Inverse identification of process-induced shrinkage strain for a B-stage thermoset resin in woven pre-impregnated lamina via warpage analysis
Year: 2026
Type: article
Abstract: Multilayer composites are often found in industrial applications where pre-impregnated (pre-preg) and laminated plies are stacked and hot pressed. Along this process, the B-stage resin within pre-pregs cures and shrinks, generating residual stresses in the assembly which need to be quantified. The B-stage resin in pre-preg is seldom available, preventing the characterization of its shrinkage strain. Existing methods enable to identify the in-plane effective shrinkage of pre-impregnated lamina, based on the warpage measurements of a bilayer assembly assuming homogeneous thickness of layers. An extension is proposed to estimate the apparent shrinkage strain of the B-stage resin. A difficulty originates from heterogeneous properties across the bilayer. Indeed, the hot pressing induces a local variation in the resin volume fraction due to the resin flow. These fluctuations in thermomechanical behavior and effective shrinkage strain of the lamina are quantified, as a function of the ply thickness, by a two-scale homogenization method. By considering the thickness-dependent behavior of the pre-preg, the experimental warpage of the bilayer is modeled and recovered accurately through the estimation of the apparent shrinkage strain of the resin. As a direct outcome, the effective process-induced shrinkage components are determined even in the out-of-plane direction through numerical homogenization.
Language: English
Topic: Composite Material Mechanics
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,480
OpenAlex ID: W7214440968