Abstract We investigate the influence of process-induced shrinkage and subsequent annealing on the thermomechanical behavior of unidirectional laminates made of continuous glass fiber-reinforced polypropylene (GFPP). We use two different industrial lamination processes: static hot-press (SHP), and double-belt press (DBP) that are characterized by different cooling rates and pressure levels and most importantly, by the use of a closed mold in the case of SHP manufacturing. We measure the longitudinal and transverse shrinkage during the manufacturing and annealing processes using embedded fiber Bragg gratings (FBGs). The SHP molding reveals much lower induced shrinkage in GFPP as compared to the DBP process, although the relatively slow cooling should promote a higher degree of crystallization. We ascribe this to the constraining effect of the metallic mold used with the SHP process. The poor thermal conductivity of the mold is also responsible for a layer-like crystal microstructure in the GFPP matrix, causing a specific relaxation effect during the post-process heating treatment. Annealing generates additional shrinkage that is due to an increased degree of crystallinity and to the partial relaxation of residual stresses. However, the thermal expansion properties remain impacted by the process-induced strain state of the GFPP laminates and are still process-dependent after annealing.

中文翻译：

---

加工收缩和退火对玻璃纤维增​​强聚丙烯热机械行为的影响

摘要 我们研究了过程引起的收缩和随后的退火对由连续玻璃纤维增​​强聚丙烯 (GFPP) 制成的单向层压板的热机械行为的影响。我们使用两种不同的工业层压工艺：静态热压机 (SHP) 和双带压机 (DBP)，它们的特点是不同的冷却速度和压力水平，最重要的是，在 SHP 的情况下使用封闭模具制造业。我们使用嵌入式光纤布拉格光栅 (FBG) 测量制造和退火过程中的纵向和横向收缩率。与 DBP 工艺相比，SHP 成型显示 GFPP 的诱导收缩率低得多，尽管相对缓慢的冷却应该促进更高的结晶度。我们将此归因于 SHP 工艺所用金属模具的约束效果。模具导热性差也是造成GFPP基体中层状晶体微观结构的原因，在后处理加热处理过程中产生特定的松弛效应。由于结晶度的增加和残余应力的部分松弛，退火会产生额外的收缩。然而，热膨胀特性仍然受到 GFPP 层压板的工艺诱导应变状态的影响，并且在退火后仍然依赖于工艺。由于结晶度的增加和残余应力的部分松弛，退火会产生额外的收缩。然而，热膨胀特性仍然受到 GFPP 层压板的工艺诱导应变状态的影响，并且在退火后仍然依赖于工艺。由于结晶度的增加和残余应力的部分松弛，退火会产生额外的收缩。然而，热膨胀特性仍然受到 GFPP 层压板的工艺诱导应变状态的影响，并且在退火后仍然依赖于工艺。