Thermal Cycling Stability in PC with Short Glass Fiber
Short untreated glass fiber is admissible as a thermal-fatigue moderating inclusion only if repeated thermal cycling delays crack initiation or reduces modulus drift relative to neat polycarbonate rather than accelerating whitening, fracture, or stiffness loss.
Thermal-fatigue mitigation is admissible only if interfacial micro-slip dissipates cycling stress over time. Earlier cracking, whitening, or modulus degradation than neat PC renders the claim non-admissible.
Crack onset is delayed or modulus drift is reduced relative to neat PC across the full thermal cycling regime.
Whitening, cracking, or modulus loss appears earlier or more severely than in neat PC under matched cycling.
Time-resolved response to repeated thermal strain, not single exposure behavior or initial stiffness alone.
Bulk expansion mismatch dominates damage
The assumption under test is that thermal cycling damage in polycarbonate is dominated by bulk thermal expansion mismatch.
This page asks whether short untreated glass fiber instead creates a controlled interfacial micro-slip regime that dissipates strain and delays cumulative thermal-fatigue damage over time.
Cycling history is the unresolved variable
This is not a short-cycle question about one or two thermal shocks. The governing issue is whether repeated excursions across a large temperature window progressively build or dissipate damage.
Entry into this branch is justified only because the decisive failure modes emerge through accumulated thermal history rather than immediate falsification.
Minimal admissible test
Subject polycarbonate containing 10 wt% short untreated glass fiber to 500–1,000 thermal cycles between −20 °C and 80 °C while monitoring crack initiation and modulus drift against neat PC.
- Material: PC + 10 wt% short untreated glass fiber
- Cycle window: −20 °C ↔ 80 °C
- Duration: 500–1,000 cycles
- Primary readouts: crack initiation, whitening, modulus drift
No compatibilizers, coatings, or interfacial rescue strategies are admissible inside the governed system.
Cycle-resolved interfacial strain behavior
The governing variable is whether repeated thermal expansion and contraction are dissipated through bounded interfacial slip or converted into cumulative damage.
- Delayed crack onset = candidate stress dissipation
- Reduced modulus drift = candidate cycling stability
- Early whitening = candidate microdamage onset
Initial stiffness or single-cycle appearance is non-admissible if repeated thermal history reverses the claim.
What breaks the claim
The claim fails if any of the following occurs relative to neat PC:
- Earlier cracking
- Earlier or greater whitening
- Greater modulus degradation
In Extended Cycle, delayed thermal-fatigue damage is not secondary noise. It is the primary falsification object.
What counts as temporal survival
The claim passes only if crack onset is delayed or modulus drift is reduced relative to neat PC across the full thermal cycling regime.
This does not establish universal utility. It establishes only that repeated cycling has not yet invalidated the micro-slip mitigation hypothesis.
What conventional composite logic may miss
Conventional materials reasoning often treats glass fiber in PC as a simple expansion-mismatch problem likely to intensify thermal-fatigue stress.
- Bulk mismatch may not be the only governing damage pathway
- Interfacial motion may dissipate strain rather than amplify it
- Repeated thermal history may reveal bounded slip unavailable to static models
This does not prove broad superiority. It defines a legitimate temporal boundary question.
Current cycle state
Final · Mid-Cycle
This status marks the entry as fixed in governed form while the dominant unresolved variable remains cumulative thermal cycling across the defined temperature window.
PASS
Crack onset is delayed or modulus drift is reduced relative to neat PC across 500–1,000 thermal cycles.
FAIL
Cracking, whitening, or modulus degradation appears earlier or more severely than in neat PC, indicating that interfacial micro-slip does not mitigate the dominant cycling damage pathway.
Thermal stability is admissible only if it survives cycling.
A polycarbonate system is not stabilized by surviving a temperature range once. It is stabilized only if repeated thermal excursions do not progressively break the claim.