Single bolt in plane tension joint tests on E-glass/epoxy composite plate

The evaluation and prediction of failure probability and safe levels of composite materials is of extreme importance in terms of manufacturing and structural design. The experimental investigations described in the present paper were conducted to study the strength and failure behaviour of composite plate under pin loaded conditions. Pin bearing tests were carried out on E-glass/epoxy composite plate fabricated by hand lay-up. The experiments investigated the effect of important parameters, including specimen geometry and stacking sequence, on the failure characteristics. Tests were performed with two different stacking sequences: [0/90/+30/-30]s and [0/90/+60/-60]s. Geometrical configurations of specimens such as ratio of edge distance to pin diameter (E/D) and ratio of specimen width to pin diameter (W/D) were suitably varied to observe all possible failure modes. A total of 150 different pin loaded composite plate specimens, two laminate configurations, five edge: pin/diameter ratios, five width: pin/diameter ratios and three samples for each condition were tested under static loading conditions. Failure strength and failure modes were observed in specimens. The specimen tested exhibited different failure modes, consisting of bearing, net tension and shear out, depending on the geometry adopted. Based on the experiments, effects of stacking sequence and geometric parameters on bearing strength, shearing and net tension stress at failure were systematically investigated. Net tension and shear out failure modes were catastrophic, therefore they were undesirable. These modes were also not as safe as bearing failure mode. Bearing failure was desirable for pin loaded composites, due to non-catastrophic damage progression with increasing load. From the experiments, it was shown that the failure mode was a strong function of W/D. The experimental measurements indicated that the load carrying capacity of a pin loaded hole could be changed by altering the specimen geometry and stacking sequence. Therefore, the geometry of the pin connected joints was designed to undertake bearing failure only. In addition, it was found that glass/epoxy with [0/90/±30]s yielded the highest bearing strengths. High bearing strengths were reached when EID and W/D ratios were 3?4 for both [0/90/+30/-30]s and [0/90/+60/-60]s stacking sequences. © 2007 Institute of Materials, Minerals and Mining

A numerical and experimental investigation of critical buckling load of rectangular laminated composite plates with strip delamination

WOS: 000237456000001In the present study, experimental measurements and numerical solutions on the buckling of single-delaminated glass-fiber composite laminates are carried out on rectangular plates. During the fabrication process, rectangular teflon films of 13 mu m thickness are introduced between plies of different orientation in order to form a macro defect. In addition, the variation in structural configurations, such as ply stacking sequence, width of the delamination, and specimen geometry (width to unsupported length), are considered. In all cases, the delamination is centrally placed through-the-thickness of the laminate. Compression tests are carried out on EP GC 203 glass/epoxy woven composites with built-in single embedded delamination in order to evaluate the critical buckling load. Finite element modeling is used to gain further understanding of the critical buckling load. ANSYS (version 6.1) are used to analyze the critical buckling load of various laminated plates in order to see how changes in the rectangular composite laminated plates would affect the buckling load. A good agreement between finite element predictions and experimental measurements are found for the delamination geometries that were tested

The bearing strength and failure behavior of bolted e-glass/epoxy composite joints

An experimental study was carried out to investigate the failure strength of a pinned-joint E-glass/epoxy composite plate. The main objective was to examine the influence of the preload moment, the edge distance to the pin diameter ratio, and the specimen width to pin diameter ratio on the strength. The load-carrying capacity of the pin-loaded hole could be changed by varying the specimen geometry and the preload moment. Guidelines for effective geometrical configurations and the preload moment for the mechanically pin-connected E-glass/epoxy composite plate were specified based on the ultimate bearing strength. © 2008 Springer Science+Business Media, Inc

Buckling optimization of composite columns with variable thickness

WOS: 000249453600004A novel approach to the optimization of flexible columns against buckling is presented. The problem of determining the shape of the column that has possibly the largest critical buckling load of columns of a given length and volume is solved for composite materials. The objective of this study was to develop and design an optimized composite column against buckling. Determining what shape of column has the largest possible buckling load of composite column of a given length and volume was considered. Clamped-clamped supported column is an important limit case because it caused debate in many publications. Moreover, in this study, the optimization problem of the clamped-clamped column under buckling load, which was previously dealt with by Tadjbakhsh and Keller [5], Olhoff and Rasmussen [6] and Masur [7] is reinvestigated. It is also proved that the solutions of Tadjbakhsh and Keller, Olhoff and Rasmussen and Masur are not optimum for columns with clamped ends. The present model formulation considers columns for which crush is taken into account in the formulation of the column optimization problem, allowing for bimodal optimum solution. This leads to the necessity for both stability and crush criterion formulation of the optimization problem. The new proposed optimum model solution has been verified with numerical analysis using ANSYS and experimental data for columns with clamped-clamped ends. It was shown that the new proposed model was given the optimum solution for the clamped-clamped case. Detailed results are presented and discussed for clamped-clamped columns having circular cross-sectional configuration. As a result of this study, it was shown that results obtained in previous studies of variation optimum cross-sectional area for columns under compressive forces clamped-clamped ends were erroneous. The corrected optimum form was obtained and results checked by numerical calculations and experimental tests of composite columns

Elastic-plastic stress analysis of a thermoplastic composite disc under linear temperature distribution

WOS: 000235778200004In the present study, an elastic-plastic stress analysis is carried out on a composite thermoplastic disc reinforced by steel fibers, curvilinearly. Radial and tangential stresses are obtained under a liner temperature distribution. The magnitude of the tangential stress component for elastic and elastic-plastic cases is higher than that of the radial stress component. The tangential stress component is compressive and tensile on the inner and outer surfaces, respectively and is the highest on the inner surface. The elastic-plastic solution is performed for the plastic region expanded around the inner surface by an analytical formulation and a numerical solution. The solution is also carried out by the finite element method (ANSYS solution). These two solutions give very similar results. The intensities of the residual stress component of the tangential stress and plastic flow are the highest at the inner surface