Phenol formaldehyde (PF) resin is a ubiquitous element used in manufacturing high temperature components. In composites, the PF resin is typically applied to a fiberglass fabric from a dispersed colloidal polymer state. The polymerization cure stress that develops during the thermoforming of composite panels is responsible for macroscopic geometric distortion or warping often leading to the rejection of experimental and industrial parts. The relative void content of the PF-fiberglass composite face-sheets in laminates is quantified by Scanning Electron Microscopy. A correlation between the void content and the warpage value is made. The solvent conditions of the PF resin are varied and used to program for voids in the PF matrix of the composites. Monitoring of the polymerization / crosslinking in the PF fiberglass composites was done using Thermogravimetric Fourier Transform Infrared Spectroscopy. The solvent definition of the PF formulation and residual solvents established by the thermal history of samples is linked to voids content; in turn these voids act to relieve cure stress. The control of the resin chemistry, solvency, fiberglass infiltration, and cure conditions permit the fabrication of composites that have relatively low amounts of geometric distortion or warping.

Controlling void development in phenolic composites

251st National Meeting (2016)

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