IIE: Exploring the impact of shear stresses from differential thermal expansion on the delamination of CLT panels

IIE：探索不同热膨胀产生的剪切应力对 CLT 板分层的影响

• 批准号: 2734870
• 金额: --
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2734870
• 关键词: IIE; Exploring; impact; shear; stresses

Cross-Laminated Timber (CLT) is an engineered mass timber construction material formed of layers of timber bonded together with an adhesive. The use of exposed engineered mass timber products such as CLT has continued to increase in popularity due to their highly desirable, aesthetic, and sustainable qualities. The increased use of exposed CLT poses a challenge when considering the fire safety of compartments due to the increase in fuel load and the capability for the CLT to continue to burn after the contents of the compartment have finished burning.To maintain the burning of timber, heat must be transferred from the hot combustion gases to the pyrolysis zone within the timber to pyrolyze the timber into a volatile gas. If the heat transferred to the pyrolysis zone is insufficient then the rate of pyrolysis will decrease, and the fire will decay and auto-extinguish. If the exposed timber auto extinguishes, the compartment will burnout after the contents of the compartment have finished burning.A key part of auto extinction is the formation a thick char layer between the hot combustion gases and the virgin timber, which provides thermal resistance. However, if the bond between the layers of CLT fails, the CLT will delaminate. This removes the charred outer layer and exposes the layer beneath, leading to an increased burning rate and delays or prevents auto extinction.The adhesive strength has been identified as a major contributor to a panel's resistance to delamination. However, I hypothesise that the shear stresses in the glue line between layers induced by differential thermal expansion of the layers also plays a key role in the delamination of CLT.To test this hypothesis, I propose a series of experiments to compare the magnitude of delamination between samples with varying differences in thermal expansion between each layer. To induce a range of thermal expansion differences, I propose testing a range of CLT panels in which the angle between the grain of each layer is varied between 0degrees (parallel) and 90degrees (perpendicular). This will work in producing a range of shear stress as in wood the coefficient of thermal expansion parallel to the grain is an order of magnitude smaller than perpendicular to the grain.To quantify the extent of delamination, I propose the combination of a range of data sources. Primarily the mass loss rate and the power of the fire will be focus of the data collection. I hypothesise that an increase in mass loss rate and power will be observed after delamination occurs. The mass loss rate will be measured through a mass balance and the power of the fire will be calculated by analysing the composition of the smoke extracted by the extraction hood. I also propose that the experiment is videoed and the internal temperatures of the CLT panel recorded using embedded thermocouple to aid in further justifying my findings.

跨层层的木材（CLT）是一种工程的质量木材建筑材料，由木材层和粘合剂一起形成。由于其高度理想，美学和可持续性的品质，使用裸露的工程大量木材产品（例如CLT）的使用不断增加。在考虑燃料负荷增加以及在隔间内容物完成后，CLT增加隔室的消防安全性时，曝光CLT的使用增加构成了挑战。为了保持木材的燃烧，必须将热量从热燃烧气体中转移到木中的热力计区域内的热力局，从而将热量转移到pyrelese pyryze timber中。如果传递到热解地区的热量不足，那么热解的速率将降低，火灾将衰减并自动脱落。如果裸露的木材自动灭火器，则在隔间的内容物完成后，该隔室将倦怠。自动灭绝的关键部分是形成热燃烧气和维京木材之间的厚炭层，该木材可提供热电阻。但是，如果CLT层之间的键失败，CLT将分层。这样可以去除烧焦的外层并暴露下面的层，从而导致燃烧率提高，并阻止自动灭绝。粘合强度已被确定为面板抵抗分层的主要贡献者。但是，我假设，由层的差分热膨胀引起的层胶系中的剪切应力在CLT的分层中也起着关键作用。用于检验该假设，我提出了一系列实验，以比较每层层之间的样品之间与样品之间的分配幅度的幅度。为了诱导一系列热膨胀差异，我提出了测试一系列CLT面板，其中每层晶粒之间的角度在0度（平行）和90度（垂直）之间变化。这将在产生一系列的剪切应力上，因为在木材中，与晶粒平行的热膨胀系数相比是比垂直于晶粒的数量级。为了量化分层的程度，我提出了一系列数据源的组合。主要是质量损失率和火力的力量将是数据收集的重点。我假设在分层发生后会观察到质量损失率和功率的提高。质量损失率将通过质量平衡来衡量，而火的功率将通过分析提取引擎盖提取的烟雾的组成来计算。我还建议对实验进行视频，并使用嵌入式热电偶记录的CLT面板的内部温度有助于进一步证明我的发现。