The increased use of composite materials in industry, for example in the design of aircraft, helicopters, ships, trains, offshore structures, civil infrastructures, helmets, bicycles, biomedical implants, rackets, skis, etc., requires a detailed understanding of the behaviour of such composite components and structures to a wide range of potential loading. Components and structures using high performance long fibre composites are invariably laminated, and therefore very vulnerable to delamination since through thickness strengths are typically less than a thirtieth of the in plane strength. This hidden menace of Barely Visible Impact Damage (BVID) can reduce compression strength by more than 60%.
The maximum potential benefits derived from utilising composites rather than more traditional materials is at present severely limited by the enormous uncertainties in the design procedure, especially the damage tolerance, and are undoubtedly an obstacle to a more
widespread, cheaper and safer use of these materials. Potentially there are huge capital and lifecycle savings to be made by employing composite materials more economically and by reducing the
unnecessarily high factors of safety and over design which are currently in use.
The main thrust of the proposal is to develop a robust, mesh insensitive, generic delamination prediction algorithms. These improved delamination algorithms will be coupled to an optimum adaptive re meshing strategy, which uses IGES surface CAD information as a starting point.
The specific objectives are:
the development of an in plane 'intelligent' adaptive re meshing algorithm for the treatment of localisation in a physically realistic fashion. The algorithm will allow for automatic (rather than by predetermining the) location and refinement of the mesh at relevant sites throughout the FE mesh, without user intervention.
the development an out of plane 'intelligent' adaptive re meshing algorithm, which following convergence from the any in plane adaptive algorithm (initial stage), will introduce where necessary additional elements in the through thickness direction, again without user intervention.
to perform fatigue and impact testing for a range of potential laminated thermoset and thermoplastic composite coupon and small structural samples.
the development of reliable, more accurate and improved delamination models based on comprehensive numerical simulation for a range of advanced thermoset and thermoplastic composites. The ability to correctly predict localisation phenomena, and size effects is consider an important parameter.
to explore the use of statistical and probabilistic arguments for (i) adaptive re meshing and (ii) material variability in delamination modelling.
to demonstrate the accuracy of the algorithms by comparing the numerical results extensive laboratory experimental test results.
All designers and users of composite materials acknowledge the inability of existing analysis methodologies to accurately predict the development of damage in their products. The proposed developments will be a major advance in overcoming this severe limitation, and will allow European industry to participate fully in a rapidlyevolving area that is set to expand dramatically in the new millennium and beyond.
Funding SchemeCSC - Cost-sharing contracts
KT1 1HN Kingston Upon Thames
SW7 2BY London
7500 AE Enschede