Hybrid vacuum-robotic forming of reinforced composite laminates

Abstract

A methodology is presented to implement robotic actuators into diaphragm forming of composite laminates. This Hybrid Vacuum-Robotic (HyVR) process is specifically targeted to prevent ‘bridging’ type defects. Examples are presented of successfully forming laminates with deep concave features that would otherwise be impossible by diaphragm forming. The robotically controlled end effectors apply localised pressure to concave regions during the diaphragm forming process. This force application is analogous to the incremental sheet forming process. A generalised methodology is presented which can be applied to develop a bespoke HyVR process for a specific mould. It can then inform what type of end effector should be used and how to apply it within the HyVR process. A key development included in this methodology is the use of the robot to ‘pin’ the laminate to the mould, preventing any unwanted movement. This process could enable automated production of more complex components using diaphragm forming, taking advantage of its lower tooling and equipment costs.

The Intra-Ply Shear Behaviour of Non-Isothermal Thermoplastic Composite Laminates

“…Since a large proportion of the intra-ply shearing occurs in the very final stages of a matched-die process, once no more in-plane bending can be accommodated [24], a significant amount of shearing may occur while under this non-isothermal thermal profile. This behaviour is only exacerbated in alternative forming processes such as diaphragm forming [25] or HyVR hybrid forming [26], in which the slower processing speed results in larger throughthickness temperature distributions. The magnitude of the non-isothermal conditions is, no doubt, influenced by the laminate thickness, an effect that is not captured in the majority of current studies that only investigate single-ply shear behaviour.…”