Applied Composite Materials

Scarselli, Gennaro; Quan, Dong; Murphy, Neal; Deegan, Brian; Dowling, Denis; Ivankovic, Alojz

doi: 10.1007/s10443-020-09854-ypmid: N/A

The present work is concerned with adhesive bonding of thermoplastic composites used in general aerospace applications, including polyphenylene sulfide (PPS), polyetherimide (PEI) and polyetheretherketone (PEEK) carbon fibre composites. Three different surface treatments have been applied to the PEEK, PPS and PEI-based composites in order to enhance the adhesion: atmospheric plasma, ultraviolet radiation (UV) and isopropanol wiping as a control. Water contact angles and free surface energies were measured following the standard experimental procedure based on the employment of three different liquid droplets. Infrared spectroscopy and X-ray photoelectron spectroscopy (XPS) were subsequently performed to characterize the surface chemistry of the samples after treatment. The single lap joints were manufactured and bonded by an Aerospace grade epoxy-based film adhesive originally developed for use on metals but with the ability to bond treated thermoplastics to good strength (supplied by Henkel Ireland). Quasi-static (QS) tests were conducted. The lap shear strength was evaluated, and the failure mechanisms of the different joints were examined for the range of surface treatments considered. It was found that the performances of the PEEK and PPS joints were considerably improved by the plasma and UV treatments resulting in cohesive and delamination failures, while PEI was unaffected by the plasma and UV treatments and performed very well throughout.

Pantano, A.; Bongiorno, F.; Marannano, G.; Zuccarello, B.

doi: 10.1007/s10443-020-09857-9pmid: N/A

Thanks to good mechanical performances, high availability, low cost and low weight, the agave sisalana fiber allows to obtain biocomposites characterised by high specific properties, potentially very attractive for the replacement of synthetic materials in various industrial fields. Unfortunately, due to the low strength versus transversal damage processes mainly related to the matrix brittleness and/or to the low fiber/matrix adhesion, the tensile performance of random short fiber biocomposites are quite low, and to date most of the fiber treatments proposed in literature to improve the fiber-matrix adhesion, have not led to very satisfactory results. In order to overcome such a drawback, this work in turn proposes the proper introduction of low fractions carbon nanotubes to activate advantageous improvements in matrix toughness as well as fiber-matrix bridging effects, that can both lead to appreciable increments of the tensile strength.Systematic experimental static and fatigue tests performed on high quality biocomposites obtained by an optimized compression molding process, have shown that the introduction of 1% of carbon nanotubes is sufficient to gives significant improvement in both stiffness and static tensile strength, respectively by approximately 28% and 30%. Furthermore, toughening the biocomposite with 1% of nanotubes results in an appreciable enhancement in lifetime of at least 3 orders of magnitude. Biocomposites with 2% of CNTs show instead more limited improvement of 13% in stiffness, 6% in strength and 150% in lifetime. Also, a thorough analysis of the damage processes by SEM micrographs, as well as of the main fatigue data, has allowed to determine the model that can be used to predict the fatigue performance of such biocomposites.

Sourki, Reza; Crawford, Bryn; Vaziri, Reza; Milani, Abbas S.

doi: 10.1007/s10443-020-09846-ypmid: N/A

Inter-ply slippage is known to be an important mechanism taking place during forming processes of textile composites, especially with respect to multi-layer fabric lay-ups. The coefficient of friction between the plies strongly depends on the structure and the orientation of forming fabric. Despite many numerical and experimental investigations, this dependency and its effect on the interaction between the plies has been overlooked. In this paper, the effect of fiber orientation on the interlayer friction of a typical thermoplastic fabric prepreg at room temperature is investigated. Results, through a polar representation of data, revealed that both static and dynamic coefficients of friction are statistically dependent on the lay-up orientation, applied normal load, along with their interaction. Further, it was identified that the repeated frictional loading of the plies results in a hysteresis, particularly for asymmetric layups due to non-negligible movement and realignment of filaments at the micro-scale. Finally, an empirical model was developed using an interpolation function (for pressure dependency) combined with a Fourier series (for orientation dependency), to predict the coefficients of friction.

Feng, Yu; Ma, Binlin; Zhang, Tiejun; Zhang, Teng; He, Yuting; Jiao, Shenbo

doi: 10.1007/s10443-020-09847-xpmid: N/A

Tension-tension fatigue experiments on composite laminates were performed under various fatigue stress levels. Static and fatigue failure modes of specimens were analyzed and compared. S–N curves of fatigue life data were built using exponent function. Fatigue life distribution was described by two different distributions, logarithm-normal and two parameters Weibull distribution. Then fatigue life under various probability of survival was calculated and R-S–N curves were built, which indicated the high probability of survival lead to smaller reliability fatigue life. Finally, a new S–N curve model was proposed, which exhibited good accuracy with experimental results.

Fu, Tianyu; Xu, Jiazhong; Hui, Zhao

doi: 10.1007/s10443-020-09852-0pmid: N/A

Electromagnetic induction can achieve rapid internal heating of the carbon fiber reinforced polymer composite (CFRP) materials, to achieve its low energy consumption and efficient curing molding. Still, the CFRP structure, heat transfer anisotropy, and the electro-magnetic-eddy current coupling during heating directly affect the curing temperature of the composite material’s field distribution and its forming quality. In this study, the mechanism of induction heating of plain weave CFRP is analyzed. Based on the finite element mesoscopic model, the induction electricity-magnetic-eddy current–temperature multi-field coupling analysis model of plain weave CFRP is established. The coupling and distribution rules of the electro-magnetic-eddy current field during induction heating were studied; the heating history and temperature distribution of carbon fiber composite materials during heating were analyzed, and the correctness of the finite element mesoscopic model was verified through experiments. An analysis model and method are provided for heating plain weave CFRP to achieve its curing and molding.

