Experimental and numerical evaluation of conduction welded thermoplastic composite joints

B.H.A.H Tijs,M.H.J Doldersum,A Turon,J.E.A Waleson,C Bisagni

doi:10.1016/j.compstruct.2021.114964

B.H.A.H Tijs, M.H.J Doldersum + Show 3 more

Open Access

https://doi.org/10.1016/j.compstruct.2021.114964

Copy DOI

Abstract

The capability of joining two thermoplastic composite parts by welding is a key technology to reduce the weight and cost of assembled parts and enables high volume manufacturing of future aeronautical structures made of thermoplastic composite materials. However, there is not much experimental understanding of the mechanisms involving welded joint failure, and the computational tools available for the simulation of thermoset composites have not yet been completely assessed for thermoplastic materials. In this work, a numerical and experimental evaluation is performed to investigate the strength and failure behavior of conduction welded thermoplastic composite joints. A welded single lap shear joint is designed, manufactured, tested and analyzed proposing two distinct modeling approaches. A simplified modeling strategy which only accounts for damage at the weld is compared to a high-fidelity model which can take into account the physical failure mechanisms at the lamina level. The high-fidelity modeling methodology is able to predict the experimental failure mode of the investigated welded joints with high accuracy and is used to gain new insights into the key-variables that influence the strength of thermoplastic welded joints. It is also found that the joint strength is highly influenced by the failure mechanisms not only of the welded interface but also of the surrounding plies.

Highlights

The use of thermoplastic composite materials is gaining momentum in the transportation sector due to their improved mechanical properties, ‘unlimited’ shelf life and offers a number of advantages that can benefit cost-efficient and high-volume manufacturing
It is found that the joint strength is highly influenced by the failure mechanisms of the welded interface and of the surrounding plies
Evaluation of the experimental results provided new insights into the complex failure behavior of the joint and of the interaction with the failure modes of the laminate

Summary

Introduction

The use of thermoplastic composite materials is gaining momentum in the transportation sector due to their improved mechanical properties, ‘unlimited’ shelf life and offers a number of advantages that can benefit cost-efficient and high-volume manufacturing. Conduction welding is based on heating the surface of the part through an induction heated tool and generating the weld bath by heat conduction through the laminate The benefit of this technique is that it does not require addition of welding specific materials such as energy directors or conductive strips. The technique is more suitable and scalable for welding of large parts and allows for absorbing of manufacturing tolerances like gaps Introducing these fastener-free joints comes with new challenges. It needs to be investigated if the joint strength is influenced by the intra- and interply failure mechanism of the composite material. This may make it difficult to predict the strength of the welded joints without the availability of advanced predictive tools

Objectives

Results

Conclusion