Constructing quasi-vertical fiber bridging behaviors of aramid pulp at interlayer of laminated basalt fiber reinforced polymer composites to improve flexural performances

Basalt Fiber Reinforced Polymer(BFRP)composites have huge potential application respects for some civil fields due to enough strength/modulus to weight and low cost by replacing carbon fiber composites.Aiming at the issues in the Resin-Rich Region(RRR)and Interfacial Transition Region(ITR)of fiber reinforced polymer composites,the characteristic Aramid Pulp(AP)fibers with micro-fiber trunk and nano-fiber branches were manufactured into multiple non-woven ultra-thin interleaving at the interlayers of BFRP composites via compression molding to reinforce the flexural strengths and elastic moduli.AP fibers were introduced into RRR to form interleaving at the interlayer,the brittle epoxy adhesive layer was improved and enabled to avoid cracking under a low external load.Free fiber branches of AP were also embedded into BF layer to construct quasi-vertical fiber bridging behaviors in ITR,stronger mechanical interlocking was created to prevent crack propagation along the bonding interface of BF/epoxy.Three-point bending testing results showed the interleaving film with 4 g/m^(2)AP exhibited the best effect among various areal densities and yielded average 315.75 MPa in flexural strength and 21.38 GPa in elastic modulus,having a 63.4%increment and a 47.1%increment respectively compared with the bases.Overall,the simple and low-cost AP interleaving is confirmed as an effective method in improving interlayer structure and flexural performance of BFRP composites,which may be considered to manufacture high-performance laminated fiber reinforced polymer composites in civil aviation industry.

Effects of Cu stress on physiological,biochemical,and spectral properties of wheat at different growth stages

To study the mechanism of Cu toxicity on wheat,the characteristics of Cu stress in pivotal growth periods of wheat were explored by field planting methods.The results showed that at the tillering stage,the concentrations of Cu in the leaf cell fluid were significantly higher than those in the cell wall,and the Cu was primarily enriched in cell fluid.At the jointing and heading stages,the Cu concentration in the leaf cell wall was significantly higher than that in the cell fluid,and the main enrichment was transferred to the cell wall.During the above three growth stages,no Cu was discovered in leaf organelles.Further studies showed that the total soluble protein content in wheat leaves at the tillering and jointing stages showed a trend of first rising and then falling with increased Cu dosage.At the heading stage,under low and medium Cu stress,the total soluble protein content showed no remarkable change.Malondialdehyde(MDA)content at the tillering stage increased with the increase of Cu concentration in the soil,while MDA content did not change noticeably at the jointing and heading stages.At the tillering and heading stages,the low concentrations of Cu increased peroxidase(POD)activity.The POD activity decreased gradually with the increased Cu concentration.However,at the high concentrations of Cu,there was no significant difference in the activity of POD.At the jointing stage,the POD activity did not change significantly under the low Cu stress while it was evidently inhibited under high Cu stress.Based on the above studies,further analyses on the correlation between canopy spectral characteristics and the Cu accumulation at different growth stages of leaf cells were performed,and a new combined index SIPI/NDVI705 performed well in Cu content prediction.The results showed that at different growth stages,different sensitive spectral characteristic parameters should be used to predict the Cu content in leaf cells.