project brief
Carbon Fiber Tubes For Italy Custom
category
Tubes
client
Italy
start date
2021/05
end date
2021/07
budget
€48,000
innovative process
The challenge
This project entailed the precision machining of high-strength, thin-walled carbon fiber composite tubes for a Tier-1 Italian supplier to Formula racing series. The components serve two critical structural functions: (i) as load-bearing members within the roll cage support subassembly, and (ii) as interface elements between the chassis and aerodynamic appendages—demanding exceptional mechanical integrity, dimensional fidelity, and functional reliability under extreme dynamic loading (≥50 g acceleration, 200 Hz vibration spectrum). Key technical challenges included:
Ultra-tight geometric tolerancing: For 1200 mm-long tubes with nominal wall thickness of 1.5 mm, the customer specified concentricity ≤ 0.1 mm and straightness ≤ 0.5 mm/m—tolerances approaching those typical of aerospace-grade metallic shafts, yet inherently difficult to maintain in anisotropic, low-stiffness composite structures during clamping and machining.
Multi-axis feature machining: Both tube ends required angularly offset positioning grooves (±15° to ±45° relative to tube axis) and Ø8.0±0.02 mm transverse bores for precision bearing integration. Conventional milling or drilling risked interlaminar delamination, fiber pull-out, and thermal matrix degradation due to inadequate chip evacuation and localized heat buildup.
Functional surface engineering: Selective surface finishing was mandated—including controlled matte grinding (Ra 3.2 µm) on mounting zones and preservation of as-cured gloss (Ra ≤ 0.8 µm) on aerodynamic surfaces—while simultaneously preparing recesses for press-fit stainless-steel EMI shielding inserts, ensuring galvanic continuity and mechanical retention under cyclic vibratory loads (>10⁷ cycles at 150 g RMS).
project goals
Aligned with the customer’s AS9100-compliant quality framework, Sunnix established the following quantifiable, auditable objectives:
1、Geometric conformance: Achieve 100% first-article compliance with GD&T specifications via in-process monitoring using a calibrated 5-axis coordinate measuring machine (CMM), supported by high-fidelity mandrel-based internal support and custom soft-jaw chucks to minimize distortion.
2、 Structural integrity assurance: Guarantee zero detectable delamination, microcracking, or fiber damage in all machined regions through process-validated cutting strategies (low-feed, high-spindle-speed, cryogenic air cooling) and post-machining verification via phased-array ultrasonic testing (PAUT) per ASTM E2737.
3、 Functional integration: Embed 316L stainless-steel inserts with interference fit ≥ 0.03 mm and torque retention ≥ 12 N·m after 10⁶ vibration cycles; validate electromagnetic shielding effectiveness ≥ 60 dB across 1–10 GHz band.
4、 End-to-end schedule adherence: Deliver fully tested, traceable components—including raw material requalification (per EN 2562), dimensional inspection reports, PAUT certification, and EMI test summaries—within the contracted 8-week timeline.
the result
Sunnix successfully delivered 40 flight-ready tubular components meeting all contractual and technical requirements:
Dimensional performance: 100% of units passed final CMM verification—mean concentricity: 0.072 mm (±0.015); mean straightness: 0.41 mm/m (±0.03)—exceeding target thresholds by >25%.
Structural validation: Third-party PAUT (certified Level III technician) confirmed absence of subsurface defects in all critical zones; destructive pull-out testing demonstrated insert retention strength of 13.8 N·m—115% of design requirement.
Functional verification: EMI shielding effectiveness measured at 62.3 dB (avg.) across 1–10 GHz; vibration endurance testing (ISO 10326-3, 150 g RMS, 10⁷ cycles) showed no insert loosening or coating delamination.
Commercial outcome: The customer formally acknowledged Sunnix’s capability equivalence to certified European Tier-2 suppliers and awarded a follow-on development contract for carbon fiber monocoque bracket assemblies—marking Sunnix’s entry into the high-integrity motorsport composites supply chain.
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