Influence of Deformation of Compliant Rollers on Tape Steering During Automated Tape Placement

Abstract

Automated tape placement with tape steering represents a process to manufacture lightweight composite structures. In our experimental studies, a Mikrosam Tape placement system with laser nip-point heating and a compliant consolidation roller has been used to quantify the limits of steering of continuous and highly aligned short fiber tapes (AS4/PEI with a fiber length of 3 mm). The minimum radius is typically limited by the compressive strain in the fiber direction that will buckle/wrinkle the inner radius of the tape. In the case of the aligned short fiber tapes, order of magnitude reduction in the minimum radius (50-100 mm) has been demonstrated by exploiting the in-plane extensibility of these tapes compared to inextensible continuous fiber (500-1000 mm). The tape deformation and path accuracy during steering experiments has been quantified using DIC methods. These results have indicated that the deformation of the compliant roller during compaction, placement and steering is a major factor. In this study, the deformation of the roller over the full range of consolidation forces (400-900 N) has been quantified to include load-deformation response, and pressure distribution within the contact area. In addition, DIC is used to measure the 3D deformation and strain fields within the roller across the width and circumference as well as to provide insight into the frictional interaction between the rubber surface and the substrate during static loading and constant velocity steering paths. A finite element model of the compliant roller is developed, and a parametric study is conducted investigating the effects of rubber durometer and friction within the rubber/substrate contact area. Relatively good correlation has been achieved using a rubber durometer of Shore hardness 45 in terms of load-deformation response. In the case of steering where the AFP head rotates, a torsional moment is imparted on the roller and the rubber is predicted to undergo shear deformation as well as compression deformation from the consolidation force. Steering of the deformable roller at 25 mm radius is simulated and shows centerline deviations of around 2 mm. To analyze the rubber deformation DIC is conducted during steering and shows that 1000 mm steering radius deforms differently from 25 mm. The results of this study show that the deformation of the roller is an important factor in controlling the tape deformation and critical for accurate path control during steering of the highly aligned short fiber tape with a small steering radius.