{"id":"ee8f6d9f-11d0-4eb8-aadf-1fed26ee4875","arxiv_id":"2607.07977","paper_version":1,"verdict":"CONDITIONAL","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":8,"one_line_summary":"Separate Puck fibre and matrix/inter-fibre phase-field fatigue channels, degrading resistance not stiffness, reproduce orientation- and notch-dependent UD composite fatigue modes with one fixed card.","lead":"A computational model treats fibre and matrix fatigue in unidirectional composites as two separate channels, each with its own history and toughness degradation, rather than one scalar damage number. With one fixed material card it reproduces the expected crack modes and life ordering across orientations and two notch geometries in pure numerical tests.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"The fixed fatigue card was post-selected after one-element studies to produce the target hierarchy, so cross-geometry consistency is shown only for a tuned demonstration set.","rationale":"The reader’s weakest assumption is exactly the load-bearing soft spot: Table 2 is a hand-selected demonstration card, not an identified IM7/8552 law, so the cross-geometry hierarchy is conditional on those free parameters remaining adequate when held fixed. No stronger internal inconsistency appears—the formulation is coherent, the shielding metrics (Supplementary Table S1) support the 0° mechanism interpretation, and the paper repeatedly scopes itself as numerical verification rather than life prediction. Because the claim is already carefully limited, the appropriate verdict remains CONDITIONAL; the concern does not push toward REJECT. Public UMAT–UEL release and an experimental mechanism campaign would be the natural next gates, but they lie outside the present manuscript’s stated boundary.","tokens_in":25226,"tokens_out":644,"duration_ms":22340,"concrete_test":"Re-run the full CNT00/45/90 and OHT00/45/90 fatigue suite (identical U_max or F_max, R=0.1, meshes, ΔN) with a single perturbed card that still separates channels in one-element tests but equalizes rates more closely (e.g. C_fat,f = C_fat,if = 4×10^{-3}, F_th,f = F_th,if = 0.08, a_f = a_if = 0.45, p unchanged). If 0° cases then activate ϕ_f before 2×10^5 or 45°/90° lives reorder or lose mode purity, the sufficiency claim for an arbitrary fixed card weakens.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper’s one-sentence claim is that separate fibre and matrix/inter-fibre channels (each degrading its own fracture resistance via χ_i(κ̄_i), not elastic stiffness) suffice to reproduce orientation-, load- and notch-dependent mechanisms with one fixed card. Section 4.2 states the Table 2 values “were selected after the one-element verification and sensitivity studies to produce stable channel separation, matrix/inter-fibre fatigue evolution on an accessible cycle scale, and a subcritical fibre channel under the selected fibre-aligned fatigue amplitudes.” Once chosen, the card is held fixed for CNT/OHT. Consequently the observed hierarchy (45°/90° collapse ~10³ cycles by inter-fibre cracking; 0° run-out to 2×10⁵ with stable longitudinal split and max ϕ_f = 0) is achieved by construction for this card. The structural benchmarks do not probe whether a different but still channel-separating card would preserve mode purity and ordering; the quasi-static Puck latch and anisotropic projectors A_i already bias crack topology, so the fatigue extension’s contribution to “sufficiency” rests on those free choices remaining adequate when frozen.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript formulates a Puck-informed, two-channel phase-field fatigue model for unidirectional plies in which fibre and matrix/inter-fibre mechanisms each carry independent fatigue histories, thresholds, and resistance-degradation laws. Fatigue lowers channel fracture resistance χ_i rather than elastic stiffness; stiffness loss and crack topology remain controlled by separate phase fields φ_f and φ_if. The model is implemented in Abaqus via a staggered UMAT–UEL architecture and exercised with one fixed IM7/8552 elastic/strength/phase-field card and one fixed fatigue card. One-element tests establish selective channel activation and parameter roles; the same card is then applied without orientation- or geometry-specific retuning to centred-notch and open-hole tension at 0°, 45°, and 90° under monotonic and cyclic loading, plus load-level and hole-size checks. The reported outcomes are mechanism-correct crack modes, the expected life ordering (matrix-dominated failure near 10³ cycles; 0° runout to 2×10⁵ with stable longitudinal splitting and inactive fibre field), and field-extracted evidence of split-induced fibre-channel shielding. The work is explicitly framed as