Advances in Ultrasonic Welding of Thermoplastic Composites: A Review

The ultrasonic welding (UW) technique is an ultra-fast joining process, and it is used to join thermoplastic composite structures, and provides an excellent bonding strength. It is more cost-efficient as opposed to the conventional adhesive, mechanical and other joining methods. This review paper presents the detailed progress made by the scientific and research community to date in the direction of the UW of thermoplastic composites. The focus of this paper is to review the recent development of the ultrasonic welding technique for thermoplastic composites to thermoplastic composites, and to dissimilar materials. Different ultrasonic welding modes and their processing parameters, namely, weld time, weld pressure, amplitude, type of energy directors (EDs) affecting the welding quality and the advantages and disadvantages of UW over other bonding techniques, are summarized. The current state of the ultrasonic welding of thermoplastic composites and their future perspectives are also deliberated.Published versio

On the Mode I and Mode II Delamination Characteristics and Surface Morphological Aspects of Composites with Carbon-Thermoplastic Hybrid Fabrics and Innovative Liquid Thermoplastic Resin

In the current research, the delamination behavior under Mode I and Mode II loading for the hybrid carbon-thermoplastic fabrics in conjunction with novel liquid thermoplastic acrylic Elium® resin processable at ambient conditions was studied. The experimentation by incorporating doublers methodology, studying the performance under Mode I and Mode II loading, and understanding failure mechanisms using surface morphological fractography is deliberated. Hybrid Carbon-Ultra-high molecular weight polyethylene (UHMWPP)/Elium® composite has shown a 22.81% higher GIC and a 22.2% higher GIIC than Carbon-UHMWPP/Epoxy composite. On the contrary, the Carbon_Ultra-high molecular weight polypropylene (UHMWPE)/Elium® has shown an 11.11% higher Mode I critical energy release rate (GIC) and a 7.58% higher Mode II critical energy release rate (GIIC) than Carbon_UHMWPE/Epoxy composite. Hybrid fiber reinforced thermoplastic composites have shown severe plastic deformation of the matrix, rough fracture surface, and micro-cracks on the de-bonding surface, extensive fiber bridging, and crack branching which contributed to the improvement in the delamination behavior. Hybrid fiber architecture is also found to be detrimental by inducing crack arresting mechanisms including the tortuous crack path and the resin-rich pockets path due to the mismatch of the size of the fiber yarns

Investigation on Ultrasonic Welding Attributes of Novel Carbon/Elium® Composites

Joining large and complex polymer–matrix composite structures is becoming increasingly important in industries such as automobiles, aerospace, sports, wind turbines, and others. Ultrasonic welding is an ultra-fast joining process and also provides excellent joint quality as a cost-effective alternative to other joining processes. This research aims at investigating the welding characteristics of novel methyl methacrylate Elium®, a liquid thermoplastic resin. Elium® is the first of its kind of thermoplastic resin, which is curable at room temperature and is suitable for mass production processes. The welding characteristics of Elium® composites were investigated by optimizing the welding parameters with specially designed integrated energy directors (ED) and manufactured using the Resin transfer molding process. The results showed a 23% higher lap shear strength for ultrasonically welded composite joints when compared to the adhesively bonded joints. The optimized welding time for the ultrasonic welded joint was found to be 1.5 s whereas it was 10 min for the adhesively bonded joint. Fractographic analysis showed the significant plastic deformation and shear cusps formation on the fractured surface, which are typical characteristics for strong interfacial bonding

Recent Advances on the Design Automation for Performance-Optimized Fiber Reinforced Polymer Composite Components

Advanced manufacturing techniques, such as automated fiber placement and additive manufacturing enables the fabrication of fiber-reinforced polymer composite components with customized material and structural configurations. In order to take advantage of this customizability, the design process for fiber-reinforced polymer composite components needs to be improved. Machine learning methods have been identified as potential techniques capable of handling the complexity of the design problem. In this review, the applications of machine learning methods in various aspects of structural component design are discussed. They include studies on microstructure-based material design, applications of machine learning models in stress analysis, and topology optimization of fiber-reinforced polymer composites. A design automation framework for performance-optimized fiber-reinforced polymer composite components is also proposed. The proposed framework aims to provide a comprehensive and efficient approach for the design and optimization of fiber-reinforced polymer composite components. The challenges in building the models required for the proposed framework are also discussed briefly

