In semi automated manufacturing processes of multilayered carbon fiber reinforced composites, defects are induced. These defects cause reduction in service life of the products and lead to decrease in structural performance. In the present work, carbon fiber reinforced epoxy composite laminate with a stacking sequence of [0/0//45/−45/90/45/−45/90/90/−45/45/90/−45/45/0/0] was fabricated by hand lay-up method using vacuum bagging technique. An artificial defect to create pre-delamination was located in this composite between 0° and 45° plies at the centre of laminate. Experiments were conducted in four-point bending to determine the stiffness behavior of composite laminate and study other damage patterns occurred due to the existence of pre-delamination. The probable reasons for occurrence of other damage forms are explained in detail. Three-dimensional digital image correlation (DIC) technique was employed to determine displacements and strains of the specimen. The out of plane displacement due to local buckling against the bending load was also quantified.
PurposeDelamination is a common and crucial damage mode which occurs during manufacturing of layered composites or their service life. Its existence leads to degradation in mechanical properties or even structural failure of composites. Hence, the purpose of this article is to study the effect of induced delamination on flexural performance of CFRP composites.Design/methodology/approachIn this article, the flexural behaviors of intact and delaminated carbon/epoxy laminates were investigated under pure bending. A circular PTFE film was introduced during fabrication to create artificial delamination. Moreover, finite element models were developed for intact and delaminated composites using ANSYS. The created models were discretized using 3D structural eight node solid elements.FindingsThe delamination influenced considerably flexural properties of composite. The composite exhibited a linear elastic nature prior to the damage of top ply on the compression side. The flexural strength and stiffness of the composite reduced to 44.5% and 18.2% respectively due to the existence of artificial delamination. The results of four point bending experiments and finite element analysis agreed for both intact and delaminated composites within acceptable error. Finally for same composites, first ply failure analysis was carried out using Tsai-Hill, Tsai-Wu and Hashin failure criteria.Originality/valueIn pure bending, beam section of the middle portion is free from shear. It is not so in case of three-point bending. Hence, the effect of embedded artificial defect on bending performance of CFRP composite due to pure bending has been investigated.
In the earlier days, the displacement and strain were being measured by conventional techniques. The most useful and efficient tool put in practice with the implementation of advances in technology to measure displacements and strains on the region of interest of the object is full field optical measurement technique. This technique is a non-contact optical method known as digital image correlation (DIC), which compares the images captured before and after deformation and stores in a computer for the measurement of displacements and strains. These can be determined considering the displacement of speckles deposited on the surface of object. In this paper, the two-dimensional digital image correlation (2D-DIC) and threedimensional digital image correlation (3D-DIC) are presented and its fundamental concepts are discussed.
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