Problems associated with the compression testing of fibre reinforced plastic composites

Compression testing of thin and slender specimens must take into consideration the inherent instability of such specimens. Four different procedures which address this problem of instability (tendency to buckle) were used to characterise a fibre reinforced plastic (FRP). It is demonstrated that the procedure adopted influences the results obtained. Use of the Celanese antibuckling guide recommended in ASTM standards gave rise to high values of compressive strength whereas complete edge support of specimens gave rise to high secant modulus values. Other guides gave results with much lower coefficients of variation. Possible explanations for these findings are presented and recommendations for use are made.