Behaviour of Rectangular Hollow Thin Ply Carbon Thermoset and Thermoplastic Composite Tubes Subjected to Bending

Tubular composites are widely used in many industrial applications, and there is need to use new material and reliable manufacturing processes to improve the performance and process aspects. The current research presents a detailed study to understand the flexure response of rectangular tubular composites based on thin ply carbon fibres and Elium® resin. Another aim was to understand the failure mechanisms of novel tubular thermoplastic composite systems and carry out a baseline comparison with Epoxy-based tubular systems. In the current research, a bladder-assisted resin transfer moulding process was used to manufacture hollow thermoplastic composite tubes, and the bending behaviour of thin ply carbon (TPC) composite parts with novel Elium® (EL) and Epoxy (EP) resin as the matrix material was studied using a detailed experimental study. A testing method with optimized support span and a saddle was used to carry out three-point bending tests on the tubular composite structures. The TPC/EL composite tubes have shown 10% higher bending strength, with a noticeable increase in deformation due the presence of extended plasticity attributes for acrylic Elium resin. Failure mechanisms studied with the detailed microscopic investigation have shown severe catastrophic failure for epoxy-based composite tubes; however, acrylic Elium®-based composite tubes have shown different damage modes such as fibre splitting, resin infragmentation, and fibre resin-interfacial cracking

Ultrasonic Welding of Novel Carbon/Elium® Thermoplastic Composites with Flat and Integrated Energy Directors: Lap Shear Characterisation and Fractographic Investigation

The current research work presents a first attempt to investigate the welding attributes of Elium® thermoplastic resin and the fusion bonding using ultrafast ultrasonic welding technique. The integrated energy director (ED) polymer-matrix composites (PMCs) panel manufacturing was carried out using the Resin Transfer Moulding (RTM) technique and the scheme is deduced to manufacture a bubble-free panel. Integrated ED configurations and flat specimens with Elium® film of different thickness at the interface were investigated for ultrasonic welding optimization. Optimised weld time for integrated ED and flat Elium® panels with film (0.5 mm thick) configuration was found to be 1 s and 5.5 s, respectively. The ED integrated configuration showed the best welding results with a lap shear strength of 18.68 MPa. The morphological assessment has shown significant plastic deformation of Elium® resin and the shear cusps formation, which enhances the welding strength. This research has the potential to open up an excellent and automated way of joining Elium® composite parts in automotive, wind turbines, sports, and many other industrial applications

Effect of PMMA Coupling Layer in Enhancing the Ultrasonic Weld Strength of Novel Room Temperature Curable Acrylic Thermoplastic to Epoxy Based Composites

The joining of composites can be performed in an extremely short time with more energy-efficient ultrasonic welding techniques. The current research investigated the performance optimization of ultrasonic welding of carbon/Elium® composite to carbon/epoxy composite using a polymethyl methacrylate (PMMA) coupling interlayer. The weld strength was quantified by static lap shear strength (LSS) testing. A new methodology was used by creating a PMMA coupling layer on the epoxy composite adherend to achieve an improved interphase and thus enhance the weld properties. The LSS of Elium (EL)-Epoxy (EP) _0.25_0.25 was found to be 190% higher compared to that of EL-EP, confirming the effectiveness of the strategy used for creating an interlayer thermoplastic coupling layer. The time required for welding was optimized to be 2s as compared to 10 min required for adhesive bonding. Scanning electron microscopic images of epoxy and PMMA/Elium matrix interphase were observed to have a rough surface and remained largely unaffected by welding. There was an interphase change further away from the interphase to a rougher texture. There was little to no effect on the penultimate layer on the weld strength, as no interphase change could be observed after welding. Fractography investigation revealed shear cusps, matrix plastic deformation, fiber imprints, fiber pull-out, and good adhesion between matrix and fiber, features seen for configuration with maximum LSS. The current research findings present a way to join Elium® with epoxy composites that could be used in applications that require a selective strengthening, such as in sporting goods and consumer products. Furthermore, a detailed investigation is ongoing to use different filler particles and coupling layers to reach the maximum welding performance

