The DIRIS (DIrectionally Reinforced Integrated Stretched Single yarn) structure is a polymer composite, isogrid sandwich structure. A core or panel is built initially and by successive bonding of cores a 3-D (support) structure is created, reinforced along all of its principal directions with a single, stretched CF reinforced tape. The patented manufacturing concept (EP1950034) is based on autogenous bonding of PEEK or PEK reinforced sheets, without intervention of another binding material (P. Michelis & V. Spitas, Composite Science & Technology, 70 (2010) 1064-71).

  • The panel consists of the preform (the skeleton 1), the stereo cells (the columns 2) and the facing sheets The DIRIS core consists only from the preform and the cells is characterized by the following outstanding properties :

Density : 0,18 gr/cm3, Compressive strength : 9,54 MPa, Specific strength : 53 MPa/gr/cm3, Shear strength : 4,77 MPa, Stiffness-to-weight-ratio: 1010 N/mm/gr
E=0,54 GPa, G=142 MPa
For dimensions : 159 x 71 x 16,5 mm3 :
Loss factor : n = 0,12, nat. frequency : 192 Hz

  • The DIRIS structures are built by bonding successive DIRIS cores or panels (modules). For each application the size of the cell, the number of the cells and their distribution is numerically defined.
  • Vibrational and hysteretic experiments on DIRIS structures revealed that, on top of the high inherent visco-elastic damping of PEEK/CNT and PEEK/CF sheets, the structure design is adding an important contribution. This is due to the fact that it imposes a significant shear straining to an extensive part of the structure. The DIRIS panel and structures were examined for building the exterior of spacecrafts/airplanes and were used for building demanding light-weight load carrying components for small and large structures, including seismic tables (p. Michelis, Smart Structures & Systems, 9(1012).