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

Abstract

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 rateindependent 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.

Viscoelastic and cyclic compaction response of prepregs tested under isothermal temperatures and various compaction speeds

“…[10] The viscoelastic compaction response of prepregs depends on several factors, such as fiber-matrix interfacial bonding, temperature, rate-effect (time), stress, target fiber volume fraction, and so forth. [26,35,36] Several microstructural changes, such as elongation and compression of fiber tows, resin distribution, voids, and so forth, occur during the compaction of prepregs, owing to the aforementioned factors. [4] These microstructural changes can be identified using destructive testing techniques, such as optical microscopy, scanning electron microscopy, and so forth.…”