What industries does newtsim serve?

newtsim serves oil and gas (flow assurance, drilling fluids, subsea pipeline), pharmaceutical and drug discovery, energy storage (battery materials, electrolytes), semiconductor process simulation, green hydrogen (electrolyser and catalyst design), nuclear decommissioning, aerospace and composites, corrosion and materials, carbon capture, agrochemicals, mining and geotechnical, and fermentation and bioprocessing.

How is newtsim different from standard CFD or simulation software?

Standard simulation tools use empirical models at a single scale. newtsim runs the full physics chain from quantum mechanics and molecular dynamics through to plant-scale CFD and structural mechanics, GPU-native, with direct data flow between every scale and no third-party solver dependencies. Constitutive behaviour is predicted from first principles rather than empirically fitted.

What does a fixed-price simulation study include?

A newtsim fixed-price study has a defined scope, clear deliverables, fixed cost agreed upfront, and is delivered in weeks rather than quarters. Studies typically include a scoping call, physics-grounded simulation using the appropriate newtsim solvers, results analysis, and a written report with actionable recommendations.

What is physics-grounded simulation?

Physics-grounded simulation derives material properties and constitutive behaviour from lower-scale physics (molecular dynamics and quantum mechanics) rather than from empirical fitting. This gives accurate predictions for novel materials and extreme conditions outside the range of experimental data, and enables root-cause analysis at the mechanistic level.

How does newtsim approach oil and gas flow assurance simulation?

newtsim runs a continuous physics chain from molecular wax crystallisation to full pipeline transient multiphase flow, with no empirical handoffs between scales. Wax appearance temperatures, gel strength, and deposition kinetics are predicted from molecular dynamics (newtsim Bond), passed directly to mesoscale morphology (newtsim Pack), and then propagated into multiphase CFD (newtsim Stream), giving flow assurance predictions that hold outside the range of laboratory data.

Can newtsim simulate battery electrolyte behaviour and degradation?

Yes. The Bond solver runs molecular dynamics for Li-ion transport and solid-electrolyte interphase (SEI) formation; Pack handles electrode morphology at the mesoscale; these results couple upward to cell-scale electrochemical models. This gives physics-grounded predictions of electrolyte degradation, capacity fade, and thermal behaviour without relying solely on empirical ageing fits.

How does physics-grounded drug discovery simulation differ from docking software?

Molecular docking software treats the protein and ligand as rigid bodies and scores binding poses by geometry. Physics-grounded simulation uses molecular dynamics to capture conformational flexibility and explicit solvation effects that rigid-body docking misses, predicting binding free energy, ADMET properties, and metabolic activation from first principles. This is particularly valuable for targets where induced-fit binding or solvent-mediated interactions drive selectivity.

What makes GPU-native simulation faster than CPU-based CFD?

GPU parallelism maps naturally to the computational kernels underlying molecular dynamics and CFD: large numbers of independent force or flux calculations that can execute simultaneously. newtsim runs all simulation scales GPU-native, avoiding the CPU-to-GPU data transfers that bottleneck traditional solvers which run physics on CPU and only offload selected operations to the GPU. This removes the transfer overhead and allows the full multiscale chain to run without the latency penalties of heterogeneous pipelines.

Does newtsim replace existing simulation tools like ANSYS or COMSOL?

newtsim fills the multiscale gap, connecting molecular-scale physics to the engineering-scale models that tools like ANSYS operate at. It is not a replacement for FEA-only or single-scale workflows where those tools are the right fit. Where newtsim adds value is in problems where constitutive behaviour, material properties, or interfacial physics need to be derived from lower-scale simulation rather than taken from a handbook or empirical fit.

How long does a fixed-price simulation study take?

Most studies complete in 4 to 8 weeks depending on scope. The standard timeline is: scoping call and problem definition in week 1; simulation execution across the relevant physics scales in weeks 2 to 4; results analysis, validation, and report delivery in weeks 5 to 6. More complex multiscale studies with broader operating envelopes may extend to 8 weeks. Scope and timeline are agreed and fixed before work begins.

What deliverables does a simulation study produce?

A newtsim simulation study delivers: a validated multiscale model calibrated to your system; an operating envelope with physics-based safety margins; a written technical report with findings and actionable recommendations; and optionally CFD visualisations or an ML surrogate model (newtsim Neural) for fast design-space exploration by your engineering team.

Does newtsim work for green hydrogen electrolyser and catalyst design?

