# Effect of Fireproof Coatings on the Post-Fire Behavior of CFRP Composite Sheets
## 2 Experimental Program
### Specim Conditions  
The test was divided into three groups: (1) unconditioned as a reference, tested without fireproof coatings at ambient temperature; (2) conditioned, tested without fireproof coatings after fire exposure; and (3) conditioned, tested with fireproof coatings after fire exposure. The ambient temperature was maintained at 23 \(\pm\) 2 \({}^{\circ}\)C. This study considered two different fire conditions, including standard fire and large-space fire conditions, to simulate the air warming of general interior fires and large-volume space fires, respectively. Both of these fire conditions are essential fire models in engineering practice. The standard fire heating curve recommended in ISO 834-1:1999 [35] was employed. This is a representative fire temperature curve derived from actual fire data through statistical analysis and theoretical derivation, as depicted in Equation (1). \[T=345\lg(8t+1)+20 \tag{1}\]  
In the above equation, \(T\) is the temperature after \(t\) minutes of heating. In addition, the large-space fire condition represents a fire scenario that occurs in large building spaces, the model of which is recommended in CECS 200-2006 [36] and depicted in Equation (2). Flame spread and heat transfer processes under large-space fire conditions are relatively complex and influenced by multiple factors, such as object distribution and ventilation conditions. \[T(x,z,t)=Tz(1-0.8\mathrm{e}-\beta t-0.2\mathrm{e}-0.1\beta t)\times[\eta+(1- \eta)\mathrm{e}-(x-b)/\mu]+20 \tag{2}\]  
In the above equation, \(T\) is the temperature after \(t\) seconds of heating. \(Tz\) is the air temperature at a vertical distance \(z\) (m) from the ground on the centerline of the fire source. \(b\) is the distance from the center of the fire shape to the outermost edge of the fire. \(\beta\) is a coefficient related to the power of the fire source and the fire growth type. \(\eta\) is the temperature attenuation coefficient at a horizontal distance of \(x\) (m) from the center of the fire source. \(\mu\) is also a coefficient. The physical significance of the relevant parameters in Equation (2) is shown in Figure 3.  
Figure 2: MTS testing machine. For the uncoated group, the fire conditions were set as the large-space fire condition for a 2 h heating period, characterized by a floor area of 500 m\({}^{2}\), a building height of 4 m, a medium speed fire growth type, and a medium power level of firepower. For the coated group, the fire conditions included exposure to standard and large-space fire conditions. The large-space fire conditions of the coated group were set up to be consistent with those of the uncoated group, while the continuous heating durations under standard fire conditions were 0.5 h, 0.75 h, and 1 h. The standard fire and large-space fire heating curves are illustrated in Figure 4.  
Based on specific structural design and fire protection specification GB14907-2018 [37], the coating thicknesses for the test CFRP specimens under the large-space fire condition were 15 mm, 25 mm, and 35 mm, corresponding to Type C1 and C2 coatings. The application of fireproof coatings with different thicknesses allows for the observation and comparison of differences in the fire resistance of CFRP sheets to evaluate the performance of the fireproof coatings. It provides references and recommendations for selecting the appropriate coating thickness for structural design and reinforcement. Under standard fire conditions, the coating thickness of the specimens was consistently maintained at 35 mm to investigate the ultimate fire-resistant duration that the CFRP sheets with the thickest coatings could withstand. Beyond the decomposition temperature, the CFRP composites may burn.