Co-authors​ :

 Faranak BAHRAMI (UNITED KINGDOM), Saeid DASHATAN (UNITED KINGDOM), Mihalis KAZILAS (UNITED KINGDOM), Andrew DAVIDSON , Derek SIMPSON , Sam WILSON , Panos SYFALAKIS , Dimitrios KARAGIANNIS (UNITED KINGDOM) 

The aim of this project (Thermally Assisted Piercing of Composite Acoustic Liners (TAPACO)) is to address the challenge of manufacturing lightweight acoustic liners utilising thermoplastic composites to replace current thermoset solutions. State-of-the-art liners are mainly made of thermoset composites and the perforation is done by drilling or robotic laser heads. The main limitation is the cutting of the load-bearing fibres during drilling which results in structural performance loss. To compensate for this, the perforated sheets must be thicker with a weight penalty of 15-20%. At the end-of-life, thermoset materials are difficult to recycle and end up in land fields, contributing to a serious environmental problem. In the TAPACO project the consortium is looking at an adaptation of TAP process for the application of noise attenuation of the aircraft engine. The reduction of noise from aircraft engines has had an increased focus over many decades. Engine nacelle features have a part to play in sound attenuation and a key part of the design is the incorporation of perforated skins in various parts of the structure. The perforate density (holes per unit area) is set by a combination of parameters to attenuate certain frequencies. This includes perforate diameter and pitch which defines the percent open area. Typically, many hole diameters/pitches can be specified according to the engine noise characteristics. Hole diameters of 1.0mm can dictate hole densities of 30k to 50k per square meter and this density increases if the hole diameter reduces. These higher numbers dictate the need for efficient processes that do not cause detriment to the skin’s mechanical properties. Thermoplastic perforated composites form another suite of materials of interest. While known for many years, they have failed to develop at scale in the commercial aircraft industry with limited applications. Thermoplastic composites however are the subject of this paper as their attraction is they have inherent toughness, a useful attribute for perforates. The TAP process utilises the capability of thermoplastic composites to melt and reshape upon heating to their processing temperature. During this process, the fibres are displaced rather than cut. The development of the TAPACO system consists of various stages. At the end of each stage, modifications take place and the coupon dimensions and number of perforations increase. In this project, four different categories have been considered. The hole diameter for all these coupons is 0.65 mm. It is expected that coupon (d) shown in Figure 2 will have approximately 1200 holes, created using the TAP process. At this stage of the project, coupon categories A and B have been achieved, and the work is now focused on coupons C and D. Based on the experimental work it was found that the temperature is one of the key factors in obtaining a good quality hole. Hence, Abaqus was used to predict the temperature distribution in the sample