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THE ROLE OF THE FIBRE MATRIX INTERFACE ON THE MECHANICAL BEHAVIOUR AND DAMAGE DEVELOPMENT IN CARBON FIBRE REINFORCED

Objective

The principal obj ective of the project is to determine the extent to which damage development in CFRP laminates may be influenced by controlling the degree of bonding between the fibre and the matrix. Subsidiary objectives are to develop techniques for characterizing the interface and treatments which control the interface properties.
The principal objective of the project is to determine the extent to which damage development in carbon fibre reinforced plastic (CFRP) laminates may be influenced by controlling the degree of bonding between the fibre and the matrix. Subsidiary objectives are to develop techniques for characterising the interface and treatments which control the interface properties.

A large batch of intermediate modulus carbon fibre was manufactured and subbatches subjected to different levels of oxidative surface treatment. Most of the fibre was converted into a prepreg using both an epoxy and a polyethersulphone (PES) matrix. The prepreg was moulded into laminates for testing.

The strength distributions of the fibres have been determined, as also has the adhesion of the fibres to an epoxy resin. Fibre surfaces have been characterised by photoelectron spectroscopy, scanning electron microscopy (SEM), scanning tunnelling microscopy (STM) and other techniques. Surface chemistry has been correlated with adhesion.

An extensive programme of mechanical testing is being completed. Matrix cracking in cross ply laminates has been studied as well as fracture toughness and fatigue, and the standard range of mechanical tests.

A strong influence of fibre surface treatment on adhesion and on the development of damage has been established. Most mechanical properties appear to be enhanced by fibre surface treatment; but the optima for different properties are observed at different levels. In general the best combination of properties is at a somewhat lower level than the standard commercial treatment.

Damage development occurred at relatively higher strain in the PES matrix material and toughness was higher. However, the response to the surface treatment was similar in the 2 systems.

The level of adhesion and damage resistance has been shown to be quite sensitive to processing conditions, especially in the epoxy matrix system.
THE PRINCIPAL OBJECTIVE OF THE PROJECT IS TO DETERMINE THE EXTENT TO WHICH DAMAGE DEVELOPMENT IN CFRP LAMINATES MAY BE INFLUENCED BY CONTROLLING THE CHEMICAL AND PHYSICAL NATURE OF THE INTERFACE, AND INTERFACE REGION, BETWEEN THE FIBRE AND THE MATRIX. IT IS ALSO ENVISAGED TO STUDY THE EFFECT OF SYSTEMATIC VARIATIONS IN MATRIX PROPERTIES LINKED TO THIS INTERFACE MANIPULATION.

THE COMPOSITE SYSTEM TO BE STUDIED WILL BE BASED ON THE HYSOL-GRAFIL "APOLLO" HIGH PERFORMANCE CARBON-FIBRE. THE FIBRE WILL BE SUBJECTED TO DIFFERENT SURFACE TREATMENTS AND INCORPORATED INTO TWO DIFFERENT RESIN MATRICES, ONE A THERMOSETTING EPOXY RESIN AND THE OTHER A THERMOPLASTIC.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

University of Surrey
Address

GU2 5XH Guildford
United Kingdom

Participants (4)

CENTRO DE QUIMICA FISICA MOLELUCAR
Portugal
Courtaulds Research Ltd
United Kingdom
Address

CV6 Coventry
Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt eV
Germany
Address
Linder Höhe
51147 Köln
KATHOLIEKE UNIVERSITEIT LEUVEN
Belgium