STATIC EXPERIMENTAL TESTING OF U-TYPE COMPOSITE SEGMENTS ENERGY ABSORPTION

The paper presents the static experimental testing of U-type (channel section) composite segments energy absorption. The segments have the overall dimensions b × h = 100 × 80 mm, rounded corners and damage initiators at their edges. The segments have been made in nine variants with respect to stacking sequence and laminate thickness. The matrix constitutes Polimal 104 N-1 P/p-503 polyester resin, i.e. elasticized and incombustible Polimal 104 resin produced by Organika-Sarzyna Co., Poland. Three types of stitched E-glass fabrics produced by Owens Corning Co., USA were used as reinforcement, i.e. D-610 (Weft 90° , uniaxial fabric [90], 607 g/m), CD-600 (Biaxial, fabric [0/90], 610 g/m), and CDDB-1200 (Quadriaxial, fabric [0/45/90/-45], 1213 g/m). Static experimental tests were performed on a SATEC 1200 testing machine, with pressure force and punch displacement under registration (kinematic excitation at 2mm/min velocity). The failure processes were recorded using a PHANTOM v12 video camera. The tests were performed on segments of 400 mm or 200 mm length due to laminate thickness, using a problem-oriented test stand in which 5 composite panels were placed in parallel. The static testing of U-type segments energy absorption focussed on the quasi-optimal stacking sequence and thickness selection. In order to perform such investigations, the following optimization criteria were adopted: 1) failure level with respect to the following mechanisms: progressive crash, delamination failure, buckling failure, catastrophic failure; 2) maximum relative energy absorption. The tests performed for subsequent segment types have been illustrated with compression force vs. punch displacement curves. The figures showing segment failure mechanisms at selected positions of the punch are presented as well. The maximum values of compression force initiating the failure processes, absorbed energy and absorbed relative energy values are set up, with an estimation of the parallel failure mechanisms level. The energy values are calculated for punch displacements belonging to the interval 0÷50 mm. For further dynamic research, U/LE3 segments with a 8xD-610 stacking sequence and [90]8 ply angles have been chosen as the authors’ preferred solution. These segments are characterized by the highest relative energy absorption, dominant progressive crash and F-s failure curve adjusted to a typical blast pressure impulse.