Purpose: The main goals of this study were to observe the damage mode and measure the strength of pin joints in selected quasi-unidirectional glass NCF composite layups and provide recommendations for their optimum design.
Theory and Methods:
The specimen preparation and the mechanical tests were conducted according to the ASTM D-5961standard test method. Damage analysis of tested specimens was carried out by optical micrography and transparent light photography.
The results of pinned joint tests are shown and compared with bolted configurations of the same layups in the Fig. A. The pin joint strength was decreased for all layups due to the lack of lateral support provided
by the bolt head and nut. However, the cross-ply layups were less sensitive to the lateral support in comparison to the quasi-isotropic layups. It was observed that the major cause of the damage initiation was fibre micro buckling at the 0° bundles due to their significantly low compressive strength. In crossply
layups, the 90° bundles restricted the buckling of the 0° bundles by acting as a lateral support. Also, stacking of the plies in the same direction together resulted in a lower resistance against the bundle buckling.
The mechanical performance of the pinned joints of the quasi-unidirectional NCF composites was evaluated experimentally including basic imaging techniques. The results showed that the cross-ply layups have a better performance against pin loading in comparison to the quasi-isotropic layups.