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Failure load analysis of C-shaped composite beams using a cohesive zone model
Truong, Viet-Hoai,Nguyen, Khanh-Hung,Park, Sang-Seon,Kweon, Jin-Hwe Elsevier 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.184 No.-
<P><B>Abstract</B></P> <P>Delamination-based failure is commonly observed in curved composite structures owing to the significant curvature-induced through-thickness stresses present therein. To gain further insights on this failure mode, we investigated the initiation/propagation of delamination in C-shaped composite beams under an opening load and determined their failure load utilizing a three-dimensional finite element simulation based on a cohesive zone model (CZM). Several cohesive parameters (e.g., initial interface stiffness, cohesive zone length, and interface strength) were examined to construct an optimal CZM for the chosen loading conditions, with all parameters except for mode II fracture toughness (directly obtained from end-notched flexure test results) determined by an extensive literature survey. The predicted beam failure loads were compared with experimental results, with the obtained maximum prediction error of 8.4% indicating good agreement. Finally, the predicted position of delamination initiation was found to be heavily dependent on the ratio of the shear strength to the normal strength of the interlayer.</P>
Delamination analysis of multi-angle composite curved beams using an out-of-autoclave material
Nguyen, Khanh-Hung,Ju, Hyun-Woo,Truong, Viet-Hoai,Kweon, Jin-Hwe Elsevier 2018 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.183 No.-
<P><B>Abstract</B></P> <P>Corners of composite curved beams can easily experience delamination under opening or closing bending moments. Existing literature on the delamination of curved laminated beams, however, is limited to unidirectional and cross-ply laminates with 0° and 90° layers and two-dimensional (2D) plane strain finite element analysis. This study experimentally and analytically investigates the failure behaviors of curved composite structures under four-point bending. Multiangle laminates manufactured using an out-of-autoclave prepreg were examined. A three-dimensional (3D) finite element model was created and analyzed with cohesive elements at the interfaces of adjacent plies. In the experiments, delamination dominated the failure of the curved laminates with several opening cracks. Multiple delamination positions were predicted in the analyses. Double cantilever beam specimens were tested and analyzed for a reference point for selecting cohesive parameters. Several cohesive parameters were selected and discussed. Predicted failure loads matched the experimental results well with 5.8% error when the model simulated a sufficient number of factors of the real test.</P>