Issue 29

M. Romano et alii, Frattura ed Integrità Strutturale, 29 (2014) 385-398; DOI: 10.3221/IGF-ESIS.29.34 396 characteristic fractured surfaces of the penetrated specimen. Whereas the top row shows the fractured surfaces on the impact side the bottom row shows the fractured surfaces on the opposite side. The specimens that only contain carbon fibres show a distinct contour due to the penetration on the impact side. The distinct contour can be interpreted as a die-cutting effect because of the relatively high stiffness of the carbon fibre reinforced material. On the opposite side a splinted surface due to brittle fracture can be observed. Due to the typical opaque property for carbon fibre reinforced plastics interlaminar delaminations are not visible yet exising. In contrast for the glass fibre reinforced specimens the interlaminar delaminations are cognizable due to the transparency of both the fibres and the matrix system. On the opposite side of the impact a clearly outlined delamination area can be identified between the last two single layers. Comparing the delamination areas on the impact side to the area on the opposite side a conical spreading of the delamination areas through the thickness can be assumed. Due to the [(0/90) n ] layups with equilibrated twill fabrics and the rectangular form of the free part of the specimen in the test panel mounting the delamination has a slight rectangular shape, too. Furthermore the lateral dimensions of the delamination on the opposite side of the impact are approx. 28 mm x 25 mm. Because the visible delaminated area is considerably smaller than the free part of the specimen in the test panel mounting the assumption that the boundary conditions are negligible can be confirmed. For the basalt fibre reinforced material the interlaminar delaminations are not clearly identifiable due to the opaque optical properties of basalt fibres. Confronted to the glass fibre reinforced material the interlaminar delaminations on the opposite side of the impact can slightly be discerned. Because of the slightly unbalanced construction of the basalt fabric the delamination on the opposite side of the impact is distinctly rectangular with lateral dimensions of approx. 25 mm x 15 mm. The contour due to the penetration on the impact side of the hybrid layups without separating layer are similar to the contours of the specimens that only contain carbon fibre reinforcement. On the opposite side of the impact the basalt fabrics cause a fine extensive fractured surface. On the opposite side of the impact the interlaminar delamination between the last single layers of basalt fabrics can slightly be discerned. Regarding the hybrid layups with separating layer the contour due to the penetration on the impact side is shaped like the ones of the hybrid layups without separating layer or the purely carbon fibre reinforced material. On the opposite side of the impact the hexagonal structure of the core material is slightly visible. The fractured area can be identified to be slightly smaller compared to the hybrid specimens without separating layer. 10 mm 10 mm 10 mm 10 mm 10 mm 10 mm 10 mm 10 mm 10 mm 10 mm Figure 7 : Characteristic failure modes of the different kinds of layups: From left to right: C (carbon), G (glass), B (basalt), C+G+B and C+G+Hex+B (Top row: Impact side, Bottom row: Opposite impact side).