Crack spacing is an important property governing the tensile strain capacity of strain-hardening cementitious composites (SHCC). This paper presents a generic model to determine the crack spacing of short and randomly oriented polymeric fiber-reinforced SHCCs, which takes into account of the fiber/matrix interface chemical bond, the fiber/matrix interface slip-hardening behavior, and two-way fiber pullout. The validity of the proposed model is assessed by comparing the crack spacing calculated from the present model with that observed from the direct tensile test. Increased chemical bond leads to reduced crack spacing at small crack opening due to increased fiber pullout force during fiber debonding. At large crack opening, however, increased chemical bond can lead to increased crack spacing due to premature fiber rupture. Furthermore, increased slip-hardening coefficient results in reduced crack spacing due to increased fiber pullout force during fiber slippage. Variation of the slip-hardening coefficient leads to more significant change of the crack spacing than that of the chemical bond. The proposed generic model can be used to determine the crack spacing of SHCC, and also to guide the design of SHCC with targeted multiple cracking pattern.

裂纹间距是控制应变硬化水泥基复合材料（SHCC）的拉伸应变能力的重要属性。本文提出了一种通用模型，用于确定短且随机取向的聚合物纤维增强的SHCC的裂纹间距，该模型考虑了纤维/基体界面化学键，纤维/基体界面滑移硬化行为和双向纤维拔出。通过比较从本模型计算出的裂纹间距与从直接拉伸试验中观察到的裂纹间距，可以评估所提出模型的有效性。由于在纤维脱粘过程中增加的纤维拉拔力，增加的化学键合会导致在较小的裂缝开口处减小裂缝间距。但是，在较大的裂纹开口处，由于纤维过早断裂，增加的化学键会导致裂纹间距增加。此外，由于在纤维打滑期间增加的纤维拉拔力，增加的滑动硬化系数会导致裂纹间距减小。滑动硬化系数的变化导致裂纹间距的变化比化学键的变化更大。提出的通用模型可用于确定SHCC的裂纹间距，也可指导有针对性的多裂纹模式的SHCC设计。