Residual stresses developed in thermoplastic composites during laser-assisted tape laying

Anaïs Barasinski,Anna Maria El Bayssari,Damien Guillon,Frédéric Jacquemin,Fédérica Daghia,Mael Péron

doi:10.25518/esaform21.2667

Abstract

The main focus of the study is the determination of residual stresses developed in thermoplastic composites during tape placement. An experimental characterization of the residual stresses is carried out and based on the measurement of the curvature variation with temperature for unsymmetrical laminates. The tested plates are made of APC-2 and processed on the SPIDE-TP, a filament winding machine based in Cetim, France. A thermo-mechanical model based on the modified laminate theory is used in this work. Heat transfer and crystallization are taken into account in the model, allowing the description of the evolution of the mechanical properties of the composite during the whole process. The model is able to predict the residual stresses present at the end of the process. The results showed stress gradients through the thickness of the laminates where the transverse residual stresses can reach up to 20 MPa. In addition, the results showed that increasing the mandrel temperature reduces the crystallization and thermal gradients in the laminate thickness.

Highlights

Thermoplastic pressure tanks and vessels are manufactured with online consolidation processes such as tape placement and filament winding
Other factors can cause the formation of residual stresses such as winding tension, geometric constraint imposed by the mandrel [1,2] and moisture gradients
Above Tg and as previously shown with the Dynamic Mechanical Analysis (DMA) test, a cold crystallization occurs for the specimens fabricated with cold mandrel, this is usually associated with a shrinkage leading to an increase in the curvature

Summary

Introduction

Thermoplastic pressure tanks and vessels are manufactured with online consolidation processes such as tape placement and filament winding These processes are usually associated with high thermal and crystallinity gradients through the parts’ thickness, causing residual stresses that arise during cooling from the processing temperature to the ambient one. Other factors can cause the formation of residual stresses such as winding tension, geometric constraint imposed by the mandrel [1,2] and moisture gradients. Their presence may cause dimensional instabilities, micro cracks, delamination and reduction of the load resistance capability [3]. Their estimation appears as a compulsory stage in the parts design process in order to assess the parts’ reliability under real service and understand the effect of the process conditions on these stresses

Methods

Results

Conclusion