26:T545,

A method is proposed to obtain the strain energy release rate and the stresses ahead of the crack in a laminated composite plate due to free edge delamination under Mode I type loading situations. A shear deformable beam finite element with nodes offset to either the top or bottom side has been developed. The thermal effects originating from the curing process are included in the formulation of the problem. Two different methods are used to calculate the strain energy release rate. The first method uses the J-integral evaluated around a zero-area path surrounding the cracktip and the strain energy release rate is expressed in terms of the force and moment resultants in the elements surrounding the crack-tip. The second method is similar to the virtual crack closure method, and the strain energy release rate is expressed in terms of the forces transmitted by a rigid element placed at the crack-tip and the displacements of the nodes behind the crack-tip. The stresses ahead of the crack are obtained by using discrete spring elements in the uncracked portion of the beam. The results calculated are in good agreement with results obtained from other studies of the same problem. The advantage of the present method lies in its simplicity; in addition it requires less computational effort than the methods that use solid elements.

27:T40f,

A study was conducted on the effect of interleaving on laminated composites. An ethylene-based ionomer of various compositions and a silane-modified ethylene-vinyl-acetate were selected as the interleaving materials. The glass transition temperatures (Tg) of the ethylene-based polymers ranged from-24 to 50'C. The fracture toughness (GIc), impact performance, and damping properties of the composites were evaluated. G₁c of interleaved composites was about 3-5 times higher than that of non-interleaved. However, G₁c was sensitive to the composition of the interleaf. The silane-modified ethylenevinyl-acetate had the highest fracture toughness. The impact properties of the interleaved materials were superior to those of non-interleaved, as evident from CAI testing where delamination occurred at an early stage in non-interleaved samples. The damping ratio of interleaved materials was found to be more than 100 times higher than in the original material.

28:T4c2,

The objective of this work has been to study the influence of processing temperature during compression molding on the consolidation quality and mechanical properties of warp-knitted fabric-based composites made of commingled yams containing glass fiber (GF)/polyethylene terephthalate (PET). The consolidation quality in terms of void content and uniformity of fiber distribution was studied on unidirectional and cross-ply laminates. The mechanical properties studied were flexural strength, flexural modulus, Izod impact strength, and drop-weight impact resistance. The influence of forming temperature on fiber-matrix adhesion was studied by measuring the transverse flexural strength and SEM analysis. SEM analysis was also used to analyze the mode of fracture during impact. The results in this paper suggest that consolidation quality as defined by fiber distribution is strongly dependent on molding temperature. The transverse strength increased significantly with processing temperature, indicating an increase in fiber-matrix interfacial adhesion with increasing processing temperature. The increased interfacial adhesion influenced the Izod strength and drop-weight impact behavior of the laminates.

29:T493,<a href="http://www.sagepub.co.uk/sagechoice.sp"><img src="http://www.sagepub.co.uk/repository/binaries/img/common/sagechoice.gif" /></a>This journal offers optional funded open access. <a href="http://www.sagepub.co.uk/sagechoice">Click here to read more...</a>The Journal of