Deformation Mechanism and Bending Limit of Textile Composite Tubes in Roll Bending Process.

Abstract

Bending limit and deformation behavior of braided thermoplastic composite tubes by a new roll bending process in thermoforming are studied. The composite tubes with four kinds of initial fiber orientation from 18 to 47 degrees are fabricated by internal pressure bonding method, and used in the experiment. The roll bending process was performed by a newly developed roll bending equipment based on locally heating and cooling technique. Bending radius, fiber orientation, bending strain and circumferential strain of grids are measured. The experimental results show that the bending limit improves with increasing initial fiber orientation. Undesirable deformation occurs easily at inside and side of bent part in the case of small initial fiber orientation. The experimental bending limit agress with the calculated one obtained from geometrical configuration. The bending limit is affected by critical fiber orientation at outside of bent part and undesirable deformation at inside to side areas. It is confirmed that kinematic deformation mode of the braid with small initial fiber orientation in bending process contains not only the trellis effect but also slipping mode which also plays an important role in the roll bending process.