Pin-loaded Hole Research Articles

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.

Analytical model for predicting brittle failures of bolted timber joints

A theoretical model is presented to calculate the stress distribution around a pin-loaded hole in a timber joint and to predict brittle failure modes in bolted connections. The analytical solution uses the stress functions expressed in terms of complex parameters, and it can be considered an application of Lekhnitskii’s theory on stress distributions in anisotropic plates. The influence of the end distance and material properties on development of failure due to the splitting and shear-plug is shown for a dowel-type timber joint. Laboratory experiments on timber joints with 15.9-mm and 9.5-mm bolts loaded parallel to grain have shown good agreement with the model predictions.

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.

Design of Stiffened Plate Lifting Beams

The American Society of Mechanical Engineers has published a new standard for the design of below-the-hook lifting devices. This standard defines allowable stress structural design requirements for lifting devices used in construction and general industry in conjunction with cranes, derricks, and other hoisting equipment. One type of lifting device that is common in construction and that is not specifically addressed in the standard is the stiffened plate lifting beam. Design issues that are applicable to this type of lifting beam are lateral-torsional buckling, combined tensile, and shear stresses in the regions around pin-loaded holes, connections among the built-up elements of the beam, and strength of the lower pin holes. This paper derives a method for the design of stiffened plate lifting beams that is compatible with the requirements of the standard.

Effects of geometric parameters on failure behavior in laminated composite plates with two parallel pin-loaded holes

The aim of this study is to investigate failure mode, failure load and bearing strength in a laminated woven glass-vinylester composite plate with two parallel circular holes which are subjected to traction forces by two parallel rigid pins. The behavior of pin loaded composite plates with various dimensions has been observed experimentally and numerically. The edge distance-to-hole diameter (E/D), the distance between two holes-to-hole diameter (M/D), and the distance from the upper or the lower edge of the specimen to the centre of hole-to-hole diameter (K/D) ratios were selected as parameters. The numerical study was performed by using finite element software, Lusas 13.6. Hashin failure criteria were used to obtain failure load and failure mode. The numerical and experimental results were compared and good agreement was obtained.

Failure behavior of laminated composite plates with two serial pin-loaded holes

Abstract The objective of this study is to investigate the effects of geometrical parameters such as the edge distance-to-hole diameter ratio ( E / D ), plate width-to-hole diameter ratio ( W / D ), and the distance between two holes-to-hole diameter ratio ( M / D ) on the failure loads and failure modes in woven-glass–vinylester composite plates with two serial pin-loaded holes, experimentally and numerically. In the numerical analysis, the Hashin failure criterion was used in order to determine failure loads and failure modes. LUSAS commercial finite element software was utilized during the analysis. The numerical and experimental results showed that the ultimate load capacity of woven-glass–vinylester laminates with pin connections increased by increasing ratios E / D , W / D , and M / D .

Stress concentration analysis of fibre-reinforced multilayered composites with pin-loaded holes

The problem of stress concentrations in the area of pin-loaded holes is of particular significance in the design of multilayered fibre-reinforced composite structures. For the purpose of simulating such problem zones in anisotropic multilayered composites, analytical methods offer decisive advantages since they, in comparison to numerical methods, allow weighting of influencing parameters and in this way permit a physical interpretation of complicated notch phenomena. At the Institut für Leichtbau und Kunststofftechnik (ILK) sophisticated analytical solution methods for the stress concentration problem in multilayered composites with pin-loaded holes were developed on the basis of layer-related solutions and have been confirmed in numerical calculations.

Failure analysis of woven laminated glass–vinylester composites with pin-loaded hole

This study deals with the bearing strength, failure mode and failure load in a woven laminated glass–vinylester composite plate with circular hole subjected to a traction force by a rigid pin. These are investigated for two variables; the distance from the free edge of the plate-to-the diameter of the hole ( E/D) ratio (1, 2, 3, 4, 5), and the width of rectangular plate-to-the diameter of the hole ( W/D) ratio (2, 3, 4, 5), numerically and experimentally. The numerical study is performed by using 3D FEM with assistance of LUSAS 13.4 finite element analysis program. Hashin failure criteria is used in the failure analysis. The woven glass–vinylester composite material is produced and the mechanical properties of the composite material are obtained from standard tests. Experimental results concerning damage progression and ultimate strength of the joint are obtained and compared with predictions. A good agreement is obtained between experimental results and numerical predictions.

