Failure analysis of composite pin-loaded joints under preload moments

In this study, failure response of pin-loaded laminated composite with different stacking sequences and different dimensions has been investigated both experimentally and numerically. The main goal is to examine failure mechanism, failure mode, failure load and bearing strengths of laminated composite plates containing two serial pin loaded hole under various preload moments. Parametric studies were carried out to determine the influences of joint geometry, ply orientation and preload moments on the failure initiation and bearing strength. The laminated composite plates were produced at Izoreel Firm in İzmir. After the production process, the material properties of unidirectional glass/epoxy composite material were determined under tension, compression and in-plane shear in static loading conditions. During the experiments, standard experimental techniques and specimen sizes for composite materials were used. The shear properties of composite plates were characterized using Iosipescu test equipment designed and prepared for a previous study in the Construction Laboratory at Dokuz Eylul University. To analyze and verify to the numerical predictions of mechanical behavior and to investigate the failure characteristics of two serial pin-loaded composites, a series of experiments was carried out with eight different material arrangements. The edge distance-to-hole diameter ratios, width-to-hole diameter ratios and two serial pin holes distance-to-hole diameter ratios of the specimens were designed from 1 to 5, 2 to 5 and 3 to 5, respectively. Each laminated plates were designed to stuck 8 laminas onto together with eight different stacking sequences under press and heat. Prior to preload moment tests, the first part of the experiments was performed without any preload. After these tests iv without applied preload moments, the tensile tests were carried out for other specimens that were applied preload moments as 2, 3, 4 and 5 Nm. During the numerical study, the model for failure response of the laminated composite plates was developed and solved using commercial finite element analysis software called LUSAS Composite, Version 13.6. Keywords : Composite plates, Failure analysis, Failure modes, Bearing strength, Finite element methods