numerical verification and cross-geometry consistency, not experimental life prediction.","tokens_in":25699,"tokens_out":1989,"duration_ms":33264,"significance":"If the formulation holds as a verified computational framework, it closes a clear gap between Puck-informed multi-phase-field fracture (previously largely monotonic) and recent composite phase-field fatigue models that do not assign independent fatigue histories to fibre versus inter-fibre channels. The separation of fatigue accumulation from stiffness loss is physically interpretable and makes the 0° split-induced shielding mechanism observable rather than conflated into a single damage variable. Strengths that should be credited include: a transparent verification-first programme (one-element channel separation, parameter-role sweeps, optional mean-stress check); a single fixed card applied across two independent notched geometries and three orientations; mesh/length-scale and cycle-block convergence documentation; and quantitative near-notch field extraction (Supplementary Table S1) supporting the shielding interpretation. Within the stated non-calibrated scope, this is a solid contribution to computational composite fatigue modelling and a usable basis for later experimental identification.","major_comments":[{"comment":"The one-sentence claim (Introduction) that mode-resolved resistance-only fatigue is “sufficient” to reproduce orientation-, load-, and notch-dependent mechanisms with one fixed card is demonstrated only for a post-selected demonstration set. Section 4.2 states that Table 2 values “were selected after the one-element verification and sensitivity studies to produce stable channel separation, matrix/inter-fibre fatigue evolution on an accessible cycle scale, and a subcritical fibre channel.” That selection is disclosed, but the structural campaign does not probe whether a different yet still channel-separating card preserves mode purity and life ordering. Because the quasi-static Puck latch, anisotropic projectors A_i, and the large G_c,f/G_c,if disparity already bias topology, the fatigue extension’s contribution to “sufficiency” needs either (i) a short robustness check (e.g. modest pertu","section":null},{"comment":"Relatedly, the manuscript should more sharply isolate what the fatigue extension adds beyond the underlying quasi-static two-phase-field Puck model. Static CNT/OHT results (Tables 7 and 9, Figs. 3 and 5) already recover transverse, off-axis, and longitudinal-split topologies; the fatigue results mainly show that, under the chosen amplitudes and Table 2 thresholds/rates, the fibre channel stays subcritical at 0° while matrix channels fail at 45°/90°. Section 9.1’s shielding argument is the right place to make this isolation quantitative: state which outcomes (runout, inactive φ_f, reduced P99(σ_⊥) and P99(τ_12) with finite P99(σ_∥)) cannot be obtained from the quasi-static model alone or from a single-channel fatigue degradation of a shared G_c. A brief single-channel or χ_f≡χ_if control comparison on one 0° fatigue case would make the mode-resolved fatigue contribution load-bearing rathe","section":null},{"comment":"Fatigue amplitude selection is case-specific and affects the reported lives, yet is only lightly justified. OHT fatigue uses U_max equal to 70% of the static displacement at which φ_if first exceeds 0.10 (Section 8.2); CNT uses separately chosen U_max values (Table 8). The fixed material/fatigue card is not retuned, but the driving levels are. For a verification claim of cross-geometry consistency of mechanisms this is acceptable; for any reading of life ordering as more than qualitative, the paper should state that absolute N_f values are amplitude-protocol dependent and report, at least for one matrix-dominated case, sensitivity of N_f to the 70% choice (e.g. 60% and 80%), analogous to the existing load-controlled OHT90 amplitude study (Table 11). Without that, Tables 8 and 10 should be labelled more clearly as protocol-dependent mechanism benchmarks rather than transferable life numbe","section":null}],"minor_comments":[{"comment":"Section 1, organization paragraph: “Section 2 the mode-resolved phase-field formulation” is missing a verb (“presents” / “introduces”).","section":null},{"comment":"Section 2.1: the θ versus paper orientation α convention (0° implemented as θ=90°, etc.) is easy to misread later; a one-line table or repeated reminder in figure captions for CNT/OHT would help.","section":null},{"comment":"Equations (11)–(13): the floor on F_raw_i,min and the cap bF_max are numerical safeguards; state briefly that all structural R=0.1 results are insensitive to the floor (or give the values used for ε and bF_max).","section":null},{"comment":"Table 4 and Section 4.4: OHT