A. Ataş

Failure Analysis of Laminated Composite Plates with Two Parallel Pin-loaded Holes

The aim of this study is to research the failure loads and failure modes of laminated woven-glass—polyester composite plates with two parallel circular holes, which are subjected to traction forces by two rigid pins. The failure behavior of two parallel pin-loaded composite plates has been observed both experimentally and numerically with different geometries and fiber orientations. While the plate width to hole diameter ratio (W/D) was held constant; the distance from the free edge of the plate to hole diameter ratio (E/D) was changed from 1 to 5, and the distance between two parallel holes to hole diameter ratio (M/D) was varied from 2 to 5. Two different ply rientations were also investigated as [0°]8 and [0°2=60° 2/]s. In a numerical study, a three-dimensional finite element method (FEM) was used with the assistance of a LUSAS 13.6 finite element analysis program. Good agreement has been shown between experimental and numerical results.

Effect of geometric parameters on the stress distribution in Al 2024‐T3 single‐lap bolted joints

Purpose – The purpose of this paper is to investigate the effect of geometric variables on the stress and strain distributions, as well as non‐linear deformation behaviour of aluminium alloy 2024‐T3 single‐lap bolted joints loaded in tension.Design/methodology/approach – The study has been conducted by using numerical and experimental approaches. In the numerical part, 3D FE models were generated using ANSYS software for different e/d and W/d ratios in which e and W are variables but the hole diameter (d) is constant. Stress and displacement results for each case have been discussed to better explain the mode of failure. In the experimental part, e/d=3 and W/d=6 ratios were selected as constant and testing specimens were produced accordingly. The aim was to obtain baseline experimental load‐strain and load‐displacement values for selected specimen geometry coordinated with the numerical analyses.Findings – The good agreement between the experimental and numerical analysis provided confidence in the numeri...

Progressive failure analysis of bolted joints in composite laminates

Abstract A three-dimensional progressive failure analysis methodology was developed to predict the strength of double lap bolted joints in [0°/90°/±45°]2s carbon fibre reinforced plastic laminates. An experimental programme was conducted to verify and validate the proposed computational model. Good agreement was obtained between the experimental data and predictive model. A parametric study was conducted for varied clamping torque and friction coefficient values. The well known effect of those variables on the joint strength was captured. Although the in-plane mode of failure of each individual layer around the fastener hole was predicted, X-ray radiographs have shown that delamination failure is particularly dominant around the washer’s outer edge. At present, the proposed model does not account for delamination onset and propagation. Future work will involve implementing cohesive zone elements in regions of interest to capture this interlaminar cracking, a work in which the authors are currently engaged in.

Open hole compressive strength and damage mechanisms: maximum stress versus Hashin criteria

Abstract The open hole compressive strength and damage mechanisms of various T800/924C carbon fiber reinforced plastic laminates were estimated by a three-dimensional progressive damage model (PDM). The emphasis was put on the effect of Hashin and maximum stress criteria on the PDM estimations. The maximum stress criterion provided better overall correlation with the experimental data in terms of the matrix damage onset, ultimate strength and fibre damage pattern at the ultimate load. Despite both criteria being essentially the same for fibre compression, a scattered fibre damage pattern was predicted by Hashin criteria including fibre tensile damage as a result of the shear stress contribution. The matrix damage onset was significantly underestimated by Hashin criteria also due to the shear stress contribution. Nevertheless, neither Hashin nor maximum stress criteria could capture a satisfactory agreement with the experimental matrix damage pattern at the ultimate load.

The Effect of Curing Conditions and Fiber End Shapes on the Mechanical Properties of Composites

The study consists of two main experimental parts. The aim of the first part of the study is to investigate the effects of the straight-short steel fibers and different curing conditions on the mechanical properties of the selected composite specimens. For this purpose, unreinforced (no fiber) specimens cured at room temperature (∼20°C) and the straight-short steel fiber reinforced polyester—calcite composite specimens cured at room temperature and at different curing conditions of 40, 80, and 120°C for 4, 8, and 12 h, have been subjected to tensile tests. In the second part of the study, unreinforced specimens and polyester—calcite composite specimens with straight-short, woven, and three different end shaped fibers cured at room temperature have been tested according to the four-point bending test procedure so as to obtain the effects of the end shapes on the mechanical properties of the composite specimens.

Mechanical performance of marine sandwich composites subjected to flatwise compression and flexural loading: Effect of resin pins

Mechanical performance of marine sandwich panels comprising E-glass/vinyl ester face sheets and perforated poly-vinyl chloride foam core was evaluated and compared with conventional foam core sandwich panels. Circular holes through the foam core thickness were drilled with 12 different arrangements in square patterns and the holes were filled with the resin during the infusion process which created the through-the-thickness solid resin pins. The effect of each pattern on the flatwise compression and core shear properties of the sandwich panels were experimentally investigated. The three-point bending maximum failure load of perforated foam core sandwich panels was increased over 133.8% by increasing the diameter of the resin pins at the expense of increased panel weight up to 67%. The flatwise compression stress to induce core crushing was significantly increased by reinforcing the resin pins.

EXPERIMENTAL CHARACTERISATION AND PREDICTION OF ELASTIC PROPERTIES OF WOVEN FABRIC REINFORCED TEXTILE COMPOSITE LAMINATES

This paper first presents the well-established analytical and numerical methods used to calculate the elastic properties of woven fabric reinforced textile composite laminates. An experimental study follows where an E-glass plain woven fabric/epoxy composite laminate was manufactured and tested in order to measure the modulus of elasticity and yarn dimensions, and also to observe the typical damage patterns. Next, a state-of-the-art geometry modelling and a finite element analysis software was used in combination to predict the modulus of elasticity using the experimentally determined yarn dimensions. Several numerical procedure alternatives were investigated to evaluate their effect on the agreement of the results with the experimental data and the computational cost.