A simple repair method for GFRP delamination using ultraviolet- curable resin
Limin Baoa*, Takuya Okazawaa, Anchang Xub and Jian Shic
aFaculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda-shi, Nagano Prefecture 386-8567, Japan; bCollege of Textile Science and Engineering, Wuhan Textile University, 1st FangZhi Road, Wuhan 430073, P.R. China; cFaculty of Systems Science and Technology, Akita Prefectural University, 84-4 Ebinokuchi Aza, Tsuchiya, Yurihonjo-shi, Akita
Prefecture, Japan
Abstract
Fiber-reinforced plastic (FRP) composites are widely used in engineering because of their high strength and light weight in comparison to monolithic metal alloys. They are mostly used in laminate form and are stronger within layers than between layers,
making them prone to cracking and peeling. This type of structural degradation can be dangerous during operation. For this reason, research on FRP composites with the ability to self-repair has attracted much attention. In this study, we developed a
new method to repair glass fiber-reinforced plastic (GFRP) composites by using ultraviolet-(UV) cured resin. As GFRP composites are UV transmissive, the repair process can be carried out externally by exposing the damaged part to UV light. The transmittance of EP GFRP is about 40%. Holes were pre-drilled with wires in order to facilitate the injection of UV resin between the layers of the composite, and this process was accomplished without degrading the mechanical properties of the material. A double cantilever beam (DCB) test was performed on the GFRP composite to induce interlaminar fracturing. UV-curable resin was then injected between the layers of the composite through a series of pre-drilled holes. Following this repair, the DCB test was performed again to evaluate the repair rate. A compressive after impact (CAI) test was also performed on the GFRP composite to induce delamination. Compressive strength before and after the repair was also evaluated.
Keywords: GFRP; repair method; ultraviolet-curable resin; DCB test; CAI test
Effect of matrix ductility on fatigue strength of unidirectional jute spun yarns impregnated with biodegradable plastics
Hideaki Katog ia*, Yoshinobu Shimamurab, Keiichiro Tohgob, Tomoyuki Fujiib and
Kenichi Takemuraa
aDepartment of Mechanical Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama, Kanagawa 221-8686, Japan; bDepartment of Mechanical Engineering, Shizuoka University, 3-5-1 Johoku, Naka-ku, Hamamatsu, Shizuoka 432-8561, Japan
Abstract
Natural fiber-reinforced composites are carbon-neutral materials that are anticipated for use as an alternative to glass fiber-reinforced plastics. This study investigated the effects of matrix ductility on the fatigue strength of unidirectional jute spun yarns
impregnated with biodegradable plastics. Polylactic acid (PLA) and polybutylene succinate (PBS) were used for the matrix. PLA is brittle, but it is widely used as a matrix of green composites. Because PBS has much higher ductility than that of PLA, it can be expected to have higher fatigue strength when subjected to the same strain amplitude as PLA. Fatigue tests were conducted with maximum stress set to 40–90% of the tensile strength. The stress ratio was set as 0.1. Results show that the matrix ductility strongly affects the fatigue strength and the fatigue mechanism of the composite. A matrix with better ductility was effective to improve fatigue strength.
Keywords: jute spun yarn; unidirectional reinforcement; fatigue; biodegradable plastics; PLA; PBS
Improved adhesion between nickel–titanium SMA and polymer matrix via acid treatment and nano-silica particles coating
Bi n Yanga*, Yongchao Zhangb, Fu-Zhen Xuana, Biao Xiaoa, Liang Heb and Yang Gaoa
aSchool of Mechanical and Power Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai, 200237, China; bCollege of Aerospace and Civil Engineering, Harbin Engineering University, Harbin, China
Abstract
Shape memory alloy (SMA) composites are the desirable candidate for smart materials that used in intelligent structures. However, the overall mechanical performance of SMA composites depends immensely on the quality of the interaction between
SMA and polymer matrix. Therefore, it is necessary to find out an approach to enhance the interfacial property of this composite. In this paper, we modified nickel–titanium SMA wire with nano-silica particles before and after acid treatment. The modification effect on the interfacial strength between SMA and epoxy resin was evaluated. Contact angle analysis, scanning electron microscopy (SEM) observation, and single fiber pull-out test were carried out. The bonding characteristics between modified wire and liquid/cured resin were investigated. We then embedded SMA wire into woven glass fabric/epoxy composite laminates, and manufactured this hybrid composites via vacuum assisted resin transfer molding processing. Three-point-bending test of the hybrid composites was performed to validate the modification effect. Fiber pull-out experiment demonstrates that the interfacial shear strength increases by 6.48% by nano-silica particles coating, while it increases by 52.21% after 8 h acid treatment and nano-silica particles coating simultaneously. For hybrid composites, flexural strength of the two specimens increases by 19.8 and
48.2%, respectively. In SEM observation, we observed large debonding region in unmodified composites, while interfacial adhesion between modified wire and epoxy keeps strong after flexural damage.
Keywords: shape memory alloy; surface modification; interfacial adhesion strength; SMA hybrid composites; fiber pull-out test
Optimal fiber distribution for tensile properties of injection molded composite
Dong-Joo Lee*
School of Mechanical Engineering, Yeungnam University, Gyungsan 712-749, South Korea
Abstract
The survival rate of a composite is the residual fiber length divided by the initial fiber length, and it decreases with the initial fiber length and fiber volume content ( Vf) during injection molding processes. The degree of damage is higher for carbon fiber than for glass fiber, and the survival rate increases with a hyperbolic tangent relationship as the nozzle diameter increases. Higher survival rate corresponds to a stronger material. Five different lengths of fiber with 29 different size fibers were selected based on the distribution and shape of residual fiber in experimental works. These were examined to study the effects of fiber distribution on the tensile properties of a short-fiber reinforced composite (SFRC). Compared with the experimental results, the modulus predicted using the Halpin-Tsai relation shows reasonable agreement with the prediction obtained using the residual fiber length instead of the initial fiber length. It was found that the tensile modulus and strength generally differ by a factor of up to 3.2, depending on the fiber distribution patterns with Vf = 30%, and the trend is more significant as the fiber aspect ratio increases. The interactions between the fiber and matrix and the staggered-type distribution are the most important factors in the reinforcement of the SFRC. With the same combination of short fiber length, an optimized fiber distribution pattern is suggested.
Keywords: fiber aspect ratio; damage during injection molding; fiber distribution; tensile strength and modulus; prediction
Rayleigh waves at the boundary surface of modified couple stress generalize d thermoelastic with mass diffusion
Rajnees h Kumara*, S.M. Abo-Dahabb,c and Shaloo Devid
aDepartment of Mathematics, Kurukshetra University, Kurukshetra, India; bMathematics Department, Faculty of Science, Taif University, Taif, Saudi Arabia; cMathematics Department, Faculty of Science, SVU, Qena, Egypt; dDepartment of Mathematics & Statistics, Himachal Pradesh University Shimla, Shimla, India
Abstract
In this problem, we have studied propagation of Rayleigh waves in an homogeneous isotropic modified couple stress generalized thermoelastic with mass diffusion solid half space in the context of Lord–Shulman (L-S), Green–Lindsay (G-L) theories of thermoelasticity. Secular equations are derived mathematically by using appropriate boundary conditions. The values of determinant of secular equation, Rayleigh wave velocity and attenuation coefficient with respect to angular velocity for different values of wave number and relaxation times in the absence and presence of mass diffusion, are computed numerically. The numerical simulated results are depicted graphically for copper material.
Keywords: Rayleigh waves; modified couple stress theory; thermoelastic diffusion; Rayleigh wave velocity; attenuation coefficient
