The Effect Of Structural Characteristics On Axial Compressive Performance Of Carbon Fibre/Epoxy Cylinder

As an important structure components, carbon fiber composite cylinder were widely used in aerospace, such as the aircraft’s thrust tube, the rocket fairing, the rocket motor case. Among them, the big load compression is the basis of various structural design and preparation. Generally speaking, it is necessary to ensure that no failure damage occurs, and the structural deformation should be controlled within the allowable range under the big load. The compressive strength and compressive modulus are the most basic indicators that are used measure the performance. The mechanical properties of composite materials are anisotropic due to the directivity and complexity of the structure which makes the problem of the fracture, fatigue and strength entangled. The process includes a series of complex failure mechanism. Such as fiber breakage, interfacial slip, separation and frictional contact, yield and cracking of the matrix. Therefore, destruction problems are worth deep studying. Based on the basic characterization of the resin matrix and composite, this paper studies the influence of geometry construction, winding angle, pre-crack angle and functionalized carbon nanotubes on the axial compression performance of the composite cylinder and reveal the influence mechanism. It provides the theoretical guidance and experimental data for actual project of the composite cylinder.1. This paper studies the mechanical properties of the resin casting body, one-way slab carbon fiber composite, NOL ring tensile process by finite element analysis. We also discuss the the effect of geometry in axial compression of the composite cylinder. The results show that strain of the fracture regino is the largest under the NOL ring tensile precess by finite element analysis and the wound size makes the cylinder axis compression performance optimization when the aspect ratio is2to1. The problem of stress concentration in the cylinder ends was overcome by reinforcing layer which improved cylinder axial stiffness significantly.2. This paper studies the effect of winding angles on axial compressive performance of carbon fibre/epoxy cylinder. The universal testing instrument is used for compression testing. The compression failure mechanism of the cylinder is analyzed by SEM, OM, finite element analysis and compressive testing. With the winding angle increasing, the axial stiffness of the cylinder will decrease gradually and the failure mode change from brittle fracture to the transverse shear damage. Finite element analysis shows that when the cylinder winding angle reach to45°, the radial displacement becomes maximum, and then the local muster characteristics happened. With the increase of the winding angle, the interlaminar shear stress reduced in the beginning, and then became increased. It achieves the minimum value at the40°which is consistent with the predicted failure mode.3. This paper studies the effect of pre-crack angles on axial compressive performance of carbon fibre/epoxy cylinder.If the pre-crack angle add, the mechanical properties of the cylinder will reduce in the beginning, and then become increased. Through the micromechanics analysis, when the pre-crack angles are close to the winding angle, the cracks occur offset after reaching the interface. Otherwise, the penetration of the crack play a major role. At the same time, from the simulated compressive strain maps, we found pre-crack region is the maximum strain value and failure paths is same with the strain distribution path.4. The groups and morphology of the functionalized carbon nanotube were characterized by SEM, FT-IR, XPS. The results prove that the hydroxy and amide have been successfully grafted onto acidification carbon nanotubes and amino carbon nanotubes respectively. Mechanical testing showed that the functionalized carbon nanotubes make the cylinder compressive stiffness improved significantly.