Adhesive bonding of composite parts for space rockets

Metering and mixing system for a process-stable processing of two-part epoxy

Space rockets have to withstand extreme forces. Composite parts provide an effective solution, as they are very robust and resilient. A specialized and leading Europan company produces composite technology payload fairings on top of these rockets.These stage adapters connect the first and the upper stage or the upper stage and the spacecraft. The payload fairings protect the payload as it exists Earth’s atmosphere. The composite parts are based on aluminium honeycomb cores with carbon reinforced plastic face sheets.

Requirements: 
Due to the high temperatures and dynamic pressure changes experienced by the fairing, as well as the high costs of the payloads therein, a high level of quality management in production is required. The company use a two-part epoxy adhesive that is applied to various configurations of the payload fairing (access doors). Both materials have high densities and are paste consistency, requiring high filler content in order to withstand the extreme environments that the product experiences. 

Until now, the materials were metered and mixed together manually. The pasty materials are difficult to mix together effectively by hand. This process creates voids and air pockets in the material that make it more difficult to apply the material. The high density and filler content of both materials also make the materials abrasive, which can be difficult to process.

Solution:
Due to these material characteristics, a reliable machine with precise and process-stable metering and mixing is required. METER MIX® provided the customer a PAR 20C piston pump metering and mixing system with special hardened pump assemblies and mixer valve to protect the machine parts against the abrasive material. The machine also includes low-level sensors, so fresh pails of new material can be loaded and there is minimal downtime between changing batches of material. 

With the PAR 20C machine, the customer eliminates the need to meter and mix the material by hand. The material is metered and mixed faster and with greater efficiency, allowing operators to ensure the correct manual application of the adhesive without having to determine if the adhesive is mixed effectively. This dramatically cuts the cycle time of the bonding and sealing step in the payload fairing production, while ensuring higher quality mixed adhesive. The process reliability was increased and ensures a high reproducibility in future.