Investigation on ultrasonic welding attributes of novel carbon/elium® composites

Joining large and complex polymer-matrix composite structures is becoming increasingly important in industries such as automobiles, aerospace, sports, wind turbines, and others. Ultrasonic welding is an ultra-fast joining process and also provides excellent joint quality as a cost-effective alternative to other joining processes. This research aims at investigating the welding characteristics of novel methyl methacrylate Elium®, a liquid thermoplastic resin. Elium® is the first of its kind of thermoplastic resin, which is curable at room temperature and is suitable for mass production processes. The welding characteristics of Elium® composites were investigated by optimizing the welding parameters with specially designed integrated energy directors (ED) and manufactured using the Resin transfer molding process. The results showed a 23% higher lap shear strength for ultrasonically welded composite joints when compared to the adhesively bonded joints. The optimized welding time for the ultrasonic welded joint was found to be 1.5 s whereas it was 10 min for the adhesively bonded joint. Fractographic analysis showed the significant plastic deformation and shear cusps formation on the fractured surface, which are typical characteristics for strong interfacial bonding.Nanyang Technological UniversityPublished versionThis research was funded by Nanyang Technological University, Singapore and ARKEMA, Franceunder RCA-18/46 and RIE2020 Advanced Manufacturing and Engineering (AME) domain—Industry AlignmentFund—Pre-positioning polymer matrix composites program

Fatigue response of ultrasonically welded carbon/Elium® thermoplastic composites

Current research aims at investigating the fatigue strength of ultrasonically welded composite joints with novel liquid acrylic thermoplastic Elium®. Fatigue response of the welded joints with integrated Energy Director (ED) and flat Elium® film was investigated and the baseline comparison was carried out with control adhesives. The results showed 10–12% higher fatigue life at 105 and 106 fatigue cycle as compared to the adhesively bonded joints. Fractographic investigation of fractured welded joints showed features such as fibre impingement and shear cusps formation which contributed to strong interfacial adhesion.Nanyang Technological UniversityThis research was funded by Nanyang Technological University, Singapore and ARKEMA, France under RCA-18/46 and RIE2020 Advanced Manufacturing and Engineering (AME) domain–Industry Alignment Fund–Pre-positioning polymer matrix composites program

Ultrasonic welding of novel carbon/Elium® thermoplastic composites with flat and integrated energy directors : lap shear characterisation and fractographic investigation

The current research work presents a first attempt to investigate the welding attributes of Elium® thermoplastic resin and the fusion bonding using ultrafast ultrasonic welding technique. The integrated energy director (ED) polymer-matrix composites (PMCs) panel manufacturing was carried out using the Resin Transfer Moulding (RTM) technique and the scheme is deduced to manufacture a bubble-free panel. Integrated ED configurations and flat specimens with Elium® film of different thickness at the interface were investigated for ultrasonic welding optimization. Optimised weld time for integrated ED and flat Elium® panels with film (0.5 mm thick) configuration was found to be 1 s and 5.5 s, respectively. The ED integrated configuration showed the best welding results with a lap shear strength of 18.68 MPa. The morphological assessment has shown significant plastic deformation of Elium® resin and the shear cusps formation, which enhances the welding strength. This research has the potential to open up an excellent and automated way of joining Elium® composite parts in automotive, wind turbines, sports, and many other industrial applications.Published versionThe authors would like to acknowledge the financial support from the Institute for Sports Research, Nanyang Technological University, Singapore and ARKEMA, France. This research is part of the collaborative project between Nanyang Technological University, Singapore and ARKEMA, France under RCA-18/46 that focuses on the thermoplastic matrix used during resin transfer moulding of structural sports products in mass production