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Title: Investigation of delamination and matrix cracking in quasi-isotropic GFRP laminates
Author: Messenger, C. R.
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1998
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Intra-laminara nd inter-laminarc rackingi n GFRPl aminatesh as beens tudied. The epoxy matrix used gave a transparent composite and was compatible with polyurethanee,n ablinga modifieds ystem(c ontaining2 0%u ethane)t o be investigated in addition to the standarde poxy. Three stacking sequenceso f quasi-isotropic laminates(,+ 45/-45/0/90),( 0/90/-45/45) and (+45/90%45/0w),e ret ested. Dataw ereo btainedfo r the growtho f damagea ndi ts effecto n laminates tiffnessu nder increasingq uasi-staticlo ad and as a function of numbero f fatigue cycles at two differents tressle vels. Using the transparensty stemse nableda morec ompletes et of damaged atat o be obtainedth anb y previousw orkers. The damagec omprised9 0-ply crackingf ollowed by +45 and -45 crackinga nd then for (+45/-45/0/90)[3a nd to a limited extenti n (+45/90/-45/0)xd],e lamination.T he initiation andg rowtho f damage wase xaminedw ith regardt o matrix type ands tackings equenceT. he onseto f matrix cracking and delaminationa re both delayedi n the urethane-containinlga minates; fracturem echanicste stss howedt hat the urethanes ystemw as significantlyt ougher. Moreover,a t a given quasi-statics tresso r numbero f fatigue cycles the urethano. modified laminatesre taina greaterp roportiono f their initial modulus. The stacking sequencein fluencesi nterlaminars tresses( thereby controlling delamination)a nd determinesp arameterssu cha s ply thicknessa nd neighbouringp ly orientationw hich in turn influencei ntralaminasc ocking. Fracture mechanics has been applied to model the initiation and growth of delamination under quasi-static and cyclic loading using a modified compliance technique. Shear-lag models have been used to determine the stiffness loss due to intralaminar cracking, enabling the stiffnessr eduction associatedw ith delamination to be deduced empirically. This enables the energy release rates associated with delamination to be derived leading to more sensible results than those obtained using an unmodified technique
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Material degradation & corrosion & fracture mechanics Materials Biodeterioration Composite materials