Yes. The Stream solver handles proton exchange membrane and alkaline electrolyser CFD: multiphase flow, bubble dynamics, and membrane transport. Bond handles catalyst surface reaction molecular dynamics, giving adsorption energies and reaction barriers from first principles rather than from empirical correlations. Neural then produces fast-to-run surrogate models for design-space exploration and stack optimisation, reducing the iteration cost for new catalyst compositions and electrode architectures.

newtsim is a physics-grounded multiscale simulation consulting firm and software platform. We deliver fixed-price simulation studies and platform licences for industrial clients, covering the full physics chain from quantum mechanics and molecular dynamics through to plant-scale CFD and structural mechanics. All solvers run GPU-native.

Does newtsim use artificial intelligence or machine learning?

Yes. newtsim Neural produces ML-trained surrogate models derived from high-fidelity physics simulations. These surrogates run in milliseconds rather than hours, enabling rapid design-space exploration and real-time control without sacrificing physical accuracy. The ML models are trained on physics simulation data, not empirical measurements, so they inherit the accuracy and extrapolation properties of the underlying physics.

How do I get started with newtsim?

Book a free technical scoping call at newtsim.com/demo. Bring a description of your engineering challenge, the physics you think are important, and any data you have. The call is 45 minutes and produces a problem definition, proposed physics chain, and outline scope that forms the basis of a fixed-price proposal.

Can newtsim simulate non-Newtonian fluids?

Yes. newtsim specialises in non-Newtonian flow: yield-stress fluids, viscoelastic materials, shear-thinning and shear-thickening systems, and complex multiphase flows. The Stream solver handles macroscale CFD for these systems; Bond provides the molecular-scale rheology predictions that replace empirical viscosity fits; and the full chain gives accurate behaviour outside the calibrated range of laboratory data.

Does newtsim work for small companies or startups?

Yes. Fixed-price studies are available to clients of any size. The fixed-price, fixed-scope model means you know the cost before committing, making it accessible for smaller organisations without large simulation teams. Many newtsim clients are startups and scale-ups who need physics-grounded analysis early in product development before investing in laboratory or pilot-scale work.

What is the difference between molecular dynamics and CFD?

Molecular dynamics (MD) simulates the motion of individual atoms and molecules to compute material properties such as viscosity, diffusivity, reaction rates, and phase behaviour, from first principles. Computational fluid dynamics (CFD) models bulk fluid flow at the engineering scale using those material properties as inputs. newtsim connects the two: MD provides accurate constitutive inputs that CFD uses for engineering-scale predictions, rather than relying on empirical correlations.

What is a surrogate model in simulation?

A surrogate model (also called a reduced-order model or emulator) is a fast mathematical approximation of a complex simulation. newtsim Neural builds ML surrogates trained on high-fidelity physics simulation data. Once trained, a surrogate evaluates in milliseconds instead of hours, enabling real-time optimisation and design-space exploration. Because surrogates are trained on physics data, they are more accurate than empirical correlations, especially outside the training range.

What deliverables does a newtsim simulation study produce?

A newtsim simulation study delivers: (1) a validated multiscale model calibrated to your system; (2) an operating envelope with physics-based safety margins; (3) a written technical report with findings and actionable recommendations; and optionally (4) CFD visualisations and an ML surrogate model for fast ongoing design-space exploration by your engineering team.

Aerospace & Advanced Manufacturing

Aerospace & Advanced Manufacturing · Case Study

Composite Repair Substantiation: Predicted Residual Strength Recovery for CFRP Nacelle Lip Skin

Executive Summary

Between 2015 and 2022, the FAA Service Difficulty Reporting database recorded 34 hail-induced CFRP nacelle damage events on CFM56-equipped narrow-body aircraft. Of those, 9 required engineering disposition exceeding Structural Repair Manual limits — the repair diameter or dent depth had gone beyond what the OEM's qualified repair procedures could address — and 6 produced aircraft-on-ground conditions. The mean AOG duration for out-of-SRM repairs was 18 days, ranging up to 47 days. These are not rare events. When hail energy at the nacelle lip skin exceeds approximately 25–30 J, damage footprints routinely exceed SRM repair diameter limits in the monolithic CFRP zone. The consequence is an aircraft that cannot legally return to service until a formal engineering analysis package — signed by an FAA DER with composite structure authority, demonstrating residual strength recovery under FAR 43.13(b), AC 20-107B Section 9, and AC 21-26 — has been produced, reviewed, and approved. The underlying composite failure mechanism is well understood: hail impact produces delamination and matrix cracking in the monolithic skin; the interlaminar fracture toughness of the repair interface, reduced further by lower-temperature field cure, governs whether a scarf repair restores full ultimate load capability or merely limit load capability. That toughness-governed failure mode transition — between interface debond and parent laminate failure — is not adequately resolved by the SRM's simplified sizing rules, which specify a fixed taper ratio without accounting for the combined effects of field-cure strength knockdown, hot/wet service conditions, and fatigue scatter.

