Study On Pultrusion Process For Composite Pipes

Compared to metal pipes, composite pipes meet the requirements of some non-fixed largescale truss structure such as the light weight and convenient transport due to its advantages such as light weight, excellent mechanical property, good corrosion resistance and convenient construction. Composite pipes were fabricated for the largescale truss with the pultrusion process in the paper and the pultrusion technics was investigated systematically which includes that the selection of the resin matrixes, curing system for the resin matrix, mould and installment, fabrication conditions and the comparement between the pultrusion pipes and winding pipes. Conclusions are listed as follows:The vinyl ester resin was adopted as the matrix resin of the composite pipes and BPO and TBPB were used as the initiators of the resin systems based on the requirement of technics properties for the pultrusion and the performance of the composite pipes. With DSC and IR analysis contents of two initiators are 0.6%BPO + 1.2%TBPB and 0.9%BPO + 0.9%TBPB respectively. The fabrication temperature of resin matrix is determined as 140—160℃according to the gel test.The preformation mould, core mould and negative mould were designed according to the features of the pipe structure and the requirements of mould system. Traction holder was designed and the moulds were installed. In order to contract the wall thickness of composite pipe precisely the position of the core mould was adjusted to change the concentricity of core moule and negative mould.The working mechanism of interal release agents was investigated and the optimal content of the interal release agents is 1.0—1.5% according to the results of tests on the mechanical properties of the resin casting body, process stable and surface quality of the composite pipes .The mould temperature and pultrusion speed were investigated based on the resin gel experiments and measurement of gel area length of the mould.The optimal initiators contents were 0.6%BPO and 1.2%TBPB respectively according to the mechanical properties and surface quality, the optimal moulding tempratures are 155/170/150℃, and the optimal prultrusion speed is 0.3 m/min. The compressive and bending strength of the composite pipes fabricated in this condition are 251MPa and 242MPa respectively, and the curing degree is 92%.The effects of the fiber content by volume on the mechanical properties of the pipes was studied and results that the bending and compressive strength of the pipes increases with the increasing of the fiber content by volume.Compared to the winding pipes, the pultrusion pipes exhibit better integrative properties such as high mechanical properties, uniform fiber and resin content distribution and high compact degree.