Michael Bannister

Review of applications for advanced three-dimensional fibre textile composites

Current and future potential applications for three-dimensional (3D) fibre reinforced polymer composites made by the textile processes of weaving, braiding, stitching and knitting are reviewed. 3D textile composites have a vast range of properties that are superior to traditional 2D laminates, however to date these properties have not been exploited for many applications. The scientific, technical and economic issues impeding the more widespread use of 3D textile composites are identified. Structures that have been made to demonstrate the possible uses of 3D composites are described, and these include applications in aircraft, marine craft, automobiles, civil infrastructure and medical prosthesis.

Tensile properties and failure mechanisms of 3D woven GRP composites

Abstract Tensile tests were performed on glass reinforced polymer (GRP) composites with three-dimensional (3D) orthogonal, normal layered interlock, and offset layered interlock woven fibre architectures. The mechanical properties and failure mechanisms under tensile loading were similar for the three composites. Cracks formed at low strains within the resin-rich channels between the fibre tows and around the through-thickness binder yarns in the composites, although this damage did not alter the tensile properties. At higher applied tensile stresses the elastic modulus was reduced by 20–30% due to inelastic tow straightening and cracking around the most heavily crimped in-plane tows. Further softening occurred at higher strains by inelastic straightening of all the tows. Composite failure occurred within a localised region and the discrete tow rupture events that have caused tow lock-up and pullout mechanisms in other 3D woven composites were not observed.

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 (∼30%) 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 composites reveal that weaving damage is responsible for a significant reduction to the tensile strength.

Challenges for composites into the next millennium — a reinforcement perspective

This paper summarises the current level of technology within the manufacturing processes of filament winding, fibre placement, pultrusion and advanced textile preforming. It also examines the current problems within each of these manufacturing techniques and the areas of predicted future development.

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.

An investigation of the mechanical performance of weft-knit Milano-rib glass/epoxy composites

Abstract An experimental programme has been carried out to study the mechanical performance of resin transfer moulded composites comprising a weft-knit glass fabric of Milano-rib architecture. A number of mechanical properties i.e. tension, compression, bearing, impact and post-impact compression, were considered for laminates containing up to 12 layers of knitted fabric. With respect to more conventional composites, the knitted composites were found to have relatively poor tension and compression properties, but comparable bearing performance, and superior energy absorption and post-damage properties.

The mechanical performance of 3D woven sandwich composites

Composite sandwich structures were manufactured from a 3D woven fabric consisting of two face fabrics interconnected by pile yarns (Distance Fabric). Specimens were produced from Distance Fabric (DF) consolidated with vinyl ester resin with and without a polyurethane foam core and compared to specimens produced from a precast polyurethane foam core with composite skins added separately. Flatwise compression, edgewise compression, climbing drum peel and flexure tests were conducted and all demonstrated a dramatic improvement in properties from the combination of DF and foam core. These improvements are postulated to arise from the mutual reinforcement of the pile yarns and foam core.

The effect of binder path on the tensile properties and failure of multilayer woven CFRP composites

An investigation has been carried out on the in-plane tensile properties of two orthogonally woven structures with different binder paths. Measurements were made along both the longitudinal (warp) and transverse (weft) axes on samples manufactured from two commercially available carbon fibres which are known to have different resistance to fibre damage induced through weaving. In general, this research revealed that the more damage-resistant fibre produces composites with higher strength and stiffness. It was also found that, independent of the fibres used, the in-plane fibre yarns in the structure with the longer binder path are less crimped and this, by and large, translates to better or unchanged tensile modulus, strength and strain-to-failure. In addition to fibre fractures, the superior strength of this composite was also observed to promote an extensive amount of longitudinal splitting, thus resulting in a relatively large failure zone. In the structure with the shorter path length where the in-plane fibres are more crimped, failure is due predominantly to fibre fractures. Groups of fibres are pulled out during failure of both structures, despite good fibre wetting and fibre/matrix adhesion having been achieved with either fibre.

The manufacture of glass/epoxy composites with multilayer woven architectures

Abstract Multilayer, integrally woven preforms have been constructed from E-glass yarn in three different weave architectures with the in-plane fibres exhibiting minimum crimping. Microscopic examination of the architectures after resin transfer moulding revealed that the binder yarn arrangement and compaction pressure have a strong influence on the distribution of fibres and resin-rich areas. However, preliminary mechanical testing indictated that, for the preforms investigated, the final weave architecture does not have a significant influence on the tensile mechanical performance of the composite structure. A procedure is described for producing a geometric model of the architecture of such multilayer woven preforms which may then be used for their visualisation and to quantify geometric characteristics for use in further analysis.

Contrast Enhancement of MicroCT Scans to Aid 3D Modelling of Carbon Fibre Fabric Composites

This paper presents a methodology for volume capture and rendering of plain weave and multi-layer fabric meso-architectures within a consolidated, cured laminate. Micro X-ray Computed Tomography (MicroCT) is an excellent tool for the non-destructive visualisation of material microstructures however the contrast between tows and resin is poor for carbon fibre composites. Firstly, this paper demonstrates techniques to improve the contrast of the microCT images by introducing higher density materials such as gold, iodine and glass into the fabric. Two approaches were demonstrated to be effective for enhancing the differentiation between the tows in the reconstructed microCT visualisations. Secondly, a method of generating three-dimensional volume models of woven composites using microCT scan data is discussed. The process of generating a model is explained from initial manufacture with the aid of an example plain weave fabric. These methods are to be used in the finite element modelling of three-dimensional fabric preforms in future work.