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.

Review of applications for advanced three-dimensional fibre textile composites

This paper reviews published research into polymer composite laminates reinforced in the through-thickness direction with z-pins. Research into the manufacture, microstructure, delamination resistance, damage tolerance, joint strength and mechanical properties of z-pinned composites is described. Benefits of reinforcing composites with z-pins are assessed, including improvements to the delamination toughness, impact damage resistance, post-impact damage tolerance and through-thickness properties. Improvements to the failure strength of bonded and bearing joints due to z-pinning are also examined. The paper also reviews research into the adverse effects of z-pins on the in-plane mechanical properties, which includes reduced elastic modulus, strength and fatigue performance. Mechanisms responsible for the reduction to the in-plane properties are discussed, and techniques to minimise the adverse effect of z-pins are described. The benefits and drawbacks of z-pinning on the interlaminar toughness, damage tolerance and in-plane mechanical properties are compared against other common types of through-thickness reinforcement for composites, such as 3D weaving and stitching. Gaps in our understanding and unresolved research problems with z-pinned composites are identified to provide a road map for future research into these materials.

Review of z-pinned composite laminates

Mechanics of mechanically fastened joints in polymer–matrix composite structures – A review

This paper reviews over fifty studies into the effect of through-the-thickness stitching on the in-plane mechanical properties of fibre-reinforced polymer composites. Reviewed are the in-plane tensile, compressive, flexure, interlaminar shear, creep, fracture and fatigue properties, although little work has been undertaken on the last three properties. When comparing studies it is apparent that many contradictions exist: some studies reveal that stitching does not affect or may improve slightly the in-plane properties while others find that the properties are degraded. In reviewing these studies it is demonstrated that predicting the influence of stitching on the in-plane properties is difficult because it is governed by a variety of factors, including the type of composite (eg. type of fibre, resin, lay-up configuration), the stitching conditions (eg. type of thread, stitch pattern, stitch density, stitch tension, thread diameter), and the loading condition. The implications of these findings for the use of stitching in lightweight engineering structures are discussed.

A review of the effect of stitching on the in-plane mechanical properties of fibre-reinforced polymer composites

Uncertainties and dynamic problems of bolted joints and other fasteners

A damage zone model for the failure analysis of adhesively bonded joints

Trajectorial fibre steering of composite tows within composite laminates has been investigated as a means of producing composite structures with increased strength. Strategies to design the fibre trajectories in laminates have included aligning the fibres with principal stress vectors and a newly developed concept of load paths. In the laminate, the steered plies were inter-mingled with unidirectional or fabric plies. A manufacturing technique for the steered plies has been proposed. Applications include a specimen containing an open hole and a specimen with a pin-loaded hole. Specific strength increases of 62 and 85%, respectively, were achieved.

Don Kelly

Papers

A damage zone model for the failure analysis of adhesively bonded joints

On the design, manufacture and testing of trajectorial fibre steering for carbon fibre composite laminates

Strength improvement by fibre steering around a pin loaded hole

Experimental and numerical investigation of the crushing response of an open section composite energy absorbing element

Failure of transversely stitched RTM lap joints