Browsing by Author "Cheng, Yi-Lieh"

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Enhancing Fracture Toughness of Glass/Epoxy Composites by Using Rubber Particles Together with Silica Nanoparticles
(2009-12-01)
Tsai, Jia-Lin
;
Huang, Bao-Hung
;
Cheng, Yi-Lieh
;
機械工程學系
;
Department of Mechanical Engineering
The research aims to investigate the interlaminar fracture toughness of glass fiber/epoxy composites, which consist of the silica nanoparticles and the rubber particles. Two kinds of rubber particles, one is the reactive liquid rubber (CTBN) and the other is the core-shell rubber (CSR), were employed to modify the fracture toughness of epoxy resin. In general, the disadvantage of adding rubber particles into polymeric resin is the dramatic reduction of stiffness although the toughness could be modified accordingly. In order to enhance the fracture toughness of the fiber composites without sacrificing their stiffness, the silica nanoparticles in conjunction with the rubber particles were introduced into the epoxy matrix to form a hybrid nanocomposite. Experimental results obtained from tensile tests on bulk epoxy confirm the presumption that the reduction of the epoxy stiffness because of the presence of rubber particles can be effectively compensated by the silica nanoparticles. Furthermore, the fracture tests conducted on the double cantilever beam specimens revealed that the inclusion of silica nanoparticles together with the CSR particle can appreciably increase the fracture toughness of the glass/epoxy composites up to 82%. On the other hand, when the epoxy matrices were modified with CTBN rubber particles and silica nanoparticles, the improvement of the interlaminar fracture toughness was around 48%. It is noted that the role of the silica nanoparticles on the fracture toughness of fiber composites with rubber-modified epoxy matrix is different. For the CSR-modified epoxy matrix, the contribution of silica nanoparticle on the fracture toughness is destructive. In contrast, for the CTBN-modified epoxy matrix, the silica nanoparticles can synchronously improve the fracture toughness of composites.
Investigating Mechanical Behaviors of Silica Nanoparticle Reinforced Composites
(2010-02-01)
Tsai, Jia-Lin
;
Hsiao, Hung
;
Cheng, Yi-Lieh
;
機械工程學系
;
Department of Mechanical Engineering
The research is aimed to investigate the mechanical behaviors of epoxy-based nanocomposites reinforced with spherical nanoparticles. Five different contents of silica nanoparticles -5, 10, 15, 20, and 40 wt% - were introduced in the samples. Through a sol-gel technique, the silica particles with a diameter of 25 nm were exfoliated uniformly in the epoxy matrix. Experimental results obtained from tensile tests indicate that the modulus of nanocomposites increases with the increment of particulate inclusions, and the enhancing behavior is coincided with the model predictions obtained from the Mori-Tanaka micromechanical model. In addition, the fracture tests conducted on single-edge-notch bending specimens reveal that the inclusion of nanoparticles can effectively increase the fracture toughness of the nanocomposites. Furthermore, the extent of the enhancement is more appreciable in the brittle matrix system rather than in the ductile matrix system. Subsequently, by inserting the silica epoxy mixture into the unidirectional glass fiber through a vacuum hand lay-up process, the glass fiber/silica/epoxy composite samples were fabricated. Results depicted that the in-plane shear strength increases until the increment of particle loadings are up to 10 wt%. In addition, results obtained from the compression tests revealed that the glass/epoxy specimens with 20 wt% silica loading exhibit superior compressive strengths than those that do not contain any silica particles.
Investigating nanoparticle effect on the Mode I fracture toughness of glass/epoxy composites
(2008)
Tsai, Jia-lin
;
Cheng, Yi-Lieh
;
機械工程學系
;
Department of Mechanical Engineering
The research is aimed to investigate the influence of spherical nanoparticles on the fracture behavior of glass fiber/epoxy composites. Two different contents of silica nanoparticles, 10wt% and 20wt%, were introduced into the composite samples. Through a sol-gel technique, the silica particles with diameter of 25 rim were dispersed uniformly into the epoxy matrix. Subsequently, the silica epoxy mixtures were impregnated into the unidirectional glass fiber mat by means of a vacuum hand lay-up process to form the unidirectional glass fiber/epoxy laminate. During the fabrication, a porous film was inserted into the mid-plane of the laminate to generate the pre-crack, The Mode I fracture toughness of the composites with different nanoparticles contents were then determined form the double cantilever beam (DCB) specimens. Based on the experimental observations, it was found that the glass fiber/epoxy composites with silica nanoparticles exhibit superior fracture toughness than those that do not contain any silica particles. Scan Electronic Microscopy (SEM) observations on the failure surfaces indicated that the enhanced fracture toughness could be due to the improved interfacial bounding in conjunction with the nanoparticle debonding from the surrounding epoxy. In general, such failure mechanisms may complicate the fracture process, dissipating more fracture energy.
Investigating Silica Nanoparticle Effect on Dynamic and Quasi-static Compressive Strengths of Glass Fiber/Epoxy Nanocomposites
(2009-12-01)
Tsai, Jia-Lin
;
Cheng, Yi-Lieh
;
機械工程學系
;
Department of Mechanical Engineering
The research is aimed to investigate the compressive strengths of glass/epoxy nanocomposites, containing various loadings of spherical silica nanoparticles. Through a sol-gel technique, the silica particles with a diameter of 25 nm were exfoliated uniformly into the epoxy resin. Subsequently, by inserting the silica-epoxy mixture into the unidirectional glass fiber through a vacuum hand lay-up process, the glass fiber/epoxy composite laminates with 10, 20, and 30wt% of silica nanoparticles were fabricated. Quasi-static and dynamic compression tests were conducted on the brick composite specimens with fiber orientations of 0 degrees, 5 degrees, 10 degrees, 15 degrees, and 90 degrees using a hydraulic MTS machine and a split Hopkinson pressure bar, respectively. Observations on the failure specimens indicated that for fiber orientations less than 15 degrees, the fiber microbuckling is the dominant failure mechanism. On the other hand, for the 90 degrees samples, the out-of-plane shear failure is the main failure mechanism. In addition, it was denoted that as the silica contents increase, the compressive strengths of the glass/epoxy composites are improved accordingly. The enhancing mechanism in the compressive strengths can be properly explicated using the microbuckling model.