Structural Means for Fire-Safe Wooden Façade Design

This study investigates five fire stop variants used to limit the spread of fire on wooden façades. For this purpose, five fire tests using various types of wooden façade claddings and different fire stops were conducted as full-scale tests and compared to the existing findings. The influences and interactions between the material qualities of the external wall behind the façade cladding, the construction type of the wooden façade cladding, the design of the substructure, the depth of the ventilation gap, and the design of the fire stops were investigated. In evaluating the fire stops, the design of the interior corners, the joint design, and the influence of thermal expansion were examined. Finally, design proposals for the design of fire stops at wooden façades in order to limit the spread of fire were derived based on this evaluation. The outlook presents further needs that need to be investigated in the future in order to clarify undiscussed aspects or points that were ultimately not evaluated within the scope of this study. Graphical Abstract

ANALYSIS OF THE INFLUENCE OF DISTANCE BETWEEN THE HEATING ELEMENT AND THE SAMPLE ON THE SMOKE FORMING ABILITY OF PINE WOOD IN VIETNAM

Series of fire tests was carried out to determine the smoke-forming ability of conifer- ous wood at different distances of the sample from the heating element. It was found that the same heat flux density leads to a difference in temperature at different distances, which significantly affects the test result.

POST MECHANICAL FAILURE FIRE DAMAGE CHARACTERIZATION OF GRAPHITE/EPOXY COMPOSITES

Fire damage involving mechanically failed composite aircraft structures can dramatically alter their exposed surface characteristics in ways that inhibit fire forensic analyses. In this work, the effects of fire exposure on mechanically failed Cytec T40- 800/Cycom® 5215 graphite/epoxy composites were examined. Coupon level vertical fire tests were performed on mechanically failed unnotched compression and in-plane shear graphite/epoxy specimens. The fire damage was characterized by visual inspection and scanning electron microscopy. The fire damage development in the specimens involved a concurrent and sequential interaction between multiple physical, chemical, and thermal processes. This damage included melt dripping, matrix decomposition, char, soot, matrix cracking, delamination, and residual thickness increases due to explosive outgassing. The composite thermal degradation due to heat conduction, combustion, and/or thermal deformation was significantly affected by the specimen layup, ply orientation relative to the heat source, and the fracture surface morphology. Plies burned with fibers oriented parallel to the flame axis conducted heat into the interior of the composite. This resulted in melt dripping, internal pockets of matrix decomposition, and surface char deposition that, in some cases, completely obscured pertinent aspects of fiber fracture surface morphology. In contrast, plies burned with fibers oriented perpendicular to the flame axis acted like a thermal protection layer that impeded (slowed) heat transfer to the specimen’s interior. Furthermore, the thermal damage development was influenced by the specimen layup and the total available free surface area created during mechanical failure. Specimens with more free surface area promoted better airflow and oxygen availability for combustion and sustained far more thermal degradation for given fire exposure. Key fractographic features in exposed fiber bundles were destroyed due to severe thermal oxidation and thinning. A thorough understanding of these coupon-level fire tests represents a critical first step in developing a coherent strategy for the Federal Aviation Authority post-crash forensic analysis of composite aircraft structures.

Expandable Graphite for Flame Retardant PA6 Applications

A new expandable graphite (EG) type was studied as a flame retardant additive in Polyamide 6 (PA6). The fire behavior was characterized by a cone calorimeter using external heat fluxes of 35, 50 and 65 kW/m2, limiting the oxygen index (LOI) and UL-94 burning tests. Additionally, electric and thermal conductivity as well as rheological properties were characterized to provide a general property overview. Fire tests were conducted using dry and humid conditioned samples. Cone Calorimeter tests showed a minimum filling degree of 15 wt.% (8.6 vol.%) EG was required to achieve a significant fire inhibiting effect in PA6 independent of the sample condition. UL-94 fire tests show a V0 classification at filling degrees greater than 20 wt.% (humid) and 25 wt.% (dry), although the associated LOI values of 39% and 38% demonstrate good flammability inhibition. Correlation analyses were conducted to identify major influences given by the sample condition for most important key figures measured in cone calorimeter tests. Accordingly, humid-conditioned samples containing between 2.5 (PA6 + 25 wt.% EG) and 4.2 wt.% (PA6) water were found to reduce the total heat evolved (THE) on average by 16% and the total smoke production (TSP) on average by 22%.

Review of large-scale fire tests on cross-laminated timber

Concerns about the environmental impact of building construction is leading to timber being more commonly used. However, it often faces scepticism regarding its safety in the event of fire. This article provides a point of reference on the fire performance of cross-laminated timber through a review of large-scale tests. Although adequately protecting CLT can make its contribution to fire insignificant, some of the internal surface of an enclosure can be exposed whilst still achieving adequate fire performance. Natural fire tests show that the charring rate and zero-strength layer thickness are higher than commonly used in guidance documents. The type of adhesive used to bond lamellae influences performance where delamination can lead to secondary flashovers, particularly in smaller enclosures. Structural elements can potentially collapse without self-extinction and/or suppression intervention. Tests to date have focussed on a residential context and knowledge gaps remain regarding larger enclosures, such as office-type buildings.