• 3D FEA modelling of laminated composites in bending and their failure mechanisms

      Meng, Maozhou; Le, Huirong; Rizvi, Jahir; Grove, Stephen; University of Plymouth (2014-10-02)
    • Effects of hygrothermal stress on the failure of CFRP composites

      Meng, Maozhou; Rizvi, Jahir; Grove, Stephen; Le, Huirong; University of Plymouth (2015-08-06)
      This paper investigates the hygrothermal effects on the failure mechanisms in bending of carbon fibre reinforced polymer (CFRP) composites. Accelerated diffusion testing was carried out by immersion at 50 °C constant temperature and 70 bar hydrostatic pressure to study the effects of fresh or sea water diffusion into pre-preg CFRP laminates. Consequently the composite laminates were tested in bending after 1 and 3 months’ immersion. A three-dimensional finite element analysis (FEA) model was developed to couple the moisture diffusion, hygrothermal expansion and bending. Optical and field emission scanning electronic microscope (SEM) were employed to analyse the failure mechanisms of CFRP composites in bending after immersion. The study showed that the mechanical properties are significantly reduced after short term immersion due to the edge effects, while the damage to the fibre/polymer interface becomes more significant to laminate degradation after longer-term immersion.
    • The effects of unequal compressive/tensile moduli of composites

      Meng, Maozhou; Le, Huirong; Rizvi, Jahir; Grove, Stephen; University of Plymouth (2015-02-28)
    • Multi-scale modelling of moisture diffusion coupled with stress distribution in CFRP laminated composites

      Meng, Maozhou; Rizvi, Jahir; Le, Huirong; Grove, Stephen; University of Derby; University of Plymouth (2015-11-29)
      Laminated composite structures operating in a marine environment are subject to moisture ingress. Due to the slow diffusion process of moisture, the distribution of moisture is not uniform so that the laminates can develop hygrothermal stresses. An accurate prediction of the moisture concentration and the associated hygrothermal stress is vital to the understanding of the effect of marine environment on failure initiation. The present paper investigates the time-dependent moisture diffusion and the stress distribution in carbon fibre reinforced polymeric (CFRP) composites by means of experimental study and Finite Element Analysis (FEA). Samples were made from CFRP pre-preg autoclave-cured, and then immersed in fresh water and sea water at a constant 50 °C for accelerated moisture diffusion. Laminates with [0]16, [90]16, [±45]4s lay-up sequences were investigated. A multiscale 3D FEA model was developed to evaluate the interfacial stresses between polymer matrix and carbon fibre and the stress distribution in the composite laminates. The analysis revealed that both the stress distribution and stress level are time-dependent due to moisture diffusion, and the interphase between fibres and matrix plays an important role in both the process of moisture diffusion and the stress/strain transfer. The interlaminar shear stresses of the laminates induced by hygrothermal expansion exhibited a significant specimen edge effect. This is correlated with the experimental observations of the flexural failure of laminates.