Effect of process parameters on mode-II interlaminar fracture toughness and fractographic features of automated fibre placement prepreg laminates

Abstract

The present study concerns the quantitive assessment of the influence of process parameters on the interlaminar properties of carbon fiber reinforced epoxy composites. Mode II interlaminar fracture toughness is evaluated based on the ENF test. Scanning electron microscopy images are used to evaluate the change in microstructures. The results indicate that the process parameters have a direct influence on the microstructural features and fracture toughness of laminates. Specifically, the elevation of layup speed leads to the increase of interlaminar porosity which results in a decline of fracture toughness. The moderate pressure could sufficiently evacuate air bubbles during the deposition which to a certain extent decreases the porosity; however, the excessive pressure squeezes resin out from the interlaminar region, which decreases the fracture toughness. Furthermore, the excessive temperature could both increase porosity and result in a thinner resin layer due to the change in resin flowability. In which case, the fracture toughness would be significantly decreased.

Analysis of New Concepts for the Consolidation Roller in Laser-Assisted Automated Tape Placement Processes

“…Compaction pressure is one of the most important process parameters regarding the final product quality [5]. Khan et al found that higher compaction pressures lead to a better overall quality of the laminate but can also result in high pressure air inclusions that lead to deconsolidation if the material is not cooled below glass transition temperature under the compaction roller [6].…”

Experimental and numerical investigations on the mode I delamination growth behavior of reinforced laminates via a ZPI (Z-pin pre-hole insertion) technique

“…4,5 Therefore, the low interlaminar fracture toughness of composite materials has become a bottleneck for their engineering applications, seriously restricting the application of composite materials in the main bearing structures of aircraft. 6,7 To overcome the disadvantages of composite laminates, such as poor mechanical properties in the thickness direction, poor interlaminar properties, and a low ability to carry impact damage, researchers invented various translaminar reinforced (TLR) technologies, such as Z-pinning, 8 3D weaving, 9,10 stitching, 11 tufting, 12 and others. Z-pinning is not only a simple process with low requirements for production equipment and low costs but also has a low impact on the intralaminar property of the laminate.…”

“…4,5 Therefore, the low interlaminar fracture toughness of composite materials has become a bottleneck for their engineering applications, seriously restricting the application of composite materials in the main bearing structures of aircraft. 6,7…”