Effect of nano‐silica on fatigue behavior of glass fiber‐reinforced epoxy composite laminates: A Weibull distribution approach
Akash Gupta,
Manjeet Singh,
J. S. Saini
Abstract:The aim of this study is to assess the impact of nano‐silica in glass fiber‐reinforced epoxy composite (GFEC) subjected to static and fatigue loading. Laminates were prepared in compression molding machine followed by the tensile test and tension‐tension fatigue testing at five different stress levels (from 50% to 90% of ultimate tensile strength). The addition of 3 wt% of nano‐silica with epoxy improved the tensile and fatigue strength as compared to neat GFEC. Scanning electron microscope (SEM) images of the… Show more
“…This dissipation results from various damage mechanisms, including interactions between fibers and matrix, as well as damping mechanisms caused by microvoids. 42 Plastics undergoing cyclic stresses which degrades interfacial shear strength, impacting the fiber-matrix interface, leading to increased strains, and ultimately contributing to a more substantial hysteresis effect. 43,44 Observing Figure 11(a) during the initial cycle, it is evident that as the stress levels increase, there is a gradual reduction in the slope of the stress-strain loop.…”
Glass Fiber Reinforce Polymer (GFRP) composite Joints were studied under monotonic loads for aerospace and marine applications, but cyclic loading is also a common and serious concern in these applications. In this current study, GFRP composite pin joints were analyzed under cyclic loading, at various geometric factors experimentally and numerically using finite element analysis (FEA) and also compared with monotonic loading. Fatigue tests were carried out using sinusoidal tension-tension loading and covering a range of stress levels from 50% to 90% of effective failure strength (EFS). Weibull distribution was utilized to predict the reliable fatigue life of joints at various joint configurations. Under cyclic loading rapid degradation of dynamic modulus indicated catastrophic failure with shorter fatigue life, while gradual degradation implied slow micro-crack growth and extended fatigue life with progressive failure while in monotonic loading, a sudden fall in the stress-strain curve represented catastrophic failure, and a zigzag curve indicated bearing failure mode before fracture. The damage rate was also determined from the hysteresis loop cycles which indicate greater loop expansion due to the stiffness degradation and higher energy dissipation shows rapid damage accumulation and shorter fatigue life at higher stress level. On the other hand at lower stress level, moderate enlargement of the hysteresis loop demonstrates extended fatigue life with slower damage propagation.
“…This dissipation results from various damage mechanisms, including interactions between fibers and matrix, as well as damping mechanisms caused by microvoids. 42 Plastics undergoing cyclic stresses which degrades interfacial shear strength, impacting the fiber-matrix interface, leading to increased strains, and ultimately contributing to a more substantial hysteresis effect. 43,44 Observing Figure 11(a) during the initial cycle, it is evident that as the stress levels increase, there is a gradual reduction in the slope of the stress-strain loop.…”
Glass Fiber Reinforce Polymer (GFRP) composite Joints were studied under monotonic loads for aerospace and marine applications, but cyclic loading is also a common and serious concern in these applications. In this current study, GFRP composite pin joints were analyzed under cyclic loading, at various geometric factors experimentally and numerically using finite element analysis (FEA) and also compared with monotonic loading. Fatigue tests were carried out using sinusoidal tension-tension loading and covering a range of stress levels from 50% to 90% of effective failure strength (EFS). Weibull distribution was utilized to predict the reliable fatigue life of joints at various joint configurations. Under cyclic loading rapid degradation of dynamic modulus indicated catastrophic failure with shorter fatigue life, while gradual degradation implied slow micro-crack growth and extended fatigue life with progressive failure while in monotonic loading, a sudden fall in the stress-strain curve represented catastrophic failure, and a zigzag curve indicated bearing failure mode before fracture. The damage rate was also determined from the hysteresis loop cycles which indicate greater loop expansion due to the stiffness degradation and higher energy dissipation shows rapid damage accumulation and shorter fatigue life at higher stress level. On the other hand at lower stress level, moderate enlargement of the hysteresis loop demonstrates extended fatigue life with slower damage propagation.
“…14,22,23,30 Although the additions of nanoparticles can improve the mechanical property of FRPs, they cannot play a full role in improving the ILSS, owing to the easy aggregation of nanoparticles and the weak interface bonding between nanoparticles and matrix/ fiber. 22,28,29,[31][32][33][34] Since the interfacial adhesion is a critical factor for the mechanical properties of FRPs, increasing the interface interaction between the fiber and matrix can enhance the mechanical properties. Generally, the modification of fiber surface such as the coating technique [35][36][37][38][39][40][41][42][43][44] and chemical grafting 24,41,45,46 can improve the interfacial adhesion between matrix and fibers.…”
We designed three‐dimensional (3D) structures through a combination of glass fiber cloth and in situ formation of nano polyphenylene oxide (PPE) fibers during the fabrication process of thermosetting cyanate ester/bismaleimide composites and developed a self‐stitching technique based on PPE fiber and interpenetrating polymer networks (IPNs) for aiding the crack self‐healing. The building of 3D structure effectively improves the interface interaction between fiber and matrix and suppresses the crack propagation process in composite, leading to significant enhancement in the mechanical properties. When PPE content is 20%, the interlaminar shear strength, flexural strength, impact strength, and tensile strength of the resulting composite are 98%, 74%, 95%, and 101% higher than those of the composite without PPE. The resulting composites possess excellent thermomechanical and lower dielectric properties. Because IPNs within composites can create interspaces and easily deform above glass‐transition temperature, PPE components may penetrate through the interspaces under thermal expansion force, and the contraction stresses of polymers generate strong locking effects in composite after cooling to room temperature, then the crack surfaces of composites can be stitched by PPE fibers, significantly recovering the mechanical properties. The healing efficiency of the composite with 30% PPE after impact and then heating at approximately 280°C can reach 96%.Highlights
3D structures were constructed during the fabrication process of glass‐fiber‐reinforced thermosetting cyanate ester/bismaleimide composite.
A self‐stitching technique was developed for aiding the crack self‐healing of composite.
3D structures significantly improved the interface interaction between fiber and matrix in laminated composite.
The mechanical properties of the resulting composite could be significantly improved by 3D structures.
The healing efficiency of the healed composite could reach 96%.
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