Modified Arcan Fixture Research Articles

A study of the non-linear behaviour of adhesively-bonded composite assemblies

The objective of this study is to define a reliable tool for dimensioning of adhesively bonded assemblies, particularly for marine and underwater applications. This paper presents experimental and numerical results, which describe the non-linear behaviour of an adhesive in a bonded assembly for various loadings. A modified Arcan fixture, well-suited for the study of the behaviour of bonded metal–metal assemblies, was developed in order to focus on the analysis of the behaviour of the adhesive in thin films. The edge effects are minimised by using an appropriate design of the substrates so that experimental results give reliable data. To analyze the kinematics of the deformation of the adhesive joint non-contact extensometry techniques were employed. Thus, various characteristics of the non-linear behaviour of the adhesive were observed. The results obtained for mixed assemblies (steel, aluminium, composite substrates) show similar behaviour of the adhesive using the proposed procedure. Furthermore, quality controls by DSC, and studies of curing by DMA have been performed to verify the bonding procedure.

Development of an improved adhesive test method for composite assembly design

This study is concerned with improving performance of composite structures through the use of adhesive bonding, particularly for marine and underwater applications. Some preliminary results from tests on simple composite/composite assemblies are given first. Difficulty in modelling the failure of even these simple joints highlighted the need for more reliable constituent input data. The first objective was to define an experimental methodology enabling the adhesives of interest to be characterised up to failure. A metal–metal assembly was considered, in order to concentrate on the analysis of the behaviour of thin adhesive films. The aims were to characterise the adhesive, analyse its non-linear behaviour, and study the influence of parameters such as film thickness and manufacturing conditions. In order to be able to study the behaviour of the adhesive as a function of the normal stress component, an important parameter, a modified Arcan fixture has been developed, which enables compression or tension to be combined with shear loads. First results from this fixture are presented, together with analysis of sources of scatter in results.

In-plane shear testing of thick-section pultruded FRP composites using a modified Arcan fixture

A modified Arcan fixture with butterfly specimen geometry is designed to measure the in-plane shear response of thick-section pultruded FRP composites. The objective of the proposed testing method is to determine both the material shear stiffness and its non-linear stress–strain response up to ultimate stress. The tested pultruded specimens include two alternating layers in the form of a unidirectional glass roving and continuous filament mat layers. Finite element models for the butterfly specimen are generated to examine the effects of the notch radius and material orthotropy on the uniformity and distribution of stresses in the gage area. Butterfly geometry with a blunted notch and roving orientation parallel to the applied load is found to have a uniform shear stress in the gage section. The axial-shear response is measured under different biaxial stress states by varying the angle of the applied load. The tested non-linear shear stress–strain responses compare favorably to results previously obtained from off-axis compression tests used to calibrate a multi-axial constitutive model for this material. Results from strain gage and Infrared thermography measurements provide confirmation for the effectiveness of the fixture and the specimen geometry.