Impact of Aggressive Media on the Interlaminar Shear Strength of Innovative Glass Fiber Reinforced Polyurea/Polysilicate Hybrid Resins

RETRACTED: Investigations on electrophoretic deposition of carbon nanotubes on glass textures to improve polymeric composites interface

In the present paper, a series of plate impact shock-reshock and shock-release experiments were conducted to study the critical shear strength of a S2 glass fiber reinforced polymer (GRP) composite under shock compression levels ranging from 0.8 to 1.8 GPa. The GRP was fabricated at ARL, Aberdeen, using S2 glass woven roving in a Cycom 4102 polyester resin matrix. The experiments were conducted by using an 82.5 mm bore single-stage gas gun at Case Western Reserve University. In order to conduct shock-reshock and shock-release experiments a dual flyer plate assembly was utilized. The shock-reshock experiments were conducted by using a projectile faced with GRP and backed with a relatively high shock impedance Al 6061-T6 plate; while for the shock-release experiments the GRP was backed by a relatively lower impedance polymethyl methacrylate backup flyer plate. A multibeam velocity interferometer was used to measure the particle velocity profile at the rear surface of the target plate. By using self-consistent technique procedure described by Asay and Chabbildas [Shock Waves and High-Strain-Rate Phenomena, in Metals, edited by M. M. Myers and L. E. Murr (Plenum, New York, 1981), pp. 417–431], the critical shear strength of the GRP (2τc) was determined for impact stresses in the range of 0.8 to 1.8 GPa. The results show that the critical shear strength of the GRP is increased from 0.108 GPa to 0.682 GPa when the impact stress is increased from 0.8 to 1.8 GPa. The increase in critical shear strength may be attributed to rate-dependence and/or pressure dependent yield behavior of the GRP.

To examine the role of nanoclays in the enhancement of interlaminar shear strength (ILSS) of glass fiber reinforced diallyl phthalate (GFR-DAP) composites, the GFR-DAP laminates were manufactured by hand lay-up techniques using two nanoclays, DK2 and MHAB-MMT, respectively. Χ-ray diffraction (XRD) were conducted to characterize the morphology of the dispersed clay particles in the DAP matrix. The mechanical performances were characterized by flexural strength and LISS measurements. XRD scans shows that the clays disperse uniformly in the DAP matrix and form an intercalated structure with a basal spacing of 3.86 nm and 3.98 nm for DK2 and MHAB-MMT, respectively. Short beam shear tests show that only 2.5 wt% clay loading in DAP matrix increased the ILSS of resulting GFR-DAP laminates by 7.64% and 14.80% for DK2 and MHAB-MMT, respectively, with respect to the neat DAP. The fractured surfaces of resulting laminates were observed by scanning electron microscope (SEM).

Interlaminar shear strength of glass fiber reinforced epoxy composites enhanced with multi-walled carbon nanotubes

Strength and stiffness properties of Glass Fiber Reinforced Plastic (GFRP) bars under various conditioning schemes with and without the application of sustained loads are described in this paper. Alkaline conditioning was more detrimental to the strength of GFRP bars as compared to salt conditioning. Increasing temperatures and stress resulted in a corresponding decrease in the strength of GFRP bars. Based on accelerated test results calibrated with respect to naturally aged results it is safe to include that the service life of the FRP bars with durable low viscosity urethane modified vinylester resin is about 60 years as a minimum with 20% sustained stress on the bar. Concrete cover protection on the GFRP bars enhanced the service life up to an additional 60 years.

The article presents experimental tests of a new type of composite bar that has been used as shear reinforcement for concrete beams. In the case of shearing concrete beams reinforced with steel stirrups, according to the theory of plasticity, the plastic deformation of stirrups and stress redistribution in stirrups cut by a diagonal crack are permitted. Tensile composite reinforcement is characterized by linear-elastic behavior throughout the entire strength range. The most popular type of shear reinforcement is closed frame stirrups, and this type of Fiber Reinforced Polymer (FRP) shear reinforcement was the subject of research by other authors. In the case of FRP stirrups, rupture occurs rapidly without the shear reinforcement being able to redistribute stress. An attempt was made to introduce a quasi-plastic character into the mechanisms transferring shear by appropriately shaping the shear reinforcement. Experimental material tests covered the determination of the strength and deformability of straight Glass Fiber Reinforced Polymer (GFRP) bars and GFRP headed bars. Experimental studies of shear reinforced beams with GFRP stirrups and GFRP headed bars were carried out. This allowed a direct comparison of the shear behavior of beams reinforced with standard GFRP stirrups and a new type of shear reinforcement: GFRP headed bars. Experimental studies demonstrated that GFRP headed bars could be used as shear reinforcement in concrete beams. Unlike GFRP stirrups, these bars allow stress redistribution in bars cut by a diagonal crack.

