The impact resistance of composite materials — a review

Toughening mechanisms of nanoparticle-modified epoxy polymers

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The introduction of carbon nanotubes (CNTs) into conventional fibre-reinforced polymer composites creates a hierarchical reinforcement structure and can significantly improve composite performance. This paper reviews the progress to date towards the creation of fibre reinforced (hierarchical) nanocomposites and assesses the potential for a new generation of advanced multifunctional materials. Two alternative strategies for forming CNT-based hierarchical composites are contrasted, the dispersion of CNTs into the composite matrix and their direct attachment onto the primary fibre surface. The implications of each approach for composite processing and performance are discussed, along with a summary of the measured improvements in the mechanical, electrical and thermal properties of the resulting hierarchical composites.

Carbon nanotube-based hierarchical composites: a review

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

Phase separation in epoxy resins containing polyethersulphone

The article provides an introduction into the technology of through-the-thickness reinforcement of thermosetting composites by the insertion of Z-Fiber® pins. The manufacture of the raw materials is described, as is the method of pin insertion. Delamination tests samples were prepared from unidirectional continuous carbon fibre/epoxy prepreg (IMS/924), made into 3 mm thick unidirectional laminates with and without a block of Z-pins in the crack path. Fracture testing was carried out under Mode I (standard DCB test) and Mode II (3-point-ENF) loading conditions. The data presented here were obtained by using the commonly used data reduction schemes; the applicability of such data treatment is considered.

Delamination resistant laminates by Z-Fiber® pinning: Part I manufacture and fracture performance

3D reinforcement of stiffener-to-skin T-joints by Z-pinning and tufting

Delamination of Z-pinned carbon fibre reinforced laminates

An analysis is made of the thermodynamic and kinetic factors affecting phase separation in blends of di-, tri- and tetrafunctional epoxy resins, cured with either diamino-diphenylsulphone (DOS) or with dicyanodiamide (Dicy), and modified with either poly(ethersulphone) (PES) or carboxyl-terminated butadiene acrylonitrile (CTBN) rubber. The applicability and limitations of the solubility parameter approach in predicting compatibility in reactive blends are considered.

Ivana K. Partridge

Papers

Phase separation in epoxy resins containing polyethersulphone

Delamination resistant laminates by Z-Fiber® pinning: Part I manufacture and fracture performance

3D reinforcement of stiffener-to-skin T-joints by Z-pinning and tufting

Delamination of Z-pinned carbon fibre reinforced laminates

Phase separation in crosslinked resins containing polymeric modifiers