Bolted joints for two-dimensional woven fabric reinforced composites. Tensile experimental photo experiments. All the connected areas of the samples were scanned by electron microscopy. The cross-section analysis away from the joint region: the fracture morphology of the warp and weft fiber bundles, they are basically along the surface of the fiber. It is smooth, indicating that the delamination failure mode is not obvious in the yarn direction, and the distribution of the fabric tissue points can be clearly seen. The weft around the fracture is the weft, and it can be seen that the surface of the weft has been split, indicating that the crack propagates in the direction of the weft. Hole wall section analysis: The section is divided into several levels, indicating that the direction of the extension of the fracture extends along the space. There are more fragments or material fragments that have been scattered, which is caused by the bolts crushing the walls of the holes. The intermediate raised portion is a warp yarn and a resin block, which is a resin-rich region. In the case of bolted joints, the tensile fracture of the plain reinforced composite material is along the texture of the tissue. The presence of the weft yarn causes the crack in the layer to evolve into an interlaminar crack. When the compressive stress of the bolt against the wall of the hole exceeds the viscous force of the material, the crack is generated and propagates simultaneously in both the warp and weft directions (the stress principal axis is the warp direction); when the crack passes through a tissue point, it will jump into the adjacent layer, expanding The direction remains the same; this continues until the entire cross section is penetrated by the crack and the plate is broken. This is consistent with the experimental phenomena and analysis observed by T. Ebeling et al. Conclusion: (1) When the fiber volume content is constant and the pre-tightening force on the bolt changes at 1.253.75 Nm, the ultimate load of the plate increases with the increase of the pre-tightening force. The pre-tightening force of the bolt has a positive effect on the load bearing capacity of the plate. (2) The tensile test of the reinforced reinforced laminate of the bolted woven fabric shows that the external force stretching causes the bolt to the main wall to be crushed. (3) By observing the scanning electron micrograph, it is found that the occurrence and expansion of the crack initiation is related to the fabric structure, that is, the structure determines the development direction of the crack.
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