Fibre damage in the manufacture of advanced three-dimensional woven composites

Fibre damage caused by the weaving of three-dimensional (3D) fabric preforms for advanced composite materials is investigated. A Jacquard loom was used to weave continuous fibreglass yarns into a 3D orthogonal woven fabric. Samples of warp and through-thickness yarns that form the 3D fabric were taken from the loom at different stages in the weaving process to examine for fibre damage and determine their residual tensile properties. It was discovered that the fibres are abraded against each other and the loom machinery during weaving, and the resulting abrasion damage and removal of sizing agent causes a reduction in yarn strength of between 30 and 50% depending on the type of yarn. Some fibres are also broken during weaving, and this causes a small reduction to the yarn stiffness and contributes to the large loss in yarn strength. The implication of these findings for the design of advanced 3D woven composites in structural applications is discussed

Effect of weaving damage on the tensile properties of three-dimensional woven composites

This research paper examines the damage mechanisms and reductions to the tensile properties of E-glass yarns during weaving of three-dimensional (3D) fabrics for polymer-based composites. The paper also assesses the influence of weaving damage to load-bearing glass yarns on the tensile properties of 3D orthogonal woven composites. It is found that damage occurs to yarns at most stages of the 3D weaving process due to abrasion and breakage caused when sliding against the loom machinery, The abrasion damage causes a large reduction (similar to30%) to the tensile strength of the dry woven yarns, although the tensile stiffness remains unaffected. The damage and reduction to the tensile properties of the dry yarns at different weaving stages are described. Tensile studies performed on single yarn/resin composites and larger coupons of 3D orthogonal woven composite; reveal that weaving damage is responsible for a significant reduction to the tensile strength

Open hole quasi-static and fatigue characterisation of 3D woven composites

This paper was accepted for publication in the journal Composite Structures and the definitive published version is available at http://dx.doi.org/10.1016/j.compstruct.2015.06.032This paper presents a comprehensive study on the open-hole quasi-static tensile and tension-tension fatigue behaviour of an orthogonal and an angle-interlock 3D woven carbon/epoxy composite. The full-field strain distribution during quasi-static tests was characterised using digital image correlation (DIC), and the fatigue damage behaviour was monitored using an infra-red camera. The notched tensile strength was less than 17% lower than the un-notched tensile strength and not very sensitive to the notch size. The fatigue specimens were loaded with maximum stress of about 60% of the ultimate failure stress and no complete fracture occurred after 5,000,000 cycles. The residual fatigue strength was also found to be similar to the quasi-static tensile strength in both weaves. The surface crack initiation and progression during fatigue loading was identified using thermoelastic stress analysis which revealed that the orthogonal weave had larger surface damage area than the angle-interlock weave

Structural design of face fabrics and the core as a premise for compression behavior of 3D woven sandwich fabric

In this work, an experimental study on compression properties of two E-glass 3D woven fabrics, known as integrally woven sandwich fabrics, has been presented. Compression properties of 2D face fabrics and the core, as structural parts of integrally woven sandwich fabric, have also been investigated. Compression behavior of the samples (compressibility, compression work, and compressive resilience) was analyzed from the aspect of the weave design of face fabrics and the core structure (shape and density of the pile yarns). Results of the investigation showed that 8 shaped core structure, the greater surface density of the pile yarns, and the less compact structure of face fabrics ensure better compression properties of 3D fabrics. Specific weave design of face fabrics and the structure of the core significantly influence the behavior of 3D fabrics during successive increases, followed by a gradual decrease of pressure. During the loading of 3D woven structures, three regions of curves can clearly be seen compared to two regions which are registered at 2D face fabrics. Concerning 3D woven fabrics, the first region represents compression of the core, the second region is prolonged core compression and the third region refers to the simultaneous compression of pile yarns in the core and face fabrics. The density of pile yarns plays an important role in the region 1. In region 2, both the shape and density of the pile yarns are significant. Influence of the weave of face fabrics on compression behavior of 3D fabric can be noticed to a lesser extent in the region 2 and, especially in the region 3, where highly packed yarns assemblies are created