NASA'S Langley Research Center has developed a new adhesively bonded joint concept for curved and flat panel sandwich architectures. A woven preform, inserted into the seam between sandwich panels, provides a larger total bonding area and multiple load paths for an improved distribution of load through the joint. NASA is able to create structures by joining sections of sandwich panels or curved shells. The new joint provides more durable load transfer and redundant load paths compared to current state-of-the-art adhesively bonded strap joints.
NASA is developing next-generation launch vehicles that will be based on high-performance composite materials and innovative manufacturing methods. As such, NASA uses adhesively bonded joints where possible, instead of mechanically fastened (bolted) joints, to design and manufacture structures. The adhesive joints are typically lighter and distribute loads more efficiently across an interface, while mechanically fastened joints are prone to stress concentrations around the bolts. The new durable redundant joint (DRJ) offers improved safety and load carrying capability for sandwich structures when compared to conventional H-type joints. The DRJ uses a composite preform to connect two ends of a curved, composite sandwich panel to form, for example, a cylindrical vehicle segment.
NASA has performed detailed finite element modeling of the new joint architecture to obtain initial indications for the structural response to a simplified hoop loading. Results indicate that the DRJ provides an improved stress-strain response without a severe mass penalty, peak stresses are independent of the joint overlap length, and the DRJ will redistribute a load to accommodate joint damage or manufacturing defects.
This technology can be used in aerospace applications, joining composites for heavy lift vehicle segments and wing sections or wing boxes. It can also be used in wind power systems for turbine propeller construction.