Pressure forward bulkheads consisted of different parts requiring an assembly process to get the final structure. Cost reduction can be achieved by using one shot injection technologies where an integrated skin-stiffening pre-form will be injected in one single shot. Further reduction of costs and energy consumption can be achieved by using Out of Autoclave resin systems. This proposal addresses the materials and processes to fulfil the requirements described in the topic description and indicates future trends related to the design and manufacturing of bulkhead manufacturing.
In the framework of the Clean Sky Joint Undertaking Green Regional Aircraft (GRA) a composite forward pressure bulkhead was designed by the National Aerospace Laboratory NLR and Airborne Technology Centre both located in the Netherlands. Based on the requirements provided by the topic leader EADSCASA the bulkhead was designed and two demonstrators were produced using the Liquid Resin Injection (LRI) process.
The project goal, as defined in the CleanSky topic description, can be summarized as follows:
“The essence of the job is to state the bases to come with a cheap but efficient manufacturing process based on LRI to produce a structurally efficient pressure bulkhead concept.”
“Justification should take place through the manufacturing of a demonstrator and correspondent preliminary test of coupons extracted from one of the manufactured specimen.”
Already at the beginning of the project it became clear that due to the high requirements related to the manufacturing tolerances a relatively expensive tooling was needed but that a “one shot” production by using the Liquid Resin Injection (LRI) process was feasible.
The analysis performed during the detailed design phase showed that the strength and stiffness requirements could be fulfilled by a sandwich composite structure but that, to cope with the bird strike requirements an additional 1.5 mm thick Dyneema add-on protection plate was needed.
Measurements performed on both demonstrators showed that the geometrical accuracy for the first demonstrator was just outside the required limits at some locations. Due to improvements made to the tooling the second demonstrator was inside the required geometrical limits.
The measured weight of the demonstrator (excluding Dyneema plate) is 7.7kg which is well below the weight of the aluminium reference, however the addition of the Dyneema plate for bird strike projection increases the total weight to 9kg which is just below the 9.2kg of the aluminium reference. As a remark it can be stated that the composite bulkhead cannot directly be compared to the reference as the area exposed to the cabin pressure is larger.