Characterization of intra-ply shear behaviors of unidirectional prepregs during hot diaphragm forming process

Intra-ply shear is the most important deformation mode in composite sheet forming. In this study, the intra-ply shear behaviors of cross-ply unidirectional carbon fiber/epoxy prepregs under double diaphragm compaction at different temperatures and cross-head rates were investigated by a home-made testing system. The experimental test results indicate that uniform temperature distribution and low forming speed in double diaphragm process help to obtain high-quality products. A modified model based on the temperature, cross-head rate and the level of compaction was proposed for shear angle prediction. Then fifth-degree polynomial and power functions combined with two rate-independent theories were used to calculate the shear force and modulus. The shear force and shear modulus are strongly influenced by the function that describing the relationship between the shear force and shear angle.

Automated summary

In this study, it was found that uniform temperature distribution and low forming speed in the double diaphragm process help to obtain high-quality products in composite sheet forming. A modified model for predicting shear angle was proposed based on temperature, cross-head rate, and level of compaction. The shear force and modulus were calculated using fifth-degree polynomial and power functions combined with two rate-independent theories, showing a strong influence of the function describing the relationship between shear force and shear angle.