Donadei Valentina, Lionetto Francesca, Wielandt Michael, Offringa Arnt, Maffezzoli Alfonso
Department of Engineering for Innovation, University of Salento, via per Monteroni, 73100 Lecce, Italy.
GKN Fokker Technologies BV, 7903 AN Hoogeveen, The Netherlands.
Materials (Basel). 2018 Jun 23;11(7):1063. doi: 10.3390/ma11071063.
The causes of delamination and porosities during press forming of pre-consolidated flat laminates (blanks) made of carbon fiber-reinforced poly(ether ketone ketone) (PEKK) were addressed in this study. In particular, the quality of the blank laminate was investigated before and after infrared heating. The consolidation quality was evaluated by thickness measurements, non-destructive inspection (NDI), and optical microscopy. The experimental results confirmed that deconsolidation phenomena can be related to residual stresses formed during blank forming in an autoclave, then released during infrared heating (IR) of the blank, determining most of the defects in IR heated blanks. These defects, generated at the pre-heating stage, were not fully removed in the consolidation stage of the press forming process. An annealing treatment, performed on autoclave-consolidated blanks above the glass transition temperature of the matrix, was proposed to reduce the formation of defects during IR heating. The stress relaxation phenomena during annealing were modelled using a simple viscoelastic model.
本研究探讨了由碳纤维增强聚（醚酮酮）（PEKK）制成的预固结扁平层压板（坯料）在模压成型过程中出现分层和孔隙的原因。具体而言，研究了红外加热前后坯料层压板的质量。通过厚度测量、无损检测（NDI）和光学显微镜对固结质量进行了评估。实验结果证实，去固结现象可能与在高压釜中坯料成型过程中形成的残余应力有关，然后在坯料的红外加热（IR）过程中释放，这决定了红外加热坯料中的大部分缺陷。这些在预热阶段产生的缺陷，在模压成型过程的固结阶段并未完全消除。建议对在高于基体玻璃化转变温度下经高压釜固结的坯料进行退火处理，以减少红外加热过程中缺陷的形成。使用简单的粘弹性模型对退火过程中的应力松弛现象进行了建模。
