TY - CONF A1 - Marotzke, Christian A1 - Feldmann, Titus T1 - Fracture mechanics of composite plies on microscale N2 - The determination of the strength and the failure behaviour of fiber reinforced composites is a complex task. This is mainly due to the anisotropy and the inhomogeneiety of the material on the microscale. The strength or the fracture toughness of the interface between fiber and matrix is the key factor controlling the failure process on microscale, especially under loads transverse to the fiber axes. The ultimate failure of a laminate is a complex process consisting of a large number of different subprocesses. Due to its highly dynamic nature on one hand and the microscopical scale on the other it is not possible to observe the ultimate failure directly or even to analyse it theoretically. However, long before ultimate failure occurs a large number of elementary failure processes take place in a rather static manner or at least at low crack Propagation speed. T2 - ICCM19 - 19th International conference on composite materials CY - Montreal, Canada DA - 28.07.2013 KW - Fracture mechanics KW - Laminate KW - Interface KW - Debonding KW - Energy release rate PY - 2013 SP - 5354 EP - 5363 AN - OPUS4-28913 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Marotzke, Christian A1 - Feldmann, Titus T1 - Failure of epoxy resins and composites under multiaxial loads N2 - The failure of laminates is originated in plies loaded transverse to the fiber direction, e.g. in the 90° ply of a cross ply laminate. The initiation of failure is due to the debonding of individual fibers At some point the interface crack kinks into the matrix and propagates towards the inter-face of the neighbouring fiber. The cracks then continue propagating through the full ply. The interface failure obviously is the dominating process of the failure of plies in high fiber volume fraction composites. Several authors investigated the interfacial crack propagation on model systems. First, Varna and Paris studied the debonding process on a single fiber embedded in pure matrix under transverse ten-sion by fracture mechanical analyses. Correa and Paris performed experimental as well as numerical studies by calculating the mixed mode energy release rate under different loading conditions. These analyses were extended to fibers surrounded by a composite material by the present authors. Among others, Comninou as well as Sun and Jih have shown that the separation into a mode I and mode II energy release rate is not universal but the mixed mode ratio depends on the length of the crack increment. Comninou developed a solution of an interface crack between dissimilar media which reveals the even a small contact zone is found near the crack tip. As a result, the mode I part of the energy release rate vanishes because no opening of the crack takes place. The contact zone, however, is extremely small. If these mathematical phenomena, however, are relevant for physical problems is not verified. T2 - Thermosets 2013 - 3rd International conference on thermosets CY - Berlin, Germany DA - 18.09.2013 KW - Fracture mechanics KW - Laminate KW - Interface KW - Debonding KW - Energy release rate PY - 2013 SN - 978-3-00-043394-8 SP - 83 EP - 86 AN - OPUS4-29164 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Marotzke, Christian A1 - Feldmann, Titus ED - Milazzo, A. ED - Aliabadi, M. H. T1 - Fracture mechanics of fiber-matrix interfaces in composites under transverse loading T2 - FDM 2013 - 12th International conference on fracture and damage mechanics CY - Sardinia, Italy DA - 2013-09-17 KW - Fracture mechanics KW - Laminate KW - Interface KW - Debonding KW - Energy release rate PY - 2013 SN - 978-3-03785-830-1 SN - 1013-9826 SN - 1662-9809 SN - 1662-9795 SP - 433 EP - 436 PB - Trans Tech Publications AN - OPUS4-29142 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Marotzke, Christian A1 - Feldmann, Titus T1 - Fracture mechanics on microscale of composite plies under transverse loading N2 - The energy release rate delivered during the debonding of a fiber inside a composite ply is analysed using a representative volume element. Two different fiber volume fractions are studied by a linear elastic fracture mechanical analysis by using the finite element method. The dependency of the mixed mode energy release rate on the length of the crack increment is analysed. It is shown that the same general behaviour found in case of a straight Interface crack is valid also for circular cracks. As a result the discrimination of the energy release rate into mode I and mode II portions is questionable. T2 - ECCM16 - 16th European conference on composite materials CY - Seville, Spain DA - 22.06.2014 KW - Composite KW - Interface crack KW - Energy release rate KW - Mode mixity PY - 2014 SN - 978-84-616-9798-4 SP - 0472-1 EP - 0472-8 AN - OPUS4-31133 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -