By Greybridge - 12/30/2018 7:07:50 PM
Issue: persistent delamination issues.
Materials: Proset inf 114/211, hexcel 3k plain weave (proprietary tow count)
Part size: aprx 8"x25"x 60 layers tapering to 20
Procedure: modified proprietary RIDFT infusion, pre-mix and post mix degas, ambient temperature 62f, post infusion lean out, pre cure under 3psi bladder compression with temperature elevated to aprx 100f, post cure 8hr at 180f + extended cool down.
This purpose of this project is to create a lower cost alternative to an existing unidirectional prepreg product. The manufacturing specs are nearing aerospace requirements so we're trying to get to the limit of the material in terms of ultimate strength as well as fatigue life. As such, in aprx October we started incrementally implementing the processes described in a paper by Ding Ding Chen (see link below) with the intention of reducing void content. Unfortunately as we approach compliance with case D (2hr degas, extended high vac lean out), which yielded .1 percent void content in the study, we're seeing progressively more pronounced delamination failure during fatigue testing. Our last test article exhibited what can only be described as catastrophic delamination problems. In short, the more we "perfect" our process, the worse the problem seems to get. If anyone has seen this issue before or has any advice to offer we would be extremely grateful. Thx
https://catalog.lib.kyushu-u.ac.jp/opac_download_md/1470615/tj0922.pdf
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