HARVEST: A General-Purpose Platform for Mean-Field and Full-Field Composite Micromechanics and Its Validation with Polymer-Based Nanocomposites

Composite micromechanics is commonly divided between rapid mean-field estimates and computationally intensive full-field representative-volume-element (RVE) simulations. When these routes use different files, conventions and post-processing procedures, discrepancies can reflect bookkeeping rather than mechanics. This paper introduces HARVEST (Homogenisation and Representative Volume Element Simulation Tool; version 0.7.0.dev0), a general-purpose platform that coordinates mean-field homogenisation, three-dimensional RVE generation, finite-element model preparation, solver execution, homogenisation, parameter studies and post-processing through common project, service and provenance boundaries. The numerical framework is material-agnostic, whereas verification and validation are demonstrated using polymer-based nanocomposites. The Mori–Tanaka bulk response for spherical inclusions reproduces the Hashin composite-sphere result to machine precision, independent orientation procedures agree to a relative difference of 1.6×10−14, and a sequential coated-particle approximation differs from an analytical composite-sphere reference by at most 0.417% over 24 polymer-relevant configurations. An archived full-field epoxy/silica-type campaign using kinematic uniform boundary conditions and 203 structured cells remains within the Hashin–Shtrikman interval at five inclusion fractions, with realisation scatter below 0.4%. For published epoxy nanocomposites, aligned halloysite-nanotube predictions differ from measured flexural moduli by −0.89 and +0.48%, while spherical carboxyl-terminated butadiene–acrylonitrile-rubber predictions differ by −7.03 and −2.25%. The main conclusion is that a shared, traceable description of constituents, morphology, loading and outputs supports rapid mean-field screening followed by selective full-field analysis using the same material definition. The principal advantage over single-route or loosely coupled workflows is cross-route consistency and reproducibility. HARVEST is applicable to formulation screening, sensitivity studies and local-field assessment in particulate, tubular, rubber-modified, porous and mixed-matrix polymer systems, and can be extended through validated constitutive, geometry, solver and result adapters.