Experimental Investigation of Delamination in Composite Continuous Fiber-Reinforced Plastic Laminates with Elastic Couplings

Abstract

This paper presents an experimental evaluation of influence of the elastic couplings on the fracture toughness as well as on delamination initiation and propagation in carbon/epoxy composite laminates. For this purpose the mode I double cantilever beam (DCB) tests according to the American Society for Testing and Materials (ASTM) D5528 Standard were performed on specimens with different delamination interfaces and specific lay-ups composition exhibiting the bending-twisting (BT) and the bending-extension (BE) couplings. The critical strain energy release rates (mode I c-SERR, GIC) were calculated by using the classical methods, namely: the modified beam theory (MBT), the compliance calibration (CCM) and the modified compliance calibration (MCC). In order to evaluate an accuracy of the different methods, the values of c-SERR obtained by using standardized data reduction schemes were compared with values calculated by using the compliance based beam method (CBBM). All the methods give rise to comparable values of the GIC, which makes the CBBM an appealing choice, since it does not depend on crack length monitoring during the test. Initiation and propagation of delamination were investigated by using the acoustic emission (AE) technique. Moreover, the scanning electron microscope (SEM) analysis were performed after the experimental tests in order to investigate a fracture surface at delamination plane.

Resistance of Polymeric Laminates Reinforced with Fabrics against the Growth of Delaminations

“…In [ 8 ], resistance against delamination under Mixed-Mode loading (G II = 34%, 85%) was investigated for 0°//0°, 0°//22.5°, 0°//45°, and 0°//90° interfaces. More recent results of similar investigations can be found, e.g., in [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], and in [ 19 , 20 , 21 , 22 ] where also R-curves were of interest.…”

“…Below, for comparison purposes, the results of the most relevant experimental works that were found [ 10 , 23 , 24 ] regarding the presented research are shortly described. Unfortunately, this comparison, as regards the research presented by the author, may have an important shortcoming since papers [ 10 , 23 , 24 ] concern mainly laminates reinforced with UD tapes and impregnated with different resins.…”

“…Although the investigations presented in [ 10 ] did not focus on the Gci vs. α relationship, in principle, one could find out certain information concerning the Gci vs. α relationship. One could extract Gci for Mode I, for θ = 60° (θ 1 = 30°, θ 2 = −30°) and α = 30°, and for θ = 90° (θ 1 = 45°, θ 2 = −45°) and α = 45°.…”

Dynamic Behavior of Aviation Polymer Composites at Various Weight Fractions of Physical Modifier

“…The numerous material solutions presented in the literature testify to the constant interest of the scientific community in making a real impact on the occurrence of synergies between the acquisition of knowledge and its practical application [15][16][17][18][19][20][21][22]. The issues related to the modification of polymer matrix composites are new with respect to materials science, although they are extremely extensive due to the intensification of research carried out in scientific centers all over the world [23][24][25][26][27][28]. The considerations presented below represent only a small part of the description of progress in this field, and the works cited are only illustrative of the multifaceted nature of the improvements.…”

“…The literature analyzed to date allowed the authors to identify several approaches in the area of modification of composites that have a real impact on the final properties obtained. Among these, the following modifications were observed [1,4,23]:…”