Had a progressive damage simulation of the scarf joint been applied during development of the SRM repair limits, the taper ratio vs. joint efficiency curve would have been mapped against the full knockdown chain (hot/wet at 0.85, 121°C field cure at 0.85, fatigue scatter at 0.92 — net 0.668). That analysis would have shown that the standard 1:25 SRM taper, while adequate for small BVID, fails to restore ultimate load capability after the combined knockdowns at large visible damage sites — precisely the cases that generate AOG events. The minimum taper ratio for full ultimate recovery, 1:35, would have been embedded in the SRM from the outset, preventing the regulatory impasse.

This simulation resolves the critical regulatory question — minimum scarf taper for SRM-exceedance repair — in 5–7 weeks instead of the 14–22 weeks of physical specimen fabrication and testing that conventional substantiation requires, directly reducing the AOG period by 50–85 days per event against a mean AOG duration of 18 days for out-of-SRM dispositions. The scarf joint analysis also maps the zones of maximum interlaminar shear stress and minimum residual strength as a function of taper ratio and damage site location; those zones are the natural placement positions for newtsim livesim monitoring on nacelle structures returned to service after out-of-SRM repair, enabling continuous strain monitoring at the repair periphery and acoustic emission detection of any delamination re-initiation under operational load cycling, with ahead-of-failure warning before residual strength reaches limit load.

Scenario Background

(illustrative reference case)

The scenario involves a fictional Part 145 Repair Station, Stratford Aviation MRO Ltd., located in Tulsa, Oklahoma, with composite structure rating (Class 4, Part 145.55) and OEM-authorised repair capability for the CFM56-7B nacelle family on Boeing 737NG aircraft.

The certification framework for the nacelle and airframe is governed by FAR Part 33 / CS-E for the engine type certificate (CFM56-7B), FAR Part 25 / CS-25 for the airframe installation certification (Boeing 737-800), FAA AC 20-107B Section 9 for composite structure repair analysis methodology, FAA AC 21-26A for quality system requirements in composite repair manufacture, FAA AC 43-214A for repairs and alterations to composite and bonded structure, FAR 43.13(b) requiring that repairs restore original structural capability, and FAR Part 145.109 addressing equipment, materials, and data requirements.

The CFM56-7B nacelle inlet lip skin is a co-cured composite structure with a sandwich-to-monolithic transition. The forward barrel is a CFRP/Nomex honeycomb sandwich with 0.5 mm CFRP face sheets and 12.7 mm core (13.7 mm total), transitioning at the inlet highlight to a solid CFRP monolithic laminate of 3.2 mm thickness with an 18-ply layup of [45/0/-45/90/0/+/-45]s. The transition zone spans 25 mm in taper length.

The monolithic zone uses Cytec Cycom 977-3 aerospace toughened epoxy with Toray T300 carbon fibre (3k, 193 g/m squared). The cured ply thickness is 0.178 mm, with autoclave cure at 177 degrees C, 6.9 bar, for 120 minutes. The fully cured resin has a glass transition temperature of 182 degrees C (dry) and a fibre volume fraction of 58%.

Cytec Cycom 977-3 Unidirectional Properties (OEM Qualified, B-basis):

Property	180 degrees C Autoclave Cure (Baseline)	121 degrees C Field Cure (Knockdown)
E_11 (longitudinal)	136 GPa	136 GPa (no change -- fibre-dominated)
F_1^T (longitudinal tensile)	1,950 MPa	1,950 MPa (no change)
F_1^C (longitudinal compressive)	1,140 MPa	1,140 MPa (no change)
F_2^T (transverse tensile)	58 MPa	49 MPa (-15% -- matrix-dominated)
F_2^C (transverse compressive)	176 MPa	150 MPa (-15%)
F_6 (in-plane shear)	84 MPa	71 MPa (-15%)
G_Ic (Mode I interlaminar)	0.28 N/mm	0.22 N/mm (-21% -- toughness reduction)
G_IIc (Mode II interlaminar)	0.95 N/mm	0.74 N/mm (-22%)

Field repair cure uses the Cycom 977-3 wet layup variant cured by heat blanket at 121 degrees C and 0.07 MPa per the OEM's Portable Heating Equipment qualified cure cycle. The strength reduction from the lower cure temperature (121 degrees C vs. 177 degrees C baseline) is 15% for all matrix-dominated properties and 21-22% for fracture toughness, per Cytec published qualification data.

