This paper presents a detailed experimental study on carbon fibre (CF) polyether etherketone (PEEK) composite fasteners designed to join conventional high performance composites (CFRP). The failure mechanisms of two CF-PEEK fasteners with countersunk heads joining two laminate plates in a single-lap configuration were investigated under static (tensile) and cyclic loading (tension–tension). The failure process of the bolted joints is described in detail using acoustic emission and microscopic cut views. For comparison the CF-PEEK fasteners were replaced by metal fasteners (Titanium) under the corresponding conditions and loadings. The experimental results are in good agreement with the newly developed “closed-form” model up to the damage point of the joints. This enhanced analytical approach is a closed-form extension of the spring-based method, where bolts and laminates are represented by an arrangement of springs and masses. The model covers in all variables influencing the joint behaviour, such as fastener position, joint material, fastener type, hole diameter, joint thickness, bolt-hole clearance, and bolt torque.