mesh sensitivity is reported for static load level only; a one-sentence note that fatigue crack mode (not only static peak) was unchanged between h=0.25 and 0.20 mm would complete the convergence story.","section":null},{"comment":"Figures 4 and 6: stage labels (“Stage 1/2/3”) are clear, but absolute cycle numbers on each panel would make the ~10³ versus 2×10⁵ contrast readable without returning to the tables.","section":null},{"comment":"Section 9.6 / Conclusions: the path to experimental validation is well stated; adding 1–2 concrete observables (e.g. split length vs N in 0° OHT, compliance growth rate vs D in 90°) would make the validation roadmap more actionable.","section":null},{"comment":"References: ensure consistent journal styling and DOI formatting; a few entries (e.g. recent 2025–2026 items) should be double-checked for final bibliographic details at production.","section":null}],"recommendation":"minor_revision","confidential_remarks":"The paper is carefully scoped and unusually transparent about being a demonstration card rather than an IM7/8552 calibration; that honesty should be rewarded rather than punished, provided the sufficiency language is tightened as in major comment 1. Novelty relative to Li et al. and Sharma & Singh is real (independent Puck-channel fatigue histories and resistance-only degradation). Fit for a computational-mechanics / composite-structures journal is good; it is not an experimental fatigue paper and should not be judged as one. I do not see load-bearing internal inconsistency; the main risk is overstated generality of a post-selected card, which is fixable in revision without new experimental campaigns."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The useful takeaway is simple: Dean puts independent fatigue histories, thresholds, and resistance-degradation laws on the two Puck channels (fibre vs matrix/inter-fibre), keeps fatigue off the elastic stiffness, and shows that one fixed IM7/8552 card produces the expected orientation- and notch-dependent mechanisms on both CNT and OHT. That combination is not in the cited multi-phase-field or composite phase-field fatigue papers; the paper is careful not to sell it as life prediction.\n\nWhat works: the separation of roles is clean (fatigue lowers χ_i; φ_f and φ_if do the stiffness and path). One-element channel separation and the parameter-role sweeps are the right first checks. The structural programme is serialized and consistent—transverse/off-axis collapse ~10³ cycles by inter-fibre cracking, 0° run-out to 2×10⁵ with stable longitudinal split and inactive fibre field—and the field-extracted shielding metrics (drop in σ_⊥ and τ_12 while σ_∥ stays large and F_eff^f stays subcritical) make the 0° story more than a contour anecdote. Mesh, length-scale, and cycle-block checks are present; load-control and hole-size trends go the right way without retuning. Citations sit in the right lineage (Puck multi-phase-field, phase-field fatigue, notched UD splitting).\n\nSoft spots, in proportion: Table 2 is a post-selected demonstration card chosen after one-element work for stable separation and accessible cycle scales (§4.2). Cross-geometry consistency is therefore shown for that card, not for the whole class of channel-separating cards. That is a real limit on the “sufficiency” claim, but the paper already frames the study as numerical verification, not calibration, so the stress-test does not collapse the argument—it just bounds it. Code is promised later, not shipped; no experimental mechanism or life data. Those are the next gates, not hidden flaws.\n\nThis is for people who build progressive-damage or phase-field fatigue models for UD plies and care about mechanism identity under cyclic load. It deserves a serious referee. I would engage, cite the formulation when I need a mode-resolved fatigue baseline, and push for public UMAT–UEL and an identified card.","headline":"Solid verification of a mode-resolved fatigue extension: real combination novelty, honest scope, and the “tuned card” stress-test is real but already scoped by the paper itself.","tokens_in":26307,"tokens_out":644,"would_cite":true,"duration_ms":7032,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"Separate fibre and matrix fatigue channels, each lowering its own fracture resistance, reproduce orientation- and notch-dependent composite fatigue with one fixed card.","keywords":["phase-field fracture","fatigue","fibre-reinforced composites","Puck failure theory","inter-fibre failure","open-hole tension","centred-notch tension","mode-resolved damage"],"falsifier":"Notched unidirectional coupons of the same material tested under the same cyclic amplitudes and orientations, with full-field or post-mortem mapping of crack