Adhesion of High Temperature Thermoplastic Composites

Julien Avenet (1) , Thomas Cender (2) , Steven Le Corre (1) , Jean-Luc Bailleul (1) , Arthur Levy (1)

1 LTeN - Laboratoire de Thermique et d’Energie de Nantes
2 Sabanci University - Faculty of Engineering and Natural Sciences

Thermoplastic composites offer new manufacturing prospects, thanks to the ability to melt the matrix. Welding, tape placement, 3D printing, overmoulding, or even stamping involve adhesion of the thermoplastic polymer at high temperature. One of the leading mechanism that enable to build up strength of adherent over the substrate is called healing. It is classically described as the diffusion of the macromolecular chains across the interface that enable bridging. In continuous processes, such as some which are used in advanced manufacturing of aerospace structures, cycle times are very short. Thus, it is unclear how suitable these materials are for fast continuous processesthe limiting factor being the time required to gain adhesion. In order to model and predict such processes, a controlled welding bench was designed enabling very short welding times (~5 seconds). The mechanical adhesion between coupons was assessed by fracture of the welded interface via double cantilever beam fracture test. The welding kinetics were observed for the initial stages of healing with a behavior that should fit the 1/2 trend. From this, it was possible to compare the accuracy and repeatability of interface healing at short time scales to that of samples which were closer to fully welded. Concurrently, the reptation of the polymer melt was assessed on a commercial rheometer, by computing relaxation time from the viscoelastic response. The correlation confirms that the mechanical quality is associated with the macromolecule diffusion. It was also observed that for high temperature thermoplastics, reticulation occurs, which inhibits molecular diffusion and increases the relaxation time. The major implication is that the preprocessing of the polymer will impact the subsequent adhesion step. For example, plates processed with an autoclave for a couple of hours would require a welding time an order of magnitude longer than the adhesion of a virgin prepreg in the tape placement process.

Mots clés: Thermoplastic; Composite; Welding; Kinetic; Experimental

Domaines: Thermique [physics.class-ph]

Julien Avenet, Thomas Cender, Steven Le Corre, Jean-Luc Bailleul, Arthur Levy. Adhesion of High Temperature Thermoplastic Composites. 23rd International Conference on Material Forming, ESAFORM 2020, May 2020, Cottbus (virtual), Germany. pp.925-932, ⟨10.1016/j.promfg.2020.04.284⟩. ⟨hal-02865278⟩