Gürgen, Selim; Fernandes, Fábio A. O.; de Sousa, Ricardo J. Alves; Kuşhan, Melih Cemal

doi: 10.1007/s10443-020-09859-7pmid: N/A

Cork composites present interesting properties for several applications such as damping, shock absorption, crashworthiness and thermal insulation. In this work, the enhancement of their impact resistance, by means of shear thickening fluid (STF) reinforcement was studied. The analysis was carried in multi-layered structures consisting of cork laminates with STF as the interfacial element. To make the study concise, a constant thickness was established for the structure and the variables were the number of cork laminates and thus, the thickness of each laminate and the amount of STF. The STF employed was based on fumed silica and polyethylene glycol (PEG). Rheological measurements were carried out on the developed STF, which was also subjected to scanning electron microscopy (SEM). The multi-layered composite structures were subjected to low-energy impact testing, for three energy levels: 5, 10 and 15 J. Direct comparison was established between cork structures with and without STF, determining the influence of STF in the impact performance. Results are promising, reducing the maximum impact force for some designs (max. reduction of 36%), showing the potential of STF to enhance the impact performance of cork composites.

Stabla, Paweł; Smolnicki, Michał; Błażejewski, Wojciech

doi: 10.1007/s10443-020-09861-zpmid: N/A

This paper is focused on radial-compression of filament-wound composite pipes. An important but frequently disregarded is the issue of the choice of the winding pattern. The influence of the pattern on the strength of pipes is the subject of the investigation. Since the real geometry of filament-wound tubes is complicated researchers use simplified models (especially in “zig-zag” area), which are insufficient to reflect real behavior of tubes. An attempt to investigate a more precise geometry is presented in this work. A python script is used to model the particular areas typical for filament-wound elements. Hashin criterion is used to reflect damage in the material during compression. Results of numerical simulations are discussed and compared with experimental from other researchers. Based on the prepared model – the influence of pattern on the strength of a composite pipe is possible. Although some improvements may be introduced, a satisfactory agreement between the experiment and numerical simulation was achieved.

Shih, Cheng-Hung; Chang, Chang-Pin; Liu, Yih-Ming; Chen, Yu-Liang; Ger, Ming-Der

doi: 10.1007/s10443-020-09860-0pmid: N/A

In order to exploit future soft body armor to achieve a more comprehensive protection than just the torso part of the body, in this study, shear thickening fluids (STFs) with different rheological properties are fabricated by planetary mixer and three-roller mills to investigate the mixing process effect on the resultant rheological behavior. Rheological results indicate the critical shear rate and the maximum viscosity of STF are deeply influenced by the dispersion degree of nano-silica particles in PEG. These STFs are then filled into a paper honeycomb partition to prepare a STF-based protective structure. Different laminating sequences of the composite panels composed one STF structure layer and nineteen layers of Kevlar fabric are obtained by simply placing the STF structure at different positions in the composite panels. The ballistic tests are conducted according to the NIJ 0101.06—Type II standard using 9 mm Full Metal Jacketed Round Nose bullets. Our results show that the absorbed energy of the composite panel with STF that thickens at higher shear rate is higher compared to that using STF that thickens at a lower shear rate. It suggests the STF with higher critical shear rate would be optimally used in ballistic impacts. In addition, ballistic testing results confirm that the STF structure placed at the rear position can significantly contribute to the increase in impact resistance.

Wang, Pei; Deng, Guanyu; Zhu, Hongtao; Yin, Jian; Xiong, Xiang; Zhang, Hongbo

doi: 10.1007/s10443-020-09862-ypmid: N/A

To improve electrical conductivity of the carbon-based pantograph strip, a sliding contact material of pyrolytic carbon (PyC) coated-copper foam/carbon composite was fabricated by chemical vapor deposition technology, followed by densifying processes of furan resin impregnation and carbonization. Morphology, electrical conductivity, wear and friction behavior of the composites are investigated to clarify the effect of PyC thickness (from 0 μm to 280 μm) on tribological behaviors and current transfer characteristic. The results show that there is a good interface combination between copper foam and resin carbon matrix in the composites after the improvement of interface wettability by inserting PyC layer. The composite has great advantages in electrical conductivity and density due to the copper foam and PyC layer with three-dimensional structure. With increasing the PyC thickness, both electrical conductivity and wear resistance of the composite have steadily increasing tendency, but friction coefficient has no obvious change. In addition, an analytical model is developed to explore current transfer mechanisms of the PyC-copper foam/carbon composite, and the theoretical predictions are in agreement with the experimental observations, in term of electrical conductivity and porosity of composite preform.

Batista, Natassia L.; Rezende, Mirabel C.; C.Botelho, Edson

doi: 10.1007/s10443-020-09863-xpmid: N/A

The purpose of this work is to investigate how the crystallinity degree of carbon fiber / poly(ether-ether-ketone (CF/PEEK) composites affects their performance when exposed to ultraviolet radiation, hygrothermal, and salt fog conditionings. Thermal characterization was performed by differential scanning calorimetry (DSC) and dynamical mechanical analyses (DMA), whereas interlaminar shear strength (ILSS), impulse excitation technique and compression tests were employed for mechanical characterization. According to the results obtained in this work, the CF/PEEK laminates with higher crystalline contents presented significantly lower water absorption. An increase in the crystallinity degree throughout the conditionings was observed for the CF/PEEK samples with lower crystalline contents, as a result of chemi-crystallization, or high temperatures, and/or water uptake. Moreover, the crystalline content also showed to affect the severity of the degradation for the UV/condensation conditioning, with the samples with lower degree of crystallinity being the most resistant. No significant changes have been observed for the mechanical properties evaluated.