In-plane properties of composite laminates with through-thickness pin reinforcement

Laminated fibre-reinforced composites can be reinforced by through-thickness pins to reduce their susceptibility to delamination. However, the presence of the pins creates resin pockets and disrupts the alignment of the fibres, and may thereby lead to a degradation of the in-plane strength of the composite. Experiments and numerical simulations show that the presence of through-thickness reinforcing pins decreases the tensile strength of the composite by 27%, and the compressive strength of the composite by at least 30%. It is also shown that the pattern in which the pins are inserted has a strong influence on the compressive strength. A pin pattern is identified in order to minimise fibre alignment disruption and thereby maximise the compressive strength.