Issue 31

J. Lopes et alii, Frattura ed Integrità Strutturale, 31 (2015) 67-79; DOI: 10.3221/IGF-ESIS.31.06 69 Stainless steel 1.4310 (X10CrNi18-8) [9] is used due to the need of a high yield point of the metallic component and the galvanic corrosion compatibility between carbon and steel. The selected CFRP is 8552/AS4 UD prepreg from Hexcel with 134 g/m 2 , a widely used CFRP in the aerospace industry. The basic properties of these materials are given in Tab. 1. Material Tensile Stiffness E 1 (GPa) Tensile Stiffness E 2 (GPa) Density ρ (g/cm 3 ) Steel 1.4310 [10] 178 178 7.9 CFRP 8552/AS4 [11] 141 10 1.58 Table 1 : Material properties. In order to assess the adhesion between the metal and CFRP two different lay-ups are used. The reference pure CFRP specimens consist of 16 layers UD [0 16 ] whereas for the hybrid specimens the steel layer is positioned as the centre layer [0 8 /St/0 8 ]. To increase comparability, the steel foil is chosen to 0.05 mm, as thin as possible during treatment. These lay- ups result in a laminate thickness of 1.98 mm for the reference beam and 2.03 mm for the hybrid beam. Two plates per treatment method are manufactured and specimens are then cut by diamond sawing. Cure temperature is 180ºC as per prepreg manufacturer’s recommendations. Adhesion performance is evaluated by determination of the apparent inter-laminar shear strength by the short-beam method EN ISO 14130 [12] a three-point bending test. Specimen length is 20±0.1 mm and width is 10±0.1 mm. Fig. 1 shows the dimensions of the hybrid specimen in which the difference to the reference beam specimen is that the steel layer is absent in the reference beam. Figure 1 : Dimensions of the short beam specimen. The testing length, the distance between supports, is 9.9±0.1 mm with a radius of 2 mm. The radius of the loading member is 5mm. A testing machine Zwick 1476 with a maximum capacity of 100 kN was used. The displacement was measured with and LVDT placed in the movable part of the machine with a range of 49.5mm and accuracy below <0.1μm. Fig. 2 shows a schematic representation of the short beam fixture. Figure 2 : Schematic representation of the short beam fixture.