An index for the indentation sensitivity of composite laminates

In this work, the effectiveness of a new empirical model, aiming to predict the indentation depth resulting in a composite laminate from a hemispherical tup impacting it at low velocity, was verified. To reach the above mentioned scopes, low velocity impact tests were carried out on two different composite systems in different stacking sequences, thickness and fibre volume fraction: a) glass/epoxy prepreg; b) graphite/epoxy prepreg. The samples were simply supported on a steel plate and struck at the centre by a hemispherical steel nose having 16 mm and 19.8 mm diameter. After impact, indentation was measured according to EN 6038 standard. The CFRP indentation data were drawn from a database: about 200 test records, generated by various researchers were individuated. The advantages of the new model is that the effect of the tup diameter is explicitly accounted for. Furthermore, a single material constant has to be experimentally determined and it can be assumed as an index for the indentation sensitivity, on the basis of which different materials can be ranked. The constant was found similar for GFRP and CFRP laminates denoting independence of constraint conditions, laminate type or laminae orientation and stacking sequence.