Thomas Rogaume

Determination of the tensile residual properties of a wound carbon/epoxy composite first exposed to fire

The use of carbon fiber/epoxy matrix composite is widely developed to store hydrogen at high pressure because of its low weight and its good specific mechanical properties. In order to secure this type of storage, it is necessary to tackle the thermal degradation and the influence of a fire or a heating source on the residual mechanical behavior of such materials. In the present study, carbon/epoxy composite samples with different fiber orientations are considered. The thermal aggression (representative of a fire) is performed by using a cone calorimeter apparatus (ISO 5660). The fire exposure is stopped at different time in order to study the influence of the thermal energy (different heat fluxes and exposure durations) on the residual mechanical tensile properties. The results obtained show that the residue thickness (char) of the samples is proportional to the incident energy. Strength and stiffness reduction can be observed even without ignition (i.e., without combustion flame) when the mechanical properties are controlled only by the resin (fiber perpendicular to the loading axis). When the fibers are mechanically loaded (quasi-isotropic samples oru2009±u200945° samples), a very little strength decrease is observed before ignition and accelerated after ignition. A proportional relationship between the ultimate stress of the exposed sample and the non-charred thickness is also observed.

Proceedings of the first workshop organized by the IAFSS Working Group on Measurement and Computation of Fire Phenomena (MaCFP)

This paper provides a report of the discussions held at the first workshop on Measurement and Computation of Fire Phenomena (MaCFP) on June 10-11 2017. The first MaCFP work-shop was both a technical meeting for the gas phase subgroup and a planning meeting for the condensed phase subgroup. The gas phase subgroup reported on a first suite of experimental- computational comparisons corresponding to an initial list of target experiments. The initial list of target experiments identifies a series of benchmark configurations with databases deemed suitable for validation of fire models based on a Computational Fluid Dynamics approach. The simulations presented at the first MaCFP workshop feature fine grid resolution at the millimeter- or centimeter- scale: these simulations allow an evaluation of the performance of fire models under high-resolution conditions in which the impact of numerical errors is reduced and many of the discrepancies between experimental data and computational results may be attributed to modeling errors. The experimental-computational comparisons are archived on the MaCFP repository [1]. Furthermore, the condensed phase subgroup presented a review of the main issues associated with measurements and modeling of pyrolysis phenomena. Overall, the first workshop provided an illustration of the potential of MaCFP in providing a response to the general need for greater levels of integration and coordination in fire research, and specifically to the particular needs of model validation.

Effect of a coupled thermomechanical loading on the residual mechanical strength and on the surface temperature of wound carbon/epoxy composite

Wound composite structures such as hyperbaric hydrogen tanks may experience accidental situations, for example in case of a fire. The FCH-JU project FireComp aims at better characterizing the conditions that need to be achieved in order to avoid a failure of a composite pressure vessel. This research program involves specific experiments to improve the understanding of loss of strength of composite high-pressure vessels in fire conditions. The present study investigates the effect of a coupled thermomechanical loading (cone calorimeter exposure and, simultaneously, mechanical stress) on the residual strength of a composite material. A specific device combining a cone and a four-point bending bench has been designed. The influence of the coupled aggression is addressed by comparing the temperature on the front and the rear sides, the mass loss, and the residual tensile strength of a set of samples subjected to a heat flux only and a set subjected to a heat flux and a four-point bending. The results do not exhibit a clear effect of the mechanical load: the thermomechanical properties of both sets of samples are similar.