Mechanically fastened splice joints like spar splice joints are essential in a large aircraft structure like wing to join inboard and outboard pieces spar members. Typically in a spar splice joint the inboard and outboard pieces of the spars are mechanically joined using splice plates. Such a splice joint often transfers large shear loads associated with bending moment and the joint behaviour is complex.13; In this paper the design procedure of a spar splice joint in a Carbon Fibre Composite (CFC) wing for a light transport aircraft is presented. The methodology of design in the preliminary design stage and the design validation with an element level test are discussed. Conventional strength of materials approach of the mechanically fastened joints is quite extensively used in the design. The fastener configuration at the splice joint location is decided based on standard design practices of web splice joints that are subjected to bending and shear loads. The fastener loads at different levels along height or span are then computed based on the linear distribution of bending strain and parabolic distribution of shear stress at the splice joint. The distribution of forces among the fasteners at each level is estimated based on fairly reasonable considerations of fastener pattern. This approach is quite novel compared to the conventional way of equally distributing the shear force and bending force. The design has been validated subsequently with static test on a spar splice specimen that has all the essential features of the splice joint in the wing. The various constraints in synthesizing the design of test specimen (which is an13; open section) to nearly simulate the wing (which is a closed box) are discussed. The splice joint specimen was subjected to the shear force that is seen in the wing. The specimen safely withstood the design ultimate load. The strains on the specimen at crucial locations were monitored during test. These strains have shown good correlation with the strains predicted from classical analysis. The testing of spar splice joint is an important step towards the certification programme.
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