Determination of Interlaminar Shear Properties of Fibre-Reinforced Composites under Biaxial Loading: A New Experimental Approach

Abstract

The complexity of biaxial tests and analysis of their results makes it difficult to study the interlaminar shear properties of fibre-reinforced composites, particularly under through-thickness compression, which occurs in thick-walled composite elements. The improvements in experimental methods to study the features of the nonlinear behaviour of composites under biaxial loading is now an important and relevant task in the development aircraft structural elements made of сarbon fibre-reinforced polymers. This study aimed to develop a new experimental approach for the reliable determination of the interlaminar shear properties of laminates under through-thickness compression using a standard testing machine. An appropriate V-notched specimen was developed based on the configuration of well-known Iosipescu and butterfly-shaped specimens. The approach is demonstrated using woven carbon/epoxy laminates. Both the preliminary assessment of the stress fields under combined compression/shear loading and the analysis of fracture mechanisms were performed with finite-element modelling in a three-dimensional formulation. The digital image correlation (DIC) method was used to obtain experimental, full-field deformations of the specimens and to estimate the uniformity of the strain distribution in the gauge section. The stress–strain curves were obtained under biaxial loading, and the corresponding features of the composite failure behaviour were analysed in detail. It was found that the maximum compression strain on the stress–strain curves, in some cases, corresponded to the discontinuity in the composite structure. In these cases, the disproportionate changes in through-thickness strains in the gauge section of the specimens were recorded at the maximum load. With the increase in through-thickness compression stresses, the difference between the shear strength values, determined by the maximum load and the maximum compressive strain, increased by up to 20%. It was shown that the assessment of the composite strength at maximum load at the design stage significantly increased the risk of premature failure of the composite elements during exploitation.

Characteristics of in-situ automated fiber placement carbon-fiber-reinforced low-melt polyaryl ether ketone laminates part 2: Effect of prepreg composition

“…Most of literature works calculate the ILSS values based on the peak force reached during the test. 26,28,29 While this value can be accepted for brittle materials, it does not necessarily coincide with the initiation of delaminations in the specimen for more ductile materials as thermoplastic composites. The determination of a crack initiation criterion is of particular importance in the generation of cohesive zone models in recent finite-element solvers.…”

Dynamic Analysis of a High-Performance Prosthetic Leg: Experimental Characterisation and Numerical Modelling

“…In Nastran, for linear structural analyses, the MAT9 definition [46] allows to assign orthotropic material properties to 3D solid elements. Since the prosthetic material is carbon fibre composite, the definition of orthotropic properties is reasonable [47][48][49]. The fibres confer strength along their length, meaning that the orientation and length of the fibres directly influence the behaviour of the composite material.…”

“…Thus, the in-plane Young moduli (E 1 and E 2 ) are assumed equal. As consequence, also ν 13 and ν 23 and G 13 and G 23 are considered equal [47,48]. Table 6 outlines the orthotropic material properties that best describe the dynamic behaviour of the component after an iterative tuning phase.…”

A Data Driven Modelling Approach for the Strain Rate Dependent 3D Shear Deformation and Failure of Thermoplastic Fibre Reinforced Composites: Experimental Characterisation and Deriving Modelling Parameters

“…They determined the interlaminar shear modulus, as well as other elastic properties, at predefined load levels by utilising supporting finite element analyses (FEA). Several authors found a V-notched specimen in combination with DIC for strain measurement to be suitable for determining quasi-static shear characteristics [10][11][12].…”