The main objective of the present study was to develop a fire thermal model able to predict the evolution of the temperature and decomposition gradient across a laminated composite structure when exposed to fire. The thermal response of composite laminate made of organic polymer matrix was investigated under severe temperature conditions as samples were exposed to high temperatures up to 750 °C. The highlight is that a behavior law for water is included in our thermo-mechanical model to estimate effects due to a moisture content field on the thermal response of composite laminates. In particular, porosity and gas pressure are strongly influenced by the presence of water in the material and modify the thermal behavior accordingly. This enabled us to propose a new approach that can be used for the prediction of hygro-thermo-chemico-mechanical post-combustion properties in a very large number of material and fire scenarios.

An advanced fire thermal model was developed to predict the evolution of the temperature and decomposition gradient across a sandwich composite structure when exposed to high temperatures (fire). This model allows the prediction of a large numbers of parameters, such as thermal expansion, gas mass storage, porosity, permeability, density, and internal pressure. The highlight of this model is that we consider, in the sandwich constituents (core and skins), additional parameters, such as changing volume porosities, other coupled constituents (as infused resin in the balsa core), and what make the main originality of the present approach: moisture content (free and bounded water). The time dependence of many parameters, i.e., among others, the combustion advancing front and mechanical properties, can be predicted in a large number of material and fire scenarios. The proposed approach was validated in the case of sandwich panels, with glass/polyester or glass/vinyl ester skins and balsa core, exposed to high temperatures up to 750 °C. The influence of water on the thermal and mechanical responses is also highlighted.

A hybrid methodology is proposed to estimate the Interlaminar Shear Strength (ILSS) of Carbon Fiber and Polyetherketoneketone (CF/PEKK) composites from Short Beam Shear (SBS) tests. Digital Image Correlation (DIC) is used to capture the apparent shear behavior during loading as well as to detect the first sign of diffuse damage, characteristic of thermoplastic behavior. Simulations based on Finite Element Method (FEM) considering the orthotropic ply behavior allowed us to estimate the shear stress fields and finally, to identify the ILSS using a DIC‐based criterion. The methodology is applied to two types of manufactured laminates prepared with a non‐optimal and an optimal manufacturing cycle, to assess the impact of consolidation on macroscopic shear behavior. The estimated ILSS values (62.3 and 70.2 MPa for each manufacturing cycle, respectively) are compared with those obtained from the standard ASTM D2344 (88.1 and 95.7 MPa, respectively) whose limitations are discussed, particularly the out‐of‐plane shear behavior hypothesis.Highlights: ILSS obtained via dialog between DIC full‐field data and FEM‐based simulations. Significant differences between SBS strength and ILSS for thermoplastic composites. SBS strength is not representative of ILSS for thermoplastic composites. ILSS is strongly correlated to the composite microstructure at the interply. ILSS is impacted by nonlinear shear behavior.