The operating loads on the nacelle inlet lip skin include an internal pressurisation differential of 0.05 MPa producing hoop tension, a hoop running load of 420 N/mm in tension (circumferential), an axial bending moment of +/-850 N-m/m at the inlet highlight under 2.5g and gust conditions, and a secondary vibratory fatigue consideration of +/-60 N/mm at 5x blade passing frequency. The critical combined load case involves the hoop load of 420 N/mm acting simultaneously with the axial bending moment of 850 N-m/m.

Challenge

Damage Inventory -- Post-Event NDI (PAUT and Tap-Test):

Site	Location	Damage Type	Dent Depth	Delamination Size	Zone	Classification
A (critical)	85 mm from highlight	Matrix crack + delamination	2.1 mm	28 mm x 35 mm	Monolithic	VD -- repair required before flight
B	145 mm from highlight	Delamination	1.4 mm	22 mm x 18 mm	Monolithic	BVID -- repair elected
C	210 mm from highlight	Surface dent	0.6 mm	14 mm x 11 mm	Sandwich	BVID -- monitor
D-G	Aft barrel region	Sub-threshold dents	0.3-0.8 mm	--	Sandwich	BVID -- within SRM disposition

The proposed repair for Sites A and B uses a scarf-and-patch method with Cycom 977-3 field-repair prepreg (wet layup variant), cured by heat blanket at 121 degrees C, 0.07 MPa, for 90 minutes. Damaged material is removed to a feather edge using a scarf grinding plate, the patch restores the laminate sequence ply-by-ply, and one additional 1.0 mm proud over-ply provides supplementary load sharing.

The standard scarf repair sizing rule in the OEM SRM specifies a taper ratio of 1:25, equalling 4 mm step per ply removed. With 7 damage-penetrated plies removed at Site A (each ply 0.178 mm) plus scarf geometry requirements, the minimum scarf diameter at 1:25 taper is 185 mm. The SRM maximum repair diameter for this zone is 150 mm. Site A therefore requires out-of-SRM engineering disposition, which per FAA AC 20-107B Section 9 must demonstrate ultimate load capability (1.5x limit load) with the repair in place, compliance after environmental knockdown for hot/wet exposure, fatigue life to the component design life, and repair quality assurance controls ensuring the repair is manufactured correctly. The engineering analysis must be signed by a DAR or DER with composite structure authority.

Real-World Basis

FAA Service Difficulty Reporting -- Hail Damage to CFRP Nacelles

The FAA SDR (Service Difficulty Reporting) database contains 34 separate reports of hail-induced CFRP nacelle damage on CFM56-equipped narrow-body aircraft for the period 2015-2022. Of those 34 reports, 21 reference lip skin delamination in monolithic and sandwich zones, 9 required engineering disposition exceeding SRM limits (damage area or depth), 6 led to an aircraft-on-ground (AOG) condition, and the mean AOG duration for out-of-SRM repairs was 18 days (range 9-47 days). The 9 out-of-SRM dispositions document the specific regulatory challenge this study addresses: when hail energy exceeds approximately 25-30 J at the nacelle lip skin, damage footprints routinely exceed SRM repair diameter limits, requiring engineering analysis packages of the type demonstrated here.

Published Composite Repair Data

NASA scarf joint testing provides the primary benchmarking dataset. Scarf joint efficiency data (failure load / pristine laminate strength) as a function of taper ratio show a clear progression: at 1:10 taper (5.7 degree scarf angle), joint efficiency is 62% with adhesive/interface shear failure; at 1:20 (2.9 degrees), efficiency rises to 79% with interface debond failure; at 1:25 (2.3 degrees), 87% with mixed-mode failure; at 1:30 (1.9 degrees), 93% with parent laminate failure adjacent to the repair; and at 1:35 (1.6 degrees), 98% with parent laminate failure. For 977-class epoxy systems, the joint efficiency transition from interface-dominated to parent-laminate-dominated failure occurs between 1:25 and 1:30 taper ratio -- the transition point that governs the minimum taper for full strength recovery.

