TY - CONF A1 - Marotzke, Christian A1 - Feldmann, Titus T1 - Fracture of fiber reinforced materials under off-axis loading N2 - The failure behaviour of unidirectional plies tested under off-axis loading is studied. The stress distribution occurring in standard off-axis tests is briefly discussed. The different failure modes, this is, pure fiber breakage, pure inter fiber failure as well as a superposition of both is analysed based on test data and fracture patterns. The large difference of the failure load depending on the failure mode at small off-axis angles is studied by comparison of a short and a long 3° off-axis angle specimen. T2 - APCF/SIF-2014 - Asian-Pacific conference on fracture and strength / International conference on structural integrity and failure - Recent advances in structural integrity analysis CY - Sydney, Australia DA - 09.12.2014 KW - Debonding KW - Off-axis strength KW - Fracture mechanics KW - Composite materials PY - 2014 SN - 978-0-08-100203-2 SN - 978-0-08-100225-4 SP - 351 EP - 355 PB - Elsevier AN - OPUS4-32324 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - 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 -