A glass fiber reinforced plastic (GFRP) with cyanate ester resin was fabricated and neutron irradiation tests up to 1×1022 n/m2 of fast neutron with over 0.1 MeV energy were carried out in fission reactor. The fabrication process of cyanate ester GFRP was established and a collaboration network to perform investigations on irradiation effect of superconducting magnet materials was constructed. Three kinds of samples were fabricated. The first was CTD403 GFRP made by NIFS, the second was (cyanate ester+epoxy) GFRP provided by Toshiba, and the last was CTD403 GFRP made by Toshiba. The irradiation was carried out at JRR‐3 in Japan Atomic Energy Agency using Rabbit capsules.After the irradiation, short beam tests were conducted at room temperature and 77 K and interlaminar shear strength (ILSS) was evaluated. The irradiation of 1×1021 n/m2 increased ILSS a little but 1×1022 n/m2 irradiation decreased ILSS to around 50 MPa. These tendencies were observed in all three kinds of GFRPs.

In this, the effect of conch shell particles on mechanical performance of glass fiber-reinforced polymer (GFRP) composite was investigated. The GFRP composites were prepared using hand layup method. The conch particles were added in the incremental levels of 0, 25, 35, 45, and 55 wt.% to GFRP composites. The C–H stretching vibration and aliphatic amine groups in conch-filled composites confirmed the dispersion of conch particles. The mechanical performance of GFRP composites was evaluated by impact strength, interlaminar shear strength (ILSS), and fatigue strength tests. The GFRP composites fabricated using 35 wt.% of conch shell particles showed higher impact toughness of 35 J in presence of centered notch compared to GFRP composites developed without conch shell particles that showed impact toughness of 13 J. The ILSS of GFRP composites drops by the addition of conch shell particles. The GFRP composites fabricated using 35 wt.% of conch shell particles showed 26.21 % reduced ILSS compared to the GFRP composites developed without conch shell particles. The GFRP composites fabricated using 45 wt.% of conch shell particles exhibited fatigue life of 10,093 cycles. These results suggest that conch filler – GFRP composites can be used for lightweight applications, which are cost-effective and ecofriendly.

In this study, undulations and their influence on the longitudinal compressive strength of a unidirectional glass fiber reinforced polymer (GFRP) composite are investigated theoretically and experimentally. The objective of this research is to explore the failure mechanisms in FRP and to characterize the mechanical properties of FRP as a function of fiber orientation. For this purpose, a multiscale material model is developed that considers a stochastic fiber orientation distribution (FOD) and models matrix fracture-initiated failure. The relationship between compressive strength and undulation is investigated experimentally on standardized specimens made of unidirectional GFRP. The fiber orientations are measured using X-ray computed tomography and ImageJ image analysis, resulting in a binormal distribution of fiber orientations in the series of samples tested. To examine the failure process in detail, the compression tests are simulated using finite element analysis (FEA). Both the FEA results and the measured compressive strengths confirm the model assumption of matrix fracture-initiated failure under longitudinal compressive loading. The presented analytical model realistically represents the correlation of compressive strength with the FOD.

Mechanical properties and microstructure of glass fiber reinforced polymer (GFRP) rebars embedded in carbonated reactive MgO-based concrete (RMC)

The unmodified and nano-SiO 2 modified glass fiber reinforced polymer (GFRP) composites were prepared by the hot-compression molding process to investigate the effects of nano-SiO 2 on the mechanical and hygric properties of the GFRP composites. The results indicate that the nano-SiO 2 modification results in an increase of 9.7% and 7.9% in the tensile and flexural strength of the GFRP composites, and a decrease of 10.6% in the interlaminar shear strength (ILSS). The maximum swelling of the unmodified GFRP is 2.6 times as that of the nano-SiO 2 modified GFRP. The normalized-ILSS decrease of the nano-SiO 2 modified GFRP is only 12% after 138 days aging, while that of the GFRP reaches 31%. After 95-days hygric-aging, the decrease of the normalized flexural strength is 15.3% for the GFRP, while the normalized flexural strength of the nano-SiO 2 modified GFRP still maintains an increase of 5.0%. It is concluded that the nano-SiO 2 particle could improve the mechanical and hygric properties of the GFRP composites.

It is well known that the strength of glass fibers increases with increasing strain rate. Consequently, impact strength of glass fiber is competitive with that of carbon fiber. This strengthening phenomenon is well recognized for bulk glass. Strain-rate dependence of the strength for bulk glass was described by considering slow crack growth in glass. The analytical model that considered the slow crack growth of glass is proposed to predict the strength of glass fibers. The proposed model considered the stress corrosion limit and a constant crack velocity region. Calculations showed almost same results with the previous model, however, some differences were confirmed. To discuss the validity of the analysis, tensile tests of E-glass fiber bundles were conducted at various strain rates. It was observed that the fracture behaviors differ with the strain rates. Experimental results showed that the strength of E-glass fibers increased with increasing strain rate. Furthermore, we confirmed that the analytical results were in good agreement with the experimental results. The strain-rate dependence of the strength of glass fibers was successfully predicted by considering the slow crack growth in glass.

Study on interlaminar performance of CNTs/epoxy film enhanced GFRP under low-temperature cycle

This paper presents an investigation on the modification of macro-scale fibre reinforcement with nano-scale filler to produce multiscale glass fibre reinforced polymer (GFRP) composites. Glass fibres were spray-coated with multi-walled carbon nanotube (MWCNT) aqueous suspension and were stacked together with epoxy binder to produce composite laminates by using hand lay-up method, followed by vacuum bagging. The stability of MWCNT aqueous suspension was analysed using zeta potential and UV-Vis and the distribution of MWCNT on the glass fibre was examined using scanning electron microscope. To evaluate the mechanical performance, flexural test and short beam test were performed. Improvement by 53.6% and 74.8% was observed in flexural strength of the 5-ply glass fibre (5GF) composites incorporated with 0.1 and 0.5 wt% of MWCNT, respectively. Meanwhile, flexural modulus of the same composites showed more than 20% improvement at both MWCNT concentrations. For interlaminar shear strength (ILSS), the highest improvement was found to be at 0.5 wt% of MWCNT which increased ILSS of the multiscale composite by 43.8% compared to the control sample (5GF). It is also interesting to note that 6-ply glass fibre (6GF) composite had lower flexural properties and ILSS in comparison to 4-ply glass fibre (4GF) and 5GF multiscale composites incorporated with MWCNT, indicating that we successfully reduced the weight of the GFRP composites by reducing the glass fibre ply but significantly enhanced their mechanical performance.KeywordsGlass fibreCarbon nanotubeMultiscale compositeFlexuralShort beam

Interface enhancement with carbon nanotubes (CNTs) provides a promising approach for improving shock strength and toughness of glass fiber reinforced plastic (GFRP) composites. The effects of incorporating flame-synthesized CNTs (F-CNTs) into GFRP were studied, including on hand lay-up preparation, microstructural characterization, mechanical properties, fracture morphologies, and theoretical calculation. The experimental results showed that: (1) the impact strength of the GFRP modified by F-CNTs increased by more than 15% over that of the GFRP modified by CNTs from chemical vapor deposition; and (2) with the F-CNT enhancement, no interfacial debonding was observed at the interface between the fiber and resin matrix on the GFRP fracture surface, which indicated strong adhesive strength between them. The theoretical calculation revealed that the intrinsic characteristics of the F-CNTs, including lower crystallinity with a large number of defects and chemical functional groups on the surface, promoted their surface activity and dispersibility at the interface, which improved the interfacial bond strength of GFRP.