sequence: if 0° specimens show early fibre cutting instead of stable matrix splitting that delays fibre failure, or if 45°/90° specimens do not fail by the predicted matrix/inter-fibre modes on the same order of cycles, the sufficiency claim fails.","tokens_in":26058,"feed_emoji":"🔧","tokens_out":640,"duration_ms":7219,"temperature":0.7,"pith_summary":"Unidirectional fibre composites fail under cycling by different physical mechanisms depending on fibre orientation: matrix and inter-fibre cracks under transverse or off-axis load, versus slow longitudinal splitting that can shield the fibres when load is fibre-aligned. A single scalar damage variable can match overall stiffness loss but cannot say which mechanism is active, so it cannot explain why some orientations fail in a thousand cycles while others run out. This paper builds a two-channel phase-field fatigue model, grounded in Puck's fibre versus inter-fibre distinction, in which each channel keeps its own fatigue history, threshold and resistance-degradation law. Fatigue never removes elastic stiffness directly; it only lowers the fracture resistance of the active channel, while the corresponding phase-field variable controls actual stiffness loss and crack path. With one fixed material and fatigue card, the same formulation is shown to produce the expected crack modes and life ordering on both centred-notch and open-hole coupons at 0°, 45° and 90°, under monotonic and cyclic loading, without orientation- or geometry-specific retuning. The work is offered as numerical verification of mechanism separation and cross-geometry consistency, not as a calibrated experimental life predictor.","feed_headline":"Two fatigue channels, one fixed card, correct composite crack modes","feed_subtitle":"Fibre and matrix paths degrade resistance separately; notch and orientation trends follow without retuning.","key_machinery":"Mode-resolved fatigue channels: two independent Puck-informed phase fields (fibre and matrix/inter-fibre), each with its own fatigue history, threshold and asymptotic resistance-degradation law that lowers effective fracture energy while leaving elastic stiffness loss to the phase fields themselves.","core_discovery":"Resolving fatigue into separate, physically interpretable fibre and matrix/inter-fibre channels—each degrading its own fracture resistance rather than elastic stiffness—is sufficient to reproduce the orientation-, load- and notch-dependent fatigue mechanisms of a unidirectional lamina with one fixed parameter card.","pith_inferences":[],"forward_implications":[],"fun_headline_variants":["Dual fatigue channels match UD composite crack modes with one card","Puck-informed fibre-matrix split reproduces orientation crack paths","Separate resistance degradation yields correct 0-45-90 fatigue modes","Mode-resolved phase-field fatigue captures multi-angle crack topology","Fixed-card dual channels drive right crack modes in notched laminates"],"cache_read_input_tokens":16512,"weakest_assumption_plain":"The structural fatigue numbers (rates, thresholds, exponents and degradation shapes for each channel) are a hand-chosen demonstration card selected for stable channel separation and accessible cycle counts, not an experimentally identified law for the material.","fun_headline_variants_meta":{"raw":{"variants":["Dual fatigue channels match UD composite crack modes with one card","Puck-informed fibre-matrix split reproduces orientation crack paths","Separate resistance degradation yields correct 0-45-90 fatigue modes","Mode-resolved phase-field fatigue captures multi-angle crack topology","Fixed-card dual channels drive right crack modes in notched laminates"]},"model":"grok-4.5","effort":"low","cost_usd":0.0053,"raw_usage":{"total_tokens":1500,"prompt_tokens":877,"num_sources_used":0,"completion_tokens":91,"cost_in_usd_ticks":53000000,"prompt_tokens_details":{"text_tokens":877,"audio_tokens":0,"image_tokens":0,"cached_tokens":128},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":532,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":877,"tokens_out":91,"duration_ms":5568,"temperature":1.0,"reasoning_tokens":532,"cache_read_input_tokens":128,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-10T14:21:20.299414+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"Notched unidirectional coupons of the same material tested under the same cyclic amplitudes and orientations, with full-field or post-mortem mapping of crack sequence: if 0° specimens show early fibre cutting instead of stable matrix splitting that delays fibre failure, or if 45°/90° specimens do not fail by the predicted matrix/inter-fibre modes on the same order of cycles, the sufficiency claim fails.","supporting_citations":[],"review_version":1}