The present invention relates to a method of bonding together two pieces of composite material 10, 26 by applying a layer of glass fibre 20, 28 to a surface of each piece of composite material 10, 26, and bonding the pieces together by means of adhesive 30 between the layers of glass fibre 10, 26. The inclusion of the glass fibre layers 20, 28 advantageously promotes failure of the bond adjacent the glass fibre-adhesive interface rather than at the glass fibre-composite material interface, with the result that damage to the composite material 10, 26 is minimised, and subsequent repair is made easier.