Predictive Thermal Modeling and Characterization of Ultrasonic Consolidation Process for Thermoplastic Composites

Abstract

Ultrasonic consolidation (USC) of thermoplastic composites is a highly attractive and promising method to manufacture high-performance composites. This work focuses on USC of dry carbon fiber (CF) fabrics with high-temperature polyphenylene sulfide (PPS) films. Experimental trials to assess feasibility of the process are time-consuming. Consequently, a predictive thermal model would facilitate process parameters selection to reduce expensive trial-and-error approaches. This paper presents a 2D finite element model of samples under consolidation, incorporating equations for viscoelastic heating, matrix phase change, and material properties. Theoretical temperature profiles for nodes of interest were compared to the corresponding experimental temperature curves for various control parameters (i.e., weld time and vertical displacement of sonotrode) and showed good agreement during heating phase. It was found that welding time values below 1750 ms were insufficient to reach melting temperature, whereas weld times above 3000 ms led to the lowest average void content (2.43 ± 0.81 %). More specifically, the time the material spent above melting temperature, i.e., residence time, was established as a parameter that could estimate cases resulting in better consolidation and lower void content (time above 2600 ms for void content below 2.5%). XRD characterization revealed that the USC process led to mostly amorphous PPS, due to the high cooling rates (70 °C/s to 108 °C/s). Overall, the thermal model and micro-structural outcomes confirmed the feasibility of the USC process for layered composites made from dry fabric and high-temperature thermoplastic films.

Theoretical Assessment of the Environmental Impact of the Preheating Stage in Thermoplastic Composite Processing: A Step toward Sustainable Manufacturing

“…Similarly to the boundary cases, we use an explicit finite difference formulation to solve this particular partial differential equation. Equation (20) outlines the explicit finite difference formulation applicable to the interior nodes of the composite laminate during the conductive and convective modes of preheating:…”

“…For this study, the preheating stage of the thermoforming process for fiber-reinforced thermoplastic polymer composites is analyzed because of the high energy consumption associated with this stage of thermoplastic composite processing. The heating stage of thermoforming processes has been extensively investigated in the literature [19][20][21]. Längauer et al [19] developed an enhanced model for the infrared heating of thermoplastic composites, highlighting that the accuracy of simulation results can be improved by incorporating anisotropic thermal conductivity and temperature and pressure dependencies of specific heat capacity.…”

Application of Neural Network Models with Ultra-Small Samples to Optimize the Ultrasonic Consolidation Parameters for ‘PEI Adherend/Prepreg (CF-PEI Fabric)/PEI Adherend’ Lap Joints

“…Ultrasonic welding (USW) of laminated polymer composites has been implemented in many high-tech industries (primarily aerospace) [ 15 , 16 ]. To form reliable welds, numerous USW parameters have to be optimized [ 17 , 18 ], including ultrasonic (US) frequency, amplitude of sonotrode vibration, clamping pressure, USW duration, duration of clamping after USW, etc. These parameters are the input data for the USW process [ 19 ], while its efficiency can be controlled by one output factor, namely the USW joint thinning, taking into account the need to insert an energy director (ED) between joined plates (adherends) [ 20 ].…”

Effect of the Energy Director Material on the Structure and Properties of Ultrasonic Welded Lap Joints of PEI Plates with CF Fabric/PEI Prepreg

“…Information on fiber-reinforced PEI lap joints might be found elsewhere in [15][16][17]. -Preliminary consolidation of carbon fiber (CF) tapes with (thermoplastic) polymer films upon the formation of semi-prepregs or automated fiber placement (AFP) [18,19].…”