Failure Behavior of Corrugated Core Panel Under Out-Of-Plane Loading

20th International Conference on Composite Materials (ICCM) -- JUL 19-24, 2015 -- Copenhagen, DENMARKThe aim of this study is to investigate the failure behaviour of a panel with a novel corrugated core design under out-of-plane loading conditions. AS4/8552 prepreg system was used for both facesheet and core material and two different core designs are compared. Three-point bending tests were performed and acoustic emission monitoring technique was used to investigate the failure modes. It was observed that first matrix failure occurred at the corner sections of the panels and delamination initiated at these regions, followed by fibre failure at the ribs and facesheet. Acoustic emission signal clustering around certain frequencies was matched to various failure modes in order to provide an insight for further research on structural health monitoring by acoustic emission.Bogazici University Research FundBogazici University [14A06S3]; Istanbul Development Agency (ISTKA)Turkiye Cumhuriyeti Kalkinma Bakanligi [ISTKA/BIL/2012/58]Authors acknowledge the support of the Bogazici University Research Fund and Istanbul Development Agency (ISTKA) under project codes 14A06S3 and ISTKA/BIL/2012/58, respectively

Experimental investigation of the effects of infrared heating mechanism on the mechanical properties of autoclave cured CFRPs

Adamant Composites Ltd.; Hellenic Aerospace Industry S.A; JEC Group; Materials Today; Photron; Shimadzu Europa GmbH18th European Conference on Composite Materials, ECCM 2018 -- 24 June 2018 through 28 June 2018 -- 155810Autoclave curing method is widely used in manufacturing of aerospace and automotive grade carbon fiber reinforced plastic (CFRP) components. However, both the autoclave operating costs and long curing times yield high component costs and limit the mass production ability. These limitations make researchers to canalize their efforts to cost effective solutions without sacrificing the product quality. These cost effective solutions can be classified into two main groups: reducing the curing times and enhancing the efficiency of the process. In this study, effects of heating mechanism on the curing and mechanical properties of autoclave cured CFRPs were investigated. Infrared and conventional resistance heating were considered and compared. For this purpose, an infrared curing oven was constructed to simulate the autoclave cure cycle without pressure. Infrared heating is a cost effective mechanism than conventional resistance heating because it just heats the material instead of whole autoclave chamber. 75 mm x 250 mm x 3 mm CFRP plates were fabricated in this infrared oven. They were cut into 3 pieces for tensile testing. Results were compared with the ones manufactured by conventional autoclave oven at the same cure cycle. A correlation of the results of the mechanical properties and curing behaviors of the products was obtained. Results showed that infrared can be used for curing of CFRPs instead of resistance heating, especially in plain geometries. But for complex shapes, a homogen heating pattern should be provided by adjusting the location of infrared heaters with regard to the product geometry. In the light of these findings, it can be deduced that hybrid autoclave ovens can be developed which are using both infrared heating and resistance heating so as to enhance the efficiency of the process in composite plate manufacturing. © CCM 2020 - 18th European Conference on Composite Materials. All rights reserved

Quantifying the delamination of L-shaped composite laminates under low velocity impact using x-ray computed tomography

33rd Technical Conference of the American Society for Composites 2018 -- 24 September 2018 through 27 September 2018 -- -- 142871Low velocity impact response and failure behavior of L-shaped composite laminates were investigated. The composite laminates with variable thickness, stacking sequences, and corner radius were manufactured using autoclave manufacturing method. Tests were conducted on a custom low velocity impact test set-up. In order to investigate and quantify the internal damage of the samples, x-ray micro-computed tomography technique was used. The results showed that the deflection of cross-ply samples was higher than the unidirectional ones, and as the thickness decreases deflection increases for the same loading conditions. In addition, as the corner radius decreased, the deflection was more pronounced. Delamination migration was observed at the mid-plane of the corner in unidirectional samples while delamination planes largely remained separate and parallel to each other in the cross-ply samples. © Copyright© (2018) by DEStech Publications, Inc. All rights reserved

Failure behavior of laminated composite plates under anticlastic bending

In this study, the failure behavior of laminated composite plates subjected to anticlastic bending is investigated. Anticlastic bending is a special case of bi-axial out-of-plane loading that produces predominantly twisting moment. A test fixture is designed to actualize anticlastic loading condition. Carbon-fiber-reinforced epoxy composite is selected as the material of the specimens. Totally nine different layup configurations are chosen and at least four specimens are tested for each configuration. Acoustic emission monitoring (AEM) is utilized to detect the first-ply-failure load and the accumulation of damage in the laminates. In this method, elastic waves resulting from initiation and progression of damage are detected, and then AE signals are processed to identify the failure modes and determine the first-ply-failure load. A finite element model is developed to simulate the anticlastic bending test. A code is developed using ANSYS parametric design language to predict the first-ply-failure loads using various failure criteria like Tsai–Wu, Hashin, and Puck. The experimental and numerical results are then compared. Relative strengths and weaknesses of the failure criteria in estimating failure of laminated composite plates under anticlastic bending are discussed