Why should hole filling fasteners, like MS20470 rivets, not be used in composite structures?

Using hole filling fasteners, such as MS20470 rivets, in composite structures can lead to delamination, which is the separation of the layers of composite material. Composite structures are typically made of layers of resin and reinforcing fibers. When a hole filling fastener is installed, it can create a stress concentration around the hole, which may exceed the adhesive bond strength of the composite layers. This increased localized stress can cause the layers to separate, compromising the structural integrity of the component.

Delamination is particularly detrimental in composite materials because they rely on their layered structure for strength and stiffness. Unlike metals, composites cannot be easily reworked or repaired when delamination occurs, and this results in a potential failure of the entire structure. Therefore, it is essential to use fasteners and joining techniques that are specifically designed for composite materials to minimize the risk of such damage.

Other factors, such as weight, installation difficulty, and cost, may be considerations in different contexts but are secondary to the crucial issue of delamination when it comes to using inappropriate fasteners in composite applications.