Evaluation of a Double Lap Composite Clamped Joint

Abstract

Double lap joints consisting of [05/905]2s, [905/05] 2s and [+455/-455]2s graphite epoxy laminates clamped between metal were pulled to failure in tension. The clamp load, loading rate and surface finish of both the composite inner and metal outer laps were varied to find their effect on the failure load. At clamp loads of 18 to 45 kN the [905/05]2s laminates had approximately equal loads at failure. However, as the clamp load increased to 45 kN, the [O 5/905]2s laminate had a higher load at failure than the [+455/-455]2s laminate. In all cases joint failure occurred as slip between the composite inner lap and the metal outer laps at static coefficients of friction of 0.3 to 1.06. The ef fect of metal or composite surface finish and loading rate on the failure load were found to be minimal for the amount of data taken. Joint efficiency (joint strength/ composite tensile strength) was between 75% and 95% for the [+455/-45 5]2s laminate and 10% to 20% for either the [05/90 5]2s or [905/05]2s laminates.