Cytec's published qualification data for the field-repair variant of Cycom 977-3 documents strength retention after 121 degrees C cure vs. 177 degrees C autoclave baseline: 85% retention for all matrix-dominated static strength properties and 78% retention for Mode I and Mode II fracture toughness.

CMH-17 Environmental Knockdown Framework

CMH-17 Rev. G defines the hot/wet environmental knockdown applicable to thermosetting CFRP composites in tropical service. The hot/wet condition (70 degrees C, 1.0% moisture by weight) produces a knockdown factor of 0.85 on matrix-dominated properties; temperature alone (70 degrees C, ambient humidity) yields 0.90; and moisture alone (ambient temperature, equilibrium) yields 0.93.

Simulation Approach

The repair substantiation analysis proceeds in three sequential stages with clearly documented hand-offs between stages.

Stage 1 -- As-Damaged Panel Analysis (newtsim Span)

The pre-repair damaged state at Site A (28 mm x 35 mm delamination, 2.1 mm dent) is reconstructed from PAUT C-scan data imported into the FEM as a delamination area map. The delamination is represented as a contact pair at the affected ply interface (frictionless sliding, no tensile load transfer across the delamination plane). The surrounding matrix crack density is estimated from the dent depth using a calibrated empirical relationship from the impact simulation library (based on the correlation for Cycom 977-3-class systems in the FAA composite damage database) and applied as a CDM-degraded stiffness zone. The as-damaged panel is loaded under the combined operating load case (hoop 420 N/mm + axial bending 850 N-m/m) to identify the as-damaged residual strength and confirm load-path criticality.

Stage 2 -- Scarf Geometry Parametric Study

Four scarf taper ratios are modelled for the Site A repair:

Taper Ratio	Scarf Diameter	Number of Repair Plies	Scarf Angle
1:20	152 mm	7	2.9 degrees
1:25	185 mm	7	2.3 degrees
1:30	218 mm	7	1.9 degrees
1:35	251 mm	7	1.6 degrees

Each repair model restores the full nominal laminate sequence with one proud over-ply. The scarf joint interface is modelled with cohesive zone elements calibrated to the Cycom 977-3 field-cure adhesive properties (G_Ic = 0.22 N/mm, G_IIc = 0.74 N/mm -- after 121 degrees C cure knockdown). The panel is loaded to failure and the failure load, mode, and location are extracted.

Stage 3 -- Environmental and Fatigue Knockdowns

The predicted static failure load from Stage 2 is reduced by a chain of knockdown factors: hot/wet condition (70 degrees C, 1.0% moisture) at 0.85 per CMH-17 Rev. G; 121 degrees C cure temperature reduction at 0.85 per Cytec 977-3 field cure qualification data; and fatigue scatter factor (B-basis, 100,000 cycles LL) at 0.92 per published NASA scarf joint fatigue data. The net knockdown chain is 0.668 (0.85 x 0.85 x 0.92). The two knockdown factors of 0.85 (hot/wet and cure temperature) are applied independently because the hot/wet condition applies to in-service usage of the repaired structure, while the cure temperature reduction applies to the baseline strength of the repair material itself; they are not double-counted.

Simulation Caveats

The delamination area extracted from PAUT C-scan is used directly as the input damage geometry for Stage 1. PAUT spatial resolution is +/-2 mm in-plane and +/-0.5 mm in depth at the operating frequency (5 MHz). Any delamination patches smaller than 6 mm x 6 mm may not be resolved; the simulation captures the principal damage features but may miss micro-delaminations outside the primary damage zone.

The CZE calibration assumes the field-repair scarf joint is manufactured to the minimum quality standard qualifying for the 121 degrees C cure knockdown factor. In practice, poor scarf preparation (grinding angle deviation greater than +/-0.5 degrees, inadequate surface preparation, porosity in the wet layup) can reduce joint efficiency by an additional 10-20% beyond the modelled knockdown. A repair manufacturing quality assurance inspection regime is specified as part of the engineering order to guard against this.

Applying the hot/wet factor (0.85) and cure temperature factor (0.85) independently in the knockdown chain may be conservative if the test data for the 121 degrees C cure variant was itself measured at hot/wet conditions. A review of Cytec's qualification test temperature and moisture conditions is recommended before finalising the knockdown chain for the DER package.

