Amorphous thermoplastic interlayer bonding techniques involve coating laminates to be bonded with a layer of amorphous polymer, using the mechanisms of molecular diffusion, mechanical keying, and fibre migration to achieve firm integration. By correct selection of that interlayer material components may then be fused at temperatures below the melting point of the composite matrix without leading to distortion of the components being bonded, thereby negating the need for complex tooling. The overall properties of the structure are therefore not compromised. Although cases where a joint may encounter extremes of environmental hostility are usually avoided, methods have been developed whereby the interlayer is able to exhibit a similar level of chemical resistance to that of a semi-crystalline peek matrix. Two methods exploiting the melting mechanisms associated with novel, semi-crystalline, polyketones exist. Excellent resistance to a range of commonly encountered aerospace fluids is demonstrated.