Biocomposite is an innovation of renewable material in engineering made

The fatigue and fracture mechanism of C/C composites material was investigated in notched and smooth specimen. Also, the initiation and growth behaviors of cracks were continuously observed. Specially, the phenomenon of fracture constraint in notched specimen was discussed. This phenomenon was related to the crack growth behavior and shear damage in the matrix. In the present study, fatigue limit was defined by the critical stress level that the specimen was not broken even after applied 1x106 stress cycles. When the fatigue life was longer than 1x106 stress cycles, the initiated crack was stopped to growth after reaching some critical length. Also, the density of crack initiation was low. When the fatigue life became shorter than that, the cracks extended rapidly and coalescences of cracks were observed. The crack growth behavior was strongly related to the fatigue limit and unstable fracture conditions. Also it is found that the compliance or elastic modulus of the specimen was related to residual fatigue life. Now, an observation of crack in C/C composites was performed effectively in the present study.

The fatigue and fracture behavior of C/C composites fabricated using fine-woven carbon fiber laminates with α = 0/90 • direction were investigated. Also, the phenomenon of crack growth behavior and the shear damage in the fiber bundle was discussed. Slits of several sizes were cut on both sides of a test section and different sizes of slit length were chosen. The effect of the slit configuration on crack initiation and growth behavior was observed. Specimens with blunt-notches and center-holes were also used to compare the fatigue strength and crack growth behavior. Non-propagating cracks were observed and fatigue limit was defined as the maximum stress at which specimen did not break for N = 10 7 cycles stress application. The longest fatigue life was obtained in the case of specimens with shorter slits. The relationships between fatigue strengths and specimen shapes were analyzed by stress concentration, Kt, and stress intensity factor, K I . The effect of slit configuration on fatigue strength was then discussed regarding both the experimental and calculated consequences.

The fatigue and fracture behavior of C/C composites fabricated using fine-woven carbon fiber laminates were investigated in several notched and smooth specimens. Slits and notches were cut in some specimens, and the effect of fiber direction and notch configuration on the fatigue behavior was examined. Axial load or bending moment was applied, and the fracture strength and the fracture mechanism were investigated. The fatigue limit was dependent on stress ratio, fiber direction and notch configuration. It was found that the fatigue limit and tensile strength of the notched specimens were higher than those of the smooth specimens. So, the fracture behavior of the material was different from metals and plastics. The local interlaminar debonding of fiber sheets and local shear deformations are important factors in the evaluation of static and fatigue strength.

Fiber metal laminates (FML) are composite structures fabricated by combining two layers of surface material with core material. The outer surface of FML used in this composite is Aluminum with Al 1100 type. The FML core material uses carbon fiber. The fabrication process of the composites utilizes vacuum infusion method, in which the resin is infused into the mold with vacuum condition. Bonds between the core and the surface layers are the variables affecting the strength of FML. In this research, the method used to increase the bonds between layers in FML was mechanical method, it's called mechanical bonding. This method involved providing roughness (Ra) on aluminum surface using sand blasting process to produce different roughness variables, with roughness value of 1,68 μm; 1,78 μm; 1,93 μm; 2,128 μm and 2,887 μm. The aim of this study was to examine the impact of aluminum surface roughness to tensile strength of fiber metal laminates composites. The highest tensile strength of FML was obtained at 2,887 μm with a value of 367 MPa.