Tensile behavior of functionally graded braided carbon fiber/epoxy composite material

Primary objective of this research work is experimentally to investigate the tensile behavior of functionally graded braided composite rods. Composite rods were made using tubular braided carbon fiber fabrics and epoxy resin. Functional gradient was achieved by changing the braiding angle continuously along the length direction of the rod. For comparison and analysis purpose, both functionally-graded-braiding-angle composite rods (FG rods) and constant-braiding-angle composite rods (CBA rods, non-FGM) were fabricated. Mechanical properties of these composite rods were determined through tensile tests. From the test results of CBA rods, the effect of braiding angle on the composite properties was established. The data were also,used to analyze the mechanical properties of FG rods. It has been demonstrated that the elastic tensile modulus of a FG rod can be estimated from the elastic tensile moduli of a series of CBA rods. It has also been found that the tensile strength of a FG rod is always higher than the tensile strength of the CBA rod whose braiding angle is equal to the largest braiding angle of this FG rod, although they were originally supposed to be equal based on the results of CBA rods.