The fatigue scatter factor of 0.92 is derived from published NASA scarf joint fatigue data at constant-amplitude R = 0.1 loading. The nacelle lip skin experiences complex multiaxial fatigue from combined hoop, bending, and vibratory loads at fan blade passing frequency. The 0.92 factor may underestimate fatigue damage accumulation under spectrum loading; this is flagged for the DER as a conservatism gap requiring test confirmation if the component is assigned a fatigue-critical classification.

The 1.0 mm proud over-ply is modelled as fully bonded to the repair surface. In a field repair, the over-ply adhesion depends on surface preparation quality. If the over-ply disbonds partially (a plausible in-service scenario), the load sharing benefit is lost and the effective repair strength reverts to the bare scarf joint performance -- approximately 5-8% lower than the modelled value.

Key Predictions / Results

Stage 1 -- As-Damaged Residual Strength:

Damage Site	As-Damaged Residual Strength	% of Pristine Ultimate	Return-to-Flight Status
Site A (2.1 mm dent, 28x35 mm delamination)	58% of pristine ultimate	58%	Not permitted -- below limit load
Site B (1.4 mm dent, 22x18 mm delamination)	74% of pristine ultimate	74%	Permitted at limit load -- repair elected

Stage 2 -- Scarf Repair Parametric Results (Static Failure, Before Knockdowns):

Taper Ratio	Diameter (mm)	Static Failure Load (% Pristine)	Failure Mode	Scarf Interface Debond?
1:20	152 mm	81%	Interface debond at 121 degrees C joint	Yes -- premature
1:25	185 mm	94%	Mixed -- interface then parent laminate	Yes -- partial
1:30	218 mm	101%	Parent laminate adjacent to repair	No
1:35	251 mm	103%	Parent laminate (correct mode)	No

Scarf repair joint efficiency vs taper ratio — Cycom 977-3 site A repair, predicted vs NASA IM7/977 reference, with post-knockdown net allowables and failure mode transition

Stage 3 -- Post-Knockdown Net Allowable Strength:

Taper Ratio	Static Failure (%)	After Hot/Wet x0.85	After Cure KD x0.85	After Fatigue x0.92	Net Allowable	Meets Limit Load (67%)?	Meets Ultimate (100%)?
1:20	81%	69%	59%	54%	54%	No	No
1:25	94%	80%	68%	63%	63%	No (marginal at 63% vs. 67%)	No
1:30	101%	86%	73%	67%	67%	Yes -- exactly at limit	No (not 100%)
1:35	103%	88%	74%	68%	68%*	Yes	Yes*

Cumulative knockdown waterfall — 1:35 scarf repair, hot/wet × 121°C cure × fatigue scatter = 0.668 net factor, ultimate and limit load compliance thresholds

*Note: 68% of pristine means 68% of 100% ultimate. Meeting the "100% ultimate recovery" requirement means the net allowable (after all knockdowns) must be at least 67% of the pristine ultimate (i.e. the structure sustains 1.5x limit load = ultimate). A net allowable of 68% of pristine just meets this threshold. The 1:35 taper is the minimum configuration meeting the full ultimate recovery requirement.

Detailed Failure Mode Analysis -- 1:35 Scarf (Recommended Configuration):

Loading Step	Location	Predicted Stress (MPa)	Allowable (Post-KD)	Margin
Hoop 420 N/mm	0 degree repair plies	131 MPa tensile	F_1^T = 1,950 MPa	+1388%
Hoop 420 N/mm	+/-45 degree repair plies	78 MPa shear	F_6 = 71 MPa x 0.85 (KD)	-0.4% at limit
Axial bending 850 N-m/m	Scarf interface (1:35)	0.81 MPa peel	G_Ic/element = 0.22 N/mm	Positive margin
Combined limit load	Parent laminate adjacent scarf	189 MPa	F_2^T (in-situ) = 201 MPa	+6.3%

Site B Repair (1:25 Scarf, within SRM Limits):

Metric	Value
Scarf diameter	145 mm (< SRM 150 mm limit)
Static failure load	97% of pristine
Net allowable after all knockdowns	76% of pristine
Meets limit load requirement (67%)?	Yes -- 13% margin
Meets ultimate recovery requirement?	Yes -- 76% > 67%
Inspection interval	Standard (600 flight cycles)

