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.
Ligament Thickness
Meaning
Physical dimension measurement between adjacent internal voids or between an internal defect and the nearest component surface establishes structural sound-wall limits in loaded components. Quality parameters defining ligament thickness determine the minimum solid resin section remaining to withstand mechanical stresses around internal voids. The parameter governs stress transfer pathways, rupture resistance, and pressure retention boundaries in thick-walled thermoplastic parts.
Its evaluation stops at the boundary of solid resin bridges, applying no direct measurement to total wall dimensions or unporous solid sections.
Structural Distance
Critical solid material paths between void walls govern localized yield behavior under tensile or shear loading conditions. Monitoring ligament thickness during quality inspections identifies dangerously thin plastic walls created by clustered micro-voids.
Wall Boundary
Internal voids located deep within a moulding may exert minimal influence on surface appearance while severely compromising structural integrity under load. When multiple gas pores coalescing near a wall reduce the ligament thickness below critical design thresholds, localized stress concentration causes sudden mechanical failure. Injection moulders control holding pressure and gate timing to suppress gas retention and preserve minimum resin wall thickness around internal channels.
Scans from computed tomography verify whether internal voids remain isolated or merge into hazardous continuous channels.
Stress Accumulation
Uncontrolled void formation near mechanical attachment points reduces solid wall material and promotes notch-sensitive brittle fracture. Tracking ligament thickness variations across tooling trials guides cooling channel modifications that ensure uniform resin solidification.