Why should hole filling fasteners not be used in composite structures?

Using hole filling fasteners in composite structures is generally discouraged due to the risk of causing delamination. Composites are layered materials that may include fibers and resin. When a hole is filled with fasteners, it can create stress concentrations around the insertion point. If this stress exceeds the shear strength of the adhesive bonding the layers, it can result in the layers separating from one another, a phenomenon known as delamination.

Delamination can significantly compromise the structural integrity of composite components, leading to potential failure under load. The design and construction of composite structures typically require careful consideration of where and how fasteners are used to maintain their strength and stability. Employing methods that could induce delamination is, therefore, avoided in high-performance applications where the material’s properties and integrity are critical.

The other options provided do not directly address the primary concern associated with fastener use in composite materials. While weight, compatibility, and cost are factors to consider in material selection and fastening methods, the safety and structural integrity risks associated with delamination are the most significant reason hole filling fasteners should be avoided.