Abstract
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.
Highlights
Thermoplastic (TP) composites are preferred due to their excellent damping, impact, fracture toughness, recyclability properties and their ability to be fused or welded to itself or with other materials.Thermoplastic resin has an inherent ability to soften once heated above the defined temperature range and retain their properties once they are cooled down
Samples were welded at the lower weld time and lower pressure at 100% amplitude, but the same phenomenon was observed
Novel carbon Elium® composites with integrated energy directors were successfully manufactured and an experimental study on the influence of different parameters such as weld time, weld pressure, amplitude, ED type, etc. on the weld strength was conducted
Summary
Thermoplastic (TP) composites are preferred due to their excellent damping, impact, fracture toughness, recyclability properties and their ability to be fused or welded to itself or with other materials.Thermoplastic resin has an inherent ability to soften once heated above the defined temperature range and retain their properties once they are cooled down. Thermoplastic (TP) composites are preferred due to their excellent damping, impact, fracture toughness, recyclability properties and their ability to be fused or welded to itself or with other materials. The major drawback of using the former is that composites are susceptible to high-stress concentration generated due to the holes and its labor intensiveness whilst the latter requires an incredibly longer curing time as well as the longer surface preparation [1,2]. Both of the conventional approaches of joining hinders the realistic chances of achieving shorter production cycles and are not suitable for automation processes. The most feasible welding techniques available for fusion bonding of thermoplastic composites are resistance [7,8,9], induction [8,10,11,12,13,14,15] and Materials 2020, 13, 1117; doi:10.3390/ma13051117 www.mdpi.com/journal/materials
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