Recommended Minimum Taper Ratios (for revised SRM entry):

Damage Classification	Dent Depth	Recommended Taper Ratio	Notes
BVID (sub-threshold)	< 1.27 mm	1:25	Within SRM limits
BVID (at threshold)	1.27 mm	1:25	Enhanced inspection 300 cycles
VD -- small	1.27-2.0 mm	1:30	Meets limit load, enhanced inspection
VD -- large	> 2.0 mm	1:35	Meets ultimate recovery; standard interval

Comparison Methodology

1. NASA Scarf Joint Efficiency Data

The predicted scarf joint efficiency vs. taper ratio curve from Stage 2 is checked against published NASA test data for IM7/977-class composite scarf joints as secondary confirmation:

Taper Ratio	NASA Efficiency (%)	Predicted (%)	Error
1:20	79%	81%	+2.5%
1:25	87%	94%	+8.0% (Cycom 977-3 is tougher than IM7 system; expected higher)
1:30	93%	101%	+8.6%
1:35	98%	103%	+5.1%

The consistently higher predictions reflect the higher fracture toughness of Cycom 977-3 vs. the IM7 reference system in the NASA study. Predictions fall within 10%, meeting the +/-10% acceptance criterion for benchmarking against a different material system.

2. ASTM D5573 Failure Mode Classification Check

ASTM D5573 classifies adhesive bond failure modes. The predicted failure mode transition from interface debond (1:20, 1:25) to parent laminate failure (1:30, 1:35) is consistent with the ASTM D5573 framework for adhesively bonded composite joints, where cohesive-to-adherend failure transition occurs at taper ratios of approximately 1:25-1:30 for 977-class adhesives, confirming the model captures the failure mode physics correctly.

3. Cytec Cycom 977-3 Cure Temperature Knockdown Validation

The predicted 15% strength reduction from 177 degrees C baseline to 121 degrees C field cure is directly compared against Cytec's published qualification test data for the field-repair variant:

Property	Cytec Measured Retention	Applied Factor	Error
F_2^T retention (121 degrees C / 177 degrees C)	85% +/- 3%	85%	0% (exact match)
G_Ic retention (121 degrees C / 177 degrees C)	78% +/- 5%	79%	+1.3%
F_6 retention	84% +/- 4%	85%	+1.2%

Agreement within 3% on all cure temperature knockdown factors.

Deliverables

As-Damaged Residual Strength Report: Sites A and B residual strength assessment with load-path criticality classification, full-field stress and delamination contour maps, and explicit return-to-flight risk statement formatted for Aircraft Maintenance Log entry and airworthiness release.
Scarf Repair Trade Study (1:20 through 1:35): Tabulated failure loads, failure modes, and post-knockdown net allowables for all four taper ratios; failure mode contour maps at the critical load step for each configuration; recommendation with justification per AC 20-107B Section 9.
Recommended Repair Configuration (1:35 Scarf, 251 mm Diameter): Complete repair specification including: scarf preparation procedure, ply layup schedule, cure cycle, NDI requirements post-repair (PAUT full coverage), and visual inspection criteria.
Environmental Knockdown Analysis: Full knockdown factor chain with source documentation (CMH-17 for hot/wet, Cytec qualification data for cure temperature, NASA scarf fatigue data for fatigue scatter) and explicit justification for independent application of each factor.
Revised SRM Entry Proposal: Taper ratio vs. damage size design chart (dent depth axis x damage diameter axis, colour-coded by required taper ratio) for Level 1 engineering dispositions. Formatted per CFM56-7B nacelle SRM supplement template for OEM review and possible incorporation.
FAA DER Engineering Package: Complete stress analysis report (newtsim Span model documentation + hand calculation checks), regulatory compliance matrix referencing FAR 43.13(b), AC 20-107B, AC 21-26A for each required showing, model validation evidence (NASA scarf data comparison, Cytec cure knockdown comparison), repair quality assurance requirements (scarf angle inspection, surface preparation protocol, post-cure PAUT), and Engineering Order number placeholder for DER signature.
newtsim Span Model Archive: Parameterised repair model with scarf geometry inputs for reuse on future repair dispositions. Documentation includes boundary condition setup, CZE calibration procedure, and PAUT data import workflow.

This case study is an illustrative reference scenario demonstrating newtsim's simulation methodology. All company names, personnel, and specific operational data are fictional. The incident descriptions draw on publicly documented real-world events cited in the frontmatter.