Accession Number : ADA260195


Title :   Mesomechanical Model for Fibre Composites: The Role of the Interface


Descriptive Note : Final rept. 1 Jun 1989-31 May 1992


Corporate Author : TORONTO UNIV (ONTARIO)


Personal Author(s) : Piggott, Michael R


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a260195.pdf


Report Date : 31 Jul 1992


Pagination or Media Count : 44


Abstract : This work was initially conceived as providing a theoretical framework linking microphenomena and macroscale properties in fibre composites. In addition, experimental data were to be obtained to lend substance to the theoretical constructs. Experiments were therefore carried out on the interface, and on composites which were particularly sensitive to interfacial effects, i.e. those containing short aligned fibres. Pull out tests were used for interface studies. These showed that most fibre-polymer interphases were strong (usually stronger than the polymer) and brittle. This brittleness was an important observation which goes a long way towards explaining the properties of fibre composites containing many fibre ends. Short aligned fibre composites were manufactured, with carbon fibres having lengths of 0.5, 1.0, 2.0 and 4.0 mm. Alignment was not perfect, nor were fibre lengths all equal to the nominal lengths, so both alignments and lengths were checked in the actual composites. Composite strengths and Young's moduli were measured and compared with predictions based on slip and shear lag theory. The agreement for moduli was moderately good, but for strengths it was very poor. Since, in addition, the stress strain plots were straight, the slip theory is not supported at all by this work. Instead, it appears highly likely that a mesomechanical theory involving crack initiation and development would work much better. Theoretical development led to the concept of the mesostructure as a basis for mesomechanical analysis. The mesostructure was defined as adventitious small- scale structures which are present in fibre composites, but normally neglected, such as fibre waviness and uneven packing.


Descriptors :   *INTERFACES , *FIBER REINFORCED COMPOSITES , TEST AND EVALUATION , EXPERIMENTAL DATA , CRACKS , CARBON , MECHANICS , SCALE , BRITTLENESS , ALIGNMENT , THEORY , OBSERVATION , POLYMERS , PREDICTIONS


Subject Categories : Laminates and Composite Materials


Distribution Statement : APPROVED FOR PUBLIC RELEASE