Evaluation Method for Fatigue Strength of FRP/Metal Adhesive Joints Considering Mean Stress

2003 ◽  
Vol 125 (4) ◽  
pp. 402-405 ◽  
Author(s):  
Masaaki Iwasa ◽  
Toshio Hattori
Keyword(s):  
Fatigue Strength ◽  
Low Temperature ◽  
Evaluation Method ◽  
Stress Singularity ◽  
Propagation Rate ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Mean Stress ◽  
Lap Joint ◽  
The Relationship

The fatigue strength of two types of FRP/metal adhesive joints at low temperature, a double lap joint and an embedded joint, was evaluated analytically and experimentally. First, the stress singularity parameters of the delamination edges under mechanical and thermal loadings were analyzed by FEM for various delamination lengths. The delamination propagation rate of the double lap joint under mechanical cyclic loadings at room temperature was measured. Using the relationship between the measured propagation rates and the analyzed ranges of stress singularity intensity, we estimated the fatigue strength of the embedded joint, which coincided well with the measured one. Second, we developed an evaluation method that separates the effects of temperature on fatigue strength into two effects: thermal residual stress and low temperature. Third, the fatigue strengths of the double lap joints were measured for various mean stresses. Fatigue limit of adhesive joints was experimentally measured and compared with analytical intensity of stress singularity. A method for evaluating the fatigue strength of adhesive joints by taking mean stress into account was developed.

Fatigue Strength of Metal / FRP Adhesive Joints Under Low Temperature

1995 ◽  
Author(s):  
Toshio Hattori ◽  
Masaaki Iwasa
Keyword(s):  
Fatigue Strength ◽  
Low Temperature ◽  
Residual Stresses ◽  
Adhesive Joint ◽  
Evaluation Method ◽  
Stress Singularity ◽  
Adhesive Joints ◽  
Strength Evaluation ◽  
Thermal Residual Stresses ◽  
Super Conducting

Abstract Fiber reinforced plastics (FRP) have the excellent thermal isolation characteristics, and are used for for cryogenic structures such as super conducting magnets. Generally these FRP materials are connected with metal structures using adhesive joint, as these FRP materials loose strength by the existence of bolt holes. In this metal/FRP adhesive joints high thermal residual stresses occur under cryogenic temperatures as the thermal expansion coefficients of both materials differ large. So, improvement of strength evaluation method of these bi-material adhesive joints under low temperature become indispensable to develop high-reliability super conducting magnet systems such as form Magnetic Levitation Liner Motor Car. In this paper we present a new fatigue strength evaluation method under high thermal residual stresses using following two stress singularity parameters K and λ at bonding edges. τ ( r ) = K / rλ Heat τ(r) is stress (MPa), r is the distance (mm) from the singular point (bonding edge), K is the intensity of stress singularity and λ is the order of stress singularity. And this evaluation method is applied to Stainless-steel/Al2O3 FRP adhesive joint models.

Using Spreadsheet Modules to Augment the Design of Adhesive Lap Joints

2007 ◽  
Author(s):  
Terry E. Shoup ◽  
Michael Drew
Keyword(s):  
Numerical Algorithms ◽  
Visual Basic ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Geometric Configuration ◽  
Lap Joint ◽  
Microsoft Excel ◽  
Traditional Design ◽  
Adhesive Type ◽  
Selection Of

This paper presents two easy-to-use spreadsheet modules in Microsoft Excel to assist with the design of adhesive joints. The modules make use of embedded Visual Basic numerical algorithms to give assistance with the selection of both the adhesive type and the geometric configuration of an adhesive lap joint. These modules facilitate the quick implementation of designs that are more accurate than was previously possible by traditional design methods. The method will be particularly helpful to students and inexperienced designers who first encounter the need to design adhesive joints. The paper also includes an example application to illustrate the use of the modules.

