments were applied as 0, 3 and 6nm, since an important target of this study is to observe the changing of failure mechanism under various preloads. The experiments were also performed under a clearance, for this reason the diameters of the bolt and the circular bolt hole were fixed 5 and 6mm, respectively. Results showed that failure modes and bearing strengths were considerable affected by the increasing of preloads. Furthermore, when the material and geometrical parameters of composite bolted-joints were changed, the failure behavior and the values of bearing strengths were fully influenced from this changing. [Copyright &y& Elsevier]

Abstract: A previously designed fatigue apparatus to test bending fatigue behaviours of glass–fiber reinforced plastic materials is improved in the scope of this research. The advantages of the improved test apparatus are as follows: It can teste 16 samples instead of 10. The square section axis was used to connect the samples more rigid by instead of the round section. So, a good balance and less vibration were obtained on the apparatus. More functional infrared sensors were used instead of proximity sensors that are sensitive to repeated cycling. While the load stress ratio is R =0 or 1 (two alternative), with a developed adjustable support device, it is R =−1, 0 and 1 (three alternatives). The fatigue behaviours of two groups (A and E) of composite fiber samples which have different directions but the same volumes were tested by this new apparatus. As a result, it was observed that the directions of the fibers have an important effect on the fatigue strength. [Copyright &y& Elsevier]