The Correlation Between Winding Tension And Properties Of Thick-walled Carbon Fibre Reinforced Composite

Filament winding process is an efficient method to fabricate composite revolved body.It has been used extensively in fabricating composite vessels,carbon filament wound composite rings for electric generator and composite tubes.There are a large number of parameters that can affect the performances of composite products,such as filament winding tension,curing cycle and stacking sequence.Filament winding tension is one of the most important parameters that affect the mechanical properties of composite products.The existence of winding tension will lead to hoop pre-stress in composites after processing and will improve rigidity and deformation resistivity of composites.This thesis is on investigating the effect of filament winding tension on mechanical properties of carbon filament wound thick-walled composite.In a filament wound composite part,the outer filament will make a relaxation effect on inner filament which has already wound on the mandrel because of the radial pressure stress caused by winding tension of outer filament.Using uniform winding tension to wind every layer will result in a consequence that the hoop pre-stress distributes unequally in the radial direction of wound composite part.To make the composite part has the best mechanical performance under internal pressure,the pre-stress in each hoop layer needs to be equal with an exact winding tension gradient.In the research work of the thesis,Abaqus software has been employed to construct the finite element model of wound composite to simulate the winding process.First the complex winding mandrel with irregular shape needs to be translated to a cylindrical mandrel for simple calculation and design of winding tension gradient.On the ground of the equations of equal pretension,two winding tension gradients are designed and then simulated using finite element method.It is found that the existed equations aiming to achieve uniform pretension in each winding layer cannot make an ideal hoop pre-stress distribution in wound thick-walled composite part.Modifying the equation and designing a new tension gradient for the wound composite part results in a better distribution in the every winding layer,as the gap of hoop pre-stress of each layer is going to decline.Then a simulation of the composite part under tensile load has been made to confirm the existence of pretension will improve the rigidity of the composite part by declining the radial deformation.Experimental research has also been implemented.Firstly,a new specialized epoxy system has been experimented for winding process with a long processing time.Dynamic contact angle,interface shear strength,gelation time and degree of cure has been investigated and then tensile test has also been conducted for resin casting body and unidirectional composite laminate.After these experiments,a kind of modified aromatic amine curing agent is confirmed to suit the long time winding process as it makes epoxy set off curing reaction under indoor temperature and the rate of curing reaction is also appropriate.And in the winding process of making thick-walled composite ring,two force sensors are used to measure actual the press force between mandrels and then the exact winding tension in the filament.The hoop pre-stress in the composite ring has been calculated with the result of measurement of winding tension and compared with the result of finite element simulation to confirm validity of the finite element model.And the improvement of rigidity and deformation resistivity of wound thick-walled composite ring is confirmed by tensile test in the presence of winding tension gradient.