Nondestructive Computed Tomography Volumetric Void Acceptance Criteria for Heavy Polymer Sections
Computed tomography volumetric void acceptance requires zoning heavy polymer walls by stress field, setting pore limits below 0.1% in tensile skins.
PEEK Thick Wall
Meaning
High-performance semi-crystalline polyether ether ketone components with nominal wall thicknesses exceeding six millimetres present elevated processing challenges compared to thin-walled standard polymer parts. Manufacturing a PEEK thick wall section requires high barrel and mold temperatures to prevent premature skin freezing and extreme thermal gradient stresses. The designation governs crystallization uniformity, core void formation, and hold pressure retention across heavy cross-sections.
Its scope stops at thick-section semi-crystalline PEEK moldings, applying no parameters to thin-wall components, unfilled amorphous polymers, or low-temperature polyolefins.
Thermal Crystallization
High melt temperatures combined with heavy wall geometry generate slow internal cooling rates that alter polymer crystalline structures across the part cross-section. Moulding a PEEK thick wall demands specialized thermal control to ensure even crystal growth from core to surface.
Volumetric Boundary
Slow thermal dissipation in heavy polyether ether ketone sections causes core resin to remain molten long after the outer gate freezes, drawing material away and generating vacuum shrinkage voids. Achieving full density across a PEEK thick wall requires high packing pressures, elevated mold temperatures above one hundred seventy degrees Celsius, and extended hold cycles. X-ray CT scanning reveals internal vacuum voids and micro-cracking caused by steep thermal gradients between the outer mold surface and interior resin mass.
Virgin resin grades with controlled molecular weight distributions mitigate void formation better than regrind blends with inconsistent flow properties. Datasheet mechanical properties measured on thin test bars overestimate the tensile strength of thick section cores.
Moulding Shrinkage
Severe internal voiding and non-uniform crystallinity lead to catastrophic premature cracking under mechanical load. Controlling cooling rates across a PEEK thick wall section maintains structural density and satisfies stringent aerospace tolerance limits.