Experimental characterization of autoclave‐cured glass‐epoxy composite laminates: Cure cycle effects upon thickness, void content, and related phenomena

Abstract

This article presents results from over 100 experimental autoclave curing fiber‐glass‐epoxy composite laminate curing runs. The primary objective was to verify shrinking horizon model predictive control—SHMPC—for thickness and void content control, using readily available secondary measurements. The secondary objective was to present and analyze the extensive experimental results obtained through this verification. Seven series of curing runs (16 per series) were performed, with cure settings governed by partial‐ or full‐factorial orthogonal array based design of experiments. Through t‐tests and two‐way analysis of variance, it was found that pressure magnitude had the largest influence on laminate thickness and void content, while first hold duration/temperature, pressure application duration, and run delay influenced void content more than thickness. Thinner laminates with lesser void contents resulted from pressure application before the second temperature ramp. Prepreg age also affected thickness and void content. Photomicrographs revealed not one large void, but void clusters. Interrupted autoclave cure cycles revealed that significant laminate thickness reduction occurred during all curing cycle stages. The percentage of resin weight loss through laminate sides increased with pressure magnitude and application duration. Ten test curing runs indicated that SHMPC met difficult thickness targets while minimizing void content.

Drawdown prepreg coating method using epoxy terminated butadiene nitrile rubber to improve fracture toughness of glass epoxy composites

“…After the ETBN rubber coating on glass/epoxy pre-pregs, the ETBN infiltrate through the thickness of glass fibre pre-preg during autoclave curing (the ETBN filtration zone is shown by enhanced pink region in Fig 3b-d).This infiltration depth varies between 50μm and 100μm in all specimens and appears not to be affected by the density of rubber coating. As a result of this infiltration, the average global thickness of the coated composite samples increased by a very small amount in the range 20-30µm, although this thickness variation that might be expected between autoclave cured laminates [26].…”

“…Mode I double cantilever beam (DCB) experiments were conducted in accordance with ASTM-D5528 [26]. Using a calibrated 1kN Instron 3343 uni-axial testing machine, displacement was applied to the sample at a crosshead extension rate of 3mm/min.…”

Magnet Assisted Composite Manufacturing: A Flexible New Technique for Achieving High Consolidation Pressure in Vacuum Bag/Lay-Up Processes

“…Fiber-reinforced polymer composites have been widely used in the automotive 1 2 , aerospace 3 4 , marine 5 6 , and construction 7 8 industries because of their unique properties such as high specific strength and modulus, favorable fatigue behavior, and corrosion resistance. Currently, high-quality composite laminates are predominantly fabricated using layers of pre-impregnated fabric (prepreg) cured in an autoclave under elevated temperature and high consolidation pressure of 0.27-0.69 MPa (40-100 psi) 9 . Somewhat lower quality composite laminates are produced by the wet lay-up process, where a higher consolidation pressure is not applied.…”

Investigation into thinning and spring back of multilayer metal forming using hydro-mechanical deep drawing (HMDD) for lightweight parts

“…The first method is employed to make huge FML structures which are relatively simple in design, such as wings, fuselages, aircraft's skins, etc. [3][4][5][6]. The second method uses the stamp forming (die/punch, etc.)…”