การประชุมวิชาการเครือขายวิศวกรรมเครื่องกลแหงประเทศไทยครั้งที่ 17 15-17 ตุลาคม 2546 จังหวัดปราจีนบุรี Finite element study of interfacial effects in the consolidation of matrix coated fibre composites Julaluk Carmai Department of Production Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology North Bangkok 1518 Pibulsongkram Rd, Bangsue Bangkok 10800 Thailand Tel: 0-29132500 Ext. 8208 Fax: 0-25870029 E-mail: jcm@kmitnb.ac.th Abstract The paper addresses finite element studies of the diffusion bonding effects at the interface between a locally reinforcing metal matrix composite and a monolithic engineering material. Diffusion bonding occurs during the consolidation of the composite during component manufacturing. The surface interaction behaviour at the interface has been described using an interface model. The model is developed by adopting an existing diffusion bonding theory and has been implemented into finite element software, ABAQUS, by mean of a user subroutine. Simulations of the surface interaction behaviour between the contacting surfaces have been carried out. The finite element simulations show that the diffusion bonding can lead to localized deformation, the inhibitation of consolidation, and a resulting inhomogeneous distribution of consolidated and unconsolidated distortion which results from the constraint imposed on the consolidating composite. 1. Introduction Continuous ceramic fibre reinforced titanium alloys are being developed for aerospace applications. They are generally used as local reinforcement in otherwise monolithic material components. Such locally reinforced composite components can be produced by inserting a bundle of continuous fibres, which are pre-coated with the titanium alloy matrix, into recesses machined into components also made from the titanium alloy. The application of pressure at an appropriate temperature causes the consolidation of the composite and also allows the fibre coatings, which are in intimate contact with the sides of the recess, to diffusion bond to the component. The surfaces of the component material and the matrix coating are not entirely flat as shown schematically in figure 1. When they are brought into contact, micro-cavities can result. As time proceeds, the asperities on the contacting surfaces are flattened and the micro-cavities reduce in size. When the surfaces are fully bonded (that is, all the micro-cavities are removed), the matrix coating on the bond plane will no longer be able to slide relative to the contacting surface. The interface is, therefore, in a state of ‘sticking friction’. This phenomenon can lead to the constraint of the deformation of the matrix coating during consolidation which in turn can inhibit subsequent consolidation resulting in a non-uniform consolidation as shown, for example, in figure 2. Die and coated fibre interfaces Figure 1 Schematic diagram showing the interface region between recess and coated fibres. Figure 2 Micrograph showing a matrix-coated composite specimen consolidated after 1 h. Coated fibres surface asperities Monolithic engineering component Die surface asperities Local reinforcement