Experimental & numerical study of dynamically loaded bolted & hybrid (bolted/bonded) joints.

摘要

Joining of composite materials is commonly achieved by bolting, bonding, or a combination of the two methods (hybrid) in engineering structures such as aircraft, marine and automotive. If not designed properly, dynamic loading of these joints can be critical to the integrity of the structure, as failure initiates at fastener-material interfaces. This demands a thorough understanding of the structural response of joints subjected to various loading conditions. The present study aims at predicting the strength of single-lap, bolted and hybrid joints with various geometric configurations under impact loading conditions. Experiments are conducted in a Drop Weight Impact Testing Machine (DWITM) where tensile loading is applied by a specially designed fixture. Results show that at room temperature, the strength of the hybrid joints with shorter edge distances is greater than or comparable to the strength of bolted joints with larger edge distances. At elevated temperatures (60°C), there is a 25-35% reduction of strength for joints with smaller edge distances while joint strength for large edge distances is invariant with respect to environmental conditions. In addition, the effect of clamping force on bolted joint strength is investigated using a Split Hopkinson Pressure Bar (SHPB). Results confirm that at higher loading rates, bolting torque plays a dominant role on the bearing strength of the joint structure. Enhanced 3D finite element (FE) models are developed to substantiate the experimental predictions and results are found to be in good agreement.