Verification of stress-intensity factors for various middle-crack tension test specimens

Recently, the stress-intensity factor equation used in the ASTM Standard Test Method for Measurement of Fatigue Crack Growth Rates (E-647) for the middle-crack tension M(T) specimens (friction-gripped or pin-loaded) has been questioned due to the influence of the specimen “height” specified in the standard. A boundary-element code has been used to calculate the stress-intensity factors for a wide range of crack-length-to-width ratios and various height-to-width ratios for M(T) specimens under remote uniform stress, remote uniform displacement, or pin-loaded holes. Comparisons are made with some of the well-known stress-intensity factor solutions and equations in the literature. Recommended specimen heights and stress-intensity factor equations have been made.

Failure analysis and behaviour of titanium alloy metal matrix composite bolted joints

Pin-loaded hole coupons with tapered geometry were tested to examine the failure behaviour of titanium alloy metal matrix composite (MMC) bolted joints at room temperature and 650°C. The average failure load at 650°C decreased almost to half of the average failure load at room temperature. Additional tests were also carried out at room temperature to investigate different methods to extend the life of the joint. A polyester film was applied around the hole on one face of the specimen, which consequently changed the failure mode and post-failure response of the specimen. Finite element (FE) analyses were performed to predict the behaviour of titanium MMC bolted joints. Failure loads were predicted by solving a boundary value problem representing a single lap bolted joint. A modified concentric cylinders model (CCM) was employed to predict the effective properties used in the FE and failure analyses. Good agreement was shown between the experimental results and the predictions.

Failure Prediction of Composite Lugs Under Axial Loads

An approach to predict failure of composite lugs under axial loading is presented. The approach relies on superposition of the solution for an infinite plate with a pin-loaded hole and an infinite plate with an unloaded hole corrected for finite width effects based on methods presented in the literature. A relatively simple equation for the net section stress is derived. For failure prediction the maximum net section stress is equated to the first-ply failure of the laminate. The approach was used to determine analytically the optimum lug configuration. For a wide variety of layups, it was found that the optimum pin-diameter-to-lug-width ratio is approximately 0.41. A test program was executed to verify the predictions of the approach with three different lug configurations with tape, fabric, or combinations of tape and fabric materials with quasi-isotropic and orthotropic layups. The specimens were tested in tension, and in all cases the test results were within 10% of the failure predictions.

Failure Strength of Woven Glass Fiber-Epoxy Composites Pinned Joints

In this paper, mechanical behavior and damage development of pin-loaded woven glass fiber-epoxy composites have been observed numerically and experimentally. Parametric studies have been performed to evaluate the effects of joint geometry and ply orientation on the failure strength and failure mode of composite laminates with a pin-loaded hole. For this purpose, a finite element program has been developed. The failure analysis was based on Hashin and Hoffman criteria that were applied at the ply level. The results (with Hashin and Hoffman criteria) were compared to each other. To verify to the numerical predictions of mechanical behavior, a series of experiments was performed with two different material configurations ([(0/90)3]S [(45)3]S) and twenty different geometries. The numerical and experimental results were compared and discussed. A good agreement between experimental results and numerical predictions was obtained.

Fibre steering for a composite C-beam

Fibre steering of composite tows within lamina is being investigated as a means of producing composite components with increased strength or stiffness when compared to the commonly adopted unidirectional and fabric laminates used in industry. The concept of fibre steering and application to a tensile plate with an open hole and a pin-loaded hole is reviewed. The design and manufacture of fibre steering along trajectories for a cantilevered C-section beam representative of an aerospace control surface spar is then described. The results of experimental testing and finite element analysis of the beam are presented. The results indicate that a significant reduction in deflection is possible over an equivalent flange-stiffened design.

A new approach for solving mixed boundary value problems along holes in orthotropic plates

A new analytical method for solving mixed boundary value problems along holes in composite plates is presented. This addresses problems, where a part of the hole boundary is stress-free, and the other part is subjected to displacement or/and load boundary conditions. The present approach simplifies and speeds up the numerical calculations for the implementation of the boundary conditions by deriving stress functions, which automatically satisfy the stress-free boundary condition over a part of the hole boundary. Only the boundary conditions on the loaded part of the hole need, therefore, to be enforced, typically by a numerical technique such as collocation. Application of this method to orthotropic laminates with a pin-loaded hole problem is discussed.