The Comparison between Mechanical Properties of Laser-Welded Ultra-High-Strength Austenitic and Martensitic Steels

2020 ◽  
Vol 841 ◽  
pp. 132-137
Author(s):  
Mikko Hietala ◽  
Markku Keskitalo ◽  
Antti Järvenpää
Keyword(s):  
Stainless Steel ◽  
Shear Strength ◽  
Fatigue Strength ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
High Strength ◽  
Lap Joints ◽  
Resistant Steel ◽  
Lap Joint ◽  
Weld Joints

The paper investigates experimentally the usability of ultra-high-strength stainless steel and abrasion resistant steel in laser-welded sandwich structures. The fatigue and shear strength of laser joints were investigated using lap joints that were welded using two very different energy inputs. Also the effect of multiple weld tracks was investigated. The properties of separate laser welds were characterized by hardness testing and optical microscopy. Results of the hardness measurements showed that there was softened area at heat-affected-zone and weld metal of the ultra-high-strength stainless steel welds. AR steels weld metal was harder than base metal and there was softened zone in heat-affected-zone of the weld. The shear strength of tested single weld joints of the ultra-high-strength stainless steel was higher compared abrasion resistant steel single weld joints, but stronger joint can be made with multiple weld seams for abrasion resistant steel. Fatigue strength of investigated ultra-high-strength stainless steel lap joint was lower than fatigue strength of abrasion resistant steel lap joint in the low-cycle regime, but there was no practical difference in fatigue limit (10e7 cycles).

A Comprehensive Model for Predicting Fatigue Life of Laser Welded Lap Joint of Galvanized High Strength Steel as a Function of Residual Stresses

2012 ◽  
Author(s):  
Joe Anago ◽  
Fanrong Kong ◽  
Blair Carlson ◽  
Radovan Kovacevic
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Thermal Loading ◽  
Axial Stress ◽  
Three Dimensional ◽  
Element Model ◽  
Lap Joints ◽  
Lap Joint

This paper presents a three-dimensional (3D) multi-physics finite element model (FEM) to predict the fatigue life of a laser welded lap joint of dual phase (DP) 980 steel sheets based upon the level of residual stress. A FEM-based thermal analysis is first performed to numerically predict the welding-induced temperature field combined with the corresponding experimental verification. The temperature histories are then loaded into the mechanical model as thermal loading to numerically calculate the evolution curves of thermally induced stress in order to calculate the level of residual stresses after cooling to room temperature. In order to calculate the equivalent fatigue strength in the laser-welded lap joint, the resultant multi-axial stress (including the induced residual stress (RS) result) is loaded into the equivalent uni-axial stress equation via the Sine Method (SM) in order to achieve the stress curve as a function of the loading cycles. A series of fatigue tests of lap joints are also performed in order to achieve the S-N curves, from which an empirical function between the alternating stress and loading cycle is derived in order to predict the fatigue life of the DP980 lap joint. Finally, the maximum fatigue strength can be predicted numerically through the proposed FEM instead of using experimental trials. The numerical results show that a greater temperature gradient and residual stress are mainly located within the fusion zone (FZ) and close to the heat affected zone (HAZ). The residual stress plays an important role in deciding the final fatigue strength and failure of the DP980 lap joint. An X-ray diffraction technique is used to experimentally measure the residual stress distribution within the weld, for which the numerically predicted results exhibit a good agreement. Also, the numerical simulation and experimental measurements of the fatigue life versus the applied load show a good correlation of results.

Effect of Interface Geometry on Strength of Single Lap Adhesive Joint of Sisal-Glass/Epoxy Laminates

2020 ◽  
Vol 858 ◽  
pp. 20-26
Author(s):  
Asad A. Khalid
Keyword(s):  
Failure Mode ◽  
Composite Laminates ◽  
Glass Fibers ◽  
Tensile Load ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Resin Matrix ◽  
Tensile Behaviour ◽  
Lap Joint ◽  
Interface Geometry

In this project, experimental work on tensile behaviour of single lap adhesive joints of sisal, glass and hybrid sisal-glass/epoxy composite laminates has been carried out. Composite laminates were fabricated by hand lay-up method using chopped strand mat sisal and glass fibers with epoxy resin matrix. Lab joints of four interface geometries; straight flat, triangular, rectangular and sinusoidal were fabricated. Tensile load-displacement relations were drawn and discussed. Effect of interface geometry and material type on maximum load and strength of the single lap joint was investigated. Failure mechanism of the fractured specimens was discussed. Results show that the glass/epoxy lap joints with semi-circular adhesive interface geometry supported load higher respectively 14.26%, 26.13%, and 30.79% than rectangular, triangular and straight flat interface geometries. Glass/epoxy lap joint with semi-circular interface geometry supported tensile load higher 5.61% and 21.83% than that obtained from hybrid sisal-glass and sisal/ epoxy adhesive joints. While the shear strength was found higher respectively 6.19% and 18.69%. Adhesive failure mode was observed for most of the single lap joints investigated. Mixed failure mode of adhesive and adherend materials was observed on the sisal/epoxy lap joints.

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