On the design, manufacture and testing of trajectorial fibre steering for carbon fibre composite laminates

Trajectorial fibre steering of composite tows within composite laminates has been investigated as a means of producing composite structures with increased strength. Strategies to design the fibre trajectories in laminates have included aligning the fibres with principal stress vectors and a newly developed concept of load paths. In the laminate, the steered plies were inter-mingled with unidirectional or fabric plies. A manufacturing technique for the steered plies has been proposed. Applications include a specimen containing an open hole and a specimen with a pin-loaded hole. Specific strength increases of 62 and 85%, respectively, were achieved.

Effects of Friction on Three-Dimensional Contact Stresses in Pin-Loaded Laminated Composites

An investigation is performed to study the effects of friction on the three-dimensional (3D) stress state around pin-loaded holes in laminated composites. The composite pinned joints are modeled as a linear elastic contact problem with friction; therefore, the interactions between the pin with the laminate follow the law of Coulomb friction. An analytical solution for the 3D stress state involved in this problem is developed based upon the variational principle of complementary energy. Compared to the previous research based on a two-dimensional stress assumption, the present solution is innovative, since the out-of-plane effects (i.e., edge effects) near the pin-loaded holes are considered. The present formulations are restricted to the laminated composites with bi-directional fiber orientations, because all the traction and displacement boundary conditions can be satisfied in such type of laminates. Numerical results for pin-loaded cross-ply laminates with different coefficients of friction are presented. It is shown that the effects of friction on the magnitude and distribution of the 3D stress state around pin-loaded holes in laminated composites are significant.

Use of a Direct Boundary Element Method for Pin-Loaded Plates

A previously developed direct boundary element method for analyzing stresses around pin-loaded holes of compositelaminates hasbeen extended witha ree ned and improved computationalalgorithm. Themethod,procedure, and computer program are verie ed by elasticity solutions in polar coordinates for eyebars and plates having an open, as well as loaded, hole. In turn, boundary tractions generated by the direct boundary element method allowing direct application of elasticity solutions are presented. Such a scheme, which couples the boundary element and analytical methods, appears to be plausible, accurate, and efe cient for practical applications.

Stresses around pin-loaded hole in composite laminates using direct boundary element method

This study is concerned with stresses around a pin-loaded hole in symmetrically stacked composite laminates of finite size using a two-dimensional direct boundary element method. Effects of friction and clearance between the pin and hole edge on the stresses are accounted for. Also geometric compatibility and force constraint between the pin and the plate are enforced. A new relation for geometric compatibility is proposed. Stress distributions and the contact angle with slip and no-slip regions around the pin-loaded hole corresponding to various parameters are investigated. Some interesting results are obtained. The present method is effective and simple to use which can be implemented with a personal computer.

Edge Effects in Laminated Composites with Pin-Loaded Holes

An analytical technique is developed for determining the three-dimensional edge effect stresses around pin-loaded holes in symmetric laminated composites. Based on the superposition principle of linear elasticity theory, the stress state around pin-loaded holes is divided into two parts, one the in-plane stress state determined using the classical laminated plate theory and the other the boundary-layer stress state arising from the edge effects that only exist in the vicinity of the holes. The equilibrium equations for boundary-layer stress state with zeroth-order approximation are written based on a set of power series expansions. A closed-form solution for the boundary-layer stress state with zeroth-order approximation is then obtained by imposing stress functions on the variational principle of complementary energy. Numerical results obtained using the present technique for cross-ply laminates are in good agreement with those obtained using finite element methods.

Delamination initiation of laminates with pin-loaded holes

A finite element analysis is conducted to determine the three-dimensional stress field in a composite laminate with a pin-loaded hole. The accuracy of computation is established by comparison with the strain gauge measurements near and away from the hole boundary. An acoustic emission technique was used to determine the initial failure load as the specimen was subjected to a quasi-static loading rate. Specimens were examined between the load steps using radiography and micrography in order to detect delamination initiation. The delamination initiation site and the corresponding load level are predicted by applying the strain energy density criterion. The critical parameters were extracted from the experimental measurements and finite element analysis of a double cantilever beam specimen. The analysis predictions indicate that delaminations could initiate close to the free surface at the interface between layers with a fiber orientation of ±45° relative to the load direction